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Effects of topical glaucoma drugs on fistulized rabbit conjunctiva
T L Young1, E J Higginbotham, X L Zou
1Department of Ophthalmology, University of Illinois, College of Medicine, Chicago.
Abstract:
Conjunctival fibroblastic proliferation with contracting scar formation has been implicated as a possible cause of glaucoma filtering surgery failure. The effects of glaucoma medications on bulbar conjunctiva were evaluated in both eyes of 20 pigmented rabbits, with 5 rabbits per group each receiving singular topically applied daily doses of either 0.5% timolol, 1% epinephrine, 4% pilocarpine, or artificial tears in a masked fashion for 4 months. Posterior lip sclerectomies were performed in 16 rabbits--4 from each treatment group. The remaining four rabbits served as nonsurgical controls. Four additional rabbits, which had not received eye drops, were included as a nonmedicated control group, with one rabbit serving as a nonsurgical control. Immunostaining was performed to identify the presence of myofibroblasts in fistulized conjunctiva. Treated surgical eyes, regardless of medication, had higher myofibroblastic cell proliferation than treated nonsurgical eyes. Among fistulized eyes, all medications increased cell proliferation, with pilocarpine eliciting the most dramatic increase compared with all other groups.
Insights
Glaucoma medications, particularly pilocarpine, increase conjunctival cell proliferation after surgery, potentially impacting glaucoma surgery success. This study evaluated medication effects on conjunctival scarring in rabbits.
Area of Science:
- Ophthalmology
- Glaucoma Research
- Surgical Complications
Background:
- Conjunctival scarring is a key factor in glaucoma filtering surgery failure.
- Myofibroblasts contribute to scar contraction and fibrosis.
- The impact of common glaucoma medications on conjunctival wound healing is not fully understood.
Purpose of the Study:
- To investigate the effects of topical glaucoma medications on conjunctival fibroblastic proliferation.
- To evaluate the role of myofibroblasts in medication-induced conjunctival changes after glaucoma surgery.
Main Methods:
- Twenty pigmented rabbits received daily topical applications of timolol, epinephrine, pilocarpine, or artificial tears for 4 months.
- Posterior lip sclerectomies were performed on 16 rabbits.
- Immunostaining was used to quantify myofibroblast presence in conjunctival tissues.
Main Results:
- All tested glaucoma medications increased myofibroblastic proliferation in surgical conjunctiva compared to nonsurgical eyes.
- Pilocarpine demonstrated the most significant increase in cell proliferation among fistulized eyes.
- Medication treatment, regardless of type, led to higher myofibroblast levels in surgical eyes.
Conclusions:
- Topical glaucoma medications can enhance conjunctival fibroblastic proliferation, potentially exacerbating scar formation.
- Pilocarpine may have a pronounced effect on increasing conjunctival cell proliferation post-surgery.
- These findings suggest a potential mechanism by which glaucoma medications could influence the success of filtering surgery.