StemCell Therapy

1. I. Cataract

Causes of Cataract

Global / National distribution & population characteristics of Cataract

Diagnosis of cataract. Distinction between immature, mature and hypermature.

Appropriate referral of cataract patient

Outline of surgical management

Visual rehabilitation of Aphakia

Outline of cataract management in young age

Ectopia Lentis (Subluxation & Dislocation)

Lenticonus

Derived from surface Ectoderm overlying the optic vesicle.

Ectoderm invaginates and break from surface as two layer structure

Basement membrane of epithelium, which is now on the outer side, forms the lens capsule.

Posterior epithelium cells expand to form the embryonic nucleus.

Anterior epithelium continues to regenerate and develop lens fibers throughout life. These fibers continue to get deposited inwards making earliest fibers the deepest.

A globular structure lies behind the iris and in a concavity in the anterior face of vitreous called the Patellar Fossa.

Suspended from the ciliary processes by Zonules

In young patients (< 35 years) lens is adherent to vitreous by Ligament of Weigert.

Layers(from without inwards):

Adult

Adolescent

Infantile

Fetal (contains anterior & posterior Y-sutures)

Embryonic

Epitheliumdivides most actively in the periphery and differentiates in the lens fibers.

Functions:

Metabolism is both aerobic and anaerobic.

Cations and fluid move actively across anterior capsule but passively across posterior capsule (Pump-Leak Mechanism).

Metabolic homeostasis is essential for maintenance of lens transparency.

Glutathione, glutathione reductase and super-oxide dismutase are actively involved in preventing damage from free O2 radical injury.

+ 18 Dioptre of refraction is contributed by the lens. And in accommodation this power increases.

Typical structure of lens in the form of anterior cortex, nucleus and posterior cortex is optically important as each of these three portions act as a separate lens (lenticules) because the refractive index of nucleus is more than that of cortex. This results in an increase in the total power of the lens, decrease in optical aberration and greater effectiveness of the accommodation.

Accommodation: Contraction of ciliary muscles results in laxity of zonules, which leads to increase convexity of lens due to its inherent elasticity.

Iris not only controls the amount of light that enters the eye by varying the size of pupil (aperture) but also covers the periphery of the lens thereby cutting the optical (spherical) aberrations from it.

Anyopacity of the lens or loss of transparency of the lens that causesdiminution or impairment of vision is called Cataract.

Althoughany lens opacity whether or not it leads to decrease in vision is technicallycataract, yet an opacity in the periphery of the lens, which is stationary andnot hampering vision should be diagnosed just Lens Opacity in order toavoid causing unnecessary anxiety to the patient.

Etiological

Morphological

Stage of Maturity

Chronological

Penetrating

Concussion (Rosette Cataract)

Infrared irradiation (Glass Blowers Cataract)

Electrocution

Ionizing Radiation

Diabetes (Snow Storm Cataract)

Hypoglycaemia

Galactosemia (Oil Drop Cataract)

Galactokinase Deficiency

Mannosidosis

Fabrys Disease

Lowes Syndrome

Wilsons Disease (Sunflower Cataract)

Hypocalcaemia

Excerpt from:
Lens & Cataract - Dr. Sanjay Dhawan

This entry was posted on September 20, 2018 at 6:41 pm and is filed under Opthalmology. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed. |