The Deterioration of Meibomian Gland Over the Duration of Sjögren Syndrome

Purpose: To investigate the correlation between Sjögren syndrome (SS) duration and ocular surface parameters in patients with SS-related dry eye. Methods: We analyzed 108 eyes of 108 female patients with primary SS-related dry eye. Meibomian gland (MG) dysfunction, MG dropout, lipid layer thickness (LLT), partial and total blinking, and partial blinking rate (PBR) were measured using a LipiView ® II ocular surface interferometer (TearScience, Morrisville, NC, USA). All patients underwent rheumatoid serologic tests and ocular surface assessments. The ocular surface assessment included the Standard Patient Evaluation of Eye Dryness (SPEED), Schirmer’s I test, non-invasive tear break-up time, and grading of corneal/conjunctival staining. The correlations between SS duration and MG dropout rates as well as other ocular surface parameters were determined. Results: The mean SS duration was 54.1±41.3 months. There was a strong positive correlation between SS duration and MG dropout (r = 0.766, p < 0.001). The average, maximum, and minimum LLTs showed a weak negative correlation with SS duration (r = -0.310, -0.211, and - 0.304, respectively, p = 0.014, 0.028, and 0.022, respectively) and MG dropout (r = -0.191, -0.326, and -0.299, respectively, p = 0.049, 0.002, and 0.009, respectively). Signi�cant positive correlations were also observed between the SPEED scores and SS duration (r = 0.303, p = 0.042) and MG dropout (r = 0.450, p = 0.029). Conclusions: Longer durations of primary SS-related dry eye were associated with worse MG dysfunction.


Introduction
Dry eye disease (DED) is a chronic disease that results from the destruction of the ocular surface, which leads to tear lm instability.Its prevalence increases with age [1].Evaporative DED is the main subtype of DED, and meibomian gland dysfunction (MGD) is a primary cause of evaporative DED [2,3].A decrease in the amount or quality of meibum reduces the lipid layer thickness (LLT) and increases the evaporation of the tear lm [4].
Sjögren syndrome (SS) is a chronic in ammatory autoimmune disease characterized by diminished lacrimal and salivary gland function following lymphocytic in ltration of these glands [5][6][7].The in ltrating cells in glandular elements lead to the secretion of cytokines and the activation of the pathways of interferon-1 and -2.The production of autoantibodies interferes with muscarine receptors and stimulates destruction [8].SS may present as a single disease, called primary SS or secondary SS, when associated with other underlying autoimmune conditions such as systemic lupus erythematosus or rheumatoid arthritis [9].The prevalence of primary SS has been reported to be between 0.1 and 0.8% [10,11].SS results in aqueous-de cient conditions and manifests with more than moderate dry eye symptoms [12].
The meibomian glands (MGs), namely the sebaceous glands, secrete a lipid coating on the tear lm surface of the cornea, which aids in preventing evaporation of the aqueous lm [4,13].The MG in SS-related dry eye patients have been reported to be severely damaged compared with that in those without SS [14,15].There are many reports on SS and MGD.Prior studies have reported signi cant destruction of MG and lower non-invasive breakup time in patients with SS [16][17][18].Another study compared the patterns in SS-related DED patients by grouping them based on the three-year duration of DED [19].However, no study has analyzed the patterns of SS-related DED according to the duration of SS.
The purpose of this study was to analyze the association between the duration of Sjögren syndrome and ocular surface clinical parameters of DED.

Sjögren syndrome diagnosis
SS was diagnosed according to the American College of Rheumatology and con rmed by both an ophthalmologist and a rheumatologist [21].Patients who had at least two of the following three objective features were diagnosed with primary SS: positive serum anti-SSA/Ro and/or anti-SSB/La (or positive rheumatoid factor and antinuclear antibody titer ≥ 1:320), positive rheumatoid factor and ANA titer ≥1:320), labial salivary gland biopsy exhibiting focal lymphocytic sialadenitis with a focus score of ≥ 1 per 4 mm 2 , and keratoconjunctivitis sicca with an ocular staining score of ≥ 3 [22,23].

Meibomian gland dropout
All meibography images were acquired from the lower eyelid using the infrared camera system of the LVII.Meibography images were obtained according to the guidelines of the manufacturer.The patients were asked to sit on the chair and lay down their chin and forehead on the indicated resting places, and the image was taken once the MGs were correctly focused.Images with the following characteristics were selected: good image quality, equivalent zoom, and lacrimal point visible with the everted eyelid.The area of MG dropout was calculated using the free-hand selection tool of the ImageJ software (a free opensource image-processing software provided by the National Institutes of Health; http://imagej.nih.gov/ij) [18].For the measurement with ImageJ, a manual selection of the total area of the everted eyelid was made, followed by a delimitation of the area with MG dropout [24].The percentage of MG dropout was calculated as the percentage of MG area loss in the entire MG area [25].

Lipid layer thickness
Lipid layer thickness (LLT) is a representative parameter of MG function [26].The LVII is a non-invasive instrument that uses live digital images of the tear lm, measures its lipid component, and calculates blink dynamics [27].The absolute thickness of the LLT was determined using the LVII by analyzing more than 1 billion data points of the interferometric image.Patients were requested to look into a camera while blinking freely for a 20-second video recording.The participants were also asked not to touch their eyes throughout the imaging.For each measurement, the participants were instructed to rest their heads on the chinrest.The interferometer was operated for its maximum lming time, and the video was instantly analyzed for LLT in nanometers based on interferometric color units (ICUs).The LLT results were transformed from ICUs into nanometers [28,29].The interferometer offers a non-invasive technique for the estimation of LLT.The LVII assesses the lipid layer thickness using an Interference Color Unit (ICU) score.LVII is capable of direct quanti cation of LLT [30].Maximum, average, and minimum LLT values were measured, and the maximum value was 100 nm in all cases.

Blinking Pattern Measurement
The LVII automatically detects and analyzes blink rate and blinking quality through the recorded videos.
Participants were asked to blink freely, and the same investigator assessed them throughout the study.
The LVII display the number of full and partial blinks and blink frequencies.Each stage during the blinking cycle was recorded during the examination, and the partial blinks were de ned as blinks without the touching of the upper and lower eyelids [31].This analysis also involved the data on the complete blinking rate and PBR [32].

Dry eye Questionnaire
All patients completed the SPEED questionnaires for evaluating eye discomfort symptoms.
The SPEED scores were graded from 0 to 5 (no symptoms), 6 to 14 (mild and moderate symptoms), and 15 to 28 (severe symptoms) [33,34].A previous study showed that the SPEED questionnaire was compatible with the Ocular Surface Disease Index (OSDI) [33].
Schirmer's I test Schirmer's I test without anesthesia was performed using sterile Schirmer strips (I-DEW Tearstrips, Entod Research Cell UK Ltd., London, UK).The standard strips were placed in the midlateral portion of the lower fornix for 5 min.During this procedure, the patients were asked to close their eyes.The length of the wet portion of the strip was recorded in millimeters.

NITBUT
The NITBUT was measured using the IDRA ® Ocular Surface Analyzer (SBM SISTEMI, Inc., Torino, Italy).The time elapsed between the last blink and the first sign of break-up of the tear lm following a ring pattern was documented as the NITBUT.The NITBUT assesses the stability of the tear lm by measuring the time from the full blink to the presence of the rst disruption of the re ected image on the cornea in seconds.

Ocular staining
Fluorescein staining showed corneal or conjunctival epithelial cell injury [19].The procedurefor scoring corneal and conjunctival uorescein staining was based on previous reports [35].The corneal staining was conducted using uorescein impregnated strips (Haag-Sterit, Bern, Switzerland).The cornea was equally divided into upper, lower, nasal, bitemporal, and middle sections.The score for each section was recorded after staining as follows: 0 = no punctate staining; 1 = less than 5 dots; 2 = between 1 and 3; 3 = whole staining.The cumulative score for each eye ranged from 0 to 15 [36].Fluorescein impregnated strips (Haag-Sterit, Bern, Switzerland) wetted with a drop of nonpreserved normal saline was instilled into the inferior conjunctiva.After gentle blinking, the degree of conjunctival staining with total scores ranging from 0 (no staining) to 6 (worst) were measured [37].

Statistical Analysis
The data were analyzed using SPSS software (version 26.0, SPSS Inc., Chicago, IL).The relationship between the measurements was evaluated using Pearson's correlation coe cient analysis and linear regression analysis.The correlation between the values was expressed as a Pearson correlation coe cient (r).Continuous variables were presented as means ± standard deviation (SD).Statistical signi cance was set at p = 0.05.

Results
One hundred and eight eyes of 108 female primary SS-related DED patients, aged 21-78 years (mean 56.7 years) were enrolled.The baseline characteristics of the study population and the median values for the ocular surface parameters are shown in Table 1.Considering that SS has a robust female predisposition [23], the research involved only female patients, and only the results of the right eye were analyzed.
The anti-SSA/Ro, anti-SSB/La, antinuclear antibody, and rheumatoid factor were 72%, 35%, 94%, and 24%, respectively.The results of the serologic test were not statistically signi cant associations with dry eye parameters.

Discussion
The results of this study showed that a longer SS duration contributed to the worsening of MG dysfunction.DED in SS patients has been classically considered as a result of aqueous De ciency [38].However, various studies have reported that SS-related DED patients presented with a signi cantly thinner lipid layer, shorter NITBUT, and a higher degree of MGD than non-SS-related DED patients.Therefore, it is thought that there are elements of evaporative dry eye associated with MGD in SS-related DED patients [39,16,17,38].Dry eye in SS patients has been speculated to be due to severe aqueous de ciency, and little attention has been paid to the possibility of evaporative dry eye.This study demonstrated that a longer duration of SS is related to deteriorative changes in MG.This is the rst study to evaluate the association between SS duration and ocular surface clinical parameters in patients with primary SS.It is di cult to pinpoint the duration of SS.Approximately one in every ten patients with a signi cant DED have primary SS, and only one-third have a known diagnosis at the time they consult the ophthalmologist [40].It has been documented previously that the incidence of MG dropout and the tear evaporation rates are signi cantly higher in SS-related aqueous-tear de cient dry eye patients than in non-SS-related dry eye patients [14].MG is thought to be a special type of sebaceous gland located in the tarsal plates of the eyelids, and MG is also damaged by in ltration of autoreactive lymphocytes, leading to evaporative dry eye [41,42].The destruction of MGs and an increase in tear evaporation are often associated with changes in the ocular surface in patients with SS.The MGs of patients with SS were more severely impaired than those of dry eye patients without SS [14,39,16].
A previous study showed a negative correlation between NITBUT and meiboscore, but our study did not show any signi cant association between NITBUT and the MG dropout rate [39].Based on the principle of interferometry using light re ection in LVII, if aqueous de ciency is severe, the LLT measurement is higher than the actual.However, if SS is prolonged, the damage to the MG becomes irreversible, and, consequently, LLT seems to decrease.LLT is considered to decrease a longer duration of SS is associated with a lower capacity for compensation.
The results of a study indicate that patients with SS have a higher degree of morphological changes in the MG [17].It has been reported that patients with DED associated with SS have higher MG dropout rates than non-SS DED patients [14,18].
To our knowledge, this is currently the only study that has evaluated the duration of SS and its correlation with ocular surface parameters, including the state of the MG.A study reported on a similar topic cited the failure to observe severe damage to the MG with the increase in the prevalence of SS as a limitation [39].
A longer duration of SS is related to major symptoms and changes in MG.SS is thought to cause in ammation not only in the lacrimal gland but also in the MG, causing damage.Based on the principle of interferometry using light re ection in LVII, if aqueous de ciency is severe, the LLT measurement is higher than the actual.However, if SS is prolonged, damage to the MG becomes irreversible, and, consequently, LLT seems to decrease.This study has several limitations.This study on various ocular surface parameters, such as LLT and PBR, failed to evaluate meibum expressibility, meibum quality, mucocutaneous junction shifts, lid telangiectasia, and lid margin irregularity.Since MG dropout and the three above indicators are closely related [43], a study involving the assessment of these parameters will be necessary in the future.The non-inclusion of participants with non-SS-related dry eye is another limitation of this study.Therefore, it is di cult to conclude that the increased MGD observed in the SS group was due to SS or dry eye, and there is the need for further studies including a control group of participants with non-SS-related dry eye.
There are various theories about the relationship between SS and MG dysfunction.A previous study suggested that SS-related ocular surface changes may result in changes in the meibomian glands in patients with SS [14].Another study reported the presence of lymphocyte in ltration in the sebaceous glands of the skin in SS patients, even though SS affects the exocrine glands and not the sebaceous glands, such as the MGs [44].The authors also indicated that gland dropout occurred because of ductal hyperkeratinization [45].It has been documented that keratinization of the ocular surface epithelium occurs in SS [46].Therefore, epithelial keratinization may play a role in the mutual pathogenesis of SS and MGD [39].
In conclusion, a longer SS duration was associated with worse MG dysfunction.This study also suggests that MGD plays an essential role in SS-related dry eye.

A
retrospective, cross-sectional, observational study was conducted at Kim's Eye Hospital, Seoul, Republic of Korea from January 2017 to October 2020.The study adhered to the tenets of the Declaration of Helsinki and was reviewed and approved by the institutional review board at Kim's Eye Hospital, Seoul, Republic of Korea (2021-01-001).The data of the subjects were deanonymized in this study.Due to the retrospective nature of the study, informed consent was waived.A single ophthalmologist diagnosed DED based on the following diagnostic criteria: Standard Patient Dry Eye Evaluation (SPEED) score of ≥ 6 points and non-invasive tear break-up time (NITBUT) of < 10 seconds [20].YY Age below 20 years, pregnancy or lactation, glaucoma or other concomitant ocular pathologies, ocular history of ocular surgery, ocular injury, ocular infection, using a punctual plug or topical eye drops other than non-preserved arti cial tears were excluded.The single investigator handled the LipiView ® II ocular surface interferometer (TearScience, Morrisville, NC, USA) (LVII) throughout the study.A single investigator assessed the clinical parameters and SPEED questionnaire scores.Only the test results for the right eye was analyzed.

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Table 1 .
Funding The author(s) received no nancial support for the research, authorship and/or publication of this article.45.Jester JV, Rife L, Nii D, Luttrull JK, Wilson L, Smith RE (1982) In vivo biomicroscopy and photography of meibomian glands in a rabbit model of meibomian gland dysfunction.Investigative ophthalmology & Demographic data and clinical characteristics of primary Sjögren syndrome dry eye patients.
Data are presented as the mean ± standard deviation.DED, dry eye disease.SPEED, standard patient evaluation of eye dryness validated questionnaire (0-28).NITBUT, Non-invasive tear break-up time.TMH, Tear meniscus height.nm, nanometer.Number of partial blinks, number of incomplete blinking per 20 seconds.Number of total blinks, number of total blinks per 20 seconds.MGD, meibomian gland dysfunction.

Table 2 .
Correlation analysis between Sjögren syndrome (SS) duration and other ocular surface clinical parameters in patients with primary SS.The correlation was statistically analyzed by linear regression.* indicates statistically signi cant association (p < 0.05).** indicates statistically signi cant association (p < 0.001).NITBUT, Non-invasive tear break-up time.TMH, Tear meniscus height.nm, nanometer.Partial blinks, number of incomplete blinks per 20 seconds.Total blinks, number of total blinks per 20 seconds.LLT, lipid layer thickness.SPEED, standard patient evaluation of eye dryness validated questionnaire (0-28).MG, meibomian gland.