Ella C. Berry, Henry N. Marshall, Sean Mullany, Lachlan S. W. Knight, Georgina Hollitt, Thi Thi Nguyen, Angela Schulz, Richard A. Mills, Ashish Agar, Anna Galanopoulos, John Landers, Paul R. Healey, Stuart L. Graham, Alex W. Hewitt, Robert Casson, Stuart MacGregor, Owen M. Siggs, Jamie E. Craig

Purpose: To investigate for association between nocturnal hypoxia and baseline and longitudinal structural thinning in early stage primary open angle glaucoma (POAG).

Methods: One hundred and sixty-three participants rec- ruited to the Predicting Risk Of Glaucoma: RElevant SNPs with Strong Association (PROGRESSA) study were fitted with afinger probe pulse oximeter (Nonin WristOx2) to measure nocturnal oxygen saturation over three consecutive nights. Macular ganglion cell inner plexiform layer (mGCIPL) and Peripapillary Retinal Nerve Fibre Layer (pRNFL) thickness was assessed in 326 eyes using spectral domain optical coherence tomography. Participants were then classified as showing predominantly mGCIPL, pre- dominantly pRNFL, both mGCIPL and pRNFL, or no structural change. Basal peripheral oxygen saturation (SpO2) levels, and oxygen desaturation index were evaluated in each of the sub-phenotypes.

Results: Following adjustment for age, gender, and intraocular pressure, individuals with predominantly mGCIPL thinning had a lower basal SpO2 (odds ratio 0.33/SD [0.15, 0.77] p = 0.008), exhibited a greater pro- portion of time below SpO2 88% (odds ratio 3.86, [1.29, 11.56] p = 0.016), and had a higher oxygen desaturation index indicating nocturnal desaturation events (odds ratio 1.81/SD [1.38, 1.80] p = 0.029) than patients with no structural change.

Conclusion: Nocturnal hypoxia may be an important risk factor for glaucoma progression. Further investigation of this association is required to evaluate the contribution of sleep apnea syndrome to these findings, and glaucoma progression.