The effect of mask usage on dry eye symptoms and meibomian gland function in OSAS patients: an observational study

Abstract

Objective

To analyze the effect of mask usage on dry eye symptoms and meibomian gland function in patients with obstructive sleep apnea syndrome (OSAS).

Methods

OSAS patients who visited our hospital from January 2022 to December 2023 were selected as research subjects. All patients were treated with continuous positive airway pressure (CPAP) therapy. The polysomnography (PSG) results before and after treatment were analyzed, including the apnea-hypopnea index (AHI) and peripheral oxygen saturation (SpO₂). Dry eye conditions and ocular surface analyzer results of patients before and after treatment were evaluated. Pearson correlation was used to assess the relationship between dry eye conditions and ocular surface analyzer results in OSAS patients, and the correlations between PSG results and dry eye conditions as well as ocular surface analyzer results were also analyzed.

Results

AHI levels in 31 OSAS patients were significantly decreased after treatment, while SpO₂ levels significantly increased, with a statistically significant difference (P<0.05). After treatment, the tear breakup time (BUT), palpebral (PL) scores, and Ocular Surface Disease Index (OSDI) scores of patients were significantly higher than those before treatment (P<0.05). Additionally, after treatment, the tear meniscus height of OSAS patients was significantly lower than that before treatment, and the lipid layer thickness and eye redness index were significantly higher than those before treatment, with a statistically significant difference (P<0.05). The results of Pearson correlation analysis showed that BUT was positively correlated with lipid layer thickness and eye redness improvement, while Schirmer’s test (Sit) was positively correlated with tear meniscus height. PL scores were negatively correlated with tear meniscus height but positively correlated with the eye redness index (P<0.05). AHI from PSG results was negatively correlated with BUT, PL scores, and OSDI scores (P<0.05), while SpO₂ was positively correlated with BUT, PL scores, and OSDI scores but negatively correlated with Sit (P<0.05). In the PSG results, AHI was negatively correlated with lipid layer thickness and eye redness index, and positively correlated with meibomian gland opening score (P < 0.05).

Conclusion

CPAP mask usage in OSAS patients may negatively impact dry eye symptoms and meibomian gland function, leading to decreased tear film stability and worsening symptoms of eye dryness.

Introduction

Obstructive sleep apnea syndrome (OSAS) is a disease caused by repeated collapse of the upper airway during sleep. It is often accompanied by symptoms such as snoring, sleep interruption, and hypoxemia, which can lead to a series of pathophysiological changes. These changes significantly increase the risk of various systemic diseases such as hypertension, stroke, and cardiovascular events [1, 2].

Continuous positive airway pressure (CPAP) is one of the main methods for treating OSAS. This method can effectively reduce the apnea hypopnea index (AHI) and respiratory disturbance index (RDI), and improve the patient’s sleep quality and daytime sleepiness symptoms [3, 4]. Dry eye is a multifactorial disease of the ocular surface. Its main characteristics are tear film instability and ocular surface damage, which can lead to symptoms such as eye discomfort and decreased vision. The mechanism of occurrence is relatively complex, primarily including insufficient tear secretion, rapid tear evaporation, and meibomian gland dysfunction [5]. Among them, meibomian gland dysfunction is a major cause of dry eye, as the lipid layer secreted by the meibomian glands reduces tear evaporation and maintains tear film stability. Studies have shown [6] that the prevalence of dry eye disease is significantly higher in patients with OSAS compared to the general population. This association may be attributed to OSAS-related intermittent hypoxia, which induces abnormal neural regulation. Specifically, it suppresses basal tear secretion via the trigeminal-parasympathetic pathway, while sleep fragmentation reduces blink frequency, thereby prolonging the tear film renewal cycle.

However, during CPAP therapy, two physical factors, including the mechanical pressure exerted by the mask on the face (particularly the meibomian gland area) and the retrograde flow of pressurized air through the nasolacrimal duct, may act synergistically on ocular tissues [7, 8]. Existing studies have shown that CPAP therapy masks (such as nasal masks/oral-nasal masks) have a significantly different physical mechanism of action compared to protective masks (such as N95 masks) due to the requirements of continuous positive airway pressure and edge sealing. CPAP masks can cause deformation of the meibomian glands under pressure-sensitive thresholds (> 10 cmH₂O) [9], and when air leakage exceeds 24 L/min, tear film evaporation rates increase to 1.8 times the baseline level [10, 11]. Although some mechanistic studies have been conducted, the differential effects of various mask designs remain to be further explored. Therefore, this study aims to investigate changes in dry eye symptoms and meibomian gland function before and after mask usage in OSAS patients through a controlled study, providing clinical treatment references.

Study subjects and methods

Study subjects

Patients with OSAS who visited our hospital from January 2022 to December 2023 were selected as study subjects. Inclusion criteria: ① Meet the diagnostic criteria for OSAS [12]; ② Aged 18 years or older; ③ Willing to participate in this study and sign the informed consent. Exclusion criteria: ① Combination with other eye diseases, such as glaucoma, retinopathy, etc.; ② Recent use of medications that affect dry eye symptoms or meibomian gland function; ③ Contraindications to CPAP treatment such as facial trauma and severe nasal diseases. ④Exclude long-term CPAP users (usage time > 3 months) to avoid confounding effects of previous ocular surface adaptation. A total of 31 patients with OSAS were included. The patient inclusion process is shown in Fig. 1.

Fig. 1.

Flow chart of patient inclusion

Methods

(1) CPAP therapy: All patients included in the study were OSAS patients receiving CPAP therapy for the first time and had not used CPAP devices prior to treatment. All patients underwent a one-week CPAP adaptation therapy (pressure 8–12 cmH₂O) prior to PSG monitoring to ensure mask compliance. The types of CPAP masks used in the study included nasal masks (ResMed AirFit N20, 74.2%) and oronasal mask masks (ResMed AirFit F20, 25.8%), both made of silicone. Leakage data were recorded in real-time using the device’s built-in sensor (ResMed S10 AutoSet).

(2) Data collection: Demographic data such as age, gender, body mass index (BMI), systolic blood pressure, diastolic blood pressure, blood sugar, and severity of OSAS were collected from all patients. Patients were divided into three groups based on the apnea–hypopnea index (AHI): mild (5–14.9 times/h, mean AHI ± SD, 10.35 ± 2.94), moderate (15–29.9 times/h, mean AHI ± SD, 22.48 ± 4.57), and severe (≥ 30 times/h, mean AHI ± SD, 40.83 ± 9.57).

(3) Polysomnography (PSG) results: Before treatment and the day after treatment, polysomnography (Beijing Yihe Jiaye, Poly Pro YH-2000 A) was used to monitor AHI (normal range: 0–5 times/h) and peripheral oxygen saturation (SpO₂) (normal range: 95-98%). AHI was calculated by the number of apnea and hypopnea events per hour. Post-treatment PSG monitoring was conducted one week after CPAP therapy to assess the long-term effects of wearing the mask.

(4) Dry eye condition: The breakup time (BUT), Schirmer I test (Sit), palpebral (PL), and Ocular Surface Disease Index (OSDI) were observed before and after treatment.

①BUT: A 0.125% sodium fluorescein solution was applied to the conjunctival sac, and the patient was asked to blink several times to evenly distribute the sodium fluorescein on the corneal and conjunctival surfaces. Then, the patient was asked to keep eyes open while a slit-lamp microscope with cobalt blue light was used to observe the corneal surface, and the time from the last blink to the appearance of the first dry spot was recorded. Normal tear film break-up time is over 10 s; less than 10 s indicates tear film instability, with abnormal values below 8 s indicating significant instability, and values below 4 s suggesting severe dry eye.

②Sit: There are two ways of testing, including the active and passive tear secretion test. The active detection method was to place a filter paper strip on the lower meibomian gland margin for 5 min, and the wetted length was measured. Normal secretion is 10–15 mm; less than 10 mm indicates low secretion, and less than 5 mm suggests dry eye. In passive secretion testing, the strip was placed in the conjunctival sac for about 5 min with closed eyes. Tear secretion below 10 mm indicates low secretion, and repeated measures below 5 mm may diagnose dry eye.

③PL: Fluorescein staining was used to divide the cornea into four quadrants, with each quadrant scored from 0 to 3. A score of 0 indicates no staining; 1 indicates 1–30 punctate stains; 2 indicates more than 30 punctate stains but no coalescence; and 3 indicates coalescence, filaments, or ulcers.

④OSDI: The OSDI questionnaire consists of 12 items, divided into three subscales: ocular symptoms, vision-related functions, and environmental triggers. Patients score each item on a scale of 0 (never) to 4 (always), with the total OSDI score calculated as: OSDI = (total score of answered questions × 100) / (total number of questions answered × 4). Based on the total score, OSDI scores are classified as normal (0–12), mild dry eye (13–22), moderate dry eye (23–32), or severe dry eye (33 or above).

(5) Ocular surface analyzer results.

The tear meniscus height, lipid layer thickness, eye redness index and meibomian gland opening score were evaluated by ocular surface comprehensive analyzer (Keratograph 5 M).

① Tear meniscus height: An ocular surface comprehensive analyzer (e.g., Keratograph 5 M) was used to take the image of the concave arc formed at the junction of the tear and the meibomian gland margin, and indirectly evaluated the tear secretion by measuring the tear retention height. A normal tear meniscus height is ≥ 0.2 mm, with lower values indicating reduced tear secretion.

② Lipid layer thickness: Assessed using an ocular surface interferometer (e.g., Lipi -View). A normal lipid layer thickness is greater than 100 nm. Thicknesses between 61 and 100 nm suggest a 50% likelihood of meibomian gland dysfunction (MGD), while values of ≤ 60 nm indicate a 90% likelihood of MGD.

③ Eye Redness Index: The eye redness index was measured by a non-invasive ocular surface comprehensive analyzer (e.g., Keratograph 5 M), which evaluates the redness of the eyes by analyzing the degree of conjunctival congestion. While specific scoring criteria were not found in the referenced data, the index typically classifies redness severity by analyzing the degree of congestion.

④ Meibomian gland opening score: Meibomian gland opening score was assessed by observing the condition of the meibomian gland openings. The method involved having the patient look upward, and then examining and grading the opening condition of the 8 meibomian glands located in the central third of the lower meibomian gland. The scoring system is as follows: 0 points for normal gland openings (rounded, with no blockages); 1 point for openings with lipid capping; and 2 points for blocked or narrowed openings with protruding lipid plugs.

Statistical methods

Analysis was performed using SPSS 22.0 software. All measurement data were first subjected to the Shapiro–Wilk normality test (P > 0.05). Data that met the criteria for normal distribution were expressed as mean ± standard deviation (SD), and intergroup comparisons were performed using the independent samples t-test; data that did not meet the criteria for normal distribution were analyzed using the Mann-Whitney U test. Correlation analysis was performed using Pearson linear correlation. When performing stratified analysis of air leakage volume and ocular surface indicators, patients were divided into a high air leakage group (n = 11) and a low air leakage group (n = 20) based on a cutoff of 24 L/min. Covariance analysis (ANCOVA) was used to control for confounding factors such as BMI and AHI. P < 0.05 was considered statistically significant.

Results

Analysis of general data of OSAS patients

A total of 31 OSAS patients were included in the study, with 21 males and 10 females. The average BMI of the patients was (26.71 ± 4.33) kg/m², which exceeds the normal range and falls within the overweight category. Blood pressure analysis showed that the average systolic pressure was (131.23 ± 12.50) mmHg, slightly above the normal range, while the average diastolic pressure was (75.50 ± 10.23) mmHg. The severity of the patients’ conditions was as follows: 8 cases (25.81%) had mild OSAS, 11 cases (35.48%) had moderate OSAS, and 12 cases (38.71%) had severe OSAS. Additional general information is provided in Table 1.

Table 1.

General information of OSAS patients

General Information		OSAS Patients (n = 31)
Age (years)		50.23 ± 10.74
Gender	Male	21(67.74)
	Female	10(32.26)
BMI (kg/m2)		26.71 ± 4.33
Systolic Blood Pressure (mmHg)		131.23 ± 12.50
Diastolic Blood Pressure (mmHg)		75.50 ± 10.23
Fasting Blood Glucose (mmol/L)		6.24 ± 2.03
OSAS Severity	Mild	8(25.81)
	Moderate	11(35.48)
	Severe	12(38.71)
Mask type	Nasal mask	23(74.20)
	Oronasal mask	8(25.80)
Leakage rate (L/min)	Nasal mask	10.80 ± 2.71
	Oronasal mask	14.72 ± 4.11

Analysis of PSG results before and after treatment in OSAS patients

To further analyze the PSG results of OSAS patients before and after CPAP treatment, this study conducted PSG testing on 31 OSAS patients before treatment and the day after treatment to assess AHI and SpO₂ levels. In the 31 OSAS patients, the mean SpO₂ level during wakefulness was 89.30 ± 3.75%. Before CPAP treatment, the average AHI was 22.80 ± 4.55 events/h, and the SpO₂ level was 85.90 ± 4.07%. After CPAP treatment, the AHI significantly decreased to 11.07 ± 3.62 events/h, although it remained within the abnormal range; meanwhile, the SpO₂ level markedly increased to 90.72 ± 4.15%. An independent samples t-test showed that the differences between pre- and post-treatment values were statistically significant (P < 0.05).

Analysis of changes in dry eye conditions in OSAS patients before and after treatment

To further analyze changes in dry eye conditions among OSAS patients after CPAP treatment, 31 patients were assessed both before treatment and a day after treatment. The evaluations included BUT, Schirmer I test (Sit), PL score, and OSDI score. The results showed no statistically significant difference in Sit between pre- and post-treatment (P > 0.05). After treatment, patients showed a significant increase in BUT (P < 0.05), while both PL scores and OSDI scores were significantly higher than before treatment, indicating improved tear film stability but worsened dry eye symptoms (P < 0.05, Table 2).

Table 2.

Analysis of changes in dry eye condition in OSAS patients before and after treatment

Time	Cases	BUT(s)	Sit(mm/5min)	PL Score	OSDI Score
Before Treatment	31	10.46 ± 2.15	12.83 ± 2.25	2.32 ± 0.88	18.01 ± 3.85
After Treatment	31	12.99 ± 3.32	12.02 ± 3.09	4.02 ± 1.56	24.58 ± 8.22
t		3.561	1.180	5.285	4.030
P		0.001	0.243	<0.001	<0.001

Ocular surface analyzer examination results of OSAS patients before and after treatment

To further analyze the changes in the ocular surface analyzer examination results of OSAS patients before and after CPAP treatment, 31 OSAS patients were examined with the ocular surface analyzer before treatment and the day after treatment. The examination items included tear meniscus height, lipid layer thickness, eye redness index, and meibomian gland opening score. The results showed that after treatment, the tear meniscus height of OSAS patients was significantly lower than before treatment, and the lipid layer thickness and eye redness index were significantly higher than before treatment. An independent samples t-test on the two sets of data revealed statistically significant differences (P < 0.05). However, the comparison of meibomian gland opening scores before and after treatment showed no statistically significant difference (P > 0.05, Table 3).

Table 3.

Results of ocular surface analyzer examination of OSAS patients before and after treatment

Time	Cases	Tear Meniscus Height (mm)	Lipid Layer Thickness (nm)	Eye Redness Index	Meibomian Gland Opening Score
Before Treatment	31	0.26 ± 0.06	64.33 ± 10.72	0.65 ± 0.12	0.65 ± 0.10
After Treatment	31	0.22 ± 0.02	70.20 ± 11.55	0.78 ± 0.14	0.62 ± 0.11
t		3.521	2.191	3.925	1.124
P		0.001	0.032	<0.001	0.266

Correlation analysis between dry eye symptoms and meibomian gland function after CPAP treatment

To further analyze the correlation between dry eye symptoms and meibomian gland function in OSAS patients before and after CPAP treatment, Pearson correlation analysis was performed. The results showed that BUT was positively correlated with lipid layer thickness and improvement of eye redness (r = 0.357, 0.286, P < 0.05). Sit was positively correlated with tear meniscus height (r = 0.294, P < 0.05), PL score was negatively correlated with tear meniscus height (r=-0.336, P < 0.05), and positively correlated with eye redness index (r = 0.251, P < 0.05), see Table 4. The correlation coefficient graph is shown in Fig. 2.

Table 4.

Correlation analysis of dry eye symptoms and meibomian gland function after CPAP treatment

Indicator	BUT		Sit		PL score		OSDI score
	r	P	r	P	r	P	r	P
Tear Meniscus Height	-1.780	0.162	0.294	0.020	-0.336	0.008	-0.183	0.154
Lipid Layer Thickness	0.357	0.004	0.039	0.763	0.101	0.434	0.172	0.183
Eye Redness Index	0.286	0.025	0.106	0.414	0.251	0.049	0.197	0.125
Meibomian Gland Opening Score	-2.229	0.073	-0.229	0.073	-0.191	0.137	-0.202	0.058

Fig. 2.

Correlation coefficient matrix of dry eye symptoms and meibomian gland function after CPAP treatment

Correlation between PSG results and changes in dry eye conditions

To further analyze the correlation between PSG results and changes in dry eye conditions in OSAS patients after CPAP treatment, Pearson correlation analysis was conducted. The results indicated that in the PSG results, the AHI was negatively correlated with BUT, PL score, and OSDI score (r=-0.444, -0.350, -0.378; P < 0.05). Additionally, SpO₂ was positively correlated with BUT, PL score, and OSDI score (r = 0.308, 0.435, 0.288; P < 0.05) and negatively correlated with Sit (r=-0.300; P < 0.05) (Table 5; Figs. 3 and 4).

Table 5.

Correlation between PSG results and changes in dry eye conditions

Indicator	AHI		SpO2
	r	P	r	P
BUT	-0.444	< 0.001	0.308	0.015
Sit	0.155	0.230	-0.300	0.018
PL Score	-0.350	0.005	0.435	< 0.001
OSDI Score	-0.378	0.002	0.288	0.023

Fig. 3.

Correlation between AHI and changes in dry eye condition in PSG results. A: Correlation between AHI and BUT; B: Correlation between AHI and Sit; C: Correlation between AHI and PL score; D: Correlation between AHI and OSDI score

Fig. 4.

Correlation between SpO₂ and changes in dry eye condition in PSG results. A: Correlation between SpO₂ and BUT; B: Correlation between SpO2 and Sit; C: Correlation between SpO₂ and PL score; D: Correlation between SpO₂ and OSDI score

Correlation between PSG results and ocular surface analyzer examination results

The correlation between PSG results and ocular surface analyzer examination results before and after CPAP treatment in OSAS patients was further analyzed. The results of Pearson correlation analysis showed that AHI in PSG results was negatively correlated with lipid layer thickness and eye redness index (r=-0.277, -0.336, P<0.05), and positively correlated with meibomian gland opening score (r = 0.345, P<0.05). SpO₂ had no correlation with tear meniscus height, lipid layer thickness, eye redness index, and meibomian gland opening score (P>0.05, Table 6; Figs. 5 and 6).

Table 6.

Correlation between PSG results and ocular surface analyzer examination results

Indicator	AHI		SpO2
	r	P	r	P
Tear Meniscus Height	0.247	0.053	-0.139	0.282
Lipid Layer Thickness	-0.277	0.029	0.230	0.072
Eye Redness Index	-0.336	0.008	0.142	0.270
Meibomian Gland Opening Score	0.345	0.006	-0.132	0.306

Fig. 5.

Correlation between AHI in PSG results and ocular surface analyzer examination results. A: Correlation between AHI and tear meniscus height; B: Correlation between AHI and lipid layer thickness; C: Correlation between AHI and eye redness index; D: Correlation between AHI and meibomian gland opening score

Fig. 6.

Correlation between SpO₂ in PSG results and ocular surface analyzer examination results. A: Correlation between SpO₂ and tear meniscus height; B: Correlation between SpO₂ and lipid layer thickness; C: Correlation between SpO₂ and eye redness index; D: Correlation between SpO₂ and meibomian gland opening score

Discussion

OSAS is a common sleep disorder. Studies have shown [13] that OSAS patients suffer from repeated breathing pauses and hypopnea at night, which leads to decreased blood oxygen saturation, thereby affecting tear secretion and tear film stability, and increasing the risk of dry eye syndrome.

In addition, OSAS patients often have changes in sleep structure, such as a decrease in rapid eye movement (REM) sleep and an increase in non-rapid eye movement (NREM) sleep. These changes can also affect tear secretion and tear film stability [14]. Studies have also found that CPAP treatment may indirectly alleviate dry eye symptoms by improving sleep quality and blood oxygen saturation [15]. In addition, the mask changes the direction of the gas, causing the airflow to be directed toward the eye above the mask. This increased airflow will also accelerate the evaporation of the tear film, causing irritation of the eye surface [16].

The results of this study showed that the AHI level of 31 OSAS patients after treatment was significantly lower than that before treatment, and the SpO₂ levels were significantly higher than that before treatment, indicating that OSAS patients have significant clinical efficacy after CPAP treatment. The CPAP mask delivers continuous positive pressure airflow into the airway, so that the airway maintains a positive pressure state throughout the respiratory cycle, thereby treating OSAS. Furthermore, daytime hypoxemia in this study population was primarily caused by OSAS itself and was associated with persistent hypoxia resulting from nocturnal apnea events. Although BMI did not meet obesity criteria, the severity of OSAS (38.71% of patients were severe) was significantly correlated with the severity of hypoxemia, suggesting that the hypoxic characteristics of this population are directly related to the progression of OSAS rather than metabolic factors. Further analysis of the results of this study showed that the BUT time of patients after treatment was significantly higher than that before treatment. The extension of BUT time indicates that CPAP treatment can relieve dry eye syndrome, which is related to CPAP treatment improving the sleep quality of OSAS patients, alleviating hypoxia symptoms, and thus reducing systemic inflammatory response. In addition, CPAP treatment may also produce a certain positive pressure effect on the eye, promote the secretion and distribution of tears, and thus improve dry eye symptoms [17]. However, the patient’s PL score and OSDI score were worse than before treatment, indicating that CPAP treatment may cause new damage to the patient’s eyes. The possible reason is that during CPAP treatment, due to the effect of pressure, gas may overflow from the edge of the mask, and the backflow of gas continuously impacts and stimulates the ocular surface tissue. This continuous stimulation may induce ocular surface diseases such as dry eye (DE) and conjunctivitis [9, 16, 18]. In addition, the use of masks may affect blink frequency, thereby affecting the secretion of meibomian glands [19]. Frequent blinking helps the renewal of tear film and the distribution of lipid layer, while the use of CPAP masks may reduce blink frequency, thereby affecting the normal secretion and function of meibomian glands [11, 20, 21]. Once the meibomian glands are obstructed, it leads to reduced secretion of lipids on the surface of the tear film, resulting in tear film instability and rapid evaporation of moisture, ultimately causing dry eyes and potentially leading to damage or rupture of the ocular surface [22]. Therefore, the use of a CPAP mask may exacerbate meibomian gland dysfunction and further worsen dry eye symptoms. Clinically, for patients experiencing dry eye symptoms and meibomian gland dysfunction, the mask should provide adequate coverage to minimize air flow stimulation to the eyes; the part of the mask in contact with the face should be made of soft materials to reduce pressure on the meibomian glands. Additionally, the mask should feature adjustable functionalities to accommodate different facial profiles for improved comfort.

The results of this study showed that the tear meniscus height of OSAS patients after treatment was significantly lower than before treatment, while the lipid layer thickness and eye redness index were significantly higher than before treatment. The meibomian gland opening score did not change before and after treatment, indicating that CPAP treatment can improve the lipid layer thickness and eye redness index of OSAS patients, but has no effect on the meibomian gland opening score. According to existing studies [23], there are significant abnormalities in the function and morphology of meibomian glands in OSAS patients, including a high incidence of meibomian gland atrophy and morphological abnormalities, and these changes are related to the severity of OSAS. In addition, as the degree of hypoxia in OSAS patients increases, the loss of meibomian glands becomes more obvious. During the use of CPAP masks, a certain amount of airflow may be generated, which may directly or indirectly affect the eye environment and cause dry eyes. Dry eyes are an important cause of meibomian gland dysfunction, because a dry environment accelerates tear evaporation, affects the stability of the tear film, and thus has a negative impact on meibomian gland function [24, 25]. Unlike protective masks (such as N95 masks), CPAP therapy masks require high airtightness to ensure positive pressure ventilation. Their continuous use at night (average 6–8 h) and dynamic leakage characteristics (leakage volume in this study: nasal mask 10.80 ± 2.71 L/min; oronasal mask 14.72 ± 4.11 L/min) result in more sustained mechanical stimulation of the ocular surface. This unique mode of action explains why CPAP masks are more likely to cause BUT shortening and increased OSDI scores, a conclusion supported by specialized CPAP studies [11, 26]. In addition, while the mask provides positive pressure airflow, it may also exert a certain amount of pressure on the eyes. This pressure may directly affect the discharge of meibomian gland secretions, leading to meibomian gland dysfunction [27]. Physicians should choose an appropriate type and size of mask based on the patient’s specific conditions, such as the severity of the disease, meibomian gland function, and dry eye symptoms. They should also pay attention to the patient’s feedback to timely adjust mask parameters for optimal treatment effectiveness.

The results of Pearson correlation analysis showed that BUT was positively correlated with lipid layer thickness and improvement of eye redness, Sit was positively correlated with tear meniscus height, PL score was negatively correlated with tear meniscus height, and positively correlated with eye redness index. Meibomian gland dysfunction is one of the common causes of dry eye, and the morphological structure and function of meibomian glands in OSAS patients also changed significantly. Studies have shown that [28–30] the morphological structure of meibomian glands and the stability of tear film in OSAS patients have changed, which may be due to the decreased sleep quality and increased tear evaporation caused by OSAS. OSAS not only directly affects the stability of tear film and increases the risk of dry eye, but also further aggravates dry eye symptoms by affecting the function of meibomian glands. Therefore, OSAS patients need to pay attention to the improvement of tear film stability and meibomian gland function during treatment to reduce the occurrence and development of dry eye symptoms. Additionally, the results of this study indicate that in PSG results, AHI negatively correlated with BUT, PL scores, and OSDI scores, while SpO₂ positively correlated with BUT, PL scores, and OSDI scores, but negatively correlated with the Sit score. In PSG results, AHI negatively correlated with lipid layer thickness and eye redness index, suggesting that CPAP treatment impacts dry eye symptoms and meibomian gland function, which can further influence clinical treatment outcomes. During the use of CPAP masks, leaks or gas backflow through the nasolacrimal duct can irritate the eyes and meibomian glands, increasing the risk of dry eye disease [31]. In addition, the sealing and pressure distribution of the mask may also affect the blood circulation and tear secretion of the eyes, thereby aggravating the symptoms of dry eye. Additionally, the seal quality and pressure distribution of the mask may also affect ocular blood circulation and tear secretion, further exacerbating dry eye symptoms. Therefore, in the treatment of OSAS, the choice of mask material is crucial for alleviating dry eye symptoms and improving meibomian gland function. Ideal materials should possess good breathability, comfort, and durability, while avoiding irritation to the eyes and surrounding skin. Commonly used mask materials on the market include silicone and foam. Researchers can conduct comparative analyses to select materials that minimally affect the eyes, thus reducing the occurrence of dry eye symptoms. CPAP therapy may indirectly improve BUT by alleviating hypoxia, but the design of this study aimed to elucidate the negative effects of mask-related physical factors (such as edge pressure and airflow backflow) on the ocular surface. The correlation between prolonged BUT and increased SpO₂ after treatment (r = 0.308, P < 0.05) suggests a protective effect from improved hypoxia, but the exacerbation of dry eye symptoms caused by the mask (increased PL scores and OSDI) indicates that mask-related factors play a dominant role. Although the impact of CPAP therapy on ocular surface parameters was observed, the dose–response relationship between air leakage rate and ocular symptoms was not quantitatively analyzed. Previous studies have shown that when the leakage rate exceeds 24 L/min, the incidence of ocular irritation symptoms increases significantly [11, 21]. Moreover, different mask types may have varying effects, with oronasal masks more likely than nasal masks to cause airflow disturbance in the palpebral fissure area [26]. In addition, the treatment pressure setting (8–12 cmH₂O on average in this study) may have a nonlinear association with tear film evaporation rate [27, 29], warranting stratified analysis in studies with larger samples. Future research should systematically document these parameters to clarify their modulatory roles.

In summary, when OSAS patients use CPAP masks for treatment, it may have a negative impact on dry eye symptoms and meibomian gland function, leading to decreased tear film stability and aggravated symptoms such as dry eyes. This study has a relatively small sample size, and the results may have certain biases. The study period is short, and the long-term effects of mask usage on dry eye symptoms and meibomian gland function remain unclear. Insufficient comparisons among different types of masks may overlook more effective treatment options. Future research could expand the sample size and lengthen the study period to conduct a more comprehensive comparison of different types of masks, aiming to provide more effective treatment strategies for OSAS patients. Moreover, exploring other adjunctive therapies, such as pharmacological or physical treatments, could further enhance treatment efficacy.

Author contribution

Shu-Yi Wei: Conceptualization, Data curation, Formal analysis, Resources, Writing– original draft. Zhen Wu: Conceptualization, Data curation, Investigation, Supervision, Writing– original draft. Yao Xu: Funding acquisition, Project administration, Software, Visualization, Writing– review and editing. Dan Li: Funding acquisition, Methodology, Project administration, Validation, Writing– review and editing. Yimin Xia: Data curation, Formal analysis, Resources, Validation, Writing– review and editing.

Funding

This study was funded by The Program of the Suzhou Industrial Park Cultivation Project of China (No. JL201803), The Program of the Suzhou Kowloon Hospital Shanghai Jiao Tong University School of Medicine (No. SZJL202116 and No. SZJL202106), The Research Programs of Science and Technology Commission Foundation of Suzhou (SKY2023112) and Suzhou Clinical Key Disease Project (LCZX202236).

Data availability

The data that support the findings of this study are available from the corresponding author, Yao Xu and Dan Li, upon reasonable request.

Declarations

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Written informed consent was obtained from all participants after a detailed explanation of the study’s purpose, methods, potential risks, and benefits.

Conflict of interest

The authors report there are no conflicts of interest in this work.