Findings from a recent study published in Medicine suggest that hyperopia—understudied in connection with cataracts—may provide a protective effect against age-related nuclear cataracts.
Give me some background first.
Previous research has established a link between myopia and both posterior subcapsular cataracts (PSC) and nuclear cataracts (NC)—with a more “robust association” between myopia and PSC.
In fact: Each 1 diopter (D) of myopia has been associated with a 21% increase in the prevalence of PSC.
What about hyperopia?
Hyperopia is much less prevalent than myopia, with an estimated 5-10% in the United States compared to myopia’s 42%.
With this in mind, the study authors utilized Mendelian randomization (MR) to analyze the “exposure factor” of hyperopia on cataract outcomes.
What is Mendelian randomization?
MR is an analytical method utilized to establish causality, following three primary assumptions:
- “[The] genetic tools should demonstrate a significant correlation with the targeted biomarker.
- [These] genetic tools ought to connect to the outcomes primarily via exposure, omitting any irrelevant biological routes.
- [These] genetic tools must not relate to any elements that could skew the relationship between exposure and outcome.”
So what data was examined?
Investigators used data from the UK Biobank, as well as data from the European Institute for Information Research for cataracts and FinnGen for age-related cataracts.
And what did they find?
Higher levels of hyperopia were associated with a lower risk of senile nuclear cataracts.
However, the study authors noted, “the level of hyperopia did not have a significant effect on the risk of early senile cataracts.”
So what does this mean?
This research has some interesting implications for how both myopia and hyperopia affect cataract development—specifically choroidal blood flow and vascular density of the deep retinal capillary plexus, both of which have been shown to be reduced or lowered in myopic patients compared to hyperopes.
Any limitations?
Three major limitations were called out:
- The study only included participants of European descent
- In order to identify the long-term impact of hyperopia, a follow-up study is needed
- No experimental study of the effect of hyperopia on cataract has been conducted
Take home.
“Our study demonstrates a causal link between higher levels of hyperopia and lower risks of senile cataract,” note the study authors.
“Moreover, higher hyperopia levels also decrease the risk of cataract extraction or a lens implant.”