Unmeasurable small size superficial and deep foveal avascular zone in nanophthalmos: the Collaborative Nanophthalmos OCTA Study

Aim To study the macular structure and vasculature in consecutive nanophthalmic eyes using optical coherence tomography angiography. Methods This is a prospective, multicentre, cross-sectional study of patients with nanophthalmos (one or both eyes). The superficial and deep foveal avascular zones (FAZ) were measured both manually and with the machine's built-in automated measurement tool. Correlations between best corrected visual acuity (BCVA), central macular thickness (CMT) and subfoveolar choroidal thickness (SFCT) were calculated. Results Sixty-five eyes of 35 subjects (16 men and 19 women) with a mean age of 37.4 years were analysed. The mean +/- SD of refractive error was 14.3 +/- 3.2 dioptres, axial length was 16.4 +/- 1.6 mm, CMT was 410.2 +/- 128.3 mu m and SFCT was 450.1 +/- 108.3 mu m. FAZ was unmeasurable small size in both the superficial and deep capillary plexus in all eyes, along with tortuosity of the superficial foveal capillaries and large vessels. Foveal folds were present in 29 eyes. Disc drusen was detected in 27 eyes and was absent in 31 eyes, while fundus autofluorescence was positive in 17 and negative in 24 eyes. BCVA varied from 20/20 to 20/800, with a mean of 20/76. Using Spearman's correlation, logarithm of the minimum angle of resolution BCVA correlated negatively with axial length (r=-0.30; p=0.015). Conclusions FAZ attenuation, capillary tortuosity, foveal folds and thickened subfoveal choroid characterise the nanophthalmic macula. These findings may result from a redundant retina and the absence of apoptotic foveolar retraction because of developmental arrest of the optic vesicle after closure of the embryonic fissure.