Comparing retinal thickness and Matrix 10-2 functional testing in diabetic macular edema

Abstract

Purpose : Diabetic macular edema (DME) is commonly managed based upon visual acuity (VA) and retinal thickness. But the patients with early-stage off-centre macular edema and good visual acuity also had significant central sensitivity loss, suggesting we should more often include functional testing in our decision making for the treatment. We conducted this study to do point-by-point comparisons of OCT macular thickness and Matrix 10-2 data in early off-centre DME.

Methods : We tested both eyes of 23 Type-2 diabetes (T2D) patients with mild off-centre DMO in at least one eye. Matrix 10-2 perimetry, with its 2x2 degree stimuli, assessed the function. Spectralis 8x8 macular thickness grid data was mapped to the 44 10-2 regions to allow point-by-point structure-function analysis (see attached Figure). We also collected the standard ETDRS retinal thickness data.

Results : Of 23 patients, 14 were males. The mean age was 60.6 ± 9.7 years, diabetes duration 11.4 ± 7.7 years, HbA1c 7.62 ± 1.43, and ETDRS VA 82.5 ± 6.5 (20/25). The median Martrix MD and PSD were -14.7 and 6.0 (median p=0.005). Central maximum thickness was 320 ± 27 um. For the central 16 10-2 points for left and right eyes, of thicker and thinner than median thickness locations, the correlation with sensitivity ranged from 0.07 ± 0.16 to -0.38 ± 0.25, only 9 of 44 (18.8%) correlations being significant. Stepwise linear models found that BCVA was determined mainly by Matrix MD and ETDRS retinal thinness variables for 3 and 6 degrees, but not central thickness (OS and OD r2= 0.84 and 0.85). Pearson correlations between BCVA and Matrix MD, PSD, and central, 3 and 6 degree ETDRS thicknesses, only showed significant correlation with Matrix MD (r= -0.58, p<e-5).

Conclusions : Despite significant sensitivity loss there was little correlation with increased retinal thickness due to DME, suggesting functional loss preceded the structural change. Surprisingly BCVA was mainly determined by off-axis thickness and average 10-2 sensitivity loss, and not central thickness. Functional testing may be useful in diagnosing early complications even before structural and clinical changes.

This is a 2020 ARVO Annual Meeting abstract.

 

A) Median retinal thickness of left eyes, mapped onto the Matrix grid. B) Median Matrix sensitivities. C) Correlations between sensitivity and thickness, > abs(0.45) is significant.