A patient’s spherical equivalent (SE) refractive error could throw off your diagnostic accuracy for glaucoma when using OCT, a new report shows. Not to worry, though, as the investigators explained how this effect could be mitigated using controls with similar refractive characteristics.

The team looked at the cases of 758 eyes from 502 primary open-angle glaucoma (POAG) patients and an additional 1,592 eyes from 1,076 healthy controls. They evaluated OCT imaging to assess their retinal nerve fiber layer (RNFL) parameters and compared them with the subjects’ visual field (VF) mean deviation from standard automated perimetry. They found RNFL thickness significantly decreased with age and increased with SE in both healthy controls and glaucoma patients. However, they noted that, in healthy subjects with refractive errors, the temporal RNFL appeared significantly thinner.

RNFL measurements significantly decreased with VF mean deviation in subjects who had POAG. Upon subgroup analysis, the researchers found that only SE showed any significance, as SE area-under-the-curve increased with glaucoma severity, most notably for the global, inferior and superior measurements.

Overall, the diagnostic performance of the inferior and global RNFL measurements were the least affected by different factors, the researchers said in their paper. In addition, OCT’s diagnostic accuracy increased with disease severity.

“These factors should be considered when using OCT for glaucoma diagnosis in practice,” they concluded.

Wong D, Chua J, Baskaran M, et al. Factors affecting the diagnostic performance of circumpapillary retinal nerve fibre layer measurement in glaucoma. Bri J Ophthalmol. May 5, 2020. [Epub ahead of print].