RNFL thinning correlated to OSA severity
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The severity of obstructive sleep apnea may be associated with the thinning of the superotemporal retinal nerve fiber layer, according to findings published in the Journal of Glaucoma.
Samantha Sze-Yee Lee, PhD, of the University of Western Australia’s Centre for Ophthalmology and Visual Science and the Lions Eye Institute, and colleagues explored the differences in optic disc measurements that may resemble preclinical glaucomatous changes in relation to obstructive sleep apnea status and severity.
“Within the past decade, contemporary versions of OCT now have the capacity to measure the minimum rim width at the Bruch membrane opening [BMO]-minimum rim widths [MRW], which has been suggested as being more sensitive for detecting early glaucoma than the RNFL [retinal nerve fiber layer] thickness,” Lee and colleagues wrote. “Yet, the link between BMO-MRW and OSA [obstructive sleep apnea] has not been investigated.”
The researchers examined data from participants of an at-home sleep study (n = 865; 45% men) where apnea-hypopnea index [AHI] and sleep oxygen saturation levels were measured. The participants’ OSA status ranged from AHI with less than 5 events per hour to more than 30 events per hour.
At a 6-year follow up visit, the optic discs of participants were imaged using spectral domain OCT to measure the Bruch membrane opening minimum rim widths and RNFL thickness, investigators wrote.
They identified that on the basis of AHI, 48% of participants had OSA, with 11% of that population receiving a diagnosis of moderate OSA. Also, within the group with OSA, 3% had severe OSA.
Participants with severe OSA had thinner RNFL superotemporally compared with participants without OSA or with mild OSA, (P < .001 for both), Lee and colleagues wrote. Superotemporal RNFL was also inversely associated with AHI (P = .004) and a sleep time with oxygen saturation level less than 90% (P = .005), they said.
“Our findings do not provide strong evidence of a link between measures of OSA and the optic disc,” Lee and colleagues wrote. “However, the association between OSA severity and thinner superotemporal RNFL has been reported consistently in previous studies and thus warrants further evaluation.”
Perspective
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Doug Rett, OD, FAAO
The first thing that I noticed about this study is that their age cohort was not nice, round numbers like 50 to 70 years, but instead the societal construct of the Baby Boomer generation. This was a first for me reading medical literature, and I found it interesting. The second thing that impressed me with this study is the length of time they waited between first confirmation of OSA and when they performed the OCT analysis of optic nerves. Six years is a long time and a strength of the study, allowing one to assume that if there are causative changes that occur due to OSA, then this study would catch them.
Yet there were no statistically significant changes in minimum rim width (MRW) between any group, and the only difference was in one quadrant in the RNFL scan. I’ve found MRW much more clinically relevant compared with RNFL, so this is a telling finding for me. But the practicing eye doctor should remember that lack of a positive correlation does not mean the study was not important. I will recall this study in clinical practice to remind myself the effects of OSA on the optic nerve are not well-correlated and perhaps best described as noisy data in the din of so many glaucoma quasi-correlations.
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