The aim of this study was to identify the factors associated with ocular surface epithelial damage in patients with pSS. We evaluated the effects of systemic parameters, laboratory findings, oral parameters, and other ocular surface parameters on ocular surface epithelial damage in patients with pSS. Ocular surface epithelial damage was measured by OSS, which is sum of corneal and conjunctival staining score. The OSS is included in the criteria for pSS with Schirmer’s test, and it is an informative marker for the severity of DED.12,14 Because ocular surface epithelial damage could affect visual disturbance and indicates the presence of ocular surface inflammation, the OSS parameter is important for determining treatment for DED patients with pSS.13,16,31
Previous studies have reported that an association between dry eye and systemic parameters, or extraocular variables.11,16,32−35 They used the symptoms of ocular dryness, tear osmolarity, or severe DED severity, as indicators of DED. Similar to our study, few studies used the OSS as the main outcome variable, but only reported correlations with laboratory findings, such as positive serologic findings.15,16 Therefore, we focused on the OSS as the main outcome and analyzed its independent association with systemic parameters, laboratory findings, oral parameters, and other ocular surface parameters after adjusting other variables.
Among the systemic parameters, age and duration of pSS were significant factors that influenced OSS in the multivariate analysis of our study. A decrease in age was significantly related to an increase in OSS after adjusting for other factors. Although the previous studies of ocular parameters in patients with pSS have reported a correlation with age, they mostly have found a correlation with onset age of pSS or with ocular symptoms other than OSS.32–36 In their study, the age was negatively related to ocular dryness, indicating older patients with severe disease tended to be less sensitive.32 In another study, young-onset SS (age at diagnosis < 35 years) correlation with xerostomia (P = 0.008), abnormality of Schirmer’s test and/or Rose Bengal staining (P = 0.03), positivity of anti-Ro/SS-A antibodies (P < 0.001), low complement C3 (P = 0.018) and low complement C4 levels (P = 0.017), compare to age at diagnosis > 35 years.33
An increase of the duration of pSS was significantly related to an increase of OSS in the current study. A previous study with a large cohort study of patients with pSS in Spain also reported a correlation between duration of pSS and ocular involvement. Patients who had longer duration of pSS (more than 10 years) showed a higher prevalence of xerophthalmia, abnormality of Schirmer’s test and/or Rose Bengal staining and other systemic involvements (parotid enlargement, lung involvement, vasculitis, or peripheral neuropathy), laboratory findings (positivity of anti-SSA/Ro antibody, anti-SSB/La antibody, and low complement C4 level) in a univariate analysis. But in a multivariate analysis, there were no significant correlations with xerophthalmia and abnormality of Schirmer’s test and/or Rose Bengal staining that influence duration of pSS after adjusting for other factors.33 According to this our study, patients with young age and long duration of pSS have higher risk of ocular surface damage; therefore, more careful monitor of DED is needed in those patients with pSS.
In our study, among the medical history, topical cyclosporine was associated with increased OSS in univariate analysis. This may have been due to the fact that topical cyclosporine was prescribed as treatment in order to improve the OSS in patients with severe ocular surface epithelial damage. However, after adjusting for other factors, no significant association was found in the multivariate analysis.
Of the laboratory findings in our study, positivity of anti-SSB/La antibody and RF were significant variables, and positivity of anti-SSA/Ro antibody and ANA were borderline significant variables in the univariate analysis. This result was similar with previous studies, that reported a correlation between the ocular surface parameters and serologic markers in patients with pSS.3,15,16 Serum RF, and ANA levels correlated with conjunctival staining score and total OSS in patients with pSS.15 Furthermore, serum anti-Ro/SSA and anti-La/SSB antibodies were significantly related with clinical severity of keratoconjunctivitis sicca based on the Oxford OSS scheme in patients with pSS.16 These studies suggested that these parameters could be considered as prognostic factors for predicting the severity and prognosis of DED in patients with pSS.15,16 However, in our multivariate analysis, there were no significant laboratory findings that influenced OSS after adjusting for other factors. This was the first multivariate analysis study of association between serologic markers and OSS, and the results might differ compare to previous studies that performed a univariate analysis.
Among the oral parameters, positive subjective oral score and NSWSF were significantly related with OSS in the univariate analysis; however after adjusting for other factors, no significant correlation was found. In a recent rheumatologic study, only the presence of inflammatory joint involvement among other systemic manifestations was associated with severe/very severe DED in patients with pSS (odds ratio, 2.079).35 Similarly, a multivariate analysis was performed in this study, thereby showing that there were no associations between other laboratory findings or oral parameters and DED severity.
Among the ocular surface parameters, FBUT and MGD were significant factors that influenced OSS in the multivariate analysis of our study. An increase in FBUT was significantly related to an increase in OSS after adjusting for other factors. The results of the Schirmer’s test were significantly related with OSS in the univariate analysis, but no significant correlation was found after adjusting for other factors. According to previous study of patients with DED and ocular surface disease, FBUT is minimally invasive test and is a more reliable than the Schirmer’s test. Furthermore, FBUT is strongly correlated with other ocular tests such as OSS.37 From these results, FBUT reflected the ocular surface epithelial damage better than the Schirmer’s test even in patients with pSS.
An increase in MGD grade was significantly related to an increase in OSS after adjusting for other factors. A previous study on MGD in patients with pSS reported that changes in the meibomian gland induced an increase of tear evaporation and subsequent worsening of the ocular surface desiccation.38 Furthermore, in another study, morphological and functional features of the meibomian gland correlated with other ocular surface parameters and disease severity in ADDE, such as pSS and graft-versus-host disease.39 According to this result, more attention is needed in pSS patients with low FBUT and severe MGD, which could cause more ocular surface epithelial damage.
There were several limitations in this study. First, the retrospective of the study might lead to unexpected various bias. Second, only a small number of patients were enrolled. Third, some of the parameters were not assessed in some of the patients. Fourth, some systemic manifestations, such as inflammatory joint involvement, were not evaluated in this study. However, our study is meaningful because it is the first multivariate regression analysis of factors associated with ocular surface epithelial damage in patients with pSS.