[Concordance of two retinal mapping techniques to detect diabetic macular edema]

Optical coherence tomography quantifies retinal thickness, localizes diabetic macular edema (DME), and determines whether it implies visual risk. Evaluation is standardized by the macular mapping technique in two versions: 6 mm and 3.45 mm. The latter version measures with greater detail the zone adjacent to the central 1000 microm but does not evaluate the entire macula. Concordance between maps was evaluated in order to define which version better evaluated DME prospectively.

The rate and 95% confidence intervals (95% CI) of eyes with DME, which had thickening adjacent to the central 1000 microm, was identified in fields of the 6-mm map and in the corresponding fields of the 3.45-mm map. The disparity between rates was identified using McNemar test, and concordance between fields was determined using kappa coefficient.

The rate of thickening in the studied area ranged from 31.9 to 50% with overlapping 95% CI between corresponding fields. Although significant differences existed (p <0.05), there was good concordance for 3/8 comparisons and very good concordance in five.

Information generated by the 6-mm macular mapping was as valid as that generated by the 3.45 mapping to identify thickening adjacent to the central 1000 microm. We recommend using the 6-mm mapping prior to surgery because it has the advantage of completely measuring the macula.