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P. Baptista, S. Nunes, J. Figueira, R. Bernardes, J. G. Cunha-Vaz; Correlation Between Central Macular Thickness and Visual Acuity Loss in Type 2 Diabetic Patients With Macular Edema. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4999.
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© ARVO (1962-2015); The Authors (2016-present)
To establish the correlation between visual acuity (VA) and retinal thickness (RT) in patients with macular edema involving the central region of the macula and to compute the risk for VA loss.
Forty-two eyes with CSME underwent RT measurements (by RTA II), and VA assessment (BCVA by ETDRS scale) just before receiving laser photocoagulation. Using a proprietary software, RT maps of 60 areas (56 areas of 1/9 optic disk area in 3 concentric rings plus 4 areas of 1/36 optic disk area in the central 500 microns in diameter) were calculated and compared to a normative database to compute maps of increased RT (over the mean + 2SD of a reference population). RT values, maximum % of increased RT (MPRT) over the reference map and area of increased RT, in the foveal region (within 500 microns in diameter) and in the perifoveal region (within radii 250 and 750 microns) were correlated with VA using the Spearman correlation coefficient.Cut-off values for each of the considered RT parameters were established for VA loss and statistical significant differences in VA between these groups (over and below the cut-off values) were tested by the Wilcoxon test. The risk for VA loss (below 80 letters) was thereafter computed for the respective groups using the Odd Ratio (OR).
The correlation between VA loss and RT is stronger when the MPRT is located in the fovea (R=0.463, p=0.002) compared to a MPRT in the perifovea (weak correlation, R=0.308, p=0.047). This correlation gets stronger when the MPRT is over 25% from the reference map (R=0.578, p=0.005). The risk for VA loss for these eyes is 4 times higher than for the eyes with a lower MPRT (OR=4.083, 95%CI=[1.122-14.863]). When the MPRT is located in the perifovea the risk for VA loss is lower and not statistically significant (OR=3.400, 95%CI=0.901-12.825]).
There is a good correlation between the increase in RT and VA loss when the edema is located in the fovea and the MPRT value is 25% over the reference (mean + 2SD of a reference population). For these eyes the risk for VA loss becomes 4 times higher.
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