Sleep apnea patients at higher risk of Normal tension glaucoma patients, suggests study

A new study published in the journal of Medicine showed that the risk ofdeveloping obstructive sleep apnea (OSA) is increased in those with normal tension glaucoma (NTG). The prevalence of obstructive sleep apnea syndrome (OSAS) in middle-aged individuals ranges from 2% to 5%, and patients without a definitive diagnosis may go undiagnosed. Insomnia, excessive daytime sleep, and loud snoring are common symptoms of OSAS. Male sex, obesity, thick necks, and abnormalities of the upper respiratory tract are risk factors for OSAS.

One of the main causes of blindness worldwide is glaucoma, a broad-spectrum condition that causes gradual visual loss. Although the mechanism of hypertensive glaucoma is complicated, the standard hypothesis holds that a rise in intraocular pressure (IOP) is caused by a malfunction in aqueous auto-regulation. But, glaucoma may be caused by the autonomic nervous system and circadian rhythms, and it is hypothesized that aberrant ocular blood flow causes optic nerve dysfunction in NTG with normal IOP.

During long-term treatment, clinicians may confuse vision loss with both OSAS and NTG, which are chronic progressive neurovascular disorders. Thus, using a visual field analysis of NTG in OSAS, this study first determined and assessed the relationship between ocular microcirculation, OCTA, and visual function.

Polysomnography (PSG) was used to analyze every participant in this cross-sectional, retrospective investigation. Standard automated perimetry (SAP) functional parameters were noted. Peripapillary whole-layer (VD NH), peripapillary superficial vessel density (VD RPC), and superficial and deep macular area (VD) were structural characteristics in optical coherence tomography angiography (OCTA). Based on their SAP results, participants were divided into perimetric and nonperimetric groups. Signal strength index <50 in OCTA and low SAP dependability were disregarded.

The apnea-hypopnea index (AHI) in PSG was used to evaluate the severity of OSAS. When compared to those with mild OSAS, those with moderate/severe OSAS expressed shorter ocular axial lengths and larger neck circumferences. Additionally, the NTG perimetric group had a greater neck circumference and a considerably higher AHI when compared to the control group.

The perimetric group showed a substantial reduction in both superficial and deep-layer peripapillary and macular region VD. Overall, structural and functional data indicate that VF MD had a positive correlation with VD NH but not substantially with VD RPC, while VF PSD had a negative correlation with both VD NH and VD RPC. The relationship between OCTA characteristics and visual field abnormalities indicates that OCTA can be used in conjunction with OSAS to track functional and morphological alterations in ocular microcirculation.

Reference:

Chuang, L.-H., Koh, Y.-Y., Chen, H. S. L., Lo, Y.-L., Yu, C.-C., Yeung, L., & Lai, C.-C. (2020). Normal tension glaucoma in obstructive sleep apnea syndrome: A structural and functional study. Medicine, 99(13), e19468. https://doi.org/10.1097/md.0000000000019468