The effect of simulated obstructive apnoea on intraocular pressure and pulsatile ocular blood flow in healthy young adults

[Primary open angle glaucoma and sleep apnea syndrome: A review of the literature]

The relationship between glaucoma and Obstructive Sleep Apnea Syndrome (OSAS) has long been discussed, with conflicting study findings. OSAS appears in the most recent studies to be more of an aggravating factor than an independent risk factor for glaucoma. Patients with OSAS may develop a more rapid progression of primary open-angle glaucoma (POAG). OSAS may damage the optic nerve not only by increasing the intraocular pressure (IOP) but also by altering the blood supply to the optic nerve as shown by more recent work with OCT-Angiography. Although the systemic benefits of Continuous Positive Airway Pressure (CPAP) have been demonstrated, few studies have evaluated its effect on the optic nerve. CPAP might act on glaucomatous neuropathy by improving the blood supply to the optic nerve. The study of this mechanism of action might provide new insights into the relationship between OSAS and glaucoma.

Increased risk of open-angle glaucoma in non-smoking women with obstructive pattern of spirometric tests

To investigate differences in the prevalence of open-angle glaucoma (OAG) between different pulmonary function types. A population-based, cross-sectional analysis was conducted using Korean National Health and Nutrition Examination Surveys from 2008 to 2011. A total of 8941 subjects  ≥ 40 years of age were analyzed. Chronic obstructive pulmonary disease (COPD) was defined as the ratio between first second of forced expiration (FEV1) and forced vital capacity (FVC) below 70%. The prevalence of glaucoma, as defined by the International Society of Geographical and Epidemiological Ophthalmology, was the main outcome. OAG was more prevalent in women with COPD (8.0% vs. 4.8% normal, P = 0.001) compared to women with normal pulmonary function. Intraocular pressure (IOP) of women with COPD were 13.3 (0.2) mmHg (13.9 (0.1) mmHg for normal function, P = 0.182). Never-smokers were more prevalent in women with COPD and glaucoma (92.9% vs. 52.4% normal function; P < 0.001). COPD was found to increase the risk of glaucoma in women (OR 2.077, P = 0.017) and even further in non-smoking women (OR 2.711, P = 0.003). Women with COPD showed a higher glaucoma prevalence despite similar IOP in comparison to women with normal pulmonary function. Non-smoking COPD is significantly associated with open-angle glaucoma in women.

Sleep apnea and eye diseases: evidence of association and potential pathogenic mechanisms

Eye diseases are an important group of increasingly prevalent disorders that contribute very significantly to disability and represent a considerable health burden. Some data suggest that several of these diseases may be associated with sleep-disordered breathing, mainly obstructive sleep apnea (OSA), due to intermediate mechanisms, such as intermittent hypoxia or sleep fragmentation. The aims of this systematic review were to identify and critically evaluate the current evidence supporting the existence of a possible relationship between OSA and the more relevant eye diseases as well as to evaluate the potential pathogenic mechanisms. There is a body of largely low-level evidence for the association of OSA with glaucoma, nonarteritic ischemic optic neuropathy, central serous chorioretinopathy, and diabetic retinopathy. Meta-analysis of available case-control studies shows that OSA increases the risk of glaucoma (pooled odds ratio: 1.50; 95% confidence interval: 1.25 to 1.80; P < .001), nonarteritic ischemic optic neuropathy (3.62; 1.94 to 6.76; P < .001), and diabetic retinopathy (1.57; 1.09 to 2.27; P = .02). Moreover, several pathogenic pathways have been identified, mainly related to hypoxic damage, mechanical stress, systemic inflammation, oxidative stress, sympathetic tone, and endothelial dysfunction. In contrast, information about the effect of apnea-hypopnea suppression on the development and progression of eye damage is either nonexistent or of a very low level of evidence. In conclusion, OSA has emerged as an additional potential risk factor for many eye diseases, although their link is weak and contradictory, so further examination is required.

CITATION

García-Sánchez A, Villalaín I, Asencio M, García J, García-Rio F. Sleep apnea and eye diseases: evidence of association and potential pathogenic mechanisms. J Clin Sleep Med. 2022;18(1):265-278.

Diseases of the retina and the optic nerve associated with obstructive sleep apnea

Many associations between ocular disorders and obstructive sleep apnea (OSA) have been studied, such as nonarteritic anterior ischemic optic neuropathy, glaucoma, papilledema, retinal vein occlusion, eyelid hyperlaxity, lower-eyelid ectropion and recurrent corneal erosions. The objective of this review is to synthetize the possible vascular disorders of the retina and the optic nerve associated with sleep apnea patients and to discuss the underlying pathophysiological hypotheses. Main mechanisms involved in the ocular complications of OSA are related to intermittent hypoxia, sympathetic system activation, oxidant stress, and deleterious effects of endothelin 1. The main evidence-based medicine data suggest that OSA should be screened in patients with ischemic optic neuropathy and diabetic retinopathy. The effect of OSA treatment and emerging therapies are discussed.

Obstructive sleep apnea-hypopnea syndrome (OSAHS) and glaucomatous optic neuropathy

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is becoming widely accepted as a risk factor for glaucoma. We discuss the proposed mechanism involved in the pathogenesis of glaucoma in OSAHS, and review the published data on the association between these two conditions, as well as papers regarding functional and structural tests related with glaucomatous damage. There is increasing evidence that the prevalence of glaucoma is higher in OSAHS patients, especially in those with severe disease with apnea-hypopnea index (AHI) >30, and also that sleep disorders may be more frequent in patients with glaucoma, especially in those with normal tension glaucoma (NTG). Several ophthalmic signs and symptoms have been associated with this condition. Raised intraocular pressure (IOP), possibly related to increased body mass index, thinning of retinal nerve fiber layer (RNFL), and alteration of visual field (VF) indices has been demonstrated in many studies, in patients with no history of glaucoma or evidence of glaucomatous changes in the ophthalmic examination. A correlation of AHI with RNFL and VF indices has been described in some studies. Finally, corneal thinning, suspicious glaucomatous disc changes and anomalies in electrophysiological tests such as multifocal visual evoked potential have been described in patients with OSAHS, even in patients with normal findings in the optic nerve and VF, suggesting subclinical optic nerve involvement not detectable in conventional ophthalmic examinations. The pathogenesis of optic nerve involvement has been related to vascular and mechanical factors. Vascular factors include recurrent hypoxia with increased vascular resistance, autonomic deregulation, oxidative stress and inflammation linked to hypoxia and subsequent reperfusion, decreased cerebral perfusion pressure and direct hypoxic damage to the optic nerve. Proposed mechanical factors include increased IOP at night related to supine position and obesity, raised intracranial pressure and elastic fiber depletion in the lamina cribosa and/or trabeculum. In conclusion, ophthalmic evaluation should be recommended in patients with severe OSAHS, and the presence of sleep disorders should be investigated in patients with glaucoma, especially in NTG patients and in those with progressive damage despite controlled IOP, as treatment with continuous positive airway pressure may contribute to stabilizing the progression of glaucomatous damage.

Is there a relationship between sleep apnea and central corneal thickness?

PURPOSE

The objective of this study was to determine the central corneal thickness (CCT) measurements in patients with Sleep Apnea Syndrome (SAS) and the relationship between the severity of SAS and minimal arterial oxygen saturation (min. SpO2) with respect to CCT.

MATERIALS AND METHODS

Two hundred and fourteen eyes of 107 patients (58 males, 49 females) who were diagnosed as SAS and 80 eyes of 40 healthy subjects (20 males, 20 females) were included in the study. The SAS patients were divided into subgroups according to their Apnea-Hypopnea Index (AHI) values as: AHI values between 5 and 15 as subgroup 1, between 15 and 30 as subgroup 2, and the values ≥30 as subgroup 3. The CCT was measured by an ultrasonic pachymetric system. Statistical analyses were an analysis of variance test and, for post-hoc analysis, the Dunnett C test.

RESULTS

Mean age was 52.5 ± 10.96 years in the study group, and 40.7 ± 10.14 years in the control group. There were 58 (54.2%) males and 49 (45.8%) females in the study group, and 20 (50%) males and 20 (50%) females in the control group. Mean CCT values were 526.65 ± 25.06, 525.26 ± 29.25, 512.93 ± 43.20 and 539.90 ± 17.28 in subgroup 1, subgroup 2, subgroup 3 and the control group, respectively. There were no statistically significant differences between gender and age groups with respect to CCT (p > 0.05). When the mean CCT values of each subgroups were compared with the control group, the differences were statistically significant (p < 0.05). There was a negative correlation between CCT and AHI values and a positive correlation between CCT and min. SpO2 values.

CONCLUSIONS

CCT measurements differ significantly in patients with SAS compared with healthy control subjects. It should be taken into consideration that SAS may reduce CCT over time and that CCT should be measured in each ophthalmic examination.

Glaucoma and obstructive sleep apnoea syndrome

Glaucoma is increasingly recognized as a manifestation of both ocular and systemic risk factors. A number of disorders associated with reduced blood flow and ischaemia, collectively termed vascular risk factors, such as migraine, Raynaud's phenomenon, atrial fibrillation and reduced nocturnal blood pressure, lead to decreased ocular perfusion pressure. During sleep, alterations occur in cardiovascular physiology that are balanced by autoregulation to maintain homeostasis. However, in obstructive sleep apnoea (OSA), the normal physiological balance is upset. A potentially modifiable risk factor, OSA has been increasingly associated with glaucoma independent of intraocular pressure. OSA may alter blood flow to the optic nerve head and, in combination with other predisposing factors, lead to decreased ocular perfusion pressure. This in turn may directly affect the optic nerve or it may indirectly increase its susceptibility to other insults. The purpose of this review is to shed light on the association between OSA and glaucoma.

Pulsatile ocular blood flow in subjects with sleep apnoea syndrome

INTRODUCTION

The aim of the study was to determine the correlation between pulsatile ocular blood flow (POBF) and sleep apnoea syndrome (SAS).

MATERIAL AND METHODS

Patients were recruited from those who underwent polysomnography in the "Sleep Unit" of the physiology department (Medical University, Lodz, Poland). A total of 52 Caucasian patients, 34 with SAS and 18 age- and gender-matched controls, were included in the study. Comprehensive ophthalmic examination included the pulsatile ocular blood flow (POBF) measurements, disc analysis with Heidelberg Retina Tomograph II and Oculus Centerfield computerized perimetry as well as the best visual acuity, a slit lamp and indirect ophthalmoscopic evaluation of anterior and posterior segments and applanation tonometry.

RESULTS

The observed prevalence of glaucoma in SAS patients was 5.9% (2 of 34). The mean values of POBF were 1069.21 ±235.94 µl/min in the SAS group and 1061.78 ±174.63 µl/min in the control group. The study revealed that the differences of mean POBF between the SAS patients and the control group were not statistically significant: Mann-Whitney U-test p > 0.05. No correlations were found between sleep apnoea syndrome and mean intraocular pressure (IOP), mean retinal nerve fibre layer (RNFL) thickness and visual field mean defect (MD).

CONCLUSIONS

No correlation was found between pulsatile ocular blood flow and sleep apnoea syndrome. Although some previous studies found an association between IOP, MD, RNFL thickness and sleep apnoea syndrome, our study did not confirm that. However, a high prevalence of glaucoma was found among SAS patients in Poland.