Pterygium has been linked to ultraviolet exposure, but a new study suggests that when this condition is caused by UV light, it may influence a specific type of cataract formation.

A team of investigators from China found that four cataract presentations—cortical, nuclear, posterior subcapsular and retrodots—were closely tied to the presence of pterygium.

After adjusting for age, sex, work history, axial length and history of diabetes, nuclear cataracts were most likely to be associated with pterygium, followed by retrodots, cortical with axle-shaped opacity, cortical with ring-shaped opacity and posterior subcapsular.

The researchers previously studied cataracts in Han residents from three regions in China and Taiwan with different UV intensities. The Han people are the largest ethnic group of China, Taiwan and Singapore, and studies have shown a higher risk of pterygium among this group compared with geographically similar ethnic populations.

From the original investigation, the researchers created a subgroup of 1,547 individuals with or without pterygium.

The investigators graded pterygium severity by corneal progress rate and stratified the main types of cataracts as cortical, nuclear or posterior subcapsular and three subtypes as retrodots, waterclefts or fiber folds. Researchers noted a high prevalence of cataracts in middle-aged and elderly people and calculated the cumulative ocular UV exposure based on both subject and NASA’s data.

The authors found an overall pterygium prevalence of about 23%, with significant variation among the three regions. The largest number of pterygium-affected eyes were in Sanya, which also had the highest UV intensity of the three regions. On the other hand, the lowest prevalence of pterygium was in Taichung, whereas Taiyuan had the lowest UV intensity. This suggests that UV intensity does not have a strictly linear relationship with the prevalence of pterygium, the authors noted. Additionally, both the prevalence and adjusted risk of pterygium increased with age in all three regions.

The authors said their study found cumulative ocular UV exposure to be a significant predictor of the risk of pterygium development, and therefore, pterygium could be a useful indicator of ocular UV exposure in other eye diseases. Furthermore, the type of cataract in eyes with pterygium may indicate the level of UV exposure.

Hatsusaka N, Yamamoto N, Miyashita H, et al. Association among pterygium, cataracts, and cumulative ocular ultraviolet exposure: a cross-sectional study in Han people in China and Taiwan. Plos One. June 15, 2021. [Epub ahead of print].