Brimonidine Tartrate for Pterygium Surgery

Pterygium excision and conjunctival autograft surgery is commonly done to treat pterygiums. Excessive bleeding during the procedure creates a challenging operating field, prolongs surgery time, and prolongs healing. Brimonidine tartrate has a vasoconstrictive effect, which helps to reduce the amount of blood flow and hyperemia to the eye. Preoperative use of brimonidine has been shown to decrease subconjunctival hemorrhage during procedures such as cataract surgery, laser assisted in situ keratomileusis, strabismus surgery, and intravitreal injections. The focus of this study is to assess the effect of preoperative application of brimonidine tartrate 0.15% (Alphagan) and 0.025% (Lumify) on reducing hemorrhage during pterygium excision and conjunctival autograft surgery.

During pterygium excision and conjunctival autograft surgery, incision into the conjunctiva of the operated eye causes a significant amount of subconjunctival hemorrhage. Brimonidine-tartrate is a selective alpha-2-adrenergic agonist. The 0.15% concentration (Alphagan) is commonly used to treat glaucoma, while the 0.025% (Lumify) is an over-the-counter drop used for its vasoconstrictive anti-hyperemia effect. Brimonidine 0.15% has been evaluated in other studies to reduce bleeding in LASIK, cataract surgery, strabismus surgery, as well as intravitreal injections. In these mentioned clinical trials, brimonidine was found to safely reduce subconjunctival hemorrhage intraoperatively and hyperemia postoperatively. Interestingly, prophylactic topical brimonidine was found to increase risk of early flap slippage in LASIK due to molecular interference with flap stabilization. Because creation of a flap is not a component of pterygium surgery, preoperative brimonidine does not interfere with healing. A recent study by Ucar et al. has validated the use of preoperative brimonidine 0.15% for conjunctival whitening prior to pterygium surgery, allowing for minimized hyperemia and reduced surgical duration (Ucar, 2020). However, the long-term clinical outcomes, and efficacy of brimonidine 0.025% has yet to be examined. This study aims to further examine the comparative efficacy of preoperative brimonidine at different concentrations to reduce subconjunctival hemorrhage during pterygium surgery. Potential side effects of topical application of brimonidine eye drop may include blurred or loss of vision, burning, dry, or itching eyes, discharge or excessive tearing, disturbed color perception, double vision, halos around lights, headache, itching of the eye, night blindness, photophobia, redness of the eye or inner lining of the eyelid, swelling of the eyelid, tearing of the eye, tunnel vision. Side effects of this medication are self-limited, and reversible after the medication is stopped. The risk of this study to the subject is negligible as the standard surgical procedure will be followed. This trial will be conducted in compliance with the protocol, GCP, and the applicable regulatory requirement as set by William Osler Health System Ethics Review Board.

Participants will be randomly assigned to one of three groups (control, brimonidine 0.15%, or brimonindine 0.025%), running in parallel.

The surgeon (care provider/investigator) will be masked to the intervention at the time of operation and during follow-ups (day 0, week 1, month 1). Outcomes assessor will be blinded to the investigation when quantifying degree of hemorrhage

Subconjunctival hemorrhage grading of images at POD0, POW1, and POM1 will be done as follows: a score of 1-4 for the number of quadrants involved, and a score of 1-4 for the amount of involvement in the quadrant (1 = 0-25% coverage, 2 = 26-50% coverage, 3 = 51-75% coverage, 4 = 76-100% coverage). A total maximum score of 16 may be given, with 0 indicating no subconjunctival hemorrhage present. This grading algorithm is adapted from previously published methods (Munoz 2009, Hong 2007, Norden 2002). Grading will be done by an independent reviewer blinded to the randomization of participants.

Subconjunctival hemorrhage grading of images will be done as follows: a score of 1-4 for the number of quadrants involved, and a score of 1-4 for the amount of involvement in the quadrant (1 = 0-25% coverage, 2 = 26-50% coverage, 3 = 51-75% coverage, 4 = 76-100% coverage). A total maximum score of 16 may be given, with 0 indicating no subconjunctival hemorrhage present. This grading algorithm is adapted from previously published methods (Munoz 2009, Hong 2007, Norden 2002). Grading will be done by an independent reviewer blinded to the randomization of participants.

Subconjunctival hemorrhage grading of images will be done as follows: a score of 1-4 for the number of quadrants involved, and a score of 1-4 for the amount of involvement in the quadrant (1 = 0-25% coverage, 2 = 26-50% coverage, 3 = 51-75% coverage, 4 = 76-100% coverage). A total maximum score of 16 may be given, with 0 indicating no subconjunctival hemorrhage present. This grading algorithm is adapted from previously published methods (Munoz 2009, Hong 2007, Norden 2002). Grading will be done by an independent reviewer blinded to the randomization of participants.

Hyperemia will be quantified in the same manner as Ucar et al. (Ucar, 2020). Vessels on the images converted to black and white with Adobe Photoshop - vessels will be converted to black, while the rest of the sclera will be white. ImageJ (public domain software) will then be used to quantify the number of black pixels (vessels). Hyperemia will be reported as the number of black pixels per image.

Hyperemia will be quantified in the same manner as Ucar et al. (Ucar, 2020). Vessels on the images converted to black and white with Adobe Photoshop - vessels will be converted to black, while the rest of the sclera will be white. ImageJ (public domain software) will then be used to quantify the number of black pixels (vessels). Hyperemia will be reported as the number of black pixels per image.

Hyperemia will be quantified in the same manner as Ucar et al. (Ucar, 2020). Vessels on the images converted to black and white with Adobe Photoshop - vessels will be converted to black, while the rest of the sclera will be white. ImageJ (public domain software) will then be used to quantify the number of black pixels (vessels). Hyperemia will be reported as the number of black pixels per image.

Hyperemia will be quantified in the same manner as Ucar et al. (Ucar, 2020). Vessels on the images converted to black and white with Adobe Photoshop - vessels will be converted to black, while the rest of the sclera will be white. ImageJ (public domain software) will then be used to quantify the number of black pixels (vessels). Hyperemia will be reported as the number of black pixels per image.

Hyperemia will be quantified in the same manner as Ucar et al. (Ucar, 2020). Vessels on the images converted to black and white with Adobe Photoshop - vessels will be converted to black, while the rest of the sclera will be white. ImageJ (public domain software) will then be used to quantify the number of black pixels (vessels). Hyperemia will be reported as the number of black pixels per image.

Inclusion Criteria: All patients over age 18 who are scheduled for pterygium surgery who have provided informed consent, in accordance with application regulations and guidelines Exclusion Criteria: Patients who are on anticoagulation or antiplatelet therapy Patients on monoamine oxidase (MOA) inhibitor therapy Patients who have undergone any conjunctival surgery in the past Any complication during pterygium excision

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