Comparison of foveal thickness measured with the retinal thickness analyzer and optical coherence tomography

Purpose: To assess and compare the reliability and reproducibility of retinal thickness measurements for the retinal thickness analyzer (RTA) and optical coherence tomography (OCT) in normal and edematous retina. Methods: The authors measured the foveal thickness of 21 normal eyes and 9 eyes with macular edema with both methods in random order. With the RTA, the fovea was measured 10 times; with the OCT, six scans (one horizontal and five vertical cross-sections) of the fovea were obtained. Results: Mean foveal thickness of normal eyes measured 153 gm with OCT and 181 gm with RTA (median for both methods 150 km). Coefficients of variation (CV) within the same subjects were 10% (OCT) and 9% (RTA) reducing to 9% (OCT) and 7% (RTA) when scans were repeated only five times for both methods. The RTA, however, yielded an interpatient CV of 33% (OCT 17%), which was caused by several falsely high readings in normal individuals. In eyes with retinal thickening the OCT measured a mean of 324 mum with 15% intra- and 58% interpatient CV, The RTA yielded a mean of 403 mum with CV of 18% and 73%, respectively. Conclusion: Both methods yield reproducible measurements of foveal thickness in normal individuals and individuals with macular edema. However, falsely high measurements may occur with the RTA, reducing its reliability as compared to the OCT.