Abstract
Purpose::
1) To describe myopia stabilization after 7 yrs of follow-up in COMET participants based on Gompertz curve fits to each subject’s refractive error data; 2) To evaluate the association between myopia stabilization and age, gender, and ethnicity.
Methods::
469 myopic, ethnically diverse, 6-11 yr old (median age 9 yrs) children who enrolled in COMET in 1997-1998 continued to be followed after the clinical trial phase ended. Non-cycloplegic autorefraction measurements were collected semi-annually for 4 yrs and annually thereafter. The Gompertz function R=Re+Rc*(0.07295)^a^(x-t0), where R is the spherical equivalent refractive error (SER) at age x, was fit to the right eye SER for each subject. Myopia was considered as stable at a visit and subsequent visits once the data point at that visit was within ±0.25D of the asymptote of the curve. The status of subjects whose SER could not be fit by the Gompertz function was determined by agreement of two independent investigators; subjects whose status at a visit could not be determined as either stable or progressing were excluded for that visit. Associations between 7-yr stabilization and SER, age, gender and ethnicity were evaluated using the t-test or Χ2 test.
Results::
Stable myopia in COMET participants increased from 14% (58/418) at yr 3 (median age 12 yrs) to 50% (206/411) at yr 7 (median age 16 yrs). Of the 420 subjects with SER data at yr 7, 411 had myopia stabilization status defined-387 based on Gompertz fits and 24 based on investigator judgment. At yr 7, SER was lower in those subjects with stable (mean±SD= –4.3±1.5D) vs. progressing myopia (–5.5±1.6D), p<0.0001, even though their baseline SER was similar (–2.6±0.77D and –2.5±0.86D, respectively). The percent with stable myopia increased with age, from 35% (14/40) for 13-14 year olds to 63% (52/82) for 18 yr olds (p=0.04). In addition, the percent with stable myopia differed by ethnicity (p=0.01): 63% (71/113) in African-Americans, 46% (85/184) in Whites, and 38% (24/64) in Hispanics. The frequency of stable myopia was similar for males and females.
Conclusions::
At a median age of 16 yrs, 50% of COMET cohort had stable myopia mainly based on Gompertz curve fits, with older or African-American subjects more likely to have stable myopia. Longer follow-up is needed in order to obtain unbiased estimates of age and amount of myopia at stabilization for this cohort.
Clinical Trial::
www.clinicaltrials.gov NCT00000113
Keywords: myopia • clinical (human) or epidemiologic studies: natural history • clinical (human) or epidemiologic studies: risk factor assessment