Measurement of retinal thickness from three-dimensional images obtained from C scan images from the optical coherence tomography ophthalmoscope

Background: One of the unique features of the optical coherence tomography (OCT) ophthalmoscope is that it can record C scan images of the retina. The purpose of this study was to determine the best recording time to measure the retinal thickness with the OCT ophthalmoscope. In addition, the accuracy of the measurements was examined by comparing the values obtained by the OCT ophthalmoscope with those obtained with the Stratus OCT Model 3000 (OCT III) assuming that the OCT III gives an accurate measurement of retinal thickness. Methods: The topography mode of the OCT ophthalmoscope was used. First, the average retinal thickness recorded with 2-s scans was compared with that recorded with 4-s scans for a recording area of 15 degrees x 15 degrees. Next, the average retinal thickness recorded by the OCT ophthalmoscope was compared with that obtained by the Fast Macular Thickness program of the OCT III in patients with macular oedema. Results: The mean retinal thickness of the central area was 208.1 mu m for both 2 and 4 s recording times. The average retinal thickness obtained by the OCT ophthalmoscope was highly correlated and not significantly different from the values obtained by the OCT III. The largest differences obtained by the two instruments were seen in the parts of the retina with accumulation of hard exudates. Conclusions: Accurate measurements of retinal thickness can be obtained with the OCT ophthalmoscope by 2-s scans, and thus, the OCT ophthalmoscope can be a valuable instrument for clinical assessments of retinal thickness.