The Effect Of Altitude On The Incidence Of Keratoconus In Isreal – A 20 Year Population Based Study

The pathogenesis of Keratoconus is yet unknown, and appears to be multifactorial, influenced by a combination of genetic and environmental factors. Studies have shown that abundant sun exposure is a risk factor for Keratoconus. Since, in high altitude, UV radiation is increased, high altitude may lead to higher incidence of Keratoconus. The purpose of this study is to determine the effect of geographical altitude on the incidence of keratoconus among the Israeli population.

We conducted a population based, retrospective observational cohort study, using electronic database data from the largest public health service organizations in israel, “Clalit Health Services”.

Medical files of over 2 million Israeli adults from “Clalit Health Services” electronic database between the years 2001-2021 were searched and keratoconus patients were identified. The incidence for every residency, city or settlement was calculated by year. The effect of the altitude of each residency on the incidence of keratoconus was examined during the years and in total.

17,403 patients with keratoconus were identified. The average incidence in Israel between the years 2001-2021 was 21.88 to 100,000. The average incidence in areas located lower than sea level, 0-500 meters above sea level and over 500 meters were 15.74 ,21.53 and 24.43 to 100,000, respectively. Differences between the groups were significant (p=0.05).

There is a correlation between geographical altitude and the incidence of keratoconus among the Israeli population. Thus, we recommend increased keratoconus screening of the population located at high altitude residencies.