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-microm-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-microm-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-microm-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-microm-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.