Trachoma: WHO Grading, SAFE Strategy and India's Elimination
Last updated: November 2026
Trachoma is the world's leading infectious cause of blindness: repeated chlamydial infection scars the upper lid, turns the lashes in and opacifies the cornea. India was validated by WHO as having eliminated trachoma as a public health problem in October 2024, but old scarring, trichiasis and exam questions remain.
Cause and spread
- Chlamydia trachomatis serotypes A, B, Ba and C (serotypes D–K cause adult inclusion conjunctivitis; L1–L3 lymphogranuloma venereum).
- Spread by eye-seeking flies, fingers and shared cloths in crowded communities with poor water and sanitation; repeated infection in childhood leads to scarring in adulthood.
WHO simplified grading
| Grade | Definition |
|---|---|
| TF: trachomatous inflammation, follicular | Five or more follicles, each at least 0.5 mm, in the central upper tarsal conjunctiva |
| TI: trachomatous inflammation, intense | Pronounced inflammatory thickening obscuring more than half of the deep tarsal vessels |
| TS: trachomatous scarring | Easily visible white scar lines or bands in the tarsal conjunctiva |
| TT: trachomatous trichiasis | At least one eyelash touching the globe, or evidence of recent epilation of in-turned lashes |
| CO: corneal opacity | Easily visible corneal opacity over the pupil, blurring part of the pupil margin |
Other classic signs: Herbert pits (limbal follicles that heal into depressions, pathognomonic), Arlt line (horizontal scar on the upper tarsus), pannus of the upper cornea.
The SAFE strategy
| Component | What it means |
|---|---|
| S: Surgery | Lid surgery for trichiasis (bilamellar tarsal rotation or posterior lamellar tarsal rotation) to prevent corneal blindness |
| A: Antibiotics | Single oral dose of azithromycin (20 mg/kg, maximum 1 g) given to whole communities (mass drug administration) where TF in children is 5% or more; topical tetracycline ointment as an alternative for infants |
| F: Facial cleanliness | Face washing, especially for children |
| E: Environmental improvement | Water, sanitation and fly control |
Elimination targets
WHO defines elimination as a public health problem as TF below 5% in children aged 1–9 years and TT unknown to the health system below 0.2% in adults aged 15 and over, with a system to manage new trichiasis cases. India met these and was validated in October 2024.
Where residents slip
- Confusing serotypes A–C (trachoma) with D–K (inclusion conjunctivitis).
- Forgetting Herbert pits as the pathognomonic sign.
- Epilating trichiasis repeatedly without offering surgery.
Test yourself: flip cards
Related: Eyelid Malpositions: Entropion, Ectropion, Trichiasis and Chalazion, SJS, Ocular Cicatricial Pemphigoid and Neurotrophic Keratopathy, Red Eye.
Key sources
- World Health Organization. Design parameters for population-based trachoma prevalence surveys and the simplified trachoma grading system (2020 revision)
- World Health Organization. Elimination of trachoma as a public health problem in India. News release, 8 October 2024. who.int
📘 Want more exam-ready material? See Most Commons in Ophthalmology on Kindle, or browse all my books.
Looking for an eye specialist in Ahmedabad? Learn about our Eye Department or book a consultation with Dr. Dhaval Patel.