Longitudinal changes in corneal curvature and its relationship to axial length in the Correction of Myopia Evaluation Trial (COMET) cohort

Abstract

PurposeTo describe longitudinal changes in corneal curvature (CC) and axial length (AL) over 14 years, and to explore the relationship between AL and CC, and the axial length/corneal radius (AL/CR) ratio.MethodsIn total 469, 6 to <12-year-old, children were enrolled in COMET. Measurements of refractive error, CC (D), CR (mm), and ocular component dimensions including AL were gathered annually. Linear mixed models were used to evaluate longitudinal changes adjusting for covariates (gender, ethnicity, lens type, baseline age and baseline refraction). The Pearson correlation coefficient between AL and CC was computed at each visit.ResultsThere was a slight but significant (p < 0.0001) flattening in CC over 14 years. At all visits females had significantly steeper CC than males (overall difference = 0.53 D, p < 0.0001). Caucasians had the steepest CC, and Hispanics the flattest (p = 0.001). The correlation between AL and CC was −0.70 (p < 0.0001) at baseline (mean age = 9.3 years) and decreased to −0.53 (p < 0.0001) at the 14-year visit (mean age = 24.1 years). The average AL/CR ratio was 3.15 at baseline and increased to 3.31 at the 14-year visit. The correlation between the magnitude of myopia and AL/CR ratio was significantly higher (p < 0.0001) at each visit than the correlation between myopia and AL alone.ConclusionsDifferences in average corneal curvature by age, gender, and ethnicity observed in early childhood remain consistent as myopia progresses and stabilizes. This study also demonstrates increases in the AL/CR ratio as myopia progresses and then stabilizes, supporting observations from previous cross-sectional data.

Ratio of Axial Length to Corneal Radius in Japanese Patients and Accuracy of Intraocular Lens Power Calculation Based on Biometric Data

“…AL/CR RATIO AND RELATIONSHIPS AMONG THE SE AND AL, CR, AND AL/CR RATIO: The distributions of the AL/CR ratio have been reported in different populations and age groups 31,[34][35][36][37][38][39][40][41] and the AL/CR ratios for myopia were between 2.9 and 3.1 and less than 2.9 for emmetropia and hyperopia. 26,27,[42][43][44][45][46] Table 4 summarizes the other studies. In the current report, the CR was approximately the same as that in those previous reports, and women had significantly steeper corneal curvature values, 43 whereas the current AL was longer than those reported previously.…”

“…26,27,[42][43][44][45][46] Table 4 summarizes the other studies. In the current report, the CR was approximately the same as that in those previous reports, and women had significantly steeper corneal curvature values, 43 whereas the current AL was longer than those reported previously. Therefore, the mean AL/CR ratio became the highest.…”

Understanding Myopia: Pathogenesis and Mechanisms

“…Longitudinal studies indicate that changes in corneal curvature during childhood [36][37][38] and early adulthood [39] are minimal and not associated with the magnitude of myopia progression. However, since the correlation between spherical equivalent refraction (SER) and the axial length to corneal radius ratio is typically stronger than that of axial length alone (by 15-20%) [40][41][42][43], corneal curvature does appear to make a modest contribution to the magnitude of myopia.…”

Features of the Choroidal Structures in Myopic Children Based on Image Binarization of Optical Coherence Tomography

“…Ocular biometrics, such as corneal radius (CR) 6 and lens thickness (LT), 7 as well as demographic factors, including age and sex, 8 have been found to be associated with axial length (AL) elongation in childhood. In addition, numerous animal and human studies have revealed a significant association between AL and choroidal thickness.…”