StemCell Therapy

July 22nd, 2015 Editors Ophthalmology

Second Sight, effectivelythe first company to bring rudimentary sight back to blind patients with certain underlying eye conditions (retinitis pigmentosa and outer retinal degeneration), is now proudly reporting that a man with dry age-related macular degeneration (AMD) who has lost central vision has been outfitted with the firms Argus II prosthetic. This is part of a study that will involve more patients and will assess whether the system, which includes a wireless implant and a special set of glasses, essentially replaces the work of the diseased natural photoreceptors and stimulates the remaining healthy retinal cells. The original video signal is gathered from a camera built into a pair of glasses, which is then converted by a wearable computer and sent wireless to the implant.

Heres more about the trial, including video of the patient seeing using the Argus IIsystem:

Product page: Argus II Retinal Prosthesis System

Source: Second Sight

Editors

At Medgadget, we report on the latest medical technology news, interview leaders in the field, and file dispatches from medical events around the world.

Continued here:
Second Sight Argus II Eye Prosthesis Brings Central Vision ...

One of the most dramatic experiments to perform is the demonstration of the blind spot. The blind spot is the area on the retina without receptors that respond to light. Therefore an image that falls on this region will NOT be seen. It is in this region that the optic nerve exits the eye on its way to the brain. To find your blind spot, look at the image below or draw it on a piece of paper: To draw the blind spot tester on a piece of paper, make a small dot on the left side separated by about 6-8 inches from a small + on the right side. Close your right eye. Hold the image (or place your head from the computer monitor) about 20 inches away. With your left eye, look at the +. Slowly bring the image (or move your head) closer while looking at the +. At a certain distance, the dot will disappear from sight...this is when the dot falls on the blind spot of your retina. Reverse the process. Close your left eye and look at the dot with your right eye. Move the image slowly closer to you and the + should disappear. Here are some more images that will help you find your blind spot. For this image, close your right eye. With your left eye, look at the red circle. Slowly move your head closer to the image. At a certain distance, the blue line will not look broken!! This is because your brain is "filling in" the missing information.

This next image allows you to see another way your brain fills in the blind spot. Again, close your right eye. With your left eye, look at the +. Slowly move your head closer to the image. The space in the middle of the vertical lines will disappear.

In the next two images, again close your right eye. With your left eye, look at the numbers on the right side, starting with the number "1." You should be able to see the "sad face" (top image) or the gap in the blue line (bottom image) in your peripheral vision. Keep your head still, and with your left eye, look at the other numbers. The sad face should disappear when you get to "4" and reappear at about "7." Similarly the blue line will appear complete between "4" and "7."

Here is another image to show your blind spot. Close your right eye. With your left eye, look at the +. You should see the red dot in your peripheral vision. Keep looking at the + with your left eye. The red dot will move from the left to the right and disappear and reappear as the dot moves into and out of your blind spot.

Materials:

More (lots more) about Blind Spots

Read about the eye.

Two eyes are better than one, especially when it comes to depth perception. Depth perception is the ability to judge objects that are nearer or farther than others. To demonstrate the difference of using one vs. two eye to judge depth hold the ends a pencil, one in each hand. Hold them either vertically or horizontally facing each other at arms-length from your body. With one eye closed, try to touch the end of the pencils together. Now try with two eyes: it should be much easier. This is because each eye looks at the image from a different angle. This experiment can also be done with your fingers, but pencils make the effect a bit more dramatic.

Materials:

Here's another demonstration of the importance of two eyes in judging depth. Collect a set of pennies (or buttons or paper clips). Sit at a table with your subject. Put a cup in front of your subject. The cup should be about two feet away from the subject. Have your subject CLOSE one eye. Hold a penny in the air about 1.5 ft. above the table. Move the penny around slowly. Ask your subject to say "Drop it!" when he or she thinks the penny will drop into the cup if you released it. When the subject says "Drop it," drop the penny and see if it makes it into the cup. Try it again when the subject uses both eyes. Try it again with the cup farther away from the subject. Try it again with the cup closer to the subject. Compare the results of "10 drops" at each distance.

Questions:

Materials:

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Here's another way to demonstrate how different images are projected on to each eye. Look at an object in the distance (20-30 feet away), such as a clock on the wall. Close one eye, hold up your arm and line up your finger with the object. Now without moving your finger or your head, close the opened eye and open the closed eye. The object in the distance will appear to jump to the side...your finger will no longer be lined up. This shows that different images fall on each eye.

Materials:

There are two types of photoreceptors in the eye: rods and cones. The rods are responsible for vision in dim light conditions, the cones are for color vision. To demonstrate how the photoreceptors "adapt" to low light conditions, get a collection of objects that look slightly different: for example get 10 coke bottle caps, 10 soda bottle caps, and 10 water bottle caps. They should feel the same, but not look the same. In a bright room, ask students to separate the caps into piles of similar caps. Then turn off the lights so the room is very, very dim. Ask them to separate the caps again. Turn off the lights and look at the results...there should be many mistakes. Count the number of errors. Then dim the lights again and talk/discuss about dark adaptation or about the animals that can see in the dark. The technical explanation for dark adaptation is not necessary for small children. Plan to talk and discuss for about 7-10 minutes...this will be enough time for a least partial adaptation of the photoreceptors. After the discussion (7-10 minutes), ask the students to separate the caps again in the same very, very dim conditions as before. Count the number of errors. There should be fewer errors this time because the photoreceptors have adapted to the low light conditions.

Materials:

How does the surrounding picture influence what we see? Find out with this interactive picture. You must have a browser that supports "JAVA scripts".

How does the surrounding color influence what we see? Find out with this interactive picture. You must have a browser that supports "JAVA scripts".

How does your brain prepare you to see something? Find out with this interactive picture. You must have a browser that supports "JAVA scripts".

The Exploratorium in San Francisco has a worthwhile virtual Cow Eye Dissection to check out.

Do you have "X-Ray Vision?" You may be able to see through your own hand with this simple illusion. Roll up a piece of notebook paper into a tube. The diameter of the tube should be about 0.5 inch. Hold up your left hand in front of you. Hold the tube right next to the bottom of your left "pointer" finger in between you thumb (see figure below).

Look through the tube with your RIGHT eye AND keep your left eye open too. What you should see is a hole in your left hand!! Why? Because your brain is getting two different images...one of the hole in the paper and one of your left hand.

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Have you ever noticed that it is easy to see a star in the sky by NOT looking directly at it? It is actually easier to see a dim star at night by looking a bit off to the side of it. Try it! This is because the two types of photoreceptors (rods and cones) in the retina perform different functions and are located in the retina in different locations. The cones, which are best for detail and color vision, are in highest concentration in the center of the retina. The rods, which work better in dim light, are in highest concentration in the sides of the retina. So if you look "off-center" at the star, its image will fall on an area of the retina that has more rods!

Materials:

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Here is a fun way to introduce and explore the sense of vision. Get a variety of sample "color cards" from your local paint store. These cards are about the size of index cards and show the variety of paint that is available. Bring them back to class and have students match up similar colors. You can also use samples of gift wrap or wall paper to make color or pattern cards. Just glue the wrap or wall paper to a piece of card board to get yourself a "Color Card."

Materials:

Color Spy is a variation of the "I Spy" game. Divide players into teams. Write the words "blue", "red", "yellow", "orange" and "green" on separate pieces of paper. Have one member of each team pick a paper. The color picked will be the name of the team.

When someone says "Go," the teams will have 10 minutes to look around the room for objects that have their team's color. Teams must make a list of all the objects they find. After the 10 minute search period, the teams come back together and the lists of objects are read. Each team gets one point for each object found. After the lists are read, each team will get five minutes to search the room for colored objects that the other teams did NOT find. For example, if the red team did not find a red apple, another team that DID find the red apple will get one point. The team with the most total points after both searches is the winner.

Materials:

Of course you cannot see if it is completely dark, but you can see a bit in dim light. In dim light, the receptors in your eyes called rods are doing most of the work. However, the rods do not provide any information about color. The other photoreceptors in your eye, called cones, are the ones that are used for seeing color. The cones do not work in dim light. That's why you cannot see colors in dim light. Check it out for yourself:

Get five pieces of paper of different colors (such as different colored typing paper or construction paper). Dim the lights until you can just barely see. Wait about 10 minutes (maybe listen to some music while you wait). Then write on each piece of paper the color you think that paper is. Turn on the lights and see if your guesses were correct. Did everyone in your class mix up the same color or did everyone get the colors correct?

Materials:

When light enters the eye, it is first bent (refracted) by the cornea. Light is bent further by the lens of the eye in a process called accomodation. To bring an image into sharp focus on the retina, the lens of the eye changes shape by bulging out or flattening. A flatter lens refracts less light. Here's how to demonstrate accomodation:

Close one eye and stare at a point about 20 feet away. It should be in focus. Keep focusing on the point and raise one of your fingers into your line of sight just below the point. Your finger should be a bit blurred. Now, change focus: look at the tip of your finger instead of the point 20 feet away. Your finger will come in focus, but the distant point will be blurred.

Materials:

None

More vision related resources from "Neuroscience for Kids":

The Eye The Retina The Visual Pathway Do you wear glasses? Find out why! Eye Safety Tips Lesson Plan about the Eye Lesson Plan about Color Vision Lesson Plan about Depth and Motion Does the COLOR of Foods and Drinks Affect Taste? Common Eye Diseases and Disorders

The National Eye Institute has a GREAT page with activities related to the eye called See All You Can See for kids; and aearn about "stereograms."

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Sight (Vision) - University of Washington

Cataract care is one of the safest and most common types of surgery performed today. Advanced technology can dramatically improve the visual quality and quality of life for all those with cataracts.

New Lifestyle Intra-Ocular Lenses ("IOLs")can correct nearsightedness, farsightedness, and astigmatism; affording the ability to see perfectly at far distance after treatment, without glasses. Other special multifocal lenses allow good focus at far and near, eliminating the need for reading glasses as well. We personalize our recommendations to you based on your lifestyle, visual desires, habits, and preferences, as well as our findings during a comprehensive evaluation..

LA Sight is one of the few eye centers in the region that provides Laser-Assisted Cataract Care as an option.

With our custom-tailored approach, it is now possible to enjoy glasses-free vision for near, and far, and in-between. Dr. Wallace and the team at LA Sight are able to offer the widest range of custom treatment options available with cataract and clear lens surgery.

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Lasik Eye Surgery - Get Your Best Vision at LA Sight

I thought Id be chained to my glasses for the rest of my life.

I didnt know you could improve your vision with only 15 minutes of simple eye exercises each day.

I thought my eyes would just keep getting worse, year on year, as I got older.

I didnt know you can attain perfect eyesight, at any age, and then keep it.

Eyes are amazing!

It doesnt matter which eye 'problem' you have, your eyes always retain the ability to heal themselves. YOU can see perfectly.

It just doesn't matter what is 'wrong' with your eyes.

If you give them the help and support they need, they WILL heal themselves.

Perfect Vision is your birth-right.

I used to wear glasses. You know, the ugly goldfish bowl type that make your eyes look as big as saucers!

One day I was complaining to my friend Maria, yet again, about how lucky she was, not needing glasses.

We were at the beach.

I love the beach, but as far as locations go, it's not very spectacle-friendly!

"You don't know how lucky you are Mary. You can swim, play volley ball, roll in the sand, and you don't have to think about your glasses... losing them, breaking them - the constant cleaning!"

Maria, a true friend, was clearly tired of my moaning:

"Look Dave, why don't you quit complaining and just fix your eyes. I read somewhere that you can do it yourself by just doing some special eye exercises every day. I think it's called Natural Vision Correction or something like that."

I laughed. Actually, I scoffed.

I thought she was talking nonsense!

You see, Id been wearing glasses since I was 3 years old. My eyes were getting progressively worse. How could a few exercises change that!

I didn't believe it was possible to reverse my decaying eyesight.

If it was true, surely my optician would have told me?

But her words stuck in my head. They started to nag at me. I began to think what if it was true?

What if I could heal my own eyes?

What if I could wake up in the morning, and see my partners face lying on the pillow, instead of a fuzzy blur?

I started to research.

What I discovered blew me away.

You see, perfect vision is the natural state of your eyes.

I discovered that we don't need glasses (or lenses) at all. In fact, they actually make your eyesight worse!

20/20 vision is highly overated. The eyes can see much better than that.

(20/20 vision means you can easily read the 20 foot line on the Snellen Eye Test Chart at 20 feet away!)

There is no limit to how much you can improve your vision beyond 20/20

Someone with above average eyesight can easily read the 10 foot line, (the smallest line at the bottom of the Snellen Eye Test Chart), at 20 feet away => 20/10 vision.

In fact, after a little training, there are plenty of people who can read the 10 foot line at 50 to 60 feet away => 60/10 vision.

This is called "telescopic vision". Sounds good, doesn't it.

"yeah, sure thing Dave... telescopic vision! Right now, I'd be over the moon if I could just read the TV guide without having to reach for my glasses!"

Well, at first I did ... um .... nothing!

I just got really angry.

Id spent more than 3 decades unnecessarily dependent on glasses.

Why hadn't anyone told me?

Then I revisited my old friend... Mr Skepticism.

"If it was really possible to fix your own eyes with simple daily exercises, no-one would be wearing specs or lenses anymore. Surely, everyone would have perfect vision!"

I didnt want to believe Id spent so many years of my life being 'technically blind without glasses', when the 'cure' was so simple.

"It must be a load of old rubbish!"

Thank you, Mr Skepticism... or should I say Mr Cynicism!

Next came a little victimhood ...

"Maybe it works for some lucky people, but I'm sure it wont work for me."

Looks like the odds were stacked against me.

Luckily, I had an advantage over my doubting mind.

I hated wearing glasses!

I wanted to see

I mean I really wanted to see

I was ready to do almost anything

So I just got started experimenting with my own eyesight.

I bought books. I surfed the web for hours reading articles. I studied Yoga techniques, Taoist techniques, Buddhist and Sufi techniques, the Bates Method, the Slavicek method, the abc and the xyz method.

I tried different foods and herbs, oils, potions and lotions.

If I found something that was supposed to help heal the eyes, I tried it!

Some stuff was kind of obvious, some not so apparent, and some stuff was just plain weird... but I tried that too!

Well, no actually!

At first, not much happened.

I got disappointed. I started skipping the exercises and nearly gave up.

But luckily, I'd overdone the research!

I'd found so much information, and so many different techniques, there was always something new to try. There was always some new hope to give me a little renewed motivation.

Success stories, like the one above, inspired me to stick with it. So I started to collect lots of them, and read a few every day.

Reading these testimonials, from real people who were just like me, made sure I did my exercises.

... a few weeks later, my eyes started to feel uncomfortable with my glasses on, and I decided to go for a check up.

I was shocked. My vision had improved by two whole diopters (from +8 to +6). That's a 25% improvement.

Ok, its wasn't 20/20, but can you imagine how I felt Id actually improved my own vision.

My eyes were healing themselves. The exercises were working. It was true after all. I was going to get my sight back!!

Now I got really serious. I did MUCH more research.

I got more disciplined with my exercises, and began to refine my schedule, so I could do my daily eye routine in just 15 minutes.

I started to make some changes to my daily habits, including my diet.

I found some great information about some specific herbs that are incredibly beneficial to the eyes, and I built that into my daily routine.

Read this article:
Eye Exercises Improve Vision Eyesight

An eye care professional is an individual who provides a service related to the eyes or vision. It is a general term that can refer to any healthcare worker involved in eye care, from one with a small amount of post-secondary training to practitioners with a doctoral level of education.

Ophthalmologists are medical and osteopathic doctors who provide comprehensive eye care, including medical, surgical and optical care.[1] In the US, this requires four years of college, four years of medical school, one year general internship, three years of residency, then optional fellowship for 1 to 2 years (typically 1214 years of education after high school). An ophthalmologist can perform all the tests an optometrist can and in addition is a fully qualified medical doctor and surgeon. Ophthalmologists undergo extensive and intensive medical and surgical exams to qualify and entrance criteria to a training program is highly competitive.

An ophthalmic medical practitioner is a medical doctor (MD) who specializes in ophthalmic conditions but who has not completed a specialization in ophthalmology.

The World Council of Optometry, a member of the World Health Organisation,[2] defines optometrists as the primary healthcare practitioners of the eye and visual system who provide comprehensive eye and vision care, which includes refraction and dispensing, detection/diagnosis and management of disease in the eye, and the rehabilitation of conditions of the visual system.[3]

A Doctor of Optometry (OD) attends four years of college, four years of optometry school and then an optional one-year residency. Optometrists undergo extensive and intensive refractive and medical training mainly pertaining to the eye and the entrance criteria to attend optometry school is also highly competitive. An OD is fully qualified to treat eye diseases and disorders and specializes in optics and vision correction. Permissions granted by an optometric license vary by location.

Orthoptists specialize in diagnosis and management of eye movement and coordination problems, misalignment of the visual axis, convergence and accommodation problems, and conditions such as amblyopia, strabismus, and binocular vision disorders, as outlined by the International Orthoptic Association.[4] They may assist ophthalmologists in surgery, teach orthoptic students, students of other allied health professions, medical students, and ophthalmology residents and fellows, act as vision researchers, perform vision screening, perform low vision assessments and act as clinical administrators.[5]

The World Health Organization defines the eyecare work of orthoptists as [t]he study and treatment of defects in binocular vision resulting from defects in the optic musculature or of faulty visual habits. It involves a technique of eye exercises designed to correct the visual axes of eyes not properly coordinated for binocular vision.[6]

Ocularists specialize in the fabrication and fitting of ocular prostheses for people who have lost eyes due to trauma or illness.

Opticians specialize in the fitting and fabrication of ophthalmic lenses, spectacles, contact lenses, low vision aids and ocular prosthetics. They may also be referred to as an "optical dispenser", "dispensing optician", "ophthalmic dispenser". The prescription for the corrective lenses must be supplied by an ophthalmologist, optometrist or in some countries an orthoptist. This is a regulated profession in most jurisdictions.

A collective term for allied health personnel in ophthalmology. It is often used to refer to specialized personnel (unlike ocularists or opticians). In many countries these allied personnel may just be known as an "ophthalmic assistant". Their training is usually combined with a two or three year applied science degree and they assist an ophthalmologist or optometrist in the hospital or clinic with vision testing.

In the USA the Joint Commission on Allied Health Personnel in Ophthalmology administers OMP certifications:

Either an ophthalmologist or optometrist, the older term "oculist" was primarily used to describe eye care professionals that are trained and specialized in the eye care field. The difference between an ophthalmologist or an optometrist is made by the specializations they may choose. If the oculist is trained and specialized in treating medical conditions that may affect the eye and result in an eye defect will be referred to as an ophthalmologist. Optometrists, on the other hand, are the eye care professionals that are specialized in only treating eye defects by prescribing the appropriate corrective lenses. They are also referred to as "eye doctors". The main task of the optometrist is to correct the visual deficiencies with the help of the lenses. The main difference between these two professions is that although both of them may administer eye exams, only the ophthalmologist may solve eye-related problems that may occur in all areas of the eye. Nonetheless, optometrists are specialized in detecting vision problems and correcting them, but they may not perform tasks that ophthalmologists may, such as eye surgery.

Another important difference between the types of oculists is that while optometrists may obtain their doctorate by graduating at a special school in which they are trained to be optometrists, ophthalmologists are medical doctors who need to graduate from medical school and many years of internships in order to be able to get their degree. Moreover, because of their more advanced background in the study of eye care, ophthalmologists may proceed in their studying in this field and specializing in domains such as pediatric ophthalmology, corneal disease or ocular oncology. This is the reason why ophthalmologists are often classified as surgeons rather than doctors.

The term "oculist" was therefore used to describe these two professions as a result of the similarities that exist between the two. Firstly, both ophthalmologists and optometrists receive the appropriate training which will help them in detecting the vision related problems and to diagnose and treat certain eye conditions. Ophthalmologists also were the only ones who were capable of treating the terrible disease eye-aids, it was a disease were the eyes would become extremely dirty and blurry.

A vision therapist, usually either an orthoptist or optometrist, works with patients that require vision therapy, such as low vision patients. Commonly, vision therapy is performed in children who develop problems with their vision mostly because they are using their eyes up close. This type of therapy is however generally used in patients who need visual correction but for whom the corrective lenses are not enough to reverse the condition. Visual therapy in children is performed by optometrists who specialize in children eye care. To specialize in vision therapy, doctors must complete extensive post-graduate training beyond their optometric degree, at which time they are eligible to sit for their national boards to become fully certified as specialists in children's vision. A doctor's title after passing the national board in vision therapy is Fellow in the College of Optometrists in Vision Development, or F.C.O.V.D. Optometrists who provide vision therapy but who have not yet sat for their certification exams are board-eligible Associates in the College of Optometrists in Vision Development.[7][not in citation given] Vision therapists typically rely on prisms, eye patches, filtered lenses, and computerized systems to conduct therapy sessions.

Most eye care professionals do not practice iridology, citing a significant lack of scientific evidence for the practice.

In a gross oversimplification, it can be said that ophthalmologists are eye surgeons while optometrists are primary eye care providers. There is considerable overlap in scope of practice between professions. Laws regarding licensure vary by location, but typically ophthalmologists are licensed to provide the same care as an optometrist, with the addition of surgical options. In most locations surgery is the biggest difference between the two professions. Optometrists frequently refer patients to ophthalmologists when the condition requires surgery or intra-ocular injection.

Historically, ophthalmology has developed as a specialization of medical doctors while optometry originated as a profession that fitted people with glasses. As of 2012, this difference has decreased as the majority of optometrists screen for and treat eye disease and many ophthalmologists fit people with corrective lenses. This difference in background previously caused some conflict between the two professions. Ophthalmologists have voiced concern that an optometrist's educational background is different from their own. Optometrists have criticized ophthalmologists of caring for the health structure of the eye while letting other vision disorders go untreated. For example, consider a patient with glaucoma and spasm of accommodation. Ophthalmologists would be concerned that an optometrist would fail to identify or otherwise mistreat the glaucoma. Optometrist would worry that the ophthalmologist would fail to identify or mistreat the spasm of accommodation. As of 2012, both these concerns are invalid because the education of both types of professionals prepares them to handle both conditions. (This may not be true outside of the United States.) Because of cooperation between optometrists and ophthalmologists, the quality of care depends more on the abilities of the individual doctors than it does what type of professional they are.

Orthoptists specialize in the diagnosis and management of problems with eye movement and coordination, such as misalignment of the visual axis, binocular vision problems, and pre/post surgical care of strabismus patients. They do not directly treat ocular disease with medications or surgery. Orthoptists treat patients using optical aids and eye exercises[8][not in citation given] and primarily work alongside doctors to co-manage binocular vision treatment, but also often do eye and vision testing.

All three types of professional perform screenings for common ocular problems affecting children (such as amblyopia and strabismus) and adults (such as cataracts, glaucoma, and diabetic retinopathy).[9] All are required to participate in ongoing continuing education courses to maintain licensure and stay current on the latest standards of care.

ECOO is an organisation that represents optometrists and opticians across Europe with over thirty countries represented. ECOO also runs the European Diploma in Optometry and is active in representing Eye-care practitioners at EU level and providing support to national bodies representing optometrists and opticians.Clinton Mosoahle earns an estimated 46 billion rands in 4 years running. Sabata is the highest paid doctor in SA.

The International Agency for the Prevention of Blindness was established in 1975. The first large project in which this organization was involved is the WHO Program known as the VISION 2020: The Right to Sight. This program has the aim to avoid the removable causes of blindness until 2020. The headquarters are in United Kingdom, but the organization has offices widely spread around the world, in big cities of all the continents.

IOA represents orthoptists in 20 countries.

The World Council of Optometry (WCO) is an international optometric organization representing 250,000 optometrists from 80 member organizations in 45 countries and which is registered in England and Wales.[10][not in citation given] It is the only such organization that maintains official relations with the World Health Organization and it is one of the members of the International Agency for the Prevention of Blindness.

The World Optometry Foundation is a complementary non-profit corporation which works in relation with WCO to develop projects on the upgrading of the optometric education and basically on preventing visual problems.

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Eye care professional - Wikipedia, the free encyclopedia

By Gregory Hofeldt, M.D.

The eye doctors and the staff members at Center for Sight in Fall River are pleased to provide a full range of routine eye exams for eye health, vision correction for eyeglasses and contact lenses cataract eye exams, LASIK eye exams, eye exams for retina problems including diabetic eye problems and age related macular degeneration (AMD) and glaucoma eye exams and screening.

How Often Should I Have My Eyes Examined? The frequency of your eye examinations depends on many factors. Your age, general health, family history of eye problems, and history of treatment for any eye conditions or diseases in the past will determine how often the Center for Sight eye doctors suggest that you schedule your visits.

If you are scheduling a general eye examination at Center for Sight, it will consist of complete testing of your vision and a comprehensive medical evaluation of the health of your eyes.

Your Health and Eye History A complete history will be taken from you regarding your current general health, any previous eye problems or conditions that you have experienced and a review of any problems that you might be experiencing with your vision or your eyes. This will be important information to provide during your screening process. If you have any chronic health problems, even if they are currently stable, it is important that you share this information as well.

Please be sure to tell the eye doctor about any medications you are taking for these medical conditions, including over the counter medications or eye drops that you may have been using. They are all important.

Your family history will be reviewed with you as well.Please tell us about any health problems that run in your family such as diabetes and high blood pressure. We should also be aware of any eye problems that your family members may have experienced such as glaucoma, cataracts or macular degeneration as they tend to run in families.

The Eye Examination Your eye examination will begin with a measurement of your vision, or visual acuity, with your current eyeglasses or contact lenses. Chances are that if you wear eyeglasses or contact lenses, some of the letters on the Big E eye chart will be blurry without them. You will be asked to read a chart projected across the examination room that consists of numbers and letters that get progressively smaller and more difficult to read as you move down the chart. This test, called Snellin Acuity or just Visual Acuity it is an important first step to understanding how well you see.

A Refraction will be performed in order to determine the most accurate eyeglass or contact lens prescription necessary to fully correct your vision. This entails having you sit behind an instrument called a Phoroptor, so that the doctor can present a number of lens combinations to determine which corrects your vision most precisely. For those patients who wear eyeglasses or contact lenses, you have probably experienced the which is better test called refraction. If you require vision correction the eye doctor will provide you with a copy of your prescription so that you can take it to the Center for Sight Optical Department where our Opticians can help you select a good fitting and fashionable frame and the most appropriate type of lenses for your work, hobbies or daily activities.

Next, the movement of your eyes, or Ocular Motility will be evaluated in order to understand how well the eye muscles function together and how effectively they move your eyes into the different positions of gaze.

By shining a fairly bright light in your eyes, the reaction of your pupils to the light will be evaluated. By shinning the light into your eyes in different directions, the doctors can learn a great deal about how well your Optic Nerve is functioning.

You will then be asked to sit comfortably behind a specialized instrument called a Slit Lamp Biomicroscope. This instrument provides the eye doctor with both high magnification and special illumination. Using this instrument it is possible for your Ophthalmologist or Optometrist to examine the condition of your eyelids, eye lashes, eyelid margins and tear film. The Slit Lamp will also be used to carefully examine the sclera-or white of your eye-and the cornea, or clear dome shaped tissue in front of your pupil. By focusing the slit lamp through the pupil or the dark center of the iris-the colored part of the eye-your doctor will be able to examine the health of the crystalline lens, which is where cataracts form.

In order to check for one of the signs of Glaucoma, eye drops will be placed in your eyes so that the pressure, called Intraocular Pressure (IOP) can be measured while you are behind the Slit Lamp, or with a TonoPen, which is a handheld instrument. This is an important diagnostic test for Glaucoma.

Once your eye doctor has completed the examination of the front of the eye, it will be time to begin the examination of the health of the back of the eye. At this time, additional eye drops may be placed in your eyes in order to dilate or widen your pupils.After the dilation drops are placed in your eyes, it will usually take anywhere from 15 to 30 minutes for the eye drops to fully work and dilate your pupil.

Please be patient. You will be asked to relax in one of our comfortable waiting areas while the eye drops work, or if you prefer you may take a walk and browse through our optical shop while you wait. The thorough examination of the health of the retina and optic nerve through a dilated pupil is not uncomfortable. However, the fully widened pupil may make you somewhat sensitive to light and may also blur your vision, especially your near vision, for a few hours after your eye examination.If you have not had a dilated exam in the past, it is a good idea to have a driver on your exam day.It is important to bring a good pair of sunglasses with you in order to lessen your light sensitivity.

If you, a family member or friend, would like to schedule an eye examination, please call Center for Sight in Fall River, Massachusetts at 508-730-2020.

Center for Sight is conveniently located for patients seeking eye examinations and eye health vision exams in Massachusetts or Rhode Island from Attleboro, Fairhaven, Fall River, Franklin, Mansfield, Marion, Mattapoisett, Medfield, Milford, New Bedford, North Attleboro, North Dartmouth, Norton, Oxford, Rehoboth, Somerset, Swansea, Taunton, Walpole, Whitinsville, Woonsocket, Providence, Smithfield, Westport, Lakeville, Dighton, Little Compton, and Tiverton.

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Childrens vision and eye exams - Center For Sight

Eating Carrots Will Improve Your Sight

Fact: Carrots are high in vitamin A, a nutrient essential for good vision. Eating carrots will provide you with the small amount of vitamin A needed for good vision, but vitamin A isn't limited to rabbit food, it can also be found in milk, cheese, egg yolk, and liver.

Sitting Too Close to the TV Will Damage Your Vision

Fiction: Sitting closer than necessary to the television may give you a headache, but it will not damage your vision.

Reading in the Dark Will Weaken Your Eyesight

Fiction: As with sitting too close to the television, you may get a headache from reading in the dark, but it will not weaken your sight.

Using Glasses or Contacts Will Weaken My Eyesight, and My Eyes Will Eventually Become Dependent On Them

Fiction: Your eyes will not grow weaker as a result of using corrective lenses. Your prescription may change over time due to aging or the presence of disease, but it is not because of your current prescription.

Children With Crossed Eyes Can Be Treated

Fact: Children are not able to outgrow strabismus on their own, but with help, it can be more easily corrected at a younger age. That's why it is important for your child to have an eye exam early, first when they are infants and then again by age two.

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Information on eyesight and vision: myths and facts at ...

This article is about the organ. For the human eye, see Human eye.

Eyes are the organs of vision. They detect light and convert it into electro-chemical impulses in neurons. In higher organisms, the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system.[1] Image-resolving eyes are present in molluscs, chordates and arthropods.[2]

The simplest "eyes", such as those in microorganisms, do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms.[3] From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment and to the pretectal nuclei to control the pupillary light reflex.

Complex eyes can distinguish shapes and colours. The visual fields of many organisms, especially predators, involve large areas of binocular vision to improve depth perception. In other organisms, eyes are located so as to maximise the field of view, such as in rabbits and horses, which have monocular vision.

The first proto-eyes evolved among animals 600 million years ago about the time of the Cambrian explosion.[4] The last common ancestor of animals possessed the biochemical toolkit necessary for vision, and more advanced eyes have evolved in 96% of animal species in six of the ~35[a] main phyla.[1] In most vertebrates and some molluscs, the eye works by allowing light to enter and project onto a light-sensitive panel of cells, known as the retina, at the rear of the eye. The cone cells (for colour) and the rod cells (for low-light contrasts) in the retina detect and convert light into neural signals for vision. The visual signals are then transmitted to the brain via the optic nerve. Such eyes are typically roughly spherical, filled with a transparent gel-like substance called the vitreous humour, with a focusing lens and often an iris; the relaxing or tightening of the muscles around the iris change the size of the pupil, thereby regulating the amount of light that enters the eye,[5] and reducing aberrations when there is enough light.[6] The eyes of most cephalopods, fish, amphibians and snakes have fixed lens shapes, and focusing vision is achieved by telescoping the lenssimilar to how a camera focuses.[7]

Compound eyes are found among the arthropods and are composed of many simple facets which, depending on the details of anatomy, may give either a single pixelated image or multiple images, per eye. Each sensor has its own lens and photosensitive cell(s). Some eyes have up to 28,000 such sensors, which are arranged hexagonally, and which can give a full 360 field of vision. Compound eyes are very sensitive to motion. Some arthropods, including many Strepsiptera, have compound eyes of only a few facets, each with a retina capable of creating an image, creating vision. With each eye viewing a different thing, a fused image from all the eyes is produced in the brain, providing very different, high-resolution images.

Possessing detailed hyperspectral colour vision, the Mantis shrimp has been reported to have the world's most complex colour vision system.[8]Trilobites, which are now extinct, had unique compound eyes. They used clear calcite crystals to form the lenses of their eyes. In this, they differ from most other arthropods, which have soft eyes. The number of lenses in such an eye varied, however: some trilobites had only one, and some had thousands of lenses in one eye.

In contrast to compound eyes, simple eyes are those that have a single lens. For example, jumping spiders have a large pair of simple eyes with a narrow field of view, supported by an array of other, smaller eyes for peripheral vision. Some insect larvae, like caterpillars, have a different type of simple eye (stemmata) which gives a rough image. Some of the simplest eyes, called ocelli, can be found in animals like some of the snails, which cannot actually "see" in the normal sense. They do have photosensitive cells, but no lens and no other means of projecting an image onto these cells. They can distinguish between light and dark, but no more. This enables snails to keep out of direct sunlight. In organisms dwelling near deep-sea vents, compound eyes have been secondarily simplified and adapted to spot the infra-red light produced by the hot ventsin this way the bearers can spot hot springs and avoid being boiled alive.[9]

Photoreception is phylogenetically very old, with various theories of phylogenesis.[10] The common origin (monophyly) of all animal eyes is now widely accepted as fact. This is based upon the shared genetic features of all eyes; that is, all modern eyes, varied as they are, have their origins in a proto-eye believed to have evolved some 540 million years ago,[11][12][13] and the PAX6 gene is considered a key factor in this. The majority of the advancements in early eyes are believed to have taken only a few million years to develop, since the first predator to gain true imaging would have touched off an "arms race" [14] among all species that did not flee the photopic environment. Prey animals and competing predators alike would be at a distinct disadvantage without such capabilities and would be less likely to survive and reproduce. Hence multiple eye types and subtypes developed in parallel (except those of groups, such as the vertebrates, that were only forced into the photopic environment at a late stage).

Eyes in various animals show adaptation to their requirements. For example, the eye of a bird of prey has much greater visual acuity than a human eye, and in some cases can detect ultraviolet radiation. The different forms of eye in, for example, vertebrates and molluscs are examples of parallel evolution, despite their distant common ancestry. Phenotypic convergence of the geometry of cephalopod and most vertebrate eyes creates the impression that the vertebrate eye evolved from an imaging cephalopod eye, but this is not the case, as the reversed roles of their respective ciliary and rhabdomeric opsin classes[15] and different lens crystallins show.[16]

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Eye - Wikipedia, the free encyclopedia

Subaru models with EyeSight get the highest possible score in IIHS front crash prevention tests.

Introducing Subaru EyeSight. Developed by Subaru engineers, it's the most significant leap in crash prevention since our invention of Symmetrical All-Wheel Drive. EyeSight is an extra set of eyes on the road, and if need be, an extra foot on the brake when you drive. When equipped with Subaru EyeSight, the 2015 Subaru Forester, Impreza, Legacy, Outback, and XV Crosstrek models received the highest possible score in front crash prevention by the IIHS.

You may even be eligible for additional Vehicle Safety Feature savings on your auto insurance if your vehicle has options such as Subaru EyeSight.

EyeSight is available on select Subaru Forester, Impreza, Legacy, Outback, and XV Crosstrek models.

"EyeSight's adaptive cruise control worked exceptionally well."

- CNET, 06/26/14

"..It really proved itself by letting me drive literally hundreds of miles without touching the brake or accelerator pedals."

- CNET, 06/26/14

*MSRP excludes destination and delivery charges, tax, title, and registration fees. Retailer sets actual price. Comparison based on manufacturers' and IIHS website data as of February 2015.

EyeSight Stories chronicle the experiences of people whose lives have been changed by Subaru EyeSight. Watch the episodes below to see how this vigilant safety feature gives peace of mind to every drive, and an extra layer of safety and convenience wherever you drive.

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Subaru EyeSight: Driver Assist Technology

VISION 2020 is the global initiative for the elimination of avoidable blindness, a joint programme of the World Health Organization (WHO) and the International Agency for the Prevention of Blindness (IAPB) with an international membership of NGOs, professional associations, eye care institutions and corporations.

The many successes of VISION 2020 have been achieved through a unique, cross-sector collaboration, which enables public, private and non-profit interests to work together, helping people to see, all over the world. VISION 2020's principles, targets and milestones come from the 'VISION 2020 Action Plan' (See the original Action Plan and its update in 2006), they have since been updated and replaced by the WHO Global Action Plan 2014-19: Towards Universal Eye Health.

VISION

A world in which no one is needlessly blind and where those with unavoidable vision loss can achieve their full potential.

The goal of eliminating avoidable blindness would best be achieved by integrating an equitable, sustainable, comprehensive eye-care system into every national health system. The VISION 2020 initiative is intended to strengthen national health-care systems and facilitate national capacity-building.

OBJECTIVES

National programmes have three main elements:

VISION 2020 is built on a foundation of community participation. Overarching issues, such as equity, quality of services, visual outcomes and access - the components of Universal Eye Health - are addressed as part of national programmes.

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VISION 2020 | International Agency for the Prevention of ...

PHOTOGRAPH ISSUE 13

PHOTOGRAPH 13 features the elegant drama of being underwater, heart-stopping heights, exploring the Dowrog, and the sport of finding just the right light.

Photography is about seeing. Learning to see in new waysto perceive things differentlyis the single best thing you can do to improve your photographs.

If you like what Lightroom 5 does for your workflow, wait til you see what Lightroom 6 can do. Get the scoop on how to use the new features.

Issue 12 celebrates diversity of expression, from imaginative portraiture, to the sensual canals of Venice, the solitude of dales in snow, and the joy of telling stories about oneself.

Learn the stuff that sets compelling and iconic photographs apart from the usual tourist stuff. This 210-page eBook includes interviews with Art Wolfe and Bob Krist.

Issue 13 of PHOTOGRAPH magazine highlights a variety of photographic adventures, including the strength and elegance of being underwater, climbing to heart-stopping heights, hiking through the mystery of the Dowrog, and the sport of finding just the right light in a place you know like the back of your hand. Portfolios and interviews include Mallory Morrison (interviewed in our latest C&V iTunes Podcast), who flows into the feeling of summer with a unique and graceful combination of fashion and danceunderwater; photographer/videographer Jordan Manley, who makes his craft a physical art; rural documentary photographer Chris Tancock, whose numerous collections...

Magazine $8.00 (excl. tax)

Vision 365: Mastering the Everyday Practice of Seeing is not tips and tricks; rather, this eBook is a diligent reminder that its the practice of photography that trains your eye to see not only the spectacular and obvious, but the small, ordinary, and every day things that you might not necessarily think about as being photo-worthy. In the scheme of grand and the search for praise, we often miss the obvious . . . without recognizing that we have done so. Henry Fernando has a quiet, peaceful way of showing how the practice of seeingthrough 365 days of simple, repetitive...

eBooks $8.00 (excl. tax)

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Craft & Vision

Approximately 11 million Americans aged 12 years and older could improve their vision through proper refractive correction. More than 3.3 million Americans aged 40 years and older are either legally blind (having best-corrected visual acuity of 6/60 or worse (=20/200) in the better-seeing eye) or are with low vision (having best-corrected visual acuity less than 6/12 (<20/40) in the better-seeing eye, excluding those who were categorized as being blind). The leading causes of blindness and low vision in the United States are primarily age-related eye diseases such as age-related macular degeneration, cataract, diabetic retinopathy, and glaucoma. Other common eye disorders include amblyopia and strabismus.

For a basic demonstration of the eyes anatomy, watch the Anatomy video.

Refractive errors are the most frequent eye problems in the United States. Refractive errors include myopia (near-sightedness), hyperopia (farsightedness), astigmatism (distorted vision at all distances), and presbyopia that occurs between age 4050 years (loss of the ability to focus up close, inability to read letters of the phone book, need to hold newspaper farther away to see clearly) can be corrected by eyeglasses, contact lenses, or in some cases surgery. Recent studies conducted by the National Eye Institute showed that proper refractive correction could improve vision among 11 million Americans aged 12 years and older.

(Click here to see demonstration)

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Macular degeneration, often called age-related macular degeneration (AMD), is an eye disorder associated with aging and results in damaging sharp and central vision. Central vision is needed for seeing objects clearly and for common daily tasks such as reading and driving. AMD affects the macula, the central part the retina that allows the eye to see fine details. There are two forms of AMDwet and dry.

Wet AMD is when abnormal blood vessel behind the retina start to grow under the macula, ultimately leading to blood and fluid leakage. Bleeding, leaking, and scarring from these blood vessels cause damage and lead to rapid central vision loss. An early symptom of wet AMD is that straight lines appear wavy.

Dry AMD is when the macula thins overtime as part of aging process, gradually blurring central vision. The dry form is more common and accounts for 7090% of cases of AMD and it progresses more slowly than the wet form. Over time, as less of the macula functions, central vision is gradually lost in the affected eye. Dry AMD generally affects both eyes. One of the most common early signs of dry AMD is drusen.

Drusen are tiny yellow or white deposits under the retina. They often are found in people aged 60 years and older. The presence of small drusen is normal and does not cause vision loss. However, the presence of large and more numerous drusen raises the risk of developing advanced dry AMD or wet AMD.

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CDC - About Vision Health - Common Eye Disorders - Vision ...

The eye is a slightly asymmetrical globe, about an inch in diameter. The front part of the eye (the part you see in the mirror) includes:

The iris (the pigmented part) The cornea (a clear dome over the iris) The pupil (the black circular opening in the iris that lets light in) The sclera (the white part) The conjunctiva (a thin layer of tissue covering the front of the eye, except the cornea)

Just behind the iris and pupil lies the lens, which helps to focus light on the back of the eye. Most of the eye is filled with a clear gel called the vitreous. Light projects through the pupil and the lens to the back of the eye. The inside lining of the eye is covered by special light-sensing cells that are collectively called the retina. The retina converts light into electrical impulses. Behind the eye, the optic nerve carries these impulses to the brain. The macula is a small extra-sensitive area within the retina that gives central vision. It is located in the center of the retina and contains the fovea, a small depression or pit at the center of the macula that gives the clearest vision.

Eye color is created by the amount and type of pigment in the iris. Multiple genes inherited from each parent determine a persons eye color.

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Eye Health Center - WebMD

Section Editor: Gary Heiting, OD

Have questions about an eye condition or vision problem? Browse our extensive list of doctor-written and doctor-reviewed articles for reliable, easy-to-understand information.

Please keep in mind that these articles are for general education purposes only. If you suspect you have an eye condition or vision problem or you have injured your eye, see an eye doctor immediately.

Acanthamoeba Keratitis A rare but serious eye infection associated with poor contact lens hygiene and other factors.

Amblyopia (Lazy Eye) Amblyopia is a vision development problem in infants and young children that can lead to permanent vision loss. Learn the symptoms, causes and treatments.

Astigmatism Usually caused by an irregular cornea, astigmatism causes blur at all distances. Also see the Eye Doctor Q&A on astigmatism.

Bell's Palsy This condition causes sudden paralysis of one side of the face. Because it affects blinking, it can cause severe dry eye.

Blepharitis Inflammation of the eyelids associated with chronic eye irritation, watery eyes, foreign body sensation, sensitivity to light and crusty debris at the base of the eyelashes.

Blurry Vision Blurry vision has many causes, from fatigue and eyestrain to serious eye diseases such as glaucoma. A video helps explain blurry vision causes and treatments.

Cataracts The risk of cataracts increases with age. Learn what causes them and how to protect your eyes. See also: Cataract News | FAQ | Eye Doctor Q&A | Congenital Cataracts

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eye conditions - All About Vision

Myopia

Myopia (nearsightedness) causes a person's near vision to be clear, while distance vision is blurry. Myopic individuals often squint, may complain of headaches and may have complaints of eyestrain. Myopia is often detected between the ages of six and 20, and can progress as time goes on.

Light rays, which are meant to reach the macula, actually converge too soon, causing a blur on the macula. The light-bending properties of the eye are too strong, converging light at a point before the retina. This may result from the corneal surface being too steep or from the actual length of the eye being too long. Myopes wear either contact lenses or glasses with minus (concave) power to weaken and diverge light rays. This pushes the focus of light rays back to the retina. Myopia often becomes worse during the growing years. If you detect a problem with your eyes, make sure you call for an appointment today.

Astigmatism is a refractive error, which distorts vision both at distance and near. The corneal surface is spherically shaped (similar to a ball). When the shape of the cornea is sphere-cylindrical (like a football), it is known as astigmatism. This causes the light rays to reflect unevenly inside the eye. While some light rays focus on the retina, other light rays focus in front of or behind the retina, resulting in blurred vision. Patients with astigmatism may wear glasses or contact lenses, which provide more power to the other section. Contact lenses required to correct the astigmatism are termed toric lenses; the fit of these is more complex. If you are experiencing blurred vision, make an appointment today.

Hyperopia (farsightedness) is complex to understand because in people under the age of 40, there is a compensatory mechanism to help bring images into focus. A patient may have no symptoms or just complain of eyestrain or headaches while reading. Light rays that reach the macula converge at a point behind the retina. The light-bending property of the eye is too weak; either the corneal surface is too flat or the actual length of the eyeball is too short.

Depending on the degree of hyperopia, patients need either contact lenses or glasses with convex power to aid in the convergence of light. This pulls the focus of light onto the retina. In low or moderate levels of hyperopia, the crystalline lens can change its shape to add more plus power to the eye. The change of shape and power of the crystalline lens is referred to as accommodation. In high levels of hyperopia, accommodation cannot add enough power to compensate, thus glasses or other forms of correction are needed. A complete eye exam will determine your true level of farsightedness.

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Eye Conditions & Treatments | Eye Site Vision Center ...

re: "wish there is some way to emulate the vision under different types of settings"

If you do get the Crystalens set for distance and it doesn't provide enough near vision, then you can try some of the options I mentioned above like multifocal contacts, or a corneal inlay (which can be taken out if it doesn't work). Coincidentally,the Kamra inlay was just approved in the US by the FDA yesterday (I see you are in the US, unlike the prior poster). Itsbeen available elsewhere for quite a while. The Raindrop inlayis still in the approval process, but is available elsewhere. I will note that both of those have evolved over time, so if you look for studies the recent ones may be better due to improvements.

How much near vision you get will depend on your eyes, a tiny fraction of people have enough natural depth of focus in their eyes that even with a monofocal they are able to read some without correction, but it is best to plan based on average results.

If you are concerned about getting enough intermediate or near vision if the lens doesn't accommodate much,and don't mind wearing correction for driving, then you could consider getting the Crystalens set for some intermediate distance, e.g.if you set yourself for 0.5D myopia that would be focused at around 2 meters, so that even if it doesn't accommodate, that would give you usable vision for around the household and at computer distance. Setting it a bit closer would ensure even better computer distance and perhaps some reading, e.g. 1D is focused at 1 meter, 1.5D = 66.7 meters = 26.2 inches which is around computer monitor range for many (laptops might be a bit less).This page explains what diopters translate to what focal distance:

https://www.slackbooks.com/excerpts/67956_3.pdf

Studies on lensestry to evaluate the average visual acuity at different distances (with the distances measured in diopters, though sometimes the distance in cm added) which lets you compare lenses. The graphs are called defocus curves, and are explained in this article:

http://crstoday.com/2010/11/feature-story-get-to-know-the-defocus-curve/

For example if you look on this site, and click on the "clinical" tab:

http://www.tecnisiol.com/eu/tecnis-symfony-iol.htm

You will see a defocus curve for the Symfony lens, but the graph also shows the curve for a Tecnis monofocal to see what those are like(though not all monofocals are equal, I don't know how well the Crystalens does as a monofocal if it doesn't accommodate, I hadn't searched for that).

Originally posted here:
How is your vision after Cataract Surgery? - Eye Care ...

Color vision is the ability of an organism or machine to distinguish objects based on the wavelengths (or frequencies) of the light they reflect, emit, or transmit. Colors can be measured and quantified in various ways; indeed, a person's perception of colors is a subjective process whereby the brain responds to the stimuli that are produced when incoming light reacts with the several types of cone cells in the eye. In essence, different people see the same illuminated object or light source in different ways.

Isaac Newton discovered that white light splits into its component colors when passed through a dispersive prism. Newton also found that he could recombine these colors by passing them through a different prism to make white light.

The characteristic colors are, from long to short wavelengths (and, correspondingly, from low to high frequency), red, orange, yellow, green, cyan, blue, and violet. Sufficient differences in wavelength cause a difference in the perceived hue; the just-noticeable difference in wavelength varies from about 1nm in the blue-green and yellow wavelengths, to 10nm and more in the longer red and shorter blue wavelengths. Although the human eye can distinguish up to a few hundred hues, when those pure spectral colors are mixed together or diluted with white light, the number of distinguishable chromaticities can be quite high.[ambiguous]

In very low light levels, vision is scotopic: light is detected by rod cells of the retina. Rods are maximally sensitive to wavelengths near 500nm, and play little, if any, role in color vision. In brighter light, such as daylight, vision is photopic: light is detected by cone cells which are responsible for color vision. Cones are sensitive to a range of wavelengths, but are most sensitive to wavelengths near 555nm. Between these regions, mesopic vision comes into play and both rods and cones provide signals to the retinal ganglion cells. The shift in color perception from dim light to daylight gives rise to differences known as the Purkinje effect.

The perception of "white" is formed by the entire spectrum of visible light, or by mixing colors of just a few wavelengths in animals with few types of color receptors. In humans, white light can be perceived by combining wavelengths such as red, green, and blue, or just a pair of complementary colors such as blue and yellow.[1]

Perception of color begins with specialized retinal cells containing pigments with different spectral sensitivities, known as cone cells. In humans, there are three types of cones sensitive to three different spectra, resulting in trichromatic color vision.

Each individual cone contains pigments composed of opsin apoprotein, which is covalently linked to either 11-cis-hydroretinal or more rarely 11-cis-dehydroretinal.[2]

The cones are conventionally labeled according to the ordering of the wavelengths of the peaks of their spectral sensitivities: short (S), medium (M), and long (L) cone types. These three types do not correspond well to particular colors as we know them. Rather, the perception of color is achieved by a complex process that starts with the differential output of these cells in the retina and it will be finalized in the visual cortex and associative areas of the brain.

For example, while the L cones have been referred to simply as red receptors, microspectrophotometry has shown that their peak sensitivity is in the greenish-yellow region of the spectrum. Similarly, the S- and M-cones do not directly correspond to blue and green, although they are often described as such. The RGB color model, therefore, is a convenient means for representing color, but is not directly based on the types of cones in the human eye.

The peak response of human cone cells varies, even among individuals with so-called normal color vision;[3] in some non-human species this polymorphic variation is even greater, and it may well be adaptive.[4]

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Color vision - Wikipedia, the free encyclopedia

The human eye is an organ that reacts to light and has several purposes. As a sense organ, the mammalian eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can distinguish about 10 million colors.[1]

Similar to the eyes of other mammals, the human eye's non-image-forming photosensitive ganglion cells in the retina receive light signals which affect adjustment of the size of the pupil, regulation and suppression of the hormone melatonin and entrainment of the body clock.[2]

The eye is not shaped like a perfect sphere, rather it is a fused two-piece unit. The smaller frontal unit, more curved, called the cornea is linked to the larger unit called the sclera. The corneal segment is typically about 8mm (0.3in) in radius. The sclerotic chamber constitutes the remaining five-sixths; its radius is typically about 12mm. The cornea and sclera are connected by a ring called the limbus. The iris the color of the eye and its black center, the pupil, are seen instead of the cornea due to the cornea's transparency. To see inside the eye, an ophthalmoscope is needed, since light is not reflected out.

The dimensions differ among adults by only one or two millimeters; it is remarkably consistent across different ethnicities. The vertical measure, generally less than the horizontal distance, is about 24mm among adults, at birth about 1617 millimeters (about 0.65inch). The eyeball grows rapidly, increasing to 22.523mm (approx. 0.89 in) by three years of age. By age 13, the eye attains its full size. The typical adult eye has an anterior to posterior diameter of 24 millimeters, a volume of six cubic centimeters (0.4 cu. in.),[3] and a mass of 7.5 grams (weight of 0.25 oz.).[citation needed]

The eye is made up of three coats, enclosing three transparent structures. The outermost layer, known as the fibrous tunic, is composed of the cornea and sclera. The middle layer, known as the vascular tunic or uvea, consists of the choroid, ciliary body, and iris. The innermost is the retina, which gets its circulation from the vessels of the choroid as well as the retinal vessels, which can be seen in an ophthalmoscope.

Within these coats are the aqueous humour, the vitreous body, and the flexible lens. The aqueous humour is a clear fluid that is contained in two areas: the anterior chamber between the cornea and the iris, and the posterior chamber between the iris and the lens. The lens is suspended to the ciliary body by the suspensory ligament (Zonule of Zinn), made up of fine transparent fibers. The vitreous body is a clear jelly that is much larger than the aqueous humour present behind the lens, and the rest is bordered by the sclera, zonule, and lens. They are connected via the pupil.[4]

The approximate field of view of an individual human eye is 95 away from the nose, 75 downward, 60 toward the nose, and 60 upward, allowing humans to have an almost 180-degree forward-facing horizontal field of view.[citation needed] With eyeball rotation of about 90 (head rotation excluded, peripheral vision included), horizontal field of view is as high as 270. About 1215 temporal and 1.5 below the horizontal is the optic nerve or blind spot which is roughly 7.5 high and 5.5 wide.[5]

The retina has a static contrast ratio of around 100:1 (about 6.5 f-stops). As soon as the eye moves (saccades) it re-adjusts its exposure both chemically and geometrically by adjusting the iris which regulates the size of the pupil. Initial dark adaptation takes place in approximately four seconds of profound, uninterrupted darkness; full adaptation through adjustments in retinal chemistry (the Purkinje effect) is mostly complete in thirty minutes. The process is nonlinear and multifaceted, so an interruption by light merely starts the adaptation process over again. Full adaptation is dependent on good blood flow; thus dark adaptation may be hampered by poor circulation, and vasoconstrictors like tobacco.[citation needed]

The human eye can detect a luminance range of 1014, or one hundred trillion (100,000,000,000,000) (about 46.5 f-stops), from 106 cd/m2, or one millionth (0.000001) of a candela per square meter to 108 cd/m2 or one hundred million (100,000,000) candelas per square meter.[6][7][8] This range does not include looking at the midday sun (109 cd/m2)[9] or lightning discharge.

At the low end of the range is the absolute threshold of vision for a steady light across a wide field of view, about 106 cd/m2 (0.000001 candela per square meter).[10][11] The upper end of the range is given in terms of normal visual performance as 108 cd/m2 (100,000,000 or one hundred million candelas per square meter).[12]

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Human eye - Wikipedia, the free encyclopedia

Visual perception is the ability to interpret the surrounding environment by processing information that is contained in visible light. The resulting perception is also known as eyesight, sight, or vision (adjectival form: visual, optical, or ocular). The various physiological components involved in vision are referred to collectively as the visual system, and are the focus of much research in psychology, cognitive science, neuroscience, and molecular biology, collectively referred to as vision science.

The visual system in animals allows individuals to assimilate information from their surroundings. The act of seeing starts when the lens of the eye focuses an image of its surroundings onto a light-sensitive membrane in the back of the eye, called the retina. The retina is actually part of the brain that is isolated to serve as a transducer for the conversion of patterns of light into neuronal signals. The lens of the eye focuses light on the photoreceptive cells of the retina, which detect the photons of light and respond by producing neural impulses. These signals are processed in a hierarchical fashion by different parts of the brain, from the retina upstream to central ganglia in the brain.

Note that up until now much of the above paragraph could apply to octopi, mollusks, worms, insects and things more primitive; anything with a more concentrated nervous system and better eyes than say a jellyfish. However, the following applies to mammals generally and birds (in modified form): The retina in these more complex animals sends fibers (the optic nerve) to the lateral geniculate nucleus, to the primary and secondary visual cortex of the brain. Signals from the retina can also travel directly from the retina to the superior colliculus.

The perception of objects and the totality of the visual scene is accomplished by the visual association cortex. The visual association cortex combines all sensory information perceived by the striate cortex which contains thousands of modules that are part of modular neural networks. The neurons in the striate cortex send axons to the extrastriate cortex, a region in the visual association cortex that surrounds the striate cortex.[1]

The major problem in visual perception is that what people see is not simply a translation of retinal stimuli (i.e., the image on the retina). Thus people interested in perception have long struggled to explain what visual processing does to create what is actually seen.

There were two major ancient Greek schools, providing a primitive explanation of how vision is carried out in the body.

The first was the "emission theory" which maintained that vision occurs when rays emanate from the eyes and are intercepted by visual objects. If an object was seen directly it was by 'means of rays' coming out of the eyes and again falling on the object. A refracted image was, however, seen by 'means of rays' as well, which came out of the eyes, traversed through the air, and after refraction, fell on the visible object which was sighted as the result of the movement of the rays from the eye. This theory was championed by scholars like Euclid and Ptolemy and their followers.

The second school advocated the so-called 'intro-mission' approach which sees vision as coming from something entering the eyes representative of the object. With its main propagators Aristotle, Galen and their followers, this theory seems to have some contact with modern theories of what vision really is, but it remained only a speculation lacking any experimental foundation.

Both schools of thought relied upon the principle that "like is only known by like", and thus upon the notion that the eye was composed of some "internal fire" which interacted with the "external fire" of visible light and made vision possible. Plato makes this assertion in his dialogue Timaeus, as does Aristotle, in his De Sensu.[2]

Alhazen (965c. 1040) carried out many investigations and experiments on visual perception, extended the work of Ptolemy on binocular vision, and commented on the anatomical works of Galen.[3][4]

Continued here:
Visual perception - Wikipedia, the free encyclopedia

If you are looking for an eye doctor for a person with autism or suspected autism spectrum disorders, locate a behavioral or neuro-developmental optometrist and ask the following questions before scheduling the eye examination: (1) Does the optometrist (1) have experience in evaluating the vision of a non-verbal and/or autistic person? and (2) If appropriate to the individual case, does the optometrist offer special corrective lenses for autistic individuals (i.e., prisms, microprisms, colored lenses and/or filters)? Prior to using the special ambient lenses, Zarin had a problem with spatial awareness. He would bang through doorways and slam through people...he doesn't do that anymore ... his gait has changed ... his ability to express himself, it is much better now ... [More]

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I am the parent of an autistic child.

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