The risk of developing high myopia as an adult is greater than 50% for those who experienced the condition’s onset at ages 7 or 8 years, according to new research published in JAMA Ophthalmology. The investigators were looking specifically to understand the myopia onset age most closely associated with the probability of developing high myopia in adulthood. They also found the risk substantially decreased to approximately 30% for onset at 9 years old, 20% for onset at 10 years old. It dropped to less than 5% for onset at 12 years or older.
The study analyzed data collected from a cohort of Chinese twins, as over the past few decades an earlier onset of myopia has been reported in East and Southeast Asia. The subjects were aged 7- to 15-years-old at baseline and follow-up visits were scheduled annually for 12 years, from July 11, 2006. Data from baseline to
August 31, 2018, In total, 443 participants were included for analysis.The study excluded anyone who had other ocular issues. The subjects included 196 (44.2%) males and 247 (55.8%) females. The mean age of myopia onset was 11.7 years, At their last follow-up visit, the mean age was 20.4.
For this analysis, myopia onset was determined using data from annual examinations for subjects who developed myopia at the baseline of the study or during the follow-up visits. The authors write, “This was determined as the age at the visit when an spherical equivalent (SE) of -0.50 D or less was first detected.”
A questionnaire survey was also administered to collect data on the participants’ medical history (including age at myopia onset if they developed myopia before the study baseline), hours of nearwork, amount of outdoor activity per day and any information on refractive corrections.
Among all participants, 54 (12.2%) developed high myopia in adulthood (The study defines high myopia as an SE of at least -6.00 D in adulthood.)
Data analysis found:
- Among subjects who were 7 or 8 years old at age of myopia onset, 14 of 26 (53.9%; 95% CI, 33.4%-73.4%) developed high myopia in adulthood;
- Among those with onset at 9 years of age 12 of 37 (32.4%; 95% CI, 18.0%-49.8%);
- Among those with onset at 10 years of age, 14 of 72 (19.4%; 95% CI, 11.1%-30.5%);
- Among those with onset at 11 years of age, 11 of 78 (14.1%; 95% CI, 7.3%-23.8%);
- Among those with onset at 12 years of age, 2 of 67 (3.0%; 95% CI, 0.4%-10.4%);
- Among those with onset at 13 years of age, 1 of 71 (1.4%; 95% CI, 0.0%-7.6%);
- Among those with onset at 14 or 15 years of age, 0 of 92.
Considering how sex factors in, the study states that among males with myopia onset at 7 or 8 years old, the risk of developing high myopia was 52.9% (95% CI, 33.4%-71.7%). For females of the same age, the risk was 55.3% (95% CI, 35.5%-73.5%).
“With a delay in the age at onset to 9 years, the risk decreased to approximately 30%,” The researchers said. “The risk further decreased to approximately 20% with a delay in the age at myopia onset to 10 years. With myopia onset after age 12 years, the risk of developing high myopia in adulthood was less than 5%.”
“These findings suggest the significance of prevention or delay of myopia onset,” the researchers concluded, suggesting mitigation strategies, such as increased outdoor time to protect vision.
Hu Y, Ding X, Guo X, et al. Association of age at myopia onset with risk of high myopia in adulthood in a 12-Year follow-up of a Chinese cohort. JAMA Ophthalmol. Published online Sept 17, 2020 doi: 10.1001/jamaophthalmol.2020.3451