Almost all antiglaucoma medications,
especially those containing preservatives, affect the ocular surface. Beta-blockers,
particularly preserved timolol maleate, disrupt tear film stability, reduce
basal and relative tear secretions, and cause xerotic alterations in
conjunctival epithelium potentially leading to conjunctival cicatrization.
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| PUNCTATE EPITHELIAL EROSIONS FROM ANTI-GLAUCOMA MEDICATIONS |
Patients with severe conjunctivochalasis have
worse TFBUT, lissamine green staining, Schirmer testing, and a higher OSDI
score.
Prostaglandin analogs apparently have the
least effect on conjunctival fibrosis, but they induce obstructive Meibomian
gland dysfunction.
Pilocarpine and timolol also directly
affect Meibomian epithelial cells and may influence their morphology, survival,
and proliferative capacity.
The Meibomian gland changes after
monotherapy prostaglandin analog use are related to worse OSD and poor
compliance.
These findings support using
preservative-free regimens to improve compliance and minimize the adverse
effects of antiglaucoma eye drops on conjunctival, corneal, and Meibomian gland
structures.
The most commonly used preservative in
anti-glaucoma medications is benzalkonium chloride (BAK). It can severely
disrupt the ocular surface and alter corneal sensitivity.
There is also conflicting evidence regarding
the role of surgically induced conjunctival modifications as a risk factor in
the pathogenesis of G-OSD.
Reports have found an increase in tear
osmolarity and a four-fold increase in the use of ocular lubricants in patients
who underwent MMC-augmented trabeculectomy.
A study found ocular surface complications
in approximately 15% of patients after trabeculectomy. The most common were corneal epitheliopathy (11%), filamentary keratitis (3%), and Dellen formation (1.7%).
Lee has pointed out that dry eye symptoms
and increased osmolarity may occur in post-trabeculectomy patients in the
absence of TBUT and Schirmer test abnormality.
However, a recent 3-year study by Ambaw et
al demonstrated that after undergoing successful trabeculectomy, patients had
reduced tear levels in 37 of 40 pro-inflammatory lipid mediators.
Laser scanning confocal microscopy and
impression cytology found an increase in goblet cell density, and a decrease in
limbal dendritic cell density, sub-basal corneal nerve inhomogeneity, Meibomian
gland density, and HLA-DR positivity, corresponding to an overall objective
improvement of the ocular surface after successful trabeculectomy surgery.
