Nuclear cataract and myopic shift in refraction.

Abstract

Nuclear cataract is thought to cause a myopic shift in refraction in older persons. The authors tested this hypothesis by assessing the correlation of nuclear opacity with spherical equivalent refraction (SER) in an older population. Population-based cross-sectional study. Three thousand six hundred and fifty-four participants aged 49 years or older were examined in the Blue Mountains Eye Study [BMES] (1992 to 1994). Eye examinations included subjective refraction and lens photographs. Nuclear opacity was assessed against four standard slit-lamp lens photographs using the Wisconsin Cataract Grading System. Nuclear cataract was defined as opacity level 4 or higher. Participants without nuclear cataract had an annual mean hyperopic shift of 0.05 diopters (P < .0001). In persons with nuclear cataract, this hyperopic shift disappeared. A myopic refractive shift occurred only in persons with nuclear opacity levels of 4 or higher. This study documents the contribution of nuclear cataract to the mild myopic shift that neutralizes the age-related hyperopic shift occurring in older persons.