A 68-year-old reports gradual, painless loss of vision in both eyes over two years, with glare in sunlight and faded colours. The pupils appear whitish. The eyes are not red and not painful. What is the most likely diagnosis? A. Chronic open-angle glaucoma B. Cataract C. Acute angle-closure glaucoma D. Diabetic retinopathy ANSWER: B — cataract. Why: gradual, painless, bilateral loss with GLARE and faded colours, plus whitish pupils, is the classic description of lens opacification. A: glaucoma takes the PERIPHERAL field silently; it does not produce a white pupil or glare in this way. C: acute angle closure is PAINFUL with a red eye — an emergency. MANAGEMENT POINT: surgery restores sight. The reason patients present late is usually access — cost, distance, fear, or believing blindness is a normal part of ageing.

Why is chronic open-angle glaucoma often advanced by the time a patient presents? ANSWER: because it destroys the PERIPHERAL visual field first, while central vision is preserved. 1. Central acuity is used for reading and recognising faces. 2. It stays sharp until late, so the patient has no complaint. 3. The field narrows silently over years. 4. By the time it is noticed, substantial optic nerve loss has occurred. AND THE LOSS IS IRREVERSIBLE: treatment preserves the remaining field but cannot restore what is gone. CONCLUSION: this is why case-finding in asymptomatic people — optic disc, visual fields and pressure, especially with a family history — is the only approach that works.

A 3-year-old is brought with a white reflex in the left pupil. The mother says the eye "looks different in photographs". What is the immediate concern? ANSWER: RETINOBLASTOMA until proven otherwise — a life-threatening malignancy of childhood. Leukocoria (a white pupil) in a child requires URGENT specialist referral. The differential also includes congenital cataract, which itself needs early surgery because of amblyopia. WHAT NOT TO DO: do not reassure, and do not arrange routine follow-up. In an adult a white pupil suggests cataract; in a child that assumption can cost the child's life.

Why must diabetic retinopathy be screened for rather than diagnosed when the patient complains of blurred vision? ANSWER: because sight-threatening retinopathy is frequently ASYMPTOMATIC. A patient may have good visual acuity while already having disease that requires treatment now. By the time vision blurs, the damage is advanced and treatment is markedly less effective. DRIVERS OF PROGRESSION: duration of diabetes above all, then glycaemic control and blood pressure. Pregnancy accelerates it. LEARNING POINT: the retinal examination is part of diabetes care, not a response to a symptom.

A 4-year-old has an intermittent convergent squint. The parents have been told he will grow out of it. Is that correct, and why does it matter? ANSWER: No. A squint in a child requires referral. WHY: the visual system must LEARN to see during a limited developmental window. If one eye's image is blurred or deviated, the brain suppresses it and that eye's vision fails to develop — AMBLYOPIA. Corrected EARLY → the eye develops normal vision. Corrected LATE → vision is permanently lost, even though the eye is structurally normal. The same reasoning applies to significant refractive error and to congenital cataract: the deadline is developmental, not surgical.

Distinguish "treatable" from "preventable" blindness and explain why the distinction matters for programme design. ANSWER: TREATABLE Sight can be RESTORED after loss. Cataract, uncorrected refractive error. Needs SERVICES, affordability and outreach. PREVENTABLE Loss can be STOPPED but not reversed. Glaucoma, diabetic retinopathy. Needs SCREENING, case-finding and follow-up of people who currently feel well. WHY IT MATTERS: the two need opposite programmes. Building surgical capacity does nothing for glaucoma, because those patients are not coming — they have no symptoms. Screening does nothing for the man already blind from cataract, who needs an operation he cannot reach.