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G. Katz, G. Treister, H. Levkovitch-Verbin, M. Belkin, J. Ilany, U. Polat; Foveal Contrast Sensitivity Assessment in Diabetic Patients Using a Novel Computerized Method. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2895.
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To demonstrate differences between diabetic patients without retinopathy and non-diabetic patients under mesopic and photopic conditions using a simple rapid computerized test for foveal contrast sensitivity (CS).
Nineteen eyes (n=10 patients with type 2 diabetes) without any signs of diabetic retinopathy were included. Ten additional eyes (n=5 non diabetic patients) served as controls. All the eyes had a visual acuity of 20/25 or better. All the patients underwent a careful ophthalmologic examination including ETDRS chart visual acuity, color photographs and optical coherence tomography (OCT). Patients with cataract were excluded. Photopic and mesopic contrast sensitivity was tested using a computerized psychophysical static method involving four forced-choice procedures. The targets were Gabor patches with spatial frequencies of 3-12 cycles per degree (cpd). The mesopic testing was conducted in a completely darkened room; the monitor was covered with a neutral density filter, allowing luminance of only 0.9 cd/m2. Before participation, all subjects provided written informed consent in accordance to the protocol approved by the Helsinki committee.
The average age was similar in both groups - 59.1 years in the diabetic group (range 54-73) vs 62.6 years in the control group (range 58-66). The average duration of diabetes was 16 years (range 6-26).The average visual acuity was 0.05 logMAR and 0.02 in the diabetic and control groups respectively. OCT was diagnosed as normal in both groups.Foveal CS was similar under photopic conditions in both groups. Significantly lower CS was found in diabetic patients under mesopic conditions at the spatial frequency of 3 cycles per degree (cpd) (p<0.012). At higher spatial frequencies the mesopic contrast sensitivities was very low in both groups and without a significant difference.
Mesopic foveal CS is impaired in diabetic patients despite good visual acuity, normal fundus examination and normal OCT. It is suggested that early central visual function impairment may occur in diabetic patients before the appearance of retinopathy. Further research is necessary to establish the role of computerized CS testing in the screening and monitoring of diabetes.
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