An international team of researchers discovered previously unknown genetic mechanisms that lead to myopia, or nearsightedness, including new associations with circadian rhythm.
Led by scientists at King’s College London, researchers from University College London, Kaiser Permanente, and 23andMe identified three ways that genetics plays a role in myopia, according to the study published in the journal Nature Genetics.
“Myopia is an amazingly complex disorder,” said Dr. Pirro Hysi, the lead author of the study and a researcher at King’s College London’s School of Life Course Sciences. “For the first time, we now have enough of the jigsaw pieces that the biology is becoming clear.”
Association with Circadian Rhythm
Myopia, or nearsightedness where far away objects look blurry, affects more than a third of adults in both the UK and the United States. And while researchers have long known that both genetics and environment influence why someone develops myopia, this very large study was able to uncover some unexpected biology. The study found that genes involved in the circadian rhythm — the inner biological clock regulating our 24-hour long sleep and wake cycles — could be an important factor.
“Changes in the day and night cycles are a possible explanation for the previous observations that myopia is more common in those who spend less time outdoors,” said Professor Jugnoo Rahi, from University College London’s Great Ormond Street Institute of Child Health.
In addition, researchers found overlapping associations with genes that play a role in pigmentation of the eyes, hair, and skin. Scientists had previously found that some genetic disorders that affect pigmentation also caused changes to the back of the eye that resulted in more severe myopia, but the strength of the association found in this study was surprising, said to Eric Jorgenson, Ph.D., an investigator with the Kaiser Permanente Northern California Division of Research and a co-author of the study.
Predictive Model
To make these findings, researchers used data from more than half a million individuals from the UK Biobank, Kaiser Permanente and 23andMe customers who consented to participate in research. Drawing on this very large dataset, the researchers were able to analyze thousands of genetic variants across more than 450 genes.
Along with the association with genes involved with circadian rhythm, the researchers found an association with the mechanisms by which light signals are transmitted by the retina in the eye to the brain.
In addition, the many genetic variants the researchers found that are associated with myopia, could be used to better predict nearsightedness. A genetic model based on the identified DNA variants successfully predicted up to 75 percent of myopia in the participants tested.