Cataract
- ICSE Class 10, Unit 3 Human Anatomy and Physiology
A cataract is an eye defect in which the eye lens becomes cloudy, or opaque, so that vision grows blurred.
The eye lens is normally clear, like glass. Light passes through it to the retina. In a cataract, the lens slowly turns milky. Less light gets through, and what does get through is scattered. The world looks hazy, as if seen through a fogged window.
It is most common in old age. Glasses cannot clear a cloudy lens. The usual cure is an operation that removes the cloudy lens and puts in a clear artificial one.
A small example
A grandfather finds that faces look faded and bright lights seem to glare. An eye doctor looks into his eye and sees a whitish patch behind the pupil. That patch is the clouded lens.
Where marks go
The 2025 ICSE Biology paper told the story of a 76-year-old with a cataract, for 2 marks. It asked which part is affected and why vision blurs. The answers are the lens, and the lens becomes opaque.
CISCE's report on the 2025 Biology paper names the errors. Some answers named the cornea, retina or iris. Some said the cornea, pupil or iris becomes opaque. Some were vague, such as "the eye is weak". The report looks for the lens by name, and for the lens becoming opaque or losing its transparency. See how to write answers that earn full marks.
Sources
Facts last checked against these sources on 30 September 2026.
About the author
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An IIT alumna (M.Sc., M.Phil.) with over 25 years in teaching, child psychology and learning assessment. As Academic Lead at EduBrahma, she leads the method TRUtesting uses to find where and why a child loses marks.
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