Clinical evaluation of meibomian gland dysfunction in patients with keratoconus

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Abstract

Purpose

To investigate the association of keratoconus (KC) with meibomian gland dysfunction (MGD) and to describe the epidemiological characteristics of MGD in this disease.

Methods

In this observational study, 120 KC patients seen in the Department of Ophthalmology of the Complexo Hospitalario Universitario de Santiago de Compostela and 87 controls were analyzed. The Ocular surface disease index (OSDI) questionnaire was administered and several DED tests and an evaluation of the meibomian glands and lid margin were performed. MGD signs and DED tests were compared between the groups. Symptoms were further analyzed in patients and controls with and without MGD.

Results

KC was significantly associated with MGD after adjusting for age and sex [adjusted odds ratio (ORa), 2.40]. The frequency of MGD in KC patients [59 (49.2%) KC patients and 25 (28.7%) controls had MGD] correlated with the severity of KC (r = 0.206) (P = 0.020). Mean OSDI score in KC patients with and without MGD was 31.1 ± 24.1 and 35.2 ± 26.0 (P = 0.326), and 17.2 ± 22.7 and 13.3 ± 14.1 in controls with and without it (P = 0.366). The most common MGD signs coincided in both groups. Staining with fluorescein (P = 0.000) and lissamine green (P = 0.019) was higher in KC patients, but no differences were detected with TBUT (P = 0.116) or the Schirmer test (P = 0.637). Hypersecretory MGD was the most prevalent variant in both groups.

Conclusions

MGD and DED are common in KC patients. MGD correlates with the severity of KC and is indistinguishable from MGD in patients without KC. No association was found with symptoms. Patients with KC should be screened for MGD because of its possible clinical implications. Further research is needed to clarify the role of MGD in KC patients.

Introduction

Keratoconus (KC) is a chronic bilateral disease characterized by asymmetric progressive thinning most commonly located in the inferotemporal and central corneal regions. Its prevalence in the different studies ranges from 0.17 to 47.9 per 1000 people [1] and its annual incidence from 1.3 to 25.0 per 100 000 people [2], [3], [4], [5], but it could be higher as there are probably many undiagnosed subclinical cases. It usually starts in puberty and progresses over time to stabilize in the third or fourth decades of life. Vision correction in this condition is often achieved with glasses or contact lenses in the mild and moderate stages of the disease, but surgery may be required in severe KC.

Although traditionally considered an ectatic non-inflammatory disease, several studies have demonstrated increased interleukine-6, interleukine-1β and interferon-γ levels in this disorder [6], [7], [8], [9]. A myriad of genetic, environmental, biomechanical and neurotrophic associated factors have also been described. In addition, systemic diseases such as thyroid disease, sleep apnea syndrome or asthma have recently been found to be associated [10], [11], [12], [13], [14], [15], [16], [17], [18], although the extent to which these different factors, including inflammation, may affect each other is unknown.

Meibomian gland dysfunction (MGD) is a chronic, diffuse abnormality of the meibomian glands characterized by terminal duct obstruction and/or qualitative/quantitative changes in glandular secretion, which may result in alteration of the tear film, clinical apparent inflammation, ocular surface disease and symptoms of eye irritation [19]. It is the most frequent risk factor for the development of dry eye disease [20], [21], [22] and its prevalence in population-based studies ranges widely from 3 to 65% probably because of differences in study populations and variable diagnostic criteria [22], [23], [24], [25].

Previous studies have reported an association of KC with DED [26], [27], [28], [29], [30], which can seriously affect quality of life [31], [32], [33]. A few investigations also suggest an increased prevalence of MGD in KC [26], [34], but there are no studies on the association of KC with MGD. The hypothesis of this study was that MGD might be an important associated factor in KC and that MGD might have distinct characteristics in patients with this disease. Being able to identify the role of MGD in KC would further the understanding of the pathophysiology of this condition and help to design strategies to manage DED in these patients. The purpose of this study was to investigate the association of KC with MGD as well as to describe the epidemiological characteristics of MGD in this disease.

Section snippets

Participants

In this observational study, the study group consisted of 120 patients previously diagnosed with KC, consecutively recruited from the corneal and external disease clinic of the Department of Ophthalmology of the Complexo Hospitalario Universitario de Santiago de Compostela from May 2015 to November 2016. The control group comprised 87 patients without this diagnosis recruited from the general ophthalmic clinic of the Department of Ophthalmology of the same hospital. Subjects were excluded from

Results

There were 65 men (54.2%) and 55 women (45.8%) in the KC group and 31 men (35.6%) and 56 women (64.4%) in the control group. Their mean age was 35.2 ± 11.3 years (range, 13–66 years) and 36.9 ± 14.2 years (range, 15–63 years), respectively (P = 0.372). A total of 35 patients in the KC group had only one eye analyzed because they had undergone KC surgery in the other: intrastromal corneal ring segment insertion (18 eyes), keratoplasty (11 eyes), corneal cross linking (3 eyes) and epikeratoplasty

Discussion

The main finding of this study was that MGD was nearly twice as common in KC patients as in controls and more prevalent in the more advanced stages of the disease. It was also found that KC patients exhibited more symptoms and signs than controls, although no differences were found with respect to the Schirmer test. The prevalence of MGD, or DED, in KC and in other pathologies varies substantially between studies [22], [23], [24], [25], [26], [27], [28], [29], [30]. These variable results may

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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