Background. Retinal thickening can be quantitatively measured by optical coherence tomography (OCT). Imaging of structural retinal changes in diabetic maculopathy allows a qualitative assessment of disease severity and progress. Previous studies indicated that clinically non apparent changes of retinal thickness can be detected by OCT.

Methods. Topographic retinal thickness mapping is performed using six radial 5 mm linear scans rotated at 30 degrees through the center of fixation, obtained by a commercially available OCT unit (Zeiss-Humphrey) with a 820nm superluminescent diode. Color coded maps show mean values of retinal thickness in 9 fields. For detection of early changes in retinal thickness, 20 diabetic patients without (group 1) and 15 patients with diabetic retinopathy (group 2) but without clinical significant macular edema were compared to 25 normal healthy subjects (group 0). 20 patients with established diabetic macular edema were studied for qualitative structural changes in the neurosensory retina.

Results. Retinal thickness topography: Mean thickness was greater in all fields of diabetic patients with retinopathy compared to diabetic patients without retinopathy. Statistically significant differences (Mann-Whitney test) were found between groups 0 and 1 and groups 0 and 2: in the inner nasal field (p=0.027 and p=0.018, respectively) and in the macula (p=0.031 and p=0.013, respectively). Qualitative imaging of diabetic macular edema: Retinal thickness in the presence of maculopathy reaches values of over 500mm. The most common and prominent features is diffuse retinal thickening, intraretinal cystoid spaces and detachment of the neurosensory retina.

Conclusion. There is a difference in retinal thickness of healthy subjects compared with diabetic patients in specific areas around and in the macula even in the absence of clinically significant macular edema. OCT produces specific images of the structural changes of the retina in diabetic macular edema. Both quantitative measurement of retinal thickness and qualitative imaging can be used as a tool for the assessment of disease severity and progress in diabetic retinopathy.