Aims To describe the incidence and epidemiology of conjunctival squamous cell carcinoma (CSCC) in South Africa over a 25-year period (1994–2018), with particular reference to the HIV epidemic.

Methods Incident cases of histologically diagnosed CSCC were identified from the pathology-based South African National Cancer Registry. Crude and direct age-standardised incidence rates (ASIRs) per 100 000 persons (Segi World Standard Population) were calculated using national population statistics and compared by age, sex and ethnicity. Trends in the incidence and demographic features of CSCC were described and analysed. Incidence rates were compared with national HIV-related statistics for the same time period.

Results In total, there were 9016 reported CSCC cases (women: 56.6%, black: 86.8%, mean age: 41.5 years). The overall ASIR was 0.78 per 100 000. Two distinct epidemiological patterns were identified: (1) older white men, and (2) younger black women. There was a sixfold increase in CSCC incidence rates between 1994 and 2009 with a corresponding shift from the first to the second disease profile. Despite rising HIV seroprevalence, CSCC incidence rates have declined since 2009. A strong ecological correlation (r=0.96) between CSCC incidence and widespread antiretroviral therapy (ART) provision was identified.

Conclusion This study highlights the evolving trends and disease burden of CSCC in South Africa. Widespread ART provision is ecologically correlated with declining CSCC rates over the last decade. These findings are in keeping with reported trends for other HIV-related cancers and have important implications for future incidence studies and public health policy.