## WHO Simplified Trachoma Grading System **Key Point:** The WHO simplified grading system identifies five clinical signs of trachoma: TF (trachomatous inflammation–follicular), TI (trachomatous inflammation–intense), TS (trachomatous scarring), TT (trachomatous trichiasis), and TrCO (trachomatous corneal opacity). TI is the hallmark of active infection. ### Clinical Signs in WHO Simplified System | Sign | Definition | Pathology | Clinical Significance | |------|-----------|----------|----------------------| | **TF** | Follicles on tarsal conjunctiva | Early immune response | Active infection (children) | | **TI** | Intense inflammatory thickening of tarsal conjunctiva with papillary hypertrophy | Severe acute inflammation | Active infection requiring treatment | | **TS** | Conjunctival scarring | Chronic fibrosis | Inactive disease (no treatment) | | **TT** | Trichiasis (≥5 lashes) | Mechanical sequela | Inactive disease (surgical intervention) | | **TrCO** | Corneal opacity involving pupil | Scarring and pannus | End-stage blindness | **High-Yield:** TI indicates active, intense inflammation and is the primary indicator for systemic antibiotic therapy (azithromycin). TS, TT, and TrCO are sequelae of past infection and do not respond to antibiotics; they require surgical management. **Clinical Pearl:** In elimination programs, TI prevalence in children aged 1–9 years is the key epidemiological indicator for treatment decisions. A TI prevalence >5% in this age group warrants population-level mass drug administration (MDA). **Mnemonic:** **TI = Treatment Indicated** (intense inflammation = active disease requiring antibiotics). 
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