39.1.1  What causes trachoma?

Look closely at the diagram of the eye in Figure 39.1. Identify the areas labelled as the conjunctiva and the cornea. In the initial stages of trachoma, the bacteria Chlamydia trachomatis primarily infect the conjunctiva (pronounced ‘kon-junk-tie-vah’). This is a thin clear membrane that covers the inner surface of the eyelid and the white part of the eyeball. First it becomes itchy and inflamed (red, swollen and painful); later it becomes scarred and the eyelashes turn inwards.

The cornea is the thick transparent tissue over the front part of the eye, covering the white, black and coloured areas. The damage to the cornea is not due to the bacteria, but by persistent scratching from the eyelashes, which have turned inwards due to scarring in the conjunctiva.

Figure 39.1  Anatomical structure of the eye. The conjunctiva lining the inside of the eyelids is the area most visibly affected by trachoma in the early stages. (Source: WHO, 1993, Primary Healthcare Level Management of Trachoma)