Functional visual assessment in diabetic patients at stages pre- and post- diabetic retinopathy.

Author(s)

Mirella Gualtieri

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Psicologia (IP/SBD)
• Defense date: 2009-09-03

Examining board members

Dora Selma Fix Ventura; Adriana Berezovsky; Augusto Paranhos Júnior; Luiz Carlos de Lima Silveira; Walter Yukihiko Takahashi

• Advisor: Dora Selma Fix Ventura

Abstract

The present study evaluated different aspects of visual function in type 2 diabetics both with and without retinopathy. The approach was to evaluate vision at several levels of the visual system by means of application of a battery of modern, sensitive psychophysical and electrophysiological tests. The goals were to characterize the changes in visual function underlying the disease prior to the onset of retinopathy, and to verify how the early losses are affected once retinopathy has occurred. Materials and methods: 31 diabetic patients with non-proliferative retinopathy (15 , 16 ; age = 59 ± 09 years; duration of diabetes = 10 ± 06 years); 36 diabetic patients without retinopathy (16 , 20 ; age = 56 ± 11 years; duration of diabetes = 06 ± 04 years) and 30 controls (13 , 17 ; age = 44 ± 10 years) were evaluated with: (1) multifocal electroretinogram - mfERG; (2) achromatic contrast sensitivity segregated into magno- (MC) and parvocellular (PC) pathways Pedestal test; (3) white-onwhite and blue-on-yellow computerized visual perimetry and (4) quantitative computerized color vision test Cambridge Colour Test (CCT). An ANOVA was performed for the statistical comparison among groups and ROC curve analysis was used to compare the diagnostic power of the different tests. Results: both diabetic patient groups manifested significant functional losses compared to controls in the mfERG, the Pedestal test and the CCT. In the mfERG, both patient groups had significantly smaller amplitudes and longer latencies than controls in one or more of the signature mfERG waveform components. For the Pedestal Test, both patient groups manifested losses in both the M-targeting and P-targeting paradigms. The CCT chromatic discrimination test found significant losses along all three color confusion axes (protan, deutan, tritan) in both patient groups. In the visual fields, only the patients with retinopathy exhibited significant losses compared to controls. In the comparison between patients with and without retinopathy, no statistical differences between results were found, except for some of the mfERG latencies and the color discrimination in the tritan axis. The ROC analysis showed that the mfERG had the higher combined sensitivity and specificity indexes, followed by the CCT, pedestal test and perimetry with decreasing indexes in this order. Conclusions: statistically significant losses were found in psychophysical and electrophysiological assessment of visual function of type 2 diabetic patients with and without diabetic retinopathy. The present work strongly confirms the growing body of evidence that functional losses with neural etiology occur in type 2 diabetes before any vascular changes are clinically detectable in the retina. In the majority of the measures, the presence of retinopathy increased the functional losses, but did not determine significant differences in relation to the losses observed in the diabetics with normal fundus. According to our results from the Pedestal Test and the Cambridge Colour Test, the neural damage is not selective to either of the visual processing pathways. The results are consistent with the hypothesis that diabetes is a neurodegenerative disease of the retina whose establishment may occur even in the presence of retinopathy. Thus, the assessment of functional status rather than morphological examination seems a better approach to identify diabetic patients under vision threat. (AU)