Meridional development of the infant crystalline lens

Purpose. We previously presented biometric data from infants 4 to 15 months of age (ARVO, 1994). We are continuing our investigation of ocular growth and refractive development by examining two meridians of the crystalline lens in older infants. Methods. We evaluated the right eye of 11 subjects ranging from 9 to 29 months under cycloplegia (cyclopentolate 1% after proparacaine 0.5%). We assessed refractive error by retinoscopy, axial dimensions by A-scan ultrasonography, and corneal radius, crystalline lens radius, and crystalline lens power using a video-based keratophakometer which records Purkinje images I, III, and IV in two orthogonal meridians. Results. In the horizontal meridian, the mean anterior crystalline lens radius was 9.10 ± 0.79mm and the mean posterior radius was 4.79 ± 0.37mm. In the vertical meridian, the mean anterior crystalline lens radius was 9.35 ± 0.88mm and the mean posterior radius was 5.03 ± 0.38mm. The posterior crystalline lens radius in the horizontal meridian flattened with age (radius=3.98+0.05(age (months)), r=0.73, p=0.03) while the anterior crystalline lens radius was not quite statistically significant for age-related flattening (radius=7.57+0.09(age (months)), r=0.64, p=0.06). There were no statistically significant age-related trends in the anterior and posterior crystalline lens radius in the vertical meridian (anterior: r=0.52, p=0.10; posterior: r=0.16, p=0.64). Conclusions. In contrast to previous pilot data in infants from 4 to 15 months, which showed no age-related changes in crystalline lens radius, our data from older infants and toddlers show flatter crystalline lens radii in the horizontal posterior meridian with increasing age. The flattening of the horizontal posterior crystalline lens radius, while the other crystalline lens radii stayed the same, may contribute to a shift toward with-the-rule astigmatism. These cross-sectional trends require confirmation by longitudinal studies.