European Journal of Ophthalmology / Vol. 12 no. 2, 2002 / pp. 102-108 PURPOSE. To define the normal retinal thickness in healthy subjects using optical coherence tomography (OCT) mapping software and to assess the ability of OCT to detect early mac- ular thickening in diabetic patients. METHODS. Six radial scans centered on the fixation point were done on 60 healthy eyes and 70 eyes of 35 diabetic patients without macular edema on biomicroscopy. Retinal thickness was measured automatically with OCT mapping software. Mean retinal thickness was com- pared in subgroups of healthy patients based on age, sex, and eye, and in the eyes of dia- betic patients and healthy subjects. Thickening was diagnosed if mean retinal thickness of an area was greater than the mean thickness + 2SD in the corresponding area in healthy subjects; or if the difference between right and left eye exceeded the mean difference + 2 SD in a given area in healthy subjects. RESULTS. In healthy subjects, mean retinal thickness in the central macular area 1000 μm in diameter was 170±18 μm. There was no significant difference according to age, or left or right eye, but central macular thickness was significantly greater in men than women (p=0.0139). No difference was observed between the eyes of healthy subjects and diabetic patients without macular edema on biomicroscopy, but OCT detected early macular thickening in 12 diabetic eyes. CONCLUSIONS. In this study average retinal thickness and mean local variations in a normal population were defined using a commercially available mapping software. OCT seems a sensitive tool for detecting early retinal thickening. (Eur J Ophthalmol 2002; 12: 102-8) KEY WORDS. Optical coherence tomography, Diabetic retinopathy, Macular edema, Retinal thickness Accepted: January 21, 2002 Retinal thickness in healthy and diabetic subjects measured using optical coherence tomography mapping software INTRODUCTION Macular edema is the expression of many macular diseases and various treatments are being tested. Un- til recently, the methods available for assessing mac- ular thickness were slit-lamp biomicroscopy and stereoscopic photography, which unfortunately do not give a quantitative measurement. In recent years, new methods of measuring retinal thickness have been de- veloped (1-5). Optical coherence tomography (OCT) is based on low-coherence interferometry and gives optical cross-sectional images of the eye (4, 5). It en- ables retinal thickness to be measured from tomo- grams by computer image processing. Since the com- mercialization of OCT equipment (Humphrey Company, San Leandro, CA) several softwares have become avail- able. A5 software can display a two-dimensional colour- coded map of retinal thickness in the posterior pole, P. MASSIN 1 , A. ERGINAY 1 , B. HAOUCHINE 1 , A. BEN MEHIDI, M. PAQUES 1 , A. GAUDRIC 1 Department of Ophthalmology, Hôpital Lariboisière, Assistance Publique - Hôpitaux de Paris, Université Paris 7, Paris - France 1120-6721/102-07$03.50/0 © Wichtig Editore, 2002