Ultrasound biometric measurements in myopia: a case-control study

ABSTRACT

Thirty emmetropic subjects [50 eyes] and one hundred thirty myopic patients [260 eyes] were selected and examined ophthalmologically and by ultrasonic biometer. These myopic patients were classified into three groups [mild, moderate and high] according to the degree of myopia. Among the biometric measurement it was found that the mean axial length showed gradual persistent significant increase from 23.34 +/- 0.58 in emmetropes to 24.2 +/- 1.02 in mild myopia to 25.06 +/- 0.77 in moderate myopia then to 25.51 +/- 0.77 in high myopia as the variance ratio [V.R.]=35.226 and P<0.001. The axial length and refraction had a significant negative correlation [r=-0.316 and P<0.05] in mild myopia. More stronger in moderate myopia [r=-0.428 and P<0.001] and strongest in high myopia [r=-0.667 and P<0.001]. The anterior chamber depth and lens thickness showed non-significant correlation with the different degrees of myopia. It was concluded that the axial length was the most influencing factor on refraction as by multiple regression the predicted refraction can be computed by the following equation predicted refraction = -1.34672 [axial length] + 29.35439