Life Sciences Term 2

The nature and treatment of visual defects

Astigmatism
This is an optical defect that results in blurred vision. It is caused by an irregular curvature of the cornea or the lens so the eye has different focal points that occur in different planes. Glasses and hard contact lenses correct the irregular focal points.

Cataracts
This is the clouding of the lens when the lens cortex liquefies to form a milky white fluid. Cataracts progress over time and may result from long-term exposure to ultra-violet light, radiation, diabetes, hypertension, old age and physical trauma. Genetically, people may have a predisposition to cataracts. Cataracts must be removed surgically. Extra-capsular surgery (ECCE) can be used to remove the lens, leaving the lens capsule intact. Intra-capsular surgery (ICCE) is used when both the lens and capsule are removed. The lens is replaced with a plastic lens in both cases.