Relationship of Axial Length to Myopic Influence on Nuclear Cataract

Abstract

Purpose: : Nuclear cataract, one of the main age-related cataracts, sometimes develops in young patients with high myopia and/or long axial length. We reported that internal spherical aberrations in eyes with nuclear cataract decreases with severity of opacity, especially in long axial length eyes. We investigated the relationship between severity of opacity and progression of myopia and examined myopic influence on nuclear cataract by axial length (AL).

Methods: : Subjects comprising 66 eyes of 40 nuclear cataract outpatients of Kanazawa Medical University Hospital were examined. AL, was measured by IOL master (ZEISS), and classified as normal (43 eyes, age 75.8±5.3 yrs, AL<24.5mm) or long (23 eyes, age 69.6±8.8 yrs, AL≥24.5mm). Opacity was evaluated by light scattering intensity (LSI) and shape of anterior region from Scheimpflug images (EAS-1000, NIDEK). Spherical equivalent refraction was calculated from wavefront aberration (KR9000PW, TOPCON) for a 4mm pupil.

Results: : Degree of myopia significantly increased with LSI in both groups. However, there was a significant difference in negative correlation of myopia with LSI between groups (normal: -0.025D/cct, long: -0.128D/cct). A significant relationship of refractive error with AL and LSI was found in the long group by multiple regression analysis of AL, LSI, and shape of anterior regions (standardized partial regression coefficient, AL: -0.719, LSI: -0.346, r² = 0.830). The thickness of anterior nucleus was significantly thicker in normal eyes than in eyes with long axial length.When thickness of the anterior nucleus and curvature radius of the cornea were included in the multiple regression analysis, r² was a higher value.

Conclusions: : Myopic progression is significantly advanced by increased severity of nuclear opacity. The effect of LSI on progression of myopia is five times higher in eyes with long axial length than those with normal. Moreover, it is suggested that the shape of nuclear cataract also affects progression of myopia.

Keywords: cataract • myopia • crystallins