Myopia stabilization and associated factors among participants in the Correction of Myopia Evaluation Trial (COMET)

Abstract

Purpose: To use the Gompertz function to estimate the age and the amount of myopia at stabilization and to evaluate associated factors in the Correction of Myopia Evaluation Trial (COMET) cohort, a large ethnically diverse group of myopic children.

Methods: The COMET enrolled 469 ethnically diverse children aged 6 to younger than 12 years with spherical equivalent refraction between -1.25 and -4.50 diopters (D). Noncycloplegic refraction was measured semiannually for 4 years and annually thereafter. Right eye data were fit to individual Gompertz functions in participants with at least 6 years of follow-up and at least seven refraction measurements over 11 years. Function parameters were estimated using a nonlinear least squares procedure. Associated factors were evaluated using linear regression.

Results: In total, 426 participants (91%) had valid Gompertz curve fits. The mean (SD) age at myopia stabilization was 15.61 (4.17) years, and the mean (SD) amount of myopia at stabilization was -4.87 (2.01) D. Ethnicity (P < 0.0001) but not sex or the number of myopic parents was associated with the age at stabilization. Ethnicity (P = 0.02) and the number of myopic parents (P = 0.01) but not sex were associated with myopia magnitude at stabilization. At stabilization, African Americans were youngest (mean age, 13.82 years) and had the least myopia (mean, -4.36 D). Participants with two versus no myopic parents had approximately 1.00 D more myopia at stabilization. The age and the amount of myopia at stabilization were correlated (r = -0.60, P < 0.0001).

Conclusions: The Gompertz function provides estimates of the age and the amount of myopia at stabilization in an ethnically diverse cohort. These findings should provide guidance on the time course of myopia and on decisions regarding the type and timing of interventions.

Keywords: Gompertz function; associated factors; myopia; myopia progression; myopia stabilization.

Figure 1

(a–f) Examples of Gompertz curves. (a) Age 6 to 7 years (baseline age) with stable myopia estimated before the last study visit (MSE [a measure of curve fit quality], 0.03). (b) Age 6 to 7 years (baseline age) with stable myopia estimated after the last study visit (MSE, 0.02). (c) Age 8 years or older (baseline age) with stable myopia estimated before the last study visit (MSE, 0.01). (d) Age 8 years or older (baseline age) with stable myopia estimated before the last study visit (MSE, 0.33). (e) Age 8 years or older (baseline age) with stable myopia estimated after the last study visit (MSE, 0.03). (f) Age 8 years or older (baseline age) with no myopia progression (MSE, 0.02).

Figure 2

Cumulative proportion of participants with stable myopia by ethnicity and the estimated age at stabilization (n = 426). The overall cumulative proportion distributions are significantly different across ethnicity groups (P < .0001, log-rank test).

Figure 3

Relationship between the age at stabilization and the amount of myopia stabilization.