Ophthalmology and ENT — Avoidable Blindness, NMC MBBS licence examination syllabus (Nepal Medical Council).
Most blindness in the world is either treatable or preventable. That single fact organises the whole subject.
A man in his seventies is led into the clinic by his grandson. He has not been able to see well for three years, and now cannot see at all. He has dense cataracts in both eyes.
An operation would restore his sight. It has been available the whole time. He did not come because it costs money he does not have, the hospital is a day's travel away, someone would have to leave work to bring him, and he had been told that going blind is simply what happens when you get old.
Nothing about that story is a failure of ophthalmology — the operation works, and works superbly. It is a failure of access. This is why blindness is a public health subject and not only a surgical one, and why the exam expects you to think about both.Treatable means sight can be restored after it has been lost. Cataract and uncorrected refractive error are the two great examples: an operation, or a pair of glasses, and the person sees again. The bottleneck is service delivery and access, not knowledge.
Preventable means the loss can be stopped from happening, but not reversed once it has. Glaucoma and diabetic retinopathy are the important ones. Here the bottleneck is finding people before they have symptoms, because by the time they notice, the damage is permanent.
Those two categories need opposite programmes. Treatable blindness needs surgical capacity, affordable services and outreach to bring people in. Preventable blindness needs screening, case-finding and reliable follow-up of people who currently feel perfectly well.
The lens becomes progressively opaque, so vision dims gradually and painlessly. Patients describe glare in bright sunlight, colours looking faded, and needing more light to read. When a cataract is dense, the pupil may look white rather than black.
Surgery removes the opaque lens and replaces it with an artificial one. It is among the most effective operations in all of medicine — brief, and frequently restoring a person from near-blindness to independence.
So why does cataract remain a leading cause of blindness? Because the barriers are not medical. Cost. Distance. Needing someone to accompany you and losing their wages too. Fear of an operation on the eye. And, commonly, simply not knowing that the condition is treatable — an assumption that blindness is a normal part of ageing.
Chronic open-angle glaucoma damages the optic nerve slowly, and it takes the peripheral field first. Central vision — the part used for reading and for recognising faces — stays sharp until late.
Why does that matter so much? Because it is exactly the pattern that produces no symptoms. The patient reads the newspaper without difficulty and has no reason to attend. Meanwhile the field is narrowing year by year, and by the time they notice, a large amount of nerve has been lost.
The damage is irreversible. Treatment lowers the pressure to preserve the field that remains; it cannot restore what has gone. This is the entire argument for case-finding — examining the optic disc, testing fields, and measuring pressure in people who feel well, particularly those with a family history.Do not confuse this with acute angle-closure glaucoma, which is a completely different clinical event — sudden, painful, with a red eye, haloes, nausea and rapidly falling vision, and an emergency requiring immediate treatment. That is covered in the eye and ENT emergencies chapter.
A note on pressure: no threshold value is given here deliberately. A pressure within the normal range does not exclude glaucoma, and a raised pressure does not by itself establish it. The diagnosis rests on the optic disc and the visual field together with the pressure, which is why a single number is a poor test.
Diabetes damages retinal blood vessels, and the crucial clinical fact is that sight-threatening retinopathy can be entirely asymptomatic. A patient with good vision today may already have disease that needs treatment now.
That is the whole justification for retinal screening. Waiting for a patient to complain of blurred vision means waiting until treatment is far less effective.
What drives progression: the duration of diabetes above all, then glycaemic control and blood pressure. Pregnancy accelerates it, which is why women with diabetes need review in pregnancy.
Treatment — laser and intravitreal injections — works considerably better before symptoms appear, and good control of glucose and blood pressure slows progression. Diabetes management itself is covered in the diabetes chapter; the point here is that the eye examination is not optional and is not something to defer until the patient notices a problem.
Uncorrected refractive error is a leading cause of visual impairment worldwide, and the correction is a pair of spectacles. It is probably the cheapest meaningful intervention in medicine, and enormous numbers of people — including schoolchildren whose education suffers for it — still go without.
Amblyopia is the reason children are different. A child's visual system has to learn to see, and that learning happens in a limited developmental window. If one eye is blurred — by a squint, by a significant refractive error, or by a congenital cataract — the brain suppresses the image from it, and that eye's vision fails to develop.
Corrected early, the eye develops normally. Corrected too late, the vision is permanently lost even though the eye itself is structurally normal. This is why a squint in a child is never something to watch and wait on, and never something a child "grows out of". It is a referral.Vitamin A deficiency remains an important cause of childhood blindness in many settings. The earliest symptom is night blindness — difficulty seeing in dim light — and progression damages the cornea and can blind permanently. It is entirely preventable, and is covered from the programme side in the community nutrition chapter.
The examinable thread through all of this is not surgical technique. It is the reasoning:
Acuity criteria for blindness, pressure thresholds, screening intervals and drug doses are deliberately not quoted here: definitions differ between WHO and national schedules, and intervals are set by programme policy. Take them from your current national guideline.
Create a free account to tick topics off, take notes as you read, watch the video lessons and get a day-by-day study plan built around your exam date.
Loading…