ABSTRACT
Conclusion:
Sarcoidosis patients had significantly higher Nelson grades in conjunctival IC, as well as significantly higher percentages of dry eye as determined by the Schirmer I test, TBUT, and OSDI. Reduced tear quantity and quality may destabilize the tear film layer, resulting in a variety of ocular symptoms.
Results:
The mean ages in Groups 1 and 2 were 49.26±3.18 and 51.91±2.89 years, respectively (p=0.720). The mean Schirmer I test, TBUT, and OSDI scores differed significantly (p<0.05 for all), with Group 1 having a significantly higher percentage of dry eyes than Group 2. Group 1 had significantly higher Nelson’s grading system grades than Group 2 based on conjunctival IC analysis (p=0.001). There were no significant differences in visual acuity (p=0.17) or intraocular pressure (p=0.14) between groups.
Materials and Methods:
This study evaluated clinical data collected between January 2019 and January 2021 from 57 right eyes of 57 sarcoidosis patients without ocular involvement (Group 1) and 33 right eyes of 33 healthy individuals with similar demographic characteristics (Group 2). The Schirmer I test, tear break-up time (TBUT), fluorescein staining, and conjunctival IC were all performed as part of the conjunctival and corneal examinations following a thorough ophthalmological examination. The Ocular Surface Disease Index (OSDI) was used to assess subjective ocular symptoms.
Objectives:
To evaluate sarcoidosis-induced tear film changes using subjective and objective diagnostic tests, particularly conjunctival impression cytology (IC), and to compare the results with healthy individuals.
Introduction
Sarcoidosis is a systemic disease of unknown etiology characterized by the presence of non-caseating granulomas.1 It is most common in people under the age of 40, with clinical manifestations that are either diffuse or limited to one or two organs.2 The diagnosis of sarcoidosis is generally complicated by the fact that symptoms may be absent or variable, and clinical and radiological signs may be confused with infections and/or malignancies.1 After excluding other potential pathologies, sarcoidosis is diagnosed based on clinical, radiological, and laboratory findings, as well as the presence of non-caseating granulomatous inflammation.3
Sarcoidosis-induced granulomatous inflammation may involve all ocular structures, resulting in ocular sarcoidosis, which is one of the most important complications and has a prevalence of 13% to 79%.4,5 Ocular findings, however, are typically asymptomatic. If sarcoidosis is suspected, a routine ocular examination is therefore recommended.6 While the cause of sarcoidosis-induced dry eye symptoms is currently unknown, objective tests show that it could occur as a result of lacrimal gland inflammation and decreased tear production.7,8 Moreover, other etiologically similar systemic inflammatory diseases, such as rheumatoid arthritis, have been linked to an increased prevalence of dry eye.9 This could explain the decreased tear production caused by autoantibody-induced inflammation.
Conjunctival impression cytology (IC) is a minimally invasive technique that enables ocular examination, particularly for dry eye, in a clinical setting. This technique may be used for diagnosis, understanding the disease mechanism, and assessing therapeutic efficacy. Over the last few years, conjunctival IC research has contributed to a better understanding of dry eye disease pathophysiology, as well as helping to confirm that ocular surface inflammation is clearly associated with clinical manifestations of this disease. Conjunctival IC research has also begun to elucidate the mechanism of action of inflammation, with studies indicating that dry eye disease is a Th1-mediated process and that local surface cells (e.g., conjunctival epithelial cells) rather than systemic cells play an important role in ocular inflammation. Cytokines released by infiltrating Th1 cells disrupt the normal cytokine balance on the ocular surface, resulting in ocular surface epithelial pathology. The results of conjunctival IC analysis have also provided justification for considering new treatments.10
This study was designed to evaluate sarcoidosis-induced tear film and ocular surface changes using subjective and objective diagnostic tests, particularly conjunctival IC, and to compare the results with those of healthy individuals.
Materials and Methods
Results
This study evaluated data of 57 right eyes of 57 sarcoidosis patients (group 1) and 33 right eyes of 33 healthy individuals (group 2). Females outnumbered males in both groups, with female-to-male ratios of 41:16 (71.9%:28.1%) and 19:14 (57.6%/42.4%) in groups 1 and 2, respectively. Group 1 had mean disease and prior therapy durations of 3.87±0.13 and 1.49±0.08 years, respectively. Table 1 shows the demographic characteristics of the participants.
Discussion
Dry eye is a tear film disorder that damages the ocular surface in the palpebral fissure and is frequently associated with subjective complaints.16,17,18 This disorder is a common but frequently overlooked symptom that usually persists even after controlling sarcoidosis. Although biopsy is a simple technique for ruling out conjunctival granulomatous inflammation, its efficacy in diagnosing sarcoidosis is debatable, with low yields reported in some studies (directed and blind biopsies) and clinically visible areas of non-caseating granulomas being difficult to identify.19
On the other hand, conjunctival IC has been successfully used to investigate many aspects of dry eye disease, including the pathophysiology, monitoring clinical studies to determine the efficacy of various treatments, developing animal models of dry eye disease, and linking dry eye disease to other systemic diseases.20 This method is primarily based on cell harvesting and processing, as well as subclinical inflammation detection methods such as flow cytometry and immunocytochemistry.21,22 Larmande and Timsit23 reported in 1954 that conjunctival IC could be used to diagnose ocular surface squamous neoplasia. Egbert et al.20 also reported in 1977 the use of IC with absorbent filter paper to obtain cells in the same manner that is still used today.
Our study revealed significantly higher IC grades in sarcoidosis patients versus healthy individuals using Nelson’s grading system, with the majority of patients displaying moderate loss of cohesion in conjunctival epithelial cells, a scarcity of goblet cells, shrinkage of cell nuclei, and more polygonal-shaped cells.14
The use of conjunctival IC to detect ocular surface changes has revealed that dry eye disease-specific changes are associated with a wide range of systemic and local conditions, indicating that this technique could be useful for assessing ocular surface changes in different conditions. This minimally invasive technique has the potential to provide detailed cytological data in both dry eyes and systemic diseases with ocular involvement, confirming the diagnosis of squamous metaplasia/dry eye.22,23
Significant cellular modifications have been detected in conjunctival IC with severe dry eye, suggesting the efficacy of conjunctival IC in evaluating squamous metaplasia and monitoring treatment response.24 Dry eye has been shown to be unaffected by the duration of inflammatory bowel disease (IBD), although IBD patients had three times the rate of dry eyes as controls.25 In other studies, conjunctival IC did not distinguish between smokers and nonsmokers in terms of goblet cell density, nor did it distinguish between sarcoidosis and dry eye, both of which showed signs of ocular surface disease.26,27
IC has typically been used to detect morphological changes in ocular surface disease, most notably squamous metaplasia, in dry eye disease. Conjunctival squamous metaplasia and subsequent goblet cell loss may result in decreased tear production, both in quantity and quality, as well as destabilization of the tear film layer, resulting in different ocular symptoms. In our study, goblet cell loss and conjunctival squamous metaplasia were more common in sarcoidosis patients, in addition to conjunctival IC-confirmed ocular inflammation, demonstrating a positive correlation of this technique with other dry eye tests. Hence, conjunctival IC has become a valuable tool for assessing ocular surface changes and will almost certainly continue to provide valuable information for diagnosing and treating patients with ocular surface disorders.
Sarcoidosis-induced tear film disorder is commonly categorized as an aqueous phase tear film disorder.15,16,28,29 The most likely cause of lacrimal gland disorder is lymphocytic infiltration of the lacrimal gland during the acute inflammatory phase, but it could also be due to glandular tissue atrophy later on.30 Low Schirmer I test levels and positive rose bengal tests have been recorded in 70% of sarcoidosis patients.29 Likewise, the Schirmer I test values in our study were lower in 64.9% of sarcoidosis patients, highlighting the prevalence of aqueous phase disorders in this group and implying that many sarcoidosis patients could have disturbances in various phases of tear film disorder.
The aqueous phase tear film may collapse abruptly as a result of decreased lacrimal gland production. Since the expression of growth factors required for surface epithelial differentiation and function is reduced in the lacrimal glands, mucin phase dysfunction may also occur. Furthermore, in addition to clinically manifested conjunctival involvement, there could be subclinical diffuse subepithelial infiltration that impairs mucin production in the goblet cells of the conjunctival epithelium. Subclinical infiltration could also be to blame for meibomian gland dysfunctions (lipid phase). An improper lipid composition may cause increased epithelial proliferation or altered bacterial flora in the ostia of the meibomian glands.28 The fluorescein test and conjunctival IC used in our study revealed clinically significant surface epithelial damage, but were insufficient to detect subepithelial infiltration.
The majority of sarcoidosis patients in our study had symptomatic dry eye, implying that tear film disorders could be much more common in sarcoidosis patients than is clinically presumed. Aside from all anterior segment parameters, the mean values of many dry eye parameters, including signs of blepharitis, TBUT, Schirmer I test, corneal and conjunctival fluorescein staining, OSDI scores, as well as conjunctival IC were significantly different in sarcoidosis patients versus healthy individuals. TBUT is the most sensitive parameter for detecting tear film instability and is commonly used to detect epithelial lesions.30 This parameter was significantly shorter in sarcoidosis patients, who also had significantly higher grade in Nelson conjunctival IC analysis. Since almost all tests revealed the presence of significant dry eye in sarcoidosis patients, it is possible that sarcoidosis is associated with decreased tear production and tear film quality. The significantly higher rate of dry eye in sarcoidosis patients suggests that our findings correspond to prior reports. Moreover, tear film tests have been shown to be age-related, and dry eye becomes more common with aging. Given the findings in our study, where the mean age of sarcoidosis patients was 49.26±3.18 years, it is reasonable to assume that many sarcoidosis patients will develop dry eye symptoms later in life.
Conclusion
Both subjective and objective tests revealed significant differences between sarcoidosis patients and healthy individuals. Dry eye percentages determined by the Schirmer I test, TBUT, and OSDI were significantly higher in sarcoidosis patients. Nelson grades in conjunctival IC were also significantly higher in sarcoidosis patients. Decreased quantity and quality of tear production could ultimately destabilize the tear film layer, leading to different ocular symptoms, as evidenced by our findings that dry eye was significantly associated with sarcoidosis.
Study Limitations
There are some drawbacks to our study. The activation status of sarcoidosis patients with dry eye symptoms could not be determined. Thus, no statistical analysis was performed to determine whether there was a link between dry eye and sarcoidosis activity. Apart from ocular sarcoidosis-related dry eye symptoms, there was no record of other sarcoidosis manifestations, implying that the relationship between dry eye and other non-ocular sarcoidosis manifestations could not be assessed. It should also be noted that conjunctival IC has a number of drawbacks, including (a) a lack of standardization in the methodology used (i.e., type of membrane, fixation procedures, areas sampled, and processing/removal techniques), (b) sampling is generally limited to the outermost tissue layers, and (c) the effects of topical anesthetics on subsequent testing have not been thoroughly studied.
Despite its drawbacks, IC has several advantages, including being less invasive than conjunctival biopsies, scraping, or brush cytology; the ability to sample specific (or multiple) conjunctival areas; simultaneous demarcation of morphological data with biomarker analysis; the absence of basement membrane disruption; and providing a biochemical “snapshot” of tissue at that point in the disease course.
