The clinical features of trachoma can be divided into active and cicatricial phases; these phases may overlap in the same patient. Conjunctival infection with particular strains of C. trachomatis leads, after several weeks, to inflammatory changes that can be visualised in the everted eyelid. Resolution of any episode of infection is accompanied by deposition of a small amount of conjunctival scar. In trachoma-endemic communities, reinfection is a frequent occurrence; with repeated infection over many years, sufficient conjunctival scar may be deposited to become visible on clinical examination. Contraction of this scar may distort the eyelids, drawing the lash-bearing margins inwards so that they rub on the eye. This damages the cornea, ultimately leading to visual impairment or blindness.
The WHO simplified system for community assessment of trachoma was developed in the 1980s as a clinical grading scheme for use in survey work by less experienced observers. Signs are not mutually exclusive: more than one – or indeed all – can coexist in the same eye. This system is widely used by trachoma control programmes.
Grade |
Clinical signs |
| TF | Trachomatous inflammation – Follicular |
| TI | Trachomatous inflammation – Intense |
| TS | Trachomatous Scarring |
| TT | Trachomatous Trichiasis |
| CO | Corneal Opacity |
A card illustrating the WHO Simplified System can be downloaded from this link.