Central retinal thickness measured with HD-OCT shows a weak correlation with visual acuity in eyes with CSME

Aims To investigate the correlation between increased retinal thickness (RT) measured with spectral domain high-definition optical coherence tomography (OCT) (Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, California, USA)) and best-corrected visual acuity (BCVA) in eyes with clinically significant macular oedema (CSME) and type 2 diabetes. Methods Seventy eyes with CSME were included in this observational study. Sixty-two eyes were considered for analysis and were classified as having/not having retinal thickening in the central fovea (central 500-μm-diameter circle) by Cirrus HD-OCT. RT measurements were computed and correlated with BCVA. For comparison purposes, the Stratus OCT (Carl Zeiss Meditec, Dublin, California, USA) central point thickness was also obtained in these eyes. Results In the 19 eyes with CMSE identified by Cirrus HD-OCT without increased RT in the central fovea (500-μm-diameter circle), no correlation was found between RT and BCVA (R=0.062; 95% CI −0.404 to 0.502). In the 43 eyes where the Cirrus HD-OCT identified an increased RT in the central fovea (central 500-μm-diameter circle), only a moderate correlation between RT and BCVA was found (R=−0.459; 95% CI −0.667 to −0.184). Conclusion Correlations between RT and BCVA in CSME are only present when the central 500-μm-diameter circle is involved. However, even in this circumstance, a correlation was found in only 48.8% of the cases. RT cannot, therefore, be used as a surrogate outcome for visual acuity changes.