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DB Elliott, K Pesudovs; Refractive Error Changes in Cortical, Nuclear and Posterior Subcapsular Cataracts . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1524.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine the effect of the three main morphological types of cataract on refractive error. Methods: Data were collected from one eye of 98 subjects (mean age 67±8 years). 77 subjects were recruited who had just one morphological type of cataract. 34 subjects had cortical cataract, 21 had nuclear cataract and 22 had posterior subcapsular (PSC) cataract. The remaining 21 subjects had normal, healthy eyes and acted as a control group. Cataracts were classified with the LOCS III system, and for the purposes of this study, nuclear or cortical opacity less than 2 on the LOCS scale were regarded as normal ageing changes. Therefore a subject with opacity graded as nuclear 3.2, cortical 1.8 was regarded as having nuclear cataract only. Recent changes in their refractive error were determined by comparing their spectacle correction with their optimal refractive correction determined by objective and subjective refraction. Spherical changes were calculated from the spherical equivalent value (sphere + cylinder /2) and cylindrical changes were determined by vector analysis. Results: As expected, the nuclear cataract group showed a significant myopic shift of mean (±1 SD) of -0.38 (±0.60) D compared to a slight hyperopic shift in the control group of +0.02 (±0.21) D. 52% of the nuclear cataract group showed a minus shift greater than the more minus 95% confidence limit from the control group (-0.40D). 19% showed a minus shift greater than 1.0D. The cortical cataract group showed a significant astigmatic change of median 0.51 D (range 0 - 2.75 D) compared to the control group median of 0.21 D (range 0 - 0.76 D). 41% of the cortical cataract group showed a change in cylindrical correction greater than the 95% confidence limit from the control group (0.60D). 21% showed an astigmatic change greater than 1.0D. Subjects with PSC cataract showed similar refractive error changes to the control group. Conclusion: Over one third of subjects with cortical cataract showed significantly larger changes in astigmatism than control subjects with normal, clear lenses and 21% showed a change of more than 1.0D. This is likely due to localised refractive index changes along spoke cortical opacities that enter the pupillary area. The well known myopic shift of some subjects with nuclear cataracts was also demonstrated. PSC cataracts showed no significant refractive changes.
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