By Gisela Steyn - B.Optom UJ(SA) CAS(SA)
A cataract is a clouding / opacification of the natural intraocular crystalline lens that focuses the light entering the eye onto the retina (the back of the eye). This cloudiness can cause a decrease in vision and may lead to eventual blindness if left untreated. Cataracts often develop slowly and painlessly, so vision and lifestyle can be affected without a person realizing it.
Cataracts are the number one cause of preventable blindness worldwide.
1. Nuclear sclerosis is the yellowing and hardening of the central portion of the crystalline lens and it occurs slowly over years. As the core of the lens hardens, it often causes the lens to increase the refractive power and causes nearsightedness. This type of cataract can also affect contrast and colours.
2. Cortical cataracts occur when the portion of lens fibers surrounding the nucleus become opacified. The impact on vision is related to how close the opacities are to the center of the visual axis and their impact can vary greatly. Progression is variable with some progressing over years and others in months. The most common symptom from cortical cataracts is glare, especially from headlights while night driving.
3. Posterior subcapsular cataracts (PSC) are opacities located in the most posterior cortical layer, directly under the lens capsule. Progression is variable but tends to occur more rapidly than in nuclear sclerosis. Symptoms are glare, difficulty seeing in bright light, and near vision is often more affected than distance.
4. Anterior subcapsular cataracts can develop idiopathically, may be secondary to trauma, or may be iatrogenic
5. Diabetic cataract has a snowflake appearance, these cataracts progress rapidly and the entire lens becomes intumescent and white.
6. A traumatic cataract can occur following both blunt and penetrating eye injuries as well as after electrocution, chemical burns, and exposure to radiation
7. Congenital cataracts may occur in one or both eyes and can be associated to systemic diseases.
8. Polychromatic / "Christmas Tree" cataract, these consist of highly reflective, iridescent corneal crystals of various colors.
Is there a treatment?
There is no medical treatment to prevent the development or progression of cataracts. Modern cataract surgery, which is the removal of the cloudy lens and implantation of a clear intraocular lens (IOL), is the only definitive treatment for cataracts.