Retrospective Assessment of Carbonic Anhydrase Inhibitors in Topical or Episcleral Implant Form for the Treatment of Equine Glaucoma.
Abstract: To assess whether topical carbonic anhydrase inhibitors (CAIs) with or without episcleral brinzolamide implants control intraocular pressure (IOP) in horses with glaucoma. Methods: 12 client-owned horses diagnosed with glaucoma. Methods: Medical records of horses treated with topical CAIs for ≥ 14 days, with a subset receiving episcleral brinzolamide implants, were reviewed. Diagnosis, signalment, concurrent ocular disease, medications, IOP, visual status, and additional procedures were recorded. Treatment failure was defined as horses with IOP > 30 mmHg resulting in phthisis bulbi or requiring a procedure or enucleation. Results: Secondary glaucoma was diagnosed in 8/12 (67%) eyes and primary glaucoma in 4/12 (33%) eyes. IOP was < 30 mmHg in 7/12 (58%) eyes after treatment with topical CAIs for a median of 28 days. Episcleral brinzolamide implants were placed in 7/12 eyes after a median of 58 days of medical therapy. Treatment failure occurred in 3/7 horses (43%) receiving brinzolamide implants at a median of 189 days and in 4/5 medical therapy-only horses (80%) at a median of 51 days. While 6/12 eyes (50%) were visual at last follow-up (median of 161 days), enucleation was the final outcome in 10/12 (83%) eyes. Conclusions: Topical CAIs appear to result in temporary IOP control in a subset of horses, though some horses may be refractory. Episcleral brinzolamide implants may extend IOP control in horses with glaucoma, but prognosis for vision remains guarded and further optimization is needed.
© 2025 The Author(s). Veterinary Ophthalmology published by Wiley Periodicals LLC on behalf of American College of Veterinary Ophthalmologists.
Publication Date: 2025-09-22 PubMed ID: 40983962PubMed Central: PMC12669945DOI: 10.1111/vop.70086Google Scholar: Lookup
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Summary
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Retrospective study evaluating the effectiveness of topical carbonic anhydrase inhibitors (CAIs), with or without episcleral brinzolamide implants, in controlling intraocular pressure (IOP) in horses diagnosed with glaucoma.
Objective and Study Design
- Purpose: To determine if topical CAIs, alone or in combination with episcleral brinzolamide implants, effectively manage IOP in equine glaucoma cases.
- Study type: Retrospective review of medical records.
- Subjects: 12 client-owned horses diagnosed with glaucoma.
- Inclusion criteria: Horses treated with topical CAIs for at least 14 days, with some receiving additional episcleral brinzolamide implants.
Data Collection and Parameters Assessed
- Diagnosis: Categorized as primary or secondary glaucoma.
- Signalment: Age, breed, and other horse-specific data.
- Concurrent ocular disease: Presence of other eye conditions that could affect treatment or prognosis.
- Medications: Detailed records of topical CAI use and additional therapies.
- Intraocular Pressure (IOP): Measured to evaluate treatment effectiveness; critical cutoff defined as IOP >30 mmHg indicating treatment failure.
- Visual status: Assessment of whether eyes remained visual during follow-up.
- Additional procedures: Including surgery or enucleation (eye removal) performed during the study period.
Results
- Glaucoma type distribution:
- Secondary glaucoma in 8 out of 12 eyes (67%).
- Primary glaucoma in 4 out of 12 eyes (33%).
- Effectiveness of topical CAIs alone:
- 7 of 12 eyes (58%) achieved IOP below 30 mmHg after a median treatment duration of 28 days.
- Use of episcleral brinzolamide implants:
- Implants were placed in 7 of 12 eyes after a median of 58 days following initial medical therapy.
- Treatment failure occurred in 3 of these 7 horses (43%) at a median of 189 days, indicating some extended control.
- Treatment failure rates:
- In horses treated only medically (without implants), failure occurred in 4 of 5 horses (80%) at a median of 51 days.
- Visual outcomes and prognosis:
- At last follow-up (median 161 days), 6 of 12 eyes (50%) remained visual.
- Despite treatment, enucleation was ultimately performed in 10 out of 12 eyes (83%), indicating a guarded visual prognosis.
Conclusions and Clinical Implications
- Topical CAIs can provide temporary control of intraocular pressure in some horses with glaucoma but are not consistently effective for all cases.
- The addition of episcleral brinzolamide implants appears to prolong the duration of IOP control compared to topical therapy alone.
- Despite some successes in controlling IOP, the overall prognosis for maintaining vision in horses with glaucoma remains guarded.
- High rates of enucleation suggest that further development and optimization of treatment strategies are necessary to improve long-term outcomes.
- This study highlights potential benefits and limitations of current CAI therapeutic approaches in equine glaucoma management, providing a basis for future prospective trials.
Cite This Article
APA
Tucker-Retter EK, Yamagata M, Gilger B, Oh A.
(2025).
Retrospective Assessment of Carbonic Anhydrase Inhibitors in Topical or Episcleral Implant Form for the Treatment of Equine Glaucoma.
Vet Ophthalmol, 28(6), 977-982.
https://doi.org/10.1111/vop.70086 Publication
Researcher Affiliations
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.
- Hawaii Veterinary Vision, Inc., Honolulu, Hawaii, USA.
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.
MeSH Terms
- Animals
- Horses
- Carbonic Anhydrase Inhibitors / administration & dosage
- Carbonic Anhydrase Inhibitors / therapeutic use
- Retrospective Studies
- Horse Diseases / drug therapy
- Glaucoma / veterinary
- Glaucoma / drug therapy
- Sulfonamides / administration & dosage
- Sulfonamides / therapeutic use
- Thiazines / administration & dosage
- Thiazines / therapeutic use
- Female
- Male
- Intraocular Pressure / drug effects
- Drug Implants
- Administration, Topical
Conflict of Interest Statement
The authors declare no conflicts of interest.
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