Foveal thickness measured with Heidelberg Retina TomographTM and optical coherence tomography

Abstract

Abstract Purpose To evaluate the test‐retest variability of foveal thickness measurements using the Heidelberg Retina Tomograph 3 (HRT) and optical coherence tomography (OCT) Methods 28 subjects were recruited among staff and students at St. Erik Eye Hospital. They all had decimal visual acuity ≥ 1.0, refractive error ≤ 12 D and no ophthalmic disease. Retinal thickness was measured using the HRT3 Retinal Module version 2.0 and OCT Stratus model 3000. The measured area (3.45 mm Ø) is divided in a 9‐zone grid which is used when analyzing the results. The grid consists of 3 circles; in the current study only data from the central circle is (1 mm in diameter) was used for the analysis. All subjects were examined by two experienced examiners at two different occasions. Four different images were obtained and compared according to the following schedule: I. Intraobserver/intravisit II. Interobserver/intravisit III. Intraobserver/intervisit IV. Interobserver/intervisit Results Mean foveal thickness for all subjects was 258.28 µm ± 24,16 SD measured with the HRT and 201.86 µm ± 4.76 SD with the OCT. There were no significant differences in foveal thickness between any of the five examinations. The coefficient of variation was significantly larger in the HRT measurements compared with the OCT (p= 0.029) Conclusion The repeatability between examinations was high for both the HRT and the OCT. However, the coefficient of variation was significantly smaller for the OCT, which may indicate that it is easier to detect and/or follow small changes in foveal thickness using this method.