A case-control study of ocular surface squamous neoplasia (OSSN) in Uganda.

HIV increases the risk of OSSN. Here we investigate other factors in a case-control study from Uganda with 318 cases (48 CIN I, 66 CIN II, 81 CIN III and 123 with invasive disease) and 762 controls. Initial analyses were stratified by HIV serostatus (204 cases and 202 controls were HIV seropositive), but since findings were similar in infected and uninfected people, the combined results are presented here. The risk of OSSN increased with increasing time spent in direct sunlight (p(trend) = 0.003, adjusted for age, sex, residential district and HIV serostatus): compared to those who reported spending up to 1 hr a day in direct sunlight, the risk was 1.7 (95% Confidence Interval [CI] 1.2-2.4) in those reporting 2-4-hr exposure and 1.8 (95% CI 1.1-3.1) in those reporting 5+ hr. The risk was also increased among people reporting a previous injury to the affected eye (OR 2.4, 95% CI 1.2-4.5). Pinguecula in the nasal quadrant of the unaffected eye were evident on clinical examination for 98% of cases (293/300) and for 91% of the same quadrant in the right eye (246/271) of controls (OR = 6.4, 95% CI 2.5-16.1). We confirm associations with exposure to solar ultraviolet radiation and with the presence of pinguecula and report a role for previous ocular trauma in the aetiology of OSSN. We did not identify any additional factors that point to an underlying infectious cause, although this is an area of on-going research.