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M. Gualtieri, M. Nishi, M. Lago, D.F. Ventura; Color Discrimination and Chromatic Contrast Sensitivity Assessed in Type 2 Diabetic Patients Without Retinopathy . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4750.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To assess the chromatic discrimination and contrast sensitivity of diabetics with no retinopathy, using recently developed psychophysical tests. Methods: color discrimination of 36 diabetic patients without clinical signs of retinopathy at the fundus examination (18 women, 18 men; age= 55.3 ± 8.4 years and mean time of disease= 6.5±5.7 yrs) was evaluated using the Cambridge Colour Test (CCT, Cambridge Research System, CRS). Chromatic contrast sensitivity function (CSF) at the red/green – R/G – and blue/yellow B/Y axes was measured using equiluminant gratings generated with PSYCHO for Windows 2.36 (CRS); the luminance CSF was measured as well. The performance of the diabetic patients was compared to that of two age–matched control groups: n= 23, age= 62.39±8.87 yrs for the CCT and n= 14, age= 61.43±13.54 yrs for the CSF. The tests were performed in the dominant eye; in a darkened room in which the only luminance came from the stimulation monitor whose mean luminance was 18 cd/m2 (CCT) and 34 cd/m2 in CSF tests. Metabolic control (glucose level at the test time and glycosylated hemoglobin, HbA) and time of diabetes of the patients were correlated with their visual data. Results: the color discrimination (CCT) of the diabetics was significantly lower from that of controls in the MacAdam ellipse u’= 0.197; v’= 0.468 (p= 0.00 Kruskal–Wallis test). The chromatic and achromatic CSFs of the patients were significantly lower at all spatial frequencies compared to those of controls (p< 0.01 Kruskal–Wallis test). The differences between CSFs of diabetics and controls for chromatic gratings were about 10 dB while for the achromatic set it was about 6 dB. The HbA levels and time of disease were correlated only with CCT results and glucose level at the test time did not correlate with either CCT or CSF. Conclusions: Diffuse color discrimination losses were detected in the non–retinopathic diabetic patients. The CSFs measured with R/G and B/Y stimuli, seem to be more sensitive to detect early visual abnormalities in these patients. This is probably due sensitivity of the CSF to hipoxia (Dean et al., 1997; Harris et al., 1996). Both examinations must be considered a useful and reliable tool for the visual follow–up of diabetics since the early stages of the disease.
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