Entoptic foveal avascular zone measurement and diabetic retinopathy.

Background: Entoptic visualization of the foveal avascular zone (FAZ) provides a noninvasive method for measurement of the FAZ. To determine if repeatability of measurement with this technique is good enough to monitor changes in diabetic retinopathy, we quantify (1) the repeatability of entoptic FAZ measurement in healthy subjects and (2) the relationship between measured FAZ diameter and the severity of retinopathy.

Methods: (1) To determine FAZ 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 subjects used a vascular entoptoscope to measure their FAZ diameters.

Results: The disease-related increase in FAZ diameter is large (approximately 400 microm) compared to the repeatability of the entoptic measurement within a subject (SD approximately 35 microm).

Conclusion: Entoptic measurements have the repeatability necessary to reliably monitor increases in FAZ diameter of the magnitude of those induced by diabetes.