To define regional patterns of macular thickening in diabetic macular edema (DME).

Retrospective case series.

setting: Retina practice. patient population: Fifty-two normal eyes of 48 patients and 100 eyes of 80 patients with DME. experimental procedure: We measured retinal thickness for nine zones and total macular volume using the 3.5-mm display of an optical coherence tomograph (OCT). We determined the normal ranges of values for zones, and then normal ranges of values for the difference in thickness between each pair of zones, termed comparisons. main outcome measures: Frequencies of increased zonal thickness, increased total macular volume, and abnormalities in zonal comparisons.

We found the following abnormalities: increased total macular volume 49% (49/100), increased foveal zone thickness 46% (46/100), increased inner parafoveal zone thickness (average 42.2% for the four zones), and increased outer zone thickness (average 34.3% for the four zones). Abnormal two-zone comparisons were found in 1027 of the 7200 possible comparisons (14.3%). Of these abnormal comparisons, the fovea was thicker relative to another zone in 26%; the four inner parafoveal zones were thicker relative to other zones in 8.7% to 15.2% (average 13.0%); and the four outer zones were thicker relative to other zones in 3.9% to 7.6% (average 6%). Eighty-eight percent (88/100) of the eyes chosen on clinical grounds as needing focal laser photocoagulation were detected.

A broader concept of OCT abnormality, which includes abnormalities in zonal relationships, may improve automated detection of DME compared with clinical judgment.