Spectral-domain OCT is quickly becoming an integral part of the glaucoma evaluation, as it can objectively measure and detect structural changes indicative of the disease years before functional visual field loss is observed. However, clinicians who use neuroretinal rim structural imaging need to know how to distinguish normal changes from those associated with glaucoma. A new study shows certain neuroretinal rim parameters are affected by age and race, but not necessarily sex, and clinicians should interpret their OCT findings carefully.

An international team of researchers recently discovered that the neuroretinal rim minimum distance band (MDB) thickness—a three-dimensional band comprised of the shortest distance between the ILM and the termination of the RPE/Bruch’s membrane complex—decreased significantly with age, was thinner for African Americans than Caucasians and was comparable between females and males.

The study evaluated 256 normal subjects who underwent high-density SD-OCT optic nerve head volume scans. One eye was randomly selected and analyzed for each subject. Neuroretinal rim MDB thickness values were calculated, and global and quadrant neuroretinal rim thickness values were determined. 

The team found that mean MDB thickness was 278.4±47.5μm. They note that thickness decreased at a rate of 0.84μm per year after adjusting for age, race and sex. They add that African Americans had thinner MDBs compared with Caucasians, while males and females had similar MDB thickness values. Hispanics had the highest average MDB thickness of (286.2±57.7μm), while African Americans had the lowest with an average of 258.6±57.5μm. 

Of note: the researchers also found only 28% of the normal studies eyes followed the ISNT rule—the mnemonic used to delineate typical rim thicknesses based on location. 

“We believe that the results of this study can better inform clinicians on how to account for the effect of normal aging when analyzing MDB thickness measurements over years,” the study authors concluded in their paper.

Antar H, Tsikata E, Ratanawongphaibul K, et al. Analysis of neuroretinal rim by age, race, and gender using high-density three-dimensional spectral domain optical coherence tomography. J Glauc. October 9, 2019. [Epub ahead of print].