Worldwide analysis of climate-related determinants of keratoconus

Abstract

Purpose : The reported prevalence of keratoconus varies widely worldwide, and the factors contributing to this variation are not well understood yet. This study explores the potential impact of relevant climate-related variables on keratoconus prevalence.

Methods : We systematically reviewed studies about keratoconus prevalence and incidence in the general population. Estimates from screening studies were excluded from the quantitative analysis to ensure interstudy comparability. Climate variables were extracted using state-of-the-art methods. More specifically, gridded climate datasets such as the ERA5 and its derivatives were utilized to find climate data for each studied region. Moreover, population density weighting was applied to enhance exposure accuracy. We took the 10 years preceding data collection of each prevalence study as the climate exposure period. Over this period, the averages of relative humidity, wind speed, ultraviolet radiation, and maximum daily temperature were calculated. Finally, the potential impact of these climate variables on keratoconus prevalence was investigated using simple and multiple linear regression. Climate variables which approached significance on simple regression (P≤ 0.1) were included in the multiple regression model.

Results : The systematic review identified 18 relevant studies reporting keratoconus prevalence across different geographical locations. Of these, 8 studies including data from 58 different areas were deemed to have comparable prevalence estimates. Simple linear regression resulted in the exclusion of maximum daily temperature (P= 0.158). The remaining climate variables were included in the multiple regression model, which showed a negative association between humidity and keratoconus prevalence (P= 0.015). Lower humidity might therefore be a risk factor for keratoconus. In contrast, maximum daily temperature, wind speed, and ultraviolet radiation did not show significant associations with keratoconus prevalence (Table 1).

Conclusions : Low humidity emerged as an unexplored environmental risk factor for keratoconus, while the other climate variables did not seem to pose significant risk. Future research is needed to confirm the role of low humidity in the pathogenesis of keratoconus, and to assess the potential therapeutic and preventive benefits of humidification.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.