Assessment of the Heidelberg Retina Tomograph in the detection of sight-threatening diabetic maculopathy

Purpose: To assess the potential role of the Heidelberg Retina Tomograph (H RT) in screening for sight-threatening macular oedema in diabetes. Methods One hundred and thirty-one eyes of 81 consecutive diabetic patients who fitted the inclusion criteria were included in the study. On HRT, the volume above the reference plane bound within a 2 mm diameter circle centre d at the fovea was measured. The volumetric indices were compared with the mean measurement index in a group of 20 age-matched controls (mean score = 1, mean +2 SD score = 1.8). We also assessed the sensitivity of the subject ive analysis of the intensity image and the addition of the three-dimension al map to the intensity image for detecting macular oedema and clinically s ignificant macular oedema (CSMO). Results One hundred and twelve eyes of 71 patients had a corrected Snellen visual acuity of 6/9 or better. When considering eyes with 6/9 or better vi sion only, the system's sensitivity for detecting CSMO was 58.33% 'per eye' examined, and 81.82% 'per patient' examined using a cut-off volumetric ind ex of 1.8. In our study eyes with 6/9 or better vision, we found a 21% prev alence of CSMO. The predictive values of a positive test were 38.89% and 45 % (cut-off score 1.8,'per eye' and 'per patient' respectively) for CSMO. Th e predictive values of a negative test were 86.84% and 90.48% (cut-off scor e 1.8,'per eye' and 'per patient' respectively) for CSMO. Conclusions The volumetric assessment of diabetic maculopathy by HRT is a p otentially useful method for screening eyes at risk. A larger group of pati ents with a greater number of eyes with minimal or no maculopathy is requir ed to establish the specificity of this technique.