Cataract: Overview and Risk Factors
Cataract is an opacification of the crystalline lens of the eye. The condition is responsible for approximately half of all cases of severe visual loss in the world, affecting an estimated 15 million people. Opacities can be either diffuse or localized, and cataracts are usually classified according to the region of the lens affected: cortical, nuclear, posterior subcapsular, or mixed. Loss of transparency occurs when lens proteins become oxidized.
Symptoms are progressive, not painful, and usually bilateral. Specific symptoms may include:
- Blurred or “double” vision.
- Excessive glare during night driving and in bright sunlight.
- Halo effect around lights.
- Deterioration of distance vision much more than near vision.
Compared with whites, African Americans have an elevated level of legal blindness due to cataracts. There is also a slightly higher prevalence of cataracts in women and in persons with lower education.
- Family history of cataract.
- Diabetes mellitus.
- Corticosteroids. Systemic, topical, or inhaled steroids increase risk of posterior subcapsular cataracts.
- Smoking is a dose–related risk factor. Overall, it roughly doubles risk. Quitting may partially reverse the disease in the nuclear and posterior subcapsular forms.
- Alcohol use. See Nutritional Considerations.
- Extensive sunlight exposure; ie, photo–oxidation secondary to UV–B. Risk is dose–related.1
- Ocular radiation exposure.
- Ocular trauma.
- Abnormal serum lipids (chylomicrons, triglycerides, VLDL, low HDL).
- Excess body weight.2,3 Compared to participants with BMI less than 23 kg/m2, those with BMI greater than or equal to 30 kg/m2 had a 36% higher risk of any type of cataract.3
- Lead exposure.
- High dairy consumption in certain individuals4,5 or deficient galactokinase activity.5–8