Identifying better and more equitable biomarkers for disease monitoring is an ongoing project. Recently, researchers have shown that Bruch’s membrane opening (BMO) rim width is more useful than retinal nerve fiber layer (RNFL) thickness for monitoring eye health in neuromyelitis optica (NMO) and multiple sclerosis (MS), as it isn’t ethnicity-dependent.

NMO and MS are both demyelinating autoimmune diseases of the central nervous system. Typically, they present with decreased RNFL and ganglion cell layer (GCL) thicknesses, with RNFL thinning more significant in NMO. BMO is primarily studied in glaucoma, and it’s been demonstrated to be a reproducible, efficient and relevant biomarker for monitoring glaucoma progression at different stages. “The BMO measures are correlated with loss of visual function and aging but unlike the RNFL, are not related to ethnicity,” the researchers said in their paper on the study.

They evaluated BMO in 34 eyes of 25 patients with NMO and in 70 eyes of 50 patients with MS. They also included a control group of 100 eyes of 51 subjects. Specifically, the researchers studied the structure-function relationship with the correlation between OCT and visual function.

Average BMO thickness was significantly reduced in NMO and MS, with or without a history of optic neuritis (ON), the researchers noted. In the absence of ON in NMO, they noticed significant thinning in the average, nasal and inferonasal BMO compared with the control group.

“To the best of our knowledge, this is the first study evaluating the correction between BMO and different areas of the visual field during demyelinating disease,” they wrote in their paper. “A high correlation was found, as for RNFL and GCL in similar studies of patients with or without a history of ON. Essentially studied during glaucoma neuropathy, the correlation between BMO and macular degeneration is at least close to or sometimes better than RNFL.”

They concluded that with its high correlation with visual function, optic nerve fiber and RNFL and GCL thickness, and its lack of variation among different ethnicities, BMO demonstrates an “improved ability” over the RNFL and GCL to “detect infraclinical impairment in patients with NMO, without a history of optic neuropathy.”

Bechet L, Cabre P, Merle H. Bruch membrane opening minimum rim width in neuromyelitis optica. N Am Neuro-Ophth Soc. 2021;1-8.