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Kazuhiko Mori, Tomomichi Nakayama, Yoko Ikeda, Morio Ueno, Haruna Yoshikawa, Yuko Maruyama, Shigeru Kinoshita; Magnification Errors after Refractive Change by Cataract Surgery on Optic Nerve Head Analysis. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2152.
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© ARVO (1962-2015); The Authors (2016-present)
Quantification of the optic disc is influenced by the magnification errors of the refractive status. All ophthalmoscopes have several methods that can be used to compensate for this problem. The purpose of this study was to evaluate the magnification errors after refractive change by cataract surgery on optic nerve head analysis using confocal laser ophthalmoscopy.
This study was conducted as a retrospective observational case series and involved 14 eyes of 17 glaucoma patients (8 females and 9 males; mean age: 72.0 ± 10.0 years) out of 478 eyes that underwent cataract surgery (including combined procedures with trabeculectomy) between January 2006 and December 2011 at the University Hospital of Kyoto Prefectural University of Medicine. Only the patients who were able to undergo examination of refractive error (RE), corneal curvature radius (CCR), axial length (AL), as well as reliable optic nerve head analysis by use of the Heidelberg Retina Tomograph II (Heidelberg Engineering GmbH, Heidelberg, Germany) during the pre- and postoperative periods were statistically analyzed. Magnification errors after correction by the measured CCR or by the automatic image alignment were evaluated utilizing the optic disc area (DA) and rim area (RA) data of the pre- and postoperative periods. The influence of other ophthalmic factors such as RE and AL on the magnification errors were also evaluated.
The mean postoperative reduction of optic DA was 9.4±17.4% when the measured CCR were used for each time periods, yet was 10.6±17.3% for the fixed CCR. On the other hand, the reduction rates of RA were 14.9±42.6%, 10.6±38.5%, and 9.2±17.8% for the fixed CCR, measured CCR, and automatic image alignment correction, respectively. However, a certain amount of error still remained after the automatic correction, and a significant correlation was found between the RE and magnification errors (Pearson’s correlation coefficient: R=0.75, P=0.0005).
The measurement of optic DA and RA changed between the pre- and postoperative periods, and was influenced by the refractive error. The existing methods using CCR or image alignment are inadequate for the correction of magnification errors.
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