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D. Van Norren, M. Pot, N.P. Zagers; Foveal Reflection Analysis in Diabetes . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4008.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: We have build an instrument for simultaneous measurement of the spectral and directional reflectance of the fovea (Appl.Opt. 2002,41:4686). In a pilot study on a group of diabetic patients, three hypotheses were tested: Optical density of the lens is increased, optical density of the macular pigment (MP) is decreased, and cone photoreceptor integrity is altered. Methods: Light reflected from a 2 deg spot concentric with the fovea was analyzed with an imaging spectrograph. The entrance slit of the spectrograph, conjugate to the pupil plane, defines a bar shaped exit pupil (1 x 12 mm). The spectrograph image contained spectral fundus reflectance versus horizontal position in the pupil plane. Model analysis of the spectral reflectance provides individual estimates of the optical density of the lens and MP (Vis.Res. 1996,36:2229). The directional characteristics provide information on the integrity of foveal cones (IOVS 1998,39:1519). Included were 16 eyes of 8 patients with diabetes, and 30 eyes of 30 controls. A subgroup of 8 controls served as age-matched controls. The mean of left and right diabetic eye was compared with single control eyes. Results: Lens density was increased in diabetes compared with age matched controls (0.46 ± 0.19 versus 0.20 ± 0.10, paired t-test, P < 0.01). MP, compared with all 30 controls, was reduced, but not significantly (0.38 ± 0.10 versus 0.46 ± 0.12, t-test, P = 0.07). The difference became just significant when comparing separate diabetic eyes with all controls (P < 0.05). Photoreceptor integrity was affected. Compared with age matched controls, the amplitude of the directional reflectance at 540 nm was decreased (0.42 ± 0.12% versus 0.80 ± 0.12%, paired t-test, P < 0.01) Conclusions: The lens density being increased in diabetes is in agreement with the literature (IOVS 1991,32:194; IOVS 2002,43:281). MP might be slightly reduced, but not to a large extend. Other have found a substantial reduction of MP in diabetes with similar degree of retinal pathology (IOVS 2002,43:281). We suggest that the discrepancy stems from the different demands on fixation of the patients. The changes in the photoreceptor reflectance corroborate an earlier study, where reduced directionality was found in eyes with macular edema (IOVS 2000,41:4048). In general, the results demonstrate the potential of the new instrument for clinical research.
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