Ophthalmology and ENT — Ocular Infection and the External Eye, NMC MBBS licence examination syllabus (Nepal Medical Council).
One infection blinds people forty years after they caught it. Most of the rest are nuisances — but you have to tell them apart.
An elderly woman comes to a rural clinic complaining that her eyes hurt constantly and that her sight is failing. Her upper eyelids are scarred, and the lashes turn inward so that they scrape the front of her eye with every blink. The corneas are cloudy.
She caught the infection that did this when she was a small child. Nothing that is done today can restore what has been lost — but surgery can stop the lashes and save what remains, and the same infection is circulating right now among the children in her village.
That gap — decades between the infection and the blindness — is the single most important idea in this chapter, because it explains why trachoma control looks nothing like treating an infection in a clinic.The organism is Chlamydia trachomatis. It spreads from eye to eye by hands, shared cloths and towels, and by flies that feed on ocular discharge. It thrives where water is scarce, faces go unwashed, and sanitation is poor.
Follow the sequence, because each step explains the next:
Why does this natural history matter for the exam? Because it tells you where each intervention acts. Antibiotics act at step 1. Surgery acts at step 4 to prevent step 5. Nothing acts on the scarring in between — which is why prevention in childhood and surgery in adulthood are needed simultaneously, in the same community, on different people.
S — SurgeryFor people who already have trichiasis. Urgent: the cornea is being abraded today. This saves the sight of the current generation of adults.
A — AntibioticsMass treatment of the whole community, not just those with visible disease — the aim is to reduce the reservoir of infection, since untreated neighbours simply reinfect treated children.
F — Facial cleanlinessA clean child's face interrupts transmission by hands, cloths and flies. Simple, and dependent on water being available.
E — Environmental improvementWater supply and sanitation, which reduce fly breeding and make face-washing possible at all.
Surgery and antibiotics treat the people who are damaged or infected today. They do nothing about the conditions that let the organism circulate, so without F and E the community is reinfected and the programme runs forever.
This is exactly the logic met in the deworming section: the drug treats the child, not the soil. Trachoma is fundamentally a disease of poverty and water scarcity — it vanished from much of Europe with sanitation and running water, before any eye programme existed. Remember that if asked why control requires more than medicine.The specific antibiotic regimen, the coverage threshold that triggers mass treatment in a district, and the criteria for declaring elimination are set by national programme policy against WHO criteria. They are not quoted here — take them from your current national guideline.
A discharging eye in the first month of life is not ordinary conjunctivitis, and it is one of the few genuinely sight-threatening presentations in general practice.
Gonococcal infection is the dangerous one: it can be aggressive enough to perforate the cornea within days. Chlamydial infection is generally slower and less destructive but still needs proper treatment. Both are acquired from the birth canal.
Why does the cause matter beyond the baby? Because the organism came from the mother. A baby with ophthalmia neonatorum means the mother has an untreated sexually transmitted infection — so she and her partner need testing and treatment. Treating only the baby's eye leaves the infection and lets it recur in the next pregnancy.
Two lumps on the eyelid are extremely common and are distinguished by two questions: is it painful, and how quickly did it appear?
A stye is an acutely painful lump at the lid margin, from an infected lash follicle or associated gland. It behaves like a small abscess and usually settles with warm compresses.
A chalazion is a painless, chronic, firm lump within the lid itself, from a blocked meibomian gland. It is a sterile granuloma rather than an infection, which is why antibiotics do little and why it may need a minor procedure if it persists.
The lump that must not be missed is the one that keeps coming back in the same place, ulcerates, bleeds, or destroys the lashes where it sits. Recurrent "chalazion" at one site is a classic presentation of eyelid malignancy, and it needs specialist assessment rather than another incision.Blepharitis is the common chronic cause of sore, gritty, crusted lid margins, often with dry-eye symptoms. It is managed with lid hygiene — warm compresses and cleaning the margins — and the crucial counselling point is that this controls rather than cures. Patients who stop when symptoms improve relapse, and conclude the treatment failed.
Dry eye is very common and often mistaken by patients for an infection, since it produces grittiness, redness and — confusingly — watering, because the reflex tearing overshoots. It is aggravated by wind, smoke, screen use and some drugs.
Pterygium is a fleshy growth of conjunctiva encroaching onto the cornea from the nasal side, associated with chronic exposure to ultraviolet light, wind and dust. Most need no treatment; the reasons to refer are encroachment threatening the visual axis, or distortion of the cornea affecting vision.
Most red eyes are benign. The full assessment of the acute red eye is covered in the eye and ENT emergencies chapter, but the discriminating features are worth restating, because they are the ones that decide whether a patient goes home:
Any of these means same-day assessment rather than topical antibiotics and review.
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