The Ocular Surface in Medically Controlled Glaucoma: an in vivo Confocal Study

Abstract

Purpose: To study, using in vivo laser scanning confocal microscopy (LSCM), the ocular surface in patients treated with anti-glaucoma medications (aGM).

Methods: We recruited 100 consecutive Caucasian patients with medically controlled primary open angle glaucoma (MCPOAG) and 50 untreated healthy controls, referred to our Glaucoma Service for family history of glaucoma or optic disc cupping. Exclusion criteria were history of ocular or systemic diseases or treatments (except aGM) in the last 12 months with known effects on the ocular surface, previous ocular surgery or trauma, end-stage glaucoma, pregnancy, contact lens wear, and history of dry eye prior to glaucoma diagnosis. Topical treatment had to be the same in both eyes without variation during the 18 months immediately prior to enrolment. Each participant completed an Ocular Surface Disease Index questionnaire and underwent a full eye exam and LSCM examination of several ocular surface components: cornea, bulbar and tarsal conjunctiva, meibomian glands, and eyelid margin.

Results: LSCM showed increased total length per frame and tortuosity of sub-basal nerves and increased density of sub-basal dendritic cells (P<0.01, t-test) in MCPOAG patients, compared to controls. Comparing MCPOAG treated with Benzalkonium Chloride (BAK)-preserved drugs (n=72) to those treated without BAK (n=28), we found a BAK-related reduction of Schirmer test values (P<0.01). Comparing MCPOAG sub-groups identified according to the type of drug (β-blockers, n=36 vs prostaglandin analogues, n=14 vs associations, n=50) we found significant differences in lissamine green conjunctival staining (P<0.05, ANOVA), in nerves total length per frame and tortuosity, and in dendritic cells density (P<0.001). Comparing MCPOAG sub-groups identified according to the number of aGM they were taking (1 drug, n=50 vs 2 drugs, n=36 vs 3 or more drugs, n=14) we found significant differences in the same variables: lissamine green staining (P<0.05), sub-basal nerves total length per frame and tortuosity, and dendritic cells density (P<0.001). All the post-hoc analyses for these variables showed the most significant cut-off to be between associations and single drug therapies.

Conclusions: In patients with good compliance to therapy and no dry eye history, the ocular surface changes due to aGM seem to be mostly sub-clinical and related to the number of daily taken drugs.

Keywords: 596 microscopy: confocal/tunneling • 486 cornea: tears/tear film/dry eye • 503 drug toxicity/drug effects