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Study: Long-term myopic shift may be linked to nuclear cataract
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A longitudinal study documenting 10-year refractive changes in an Australian population has identified a hyperopic shift in subjects younger than 65 years and a myopic shift in older subjects. In addition, this myopic shift appears to be caused by the development of nuclear cataract.
"Although underlying causes for this age-related hyperopic shift are unknown, it does not appear related to axial length," the study authors said in the August issue of Ophthalmology.
Reena Fotedar, MD, and colleagues at the University of Sydney evaluated factors contributing to temporal refractive changes among 3,654 participants in the Blue Mountains Eye Study who were 49 years or older at baseline. Subsequently, 2,335 of these participants were examined at 5 years and 1,952 participants were examined at 10 years. Of these, 1,340 subjects who had right phakic eyes with a best corrected visual acuity greater than 20/40 at baseline and at 10-year follow-up were included for analysis.
Over 10 years, the investigators observed a hyperopic shift among subjects who were younger than 65 years and a slight myopic shift among subjects between 65 and 74 years that grew significantly among subjects who were 75 years and older.
In addition, they found a strong association between myopic refractive change and nuclear cataract at baseline; refractive changes averaged –0.96 D in eyes with nuclear cataract and 0.26 D in eyes without nuclear cataract (P < .001).
"A birth cohort effect on refraction was also observed," they said.
After adjusting for age and nuclear cataract, the investigators found no significant relationship between changes in refraction and baseline refractive status, education and diabetes.
There was a 10% rise in against-the-rule astigmatism over 10 years.
While axial length showed an age-related reduction in 10-year cross-sectional data, after adjusting for age, education and nuclear cataract, axial length measured at 10 years was not associated with a change in spherical equivalent refraction, according to the study.