Conjunctiva: conjunctivitis, trachoma and pterygium
- Lesion
The conjunctiva reacts to infection, allergy and sun: trachoma scars it and can blind; pterygium is a sun-damaged growth onto the cornea.
What it is
The conjunctiva is a mucous membrane covering the inner eyelids and the white of the eye. It responds to injury with papillae, follicles, discharge and, if chronic, scarring. Trachoma, caused by repeated Chlamydia trachomatis infection in poor sanitary conditions, scars the upper lid so that lashes turn in and abrade the cornea, a leading infectious cause of blindness. Scarring from drugs, autoimmune disease or surgery can also destroy the tear film. Pterygium and pinguecula are sun-related elevations at the lid fissure.
Step by step
- Repeated chlamydial infection spreads by hands, cloth and flies in crowded homes without water.
- Each episode inflames the conjunctiva with follicles under the upper lid.
- Chronic inflammation lays down scar in the tarsal conjunctiva.
- Scar contracts, turning the lid and lashes inward (entropion, trichiasis).
- Lashes scratch the cornea, which ulcerates and becomes opaque.
Conjunctival reactions and lesions
| Lesion | Cause | Pathology |
|---|---|---|
| Bacterial conjunctivitis | Staphylococcus, pneumococcus, Haemophilus; gonococcus in newborns | Purulent exudate, papillae |
| Viral conjunctivitis | Adenovirus | Follicles, watery discharge |
| Allergic conjunctivitis | Type I hypersensitivity | Papillae, eosinophils, mast cells |
| Trachoma | Chlamydia trachomatis, repeated | Follicles, tarsal scarring, entropion |
| Cicatrising conjunctivitis | Mucous membrane pemphigoid, drugs, Stevens-Johnson | Subepithelial fibrosis, fornix shortening |
| Pterygium | Ultraviolet light | Fibrovascular tissue invading cornea, elastosis |
| Pinguecula | Ultraviolet light | Elastotic degeneration, no corneal invasion |
Clinical notes
- WHO's SAFE strategy (surgery, antibiotics, facial cleanliness, environmental improvement) aims to eliminate trachoma; foci persist in the Amazon region, including Colombia's Vaupés.
- Pterygium is common in sunny, dry and high-altitude regions of Latin America.
Test yourself
Think of the answer, then tap the question to see it.
How does trachoma lead to blindness?
Repeated infection scars the upper lid, which turns inward so lashes scratch and opacify the cornea.
What distinguishes a pterygium from a pinguecula?
A pterygium grows onto the cornea as a fibrovascular wing; a pinguecula stays on the conjunctiva.
Which conjunctival reaction suggests a viral or chlamydial cause?
Follicles, small lymphoid aggregates with germinal centres.
Elsewhere in DurgiPedia
- Red eye: what is serious and what is not
- The tear film and ocular surface
- Avoidable blindness: the main causes in the world and in Colombia
- Conjunctiva, eyelid glands and lacrimal gland
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Conjunctivitis Overview (StatPearls (NCBI Bookshelf), 2026); Trachoma (World Health Organization, 2026).
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Representative model, for educational purposes only.