Ocular Complications of Obstructive Sleep Apnea
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Journal of Clinical Medicine Review Ocular Complications of Obstructive Sleep Apnea Pei-Kang Liu 1,2,3,4 , Tzu-Yu Chiu 1,2 , Nan-Kai Wang 4 , Sarah R. Levi 4 and Ming-Ju Tsai 5,6,7,8,* 1 Department of Ophthalmology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung 807, Taiwan; [email protected] (P.-K.L.); [email protected] (T.-Y.C.) 2 School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan 3 Institute of Biomedical Sciences, National Sun Yat-sen University, Kaohsiung 804, Taiwan 4 Department of Ophthalmology, Edward S. Harkness Eye Institute, Columbia University, New York, NY 10032, USA; [email protected] (N.-K.W.); [email protected] (S.R.L.) 5 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung 807, Taiwan 6 Sleep Disorders Center, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung 807, Taiwan 7 Department of Respiratory Care, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan 8 Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan * Correspondence: [email protected]; Tel.: +886-7-3121101 (ext. 5601) Abstract: Obstructive sleep apnea (OSA), the most common form of sleep-disordered breathing, is characterized by repetitive episodes of paused breathing during sleep, which in turn induces transient nocturnal hypoxia and hypercapnia. The high prevalence of OSA and its associated health consequences place a heavy burden on the healthcare system. In particular, the consequent episodic oxygenic desaturation/reoxygenation series and arousals from sleep in patients with OSA have the potential to trigger oxidative stress, elevated systemic inflammatory responses, and autonomic Citation: Liu, P.-K.; Chiu, T.-Y.; dysfunction with sympathetic activation. Given these adverse side-effects, OSA is highly correlated Wang, N.-K.; Levi, S.R..; Tsai, M.-J. to many eye diseases that are common in everyday ophthalmic practices. Some of these ocular Ocular Complications of Obstructive consequences are reversible, but they may permanently threaten a patient’s vision if not treated ap- Sleep Apnea. J. Clin. Med. 2021, 10, propriately. Here, this article seeks to review the ocular consequences and potential pathophysiologic 3422. https://doi.org/ associations in patients with OSA. Understanding these OSA-related eye diseases may help clinicians 10.3390/jcm10153422 provide comprehensive care to their patients. Academic Editor: Bryan J. Winn Keywords: obstructive sleep apnea; sleep-disordered breathing; nocturnal hypoxia; eye; complica- tions; oxidative stress; inflammation; sympathetic activation Received: 27 June 2021 Accepted: 28 July 2021 Published: 31 July 2021 1. Introduction Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in Sleep apnea (SA), the most common form of sleep-disordered breathing, causes re- published maps and institutional affil- current pauses in breathing during sleep and transient nocturnal hypoxia and hypercap- iations. nia [1–3]. The diagnosis of SA is usually confirmed by polysomnography (PSG) [4,5]. Obstructive SA (OSA) is the most common type, accounting for over 85% of all SA cases, whereas central SA (CSA) is a rarer presentation [6]. OSA is characterized by repetitive bouts of complete or partial upper airway obstruction during sleep, which induces loud snoring and airflow reduction [7,8]. These episodic oxygenic desaturation/reoxygenation Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. series and arousals from sleep/sleep fragmentation in patients with OSA have severe This article is an open access article consequences, including oxidative stress, autonomic dysfunction with sympathetic acti- distributed under the terms and vation, blood pressure spikes, increased heart rate, insulin resistance, enhanced platelet conditions of the Creative Commons aggregation, endothelial dysfunction, and heightened systemic inflammation [9–19]. The Attribution (CC BY) license (https:// Apnea–Hypopnea Index (AHI, total number of apnea and hypopnea events divided by creativecommons.org/licenses/by/ total sleep time) is usually used to determine the severity of OSA, classifying patients into 4.0/). four categories: subjects without OSA have an AHI of <5/h, patients with mild OSA have J. Clin. Med. 2021, 10, 3422. https://doi.org/10.3390/jcm10153422 https://www.mdpi.com/journal/jcm J. Clin. Med. 2021, 10, 3422 2 of 23 J. Clin. Med. 2021, 10, 3422 2 of 22 four categories: subjects without OSA have an AHI of <5/h, patients with mild OSA have an AHI of 5–15/h, patients with moderate OSA have an AHI of 15–30/h, and patients with severe OSA have an AHI of >30/h [20]. As an emerging health issue in the contemporary an AHI of 5–15/h, patients with moderate OSA have an AHI of 15–30/h, and patients with world,severe OSA OSA is have estimated an AHI to of affect >30/h 22–24% [20]. As of anmen emerging and 9–17% health of women issue in globally, the contemporary while it isworld, also associated OSA is estimated with an tooverweight affect 22–24% body of mass men index and 9–17% (BMI) of [21,22]. women globally, while it is alsoWith associated all the withadverse an overweighteffects associated body masswith OSA, index its (BMI) secondary [21,22]. effects cause a number of ocularWith complications all the adverse [16,23,24]. effects associated Previous with studies OSA, have its secondary shown that effects OSA cause is associated a number withof ocular increased complications risks of several [16,23 ,vision-threate24]. Previousning studies and have nonthreatening shown that OSAocular is disorders, associated includingwith increased senile cataract, risks ofseveral normal vision-threateningtension glaucoma, andretinal nonthreatening ischemia, conjunctival ocular disorders, hyper- emia,including and dry senile eye cataract, [23]. Several normal contributory tension glaucoma, mechanisms retinal to ischemia,the ocular conjunctival complications hyper- of OSAemia, have and been dry eyereported, [23]. Several including contributory intermitte mechanismsnt hypoxia, oxidative to the ocular stress, complications systemic in- of flammatoryOSA have been responses reported, (such including as interleukin-6 intermittent (IL-6), hypoxia, IL-8,tumor oxidative stress,necrosis systemic factor-alpha inflam- (TNF-matoryα), responsesC-Reactive (such protein as interleukin-6(CRP), matrix (IL-6), metalloproteinase IL-8,tumor necrosis 9 (MMP factor-alpha-9), vascular (TNF-cell ad-α), hesionC-Reactive molecule protein (VCAM), (CRP), intercellular matrix metalloproteinase adhesion molecule 9 (MMP-9), (ICAM), vascular selectins), cell adhesionsympa- theticmolecule system (VCAM), overaction, intercellular damage adhesion effects moleculeof endothelin-1, (ICAM), and selectins), disruption sympathetic of the blood– system retinaloveraction, barrier damage (BRB) (Table effects 1) of[11–16,18,19,24–26]. endothelin-1, and In disruption addition, ofOSA-mediated the blood–retinal chronic barrier up- regulation(BRB) (Table of systemic1)[11–16 ,inflammation18,19,24–26] . may In addition, provoke OSA-mediated both ocular and chronic non-ocular upregulation complica- of tions,systemic such inflammation as psoriasis and may rheumatoid provoke both arth ocularritis, which and non-ocular may cause complications,further ocular abnor- such as malitiespsoriasis [27,28]. and rheumatoid arthritis, which may cause further ocular abnormalities [27,28]. TableTable 1. 1. PossiblePossible common common pathophysiology pathophysiology between between OSA OSA and and associated associated ocular ocular complications. complications. • OxidativeOxidative stress stress • AutonomicAutonomic dysfunction dysfunction with with sympathetic sympathetic activation activation • UpregulationUpregulation of of systemic systemic inflammation inflammation • EndotheliumEndothelium dysfunction dysfunction and and disruption disruption of of the the blood–retinal blood–retinal barrier barrier (BRB) (BRB) • DysregulationDysregulation of of circadian circadian genes genes DueDue to to the the prevalence prevalence of ofOSA OSA in inthe the working working age age population, population, an understanding an understanding of theof ocular the ocular conditions conditions associated associated with OSA with and OSA their and underlying their underlying pathophysiological pathophysiological mech- anismsmechanisms is essential is essential for the forcomprehensive the comprehensive care of carepatients. of patients. Herein, Herein,we review we the review ocular the consequencesocular consequences and associated and associated underlying underlying pathop pathophysiologicalhysiological mechanisms mechanisms in patients in patients with SAwith (Figure SA (Figure 1). Ultimately,1). Ultimately, this article this aims article to assist aims clinicians to assist cliniciansin understanding in understanding and diag- nosingand diagnosing ocular conditions ocular conditions in patients in with patients OSA within the OSA hope in of the preventing hope of preventing future irreversi- future bleirreversible eye complications. eye complications. FigureFigure 1. 1. SchematicSchematic interactions interactions of of OSA OSA and and eye eye diseases diseases in in terms terms of of common common pathophysiological pathophysiological mechanismsmechanisms.. OSA OSA has has been been directly/indirectly