Characteristics of the capillary-free zone in the normal human macula.

The dimensions of the foveal avascular zone (FAZ) were determined on fluorescein angiograms in 45 normal subjects, 25 men and 20 women, by means of a digital image processing system. The shape of the FAZ was usually irregular and showed considerable individual variations. The mean longest diameter was 0.88 +/- 0.16 mm (SD), the horizontal diameter was 0.73 +/- 0.15 mm, vertical diameter was 0.70 +/- 0.17 mm and the area averaged 0.43 +/- 0.16 mm2. The area of the FAZ and the age of the subjects showed a statistically significant positive correlation (r = 0.383, P less than 0.005). The enlargement of the FAZ with advancing age may be related to senescent changes of the retinal capillaries. It was stressed that it is of importance to measure the size of the FAZ by fluorescein angiography before laser photocoagulation is carried out near the macular region.