Sectoral Changes in Neuroretinal Rim Pallor Across Refractive Error.

PURPOSE

To investigate the association between spherical equivalent refraction (SER) and pallor in different neuroretinal rim (NRR) sectors.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

Normal eyes of 24 057 healthy participants aged 40 to 70 years from the UK Biobank.

METHODS

Pallor in different NRR sectors was quantitatively derived from color fundus photographs using automated software. We first examined the association between SER and pallor in each NRR sector-controlling for age, sex, ethnicity (White vs. non-White), intraocular pressure, and mean blood pressure. We then incorporated disc-fovea distance (the shortest distance from the center of the disc to the fovea) and temporal arterial/venous concavity (extent to which the temporal artery/vein curved inwardly toward the fovea) as additional independent variables, as these features have been suggested to reflect the degree of axonal stretching at the posterior pole.

MAIN OUTCOME MEASURES

Pallor in the temporal, temporal inferior, nasal inferior, nasal, nasal superior, and temporal superior sectors of the NRR.

RESULTS

Moving from the temporal sector to the temporal superior sector, NRR pallor varied in an asymmetrical U-shaped pattern, with the least pallor observed nasally. White participants tended to have paler NRR, but the association between SER and pallor did not differ between ethnic groups (no interaction effect between SER and ethnicity). Decreasing SER was associated with increasing pallor in all 6 NRR sectors (all  < 0.001), but the temporal (ß: -0.009, 95% confidence interval: -0.011 to -0.008) and temporal inferior (ß: -0.008, 95% confidence interval: -0.009 to -0.007) sectors exhibited the steepest increase. The rate of increase diminished by half toward the more nasal/central sectors, and by another half in the nasal-most sector. Consistent with these changes, increasing disc-fovea distance and temporal arterial/venous concavity resulted in up to 4 times as much pallor temporally compared with nasally. These retinal changes accounted for approximately ≥50% of the effect of SER on NRR pallor.

CONCLUSIONS

Decreasing SER increases NRR pallor approximately 4 times faster temporally than nasally. The association between SER and NRR pallor is primarily attributable to changes in disc-fovea distance and temporal arterial/venous concavity. These findings suggest that the papillomacular nerve fiber bundle, linked to the temporal NRR, is most susceptible to myopic stretching.

FINANCIAL DISCLOSURES

The author(s) have no proprietary or commercial interest in any materials discussed in this article.