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Editors Selection IGR 13-2

Anatomical Structures: Sleep apnea syndrome and RNFL thickness

Comment by Robert Fechtner on:

45877 Decreased retinal nerve fiber layer thickness in patients with obstructive sleep apnea/hypopnea syndrome, Lin P-W; Friedman M; Lin H-C et al., Graefe's Archive for Clinical and Experimental Ophthalmology, 2011; 249: 585-593

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This article by Lin et al. (872) adds to the body of work by the authors regarding sleep apnea and glaucoma. Sleep apnea and an optic neuropathy that resembles glaucoma have been linked. The underlying causative mechanism of optic neuropathy in sleep apnea remains incompletely explored. It is not clear to me whether this is 'another glaucoma' or deserves its own diagnostic category. In the current study, Lin et al. recruited a population with daytime sleepiness and snoring that underwent polysomnography to determine severity of obstructive sleep apnea/hypopnea syndrome (OSAHS). They then underwent ophthalmic evaluation including OCT examination with Stratus OCT (Carl Zeiss Meditec Inc.) Of 127 subjects studied 22 were classified as not having OSAHS. These served as controls. Those diagnosed with OSAHS were classified as mild or severe.

Patients diagnosed with sleep apnea should be referred for ophthalmic evaluation

Three measurements were obtained for RNFL and the fast RNFL algorithm was used to calculate thickness. ONH measurements were obtained by the fast optical disk scanning protocol. Macular thickness measurements were obtained by the fast macular thickness protocol. No significant differences were detected for ONH or macular parameters. For RNFL parameters, the severe OSAHS group had significantly lower average and superior quadrant values than the mild or control. With mild and control grouped together the severe group had significantly lower average, superior, inferior and temporal quadrant values. Severe sleep apnea appears to produce detectable abnormalities in RNFL parameters measured by Stratus OCT using the fast RNFL algorithm. The OSAHS syndrome is becoming more widely recognized and diagnosed. The literature continues to accumulate suggesting an association between this syndrome and an optic neuropathy. There are two clinical important caveats. Patients diagnosed with OSAHS should be referred for ophthalmic evaluation. For the ophthalmologist, OSAHS must be in the differential diagnosis for glaucoma and optic neuropathy.

Sleep apnea must be in the differential diagnosis for glaucoma and optic neuropathy

Sleep apnea can be treated with lifestyle change, mouthpieces, breathing devices and surgery. Does treatment of OSAHS arrest the progression of optic neuropathy? Does lowering IOP have any role in the treatment of these patients? The Stratus OCT no longer represents the state of the art for OCT examination. There is relatively sparse sampling around the RNFL circle and only rudimentary analysis tools. I hope that the careful characterization and longitudinal follow up of large groups such as in this study will provide further insights.

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