Researchers recently discovered that sex had a substantial effect on retinal nerve fiber layer (RNFL) thickness at 56.8% of 768 circumpapillary locations. Over large regions, this effect was at least as important in explaining RNFL thickness variance as was age—a well-established risk factor for such variations.

This population-based, cross-sectional study investigated 5,646 eyes of 5,646 healthy subjects, of which 54.8% were female. All participants underwent standardized systemic assessments, ocular imaging and circumpapillary RNFL thickness measurements at 768 points equidistant from the optic nerve head.

The team found that the global nerve fiber thickness was 1μm greater in females than males; however, detailed analysis at each of the 768 locations revealed substantial location specificity of the sex effects, with RNFL thickness deviations ranging from -9.98μm to +8.00μm. They note that females had significantly thicker RNFLs in the temporal, superotemporal, nasal, inferonasal and inferotemporal regions (43.6% of the 768 locations), while males had a significantly thicker RNFL in the superior region (13.2%). The results were similar after adjusting for age, body height and scanning radius.

The investigators also learned that the superotemporal and inferotemporal nerve fiber layer peaks were temporally shifted in females by 2.4° and 1.9°, respectively. In regions with significant sex effects, the finding explained more variance than did age; whereas the major peak locations and interpeak angle explained most of the RNFL variance otherwise unexplained by sex differences among subjects.

Including consideration of the patient’s sex in RNFL analysis “could therefore improve glaucoma diagnosis and monitoring,” the study authors concluded in their paper.