Is keratoconus solely a noninflammatory, ectatic condition, or an ocular response from genetic and inflammatory factors? An investigation published in Contact Lens and Anterior Eye looks at connections between the stages of keratoconus and meibomian gland dysfunction (MGD) prevalence, and examines categories of meibomian gland secretion in those with keratoconus (KC).
Of 207 participants, 120 individuals diagnosed with KC and 87 general eye clinic patients were recruited at the Department of Ophthalmology, Complexo Hospitalario Universitario de Santiago de Compostela, Spain. The observational study was conducted from May 2015 to November 2016, and its protocol included 2 examinations spaced apart 4 to 10 days. Exams comprised of corneal topography, Schirmer testing, Ocular Surface Disease Index (OSDI), tear-film break-up time (TBUT), meibomian gland evaluation, and others.
Significantly increased systemic illnesses experienced in the KC group were environmental allergies for 42.5%, compared with 13.8% in the control group; and bronchial hyperreactivity in 19.2% of those with KC compared with 1.1% for patients without the disorder.
This investigation and a number of prior studies show increased fluorescein and lissamine green staining of conjunctiva and cornea in those with KC, but no differences in TBUT or Schirmer tests. Thus, pathophysiology of dry eye disease for individuals with KC may be based on changes in the tear film instead of quantitative loss, researchers speculate. However, the study adds that “the role of MGD or other factors, such as the ectatic condition of these patients itself,” to trigger signs and symptoms is not yet fully known.
MGD was found in 59 (49.2%) KC patients and 25 (28.7%) individuals without KC (P =.004). The prevalence of MGD in the KC cohort was 49.2% for stage 1 KC, 43.3% in stage 2, 66.7% at stage 3, and 50.0% in stage 4. Despite no differences in meibum quality for those with KC, fewer patients had expressible meibomian glands (P =.01). Considering all study patients with MGD, 10% of the case set and no control participants had the hyposecretory variant; and 39.2% in the KC group, as well as 28.7% of control individuals displayed hypersecretory MGD.
A significant difference was discovered in mean OSDI scores (range 0 to 100) between cohorts; 33.4 in case individuals and 14.4 in the control group. However, scores for those with and without MGD did not meaningfully differ within each cohort. The correlation of MGD with progression of KC may indicate KC’s impact on MGD, or MGD influencing the evolution of KC, but the study also noted questionnaire-reported symptoms showed no significant associations between MGD and symptoms.
In an observational study such as this, related data may not signify cause-and-effect. Other limitations of this analysis include a single evaluator, therefore unmasked, and lack of additional participant tests such as interferometry. However, this is one of the first papers to explore MGD related to stages of KC. “Conceivably, the histopathologic effect of an altered meibomian gland secretion could contribute to causing, or enhancing, the inflammatory reaction on the ocular surface of these patients,” the investigation explains.
Martínez-Pérez L, Viso E, Touriño R, et al. Clinical evaluation of meibomian gland dysfunction in patients with keratoconus. Cont Lens Ant Eye. Published online July 27, 2021. doi:10.1016/j.clae.2021.101495