Retinal Nerve Fiber Bundle Damage Indicated by Reflectance Defects

Objectively-detected retinal nerve fiber bundle (RNFB) defects have strong concordance with conventional circumpapillary retinal nerve fiber layer thickness (cpRNFLT) and perimetry, according to research published in Ophthalmology Retina.

Investigators enrolled 16 patients with glaucoma who had early to moderate vision loss and 29 healthy control individuals in the cross-sectional analysis. All participants underwent cpRNFLT scans, visual field examination, and wide-field optical coherence tomography (OCT). Researchers assessed en face reflectivity using a summary of multiple anatomically-adjusted slabs (SMAS) and declared en face defects concordant with cpRNFLT if they had at least 1 cpRNFLT point with P <1%, within ±15° of the predicted insertion on the optic disc. The primary objective was to examine how RNFB reflectance defects correlate with cpRNFLT and visual field defects in en face OCT.  

Researchers assessed participants’ visual fields using 2 perimetric strategies and measured agreement in each participant. Corresponding reflectance in visual fields was classified as abnormal if en face superpixels within ±1° were abnormal.

Overall, standard automated perimetry defects and normal reflectivity were observed in approximately 25% of cases with poor agreement. In approximately 75% of cases,  reflectance loss could be subjectively detected in en face images. Further refinement of SMAS analysis could aid concordance, according to the report.

Both perimetric strategies demonstrated moderate-good raw agreement with en face analysis. Normal findings (0.77-0.78) had stronger agreement compared with defects (0.4-0.44).

“This study further validated SMAS analysis of en face images by establishing correspondence between reflectance abnormalities and conventional measures of glaucoma damage,” according to the investigators. “A framework to objectively assess pointwise relationships between structure-structure and structure-function was introduced. The majority of retinal locations with abnormal reflectance presented a matched cpRNFL thickness defect at the estimated insertion on the [optic nerve head].”

Study limitations include the use of different scans to convert en face imaging from superpixels to degrees and a small sample size.

Disclosure: One study author declared an affiliation with biotech, pharmaceutical, and/or clinical research organizations. Please see the original reference for a full list of authors’ disclosures.

Reference

Cheloni R, Denniss J. Concordance of objectively-detected retinal nerve fiber bundle defects in en face OCT images with conventional structural and functional changes in glaucoma. Ophthalmol Glaucoma. Published online July 12, 2022. doi:10.1016/j.ogla.2022.07.001