Entoptic foveal avascular zone measurement and diabetic retinopathy

Background: Entoptic visualization of the foveal avascular zone (FAZ) provi des a noninvasive method for measurement of the FAZ, To determine if repeat ability of measurement with this technique is good enough to monitor change s in diabetic retinopathy, we quantify (1) the repeatability of entoptic FA Z measurement in healthy subjects and (2) the relationship between measured FAZ diameter and the severity of retinopathy, Methods: (1) To determine FA Z measurement repeatability, 10 healthy adults entoptically measured their FAZ diameters in 11 separate testing sessions. (2) In a separate experiment , 53 patients with varying levels of diabetic retinopathy and 21 control su bjects used a vascular entoptoscope to measure their FAZ diameters, Results : The disease-related increase in FAZ diameter is large (approximately 400 mu m) compared to the repeatability of the entoptic measurement within a su bject (SD approximate to 35 mu m). Conclusion: Entoptic measurements have t he repeatability necessary to reliably monitor increases in FAZ diameter of the magnitude of those induced by diabetes.