RNFL Thinning May Best Indicate Structural Changes in Glaucoma

Retinal nerve fiber layer (RNFL) thinning may be a better indicator of structural deterioration in moderate to advanced glaucoma than Bruch membrane opening- minimum rim width (BMO-MRW), according to a study published in the American Journal of Ophthalmology.

Researchers sourced data from the Advanced Glaucoma Progression Study (ClinicalTrials.gov Identifier: NCT01742819), an ongoing, prospective, longitudinal study conducted at the University of California, Los Angeles. The team included 113 participants (mean age, 67.7 years; 62% women) with moderate to advanced glaucoma or central damage who underwent longitudinal optical coherence tomography (OCT) scans to evaluate change rates for RNFL and BMO-MRW thicknesses.

At baseline, mean global RNFL thickness was 60.3 mm, BMO-MRW thickness was 154.3 mm, BMO area was 1.90 mm², and 24-2 visual field mean deviation was -9.2 dB.

The estimated average RNFL thinning ranged from 0.91 mm per year in the inferonasal region to 0.42 mm per year in the temporal region. BMO-MRW thinning ranged from 1.41 mm per year in the temporal region to 0.72 mm per year in the inferonasal region. The overall change rates were -0.64 mm per year and -1.1 mm per year for the RNFL and BMO-MRW thicknesses, respectively.

The report shows a greater proportion of negative change rates for the RNFL in the inferonasal (42% vs 17%; P <.001) and inferotemporal (35% vs 20%; P =.015) sectors and fewer positive changes in the inferotemporal sector (2.6% vs 9.7%; P =.04) compared with BMO-MRW.

The longitudinal signal to noise ratio was significantly more negative for RNFL than for BMO-MRW globally (P =.007), and in the inferonasal (P <.001), inferotemporal (P <.001), and superonasal (P <.001) sectors.

“Since the introduction of the BMO-MRW as the preferred measure for assessing the neuroretinal rim with OCT in glaucoma, there have been studies exploring the utility of this measurement for detection of glaucoma, evaluating structure-function relationships, and identifying structural glaucoma deterioration.” the study authors explain. “The latter task is highly relevant clinically as timely detection of structural changes in glaucoma patients can pave the way for an earlier change in treatment and prevention of glaucoma
progression.”

This study may have been limited by the assumption that longitudinal change in the RNFL and BMO-MRW thicknesses are linear.

Disclosure: This research was supported by Heidelberg Engineering. Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.