Study: Laser Glaucoma Treatment Helps, But Doesn't Cure

A specially designed surgical laser can help control fluid pressures in the eyes of horses with glaucoma and help maintain vision, but it does not alleviate the need for the continued use of topical eye medications, according to David A. Wilkie, DVM, MS, Dipl. ACVO, and colleagues from the Colleges of Veterinary Medicine at Michigan State University and The Ohio State University (OSU).

Glaucoma is characterized by an increase in the intraocular pressure of the eye to a level that is not compatible with the health of the eye and vision. While it is not very common (it only affects approximately 0.07% of horses in the United States), it is frequently seen in horses with equine recurrent uveitis or moon blindness. Glaucoma in horses can be challenging to treat.

"Long-term use of topical medications is often impractical or, in some cases, impossible, depending on the location and/or temperament of the horse," said Wilkie.

He added, "In many instances, medical treatment alone does not adequately control the pressure inside the eyes of many horses with glaucoma."

The surgical technique, called semiconductor diode laser transscleral cyclophotocoagulation (TSCP), was designed to control intraocular pressure (IOP). The veterinarian performing the procedure essentially destroys the part of the eye responsible for producing the extra fluid (called aqueous humor) to ultimately lower the intraocular pressure.

Wilkie et al. reviewed data from 42 surgeries performed between 1995 and 2007 at OSU. Key findings were:

  • Three to five weeks post-TSCP, mean IOP had decreased from 37.17 to 19.36 mmHg (normal ranges from 15 to25 mmHg);
  • The patients' need for topical eye medications did not change;
  • Hyphema (bleeding inside the eye) was the only complication, and it developed in 5/42 eyes;
  • Only 2/27 eyes required removal post-TSCP; and
  • 21/22 owners reported that they felt the treatment had been of value.

"While IOP was lower post-TSCP, treated horses still required long-term use of topical medications to help keep the pressures down," said Wilkie. "It is feasible that adjustments in the site or energy settings of the laser might improve the outcome and eliminate the need for long-term topical medications."

The study, "Semiconductor diode laser transscleral cyclophotocoagulation for the treatment of glaucoma in horses: a retrospective study of 42 eyes," was published in the May 2010 edition of the journal Veterinary Ophthalmology.

The abstract is available on PubMed.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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