Evaluation of the anatomic and refractive differences in hyperopic anisometropia

The purpose of this study was to investigate the interocular symmetry of ultrasonic biometric characteristics and anterior segment measurements between the fellow eyes of hyperopic anisometropes. Forty-two healthy hyperopic anisometropic cases (1 D mean spherical equivalent difference between eyes) without strabismus were recruited. A range of refractive and ultrasonic biometric parameters were measured in both eyes of each subject including keratometry, mean spherical equivalent, anterior chamber depth (ACD), lens thickness, vitreous depth (VD), axial length (AL), and anterior segment parameters (central corneal thickness (CCT), ACD, anterior chamber volume (ACV)) with Pentacam. Mean spherical equivalent anisometropia was 2.66 ± 1.233 (range 1.125 and 6.25) D, and there was a strong correlation between the degree of anisometropia and the interocular difference in AL (r = 0.632, P < 0.001). A total of 61.3 % of the anisometropia was related with AL (50.7 %) and mean keratometry (10.6 %). Every 1 mm change in AL and every 1 D change in mean keratometry caused a total of 2.82 D and 2.14 D refractive difference, respectively. Among Pentacam parameters, ACD was correlated with ACV (r = 0.528; P < 0.001) and AL (r = 0.510; P = 0.001); ACV was correlated with VD (r = 0.358; P = 0.020); and CCT was correlated with ACV (r = 0.510; P = 0.001) and AL (r = 0.318; P = 0.040). Among ultrasonographic measurements, ultrasonic-ACD was correlated with CCT (r = 0.510; P = 0.001) and lens thickness (r = -0.556; P < 0.001), and VD was correlated with AL (r = 0.937, r ² = 0.877, P < 0.001). The hyperopic and the fellow eyes displayed a high degree of interocular symmetry for the other measured parameters. AL and mean keratometry are the leading causes of hyperopic anisometropia. However, ACD as measured with Pentacam also shows difference in hyperopic anisometropic eyes.