The glaucoma surgery that works better from the back of the eye, and why almost nobody does it

Endocyclophotocoagulation for canine glaucoma comes in two surgical approaches, and the one with better visualization and lower postoperative inflammation is the one almost no one performs.

The anterior approach, through a corneal limbal incision, is the established technique in veterinary ophthalmology. The pars plana approach, inserting the laser endoscope through a fixed scleral port 6 mm posterior to the limbus, offers 360-degree access to the ciliary processes, enhanced direct visualization, and what the author of a new spotlight article in Veterinary Practice News believes is less postoperative uveitis. But it requires a vitreoretinal surgery skill set, a three-port setup with valved cannulas, and a 23-gauge endoscope system with external argon laser. As of the article's writing, there is one published case report of pars plana ECP in a dog.

What the anterior approach can and cannot see

The anterior approach works in phakic, aphakic, and pseudophakic eyes. It accesses the ciliary processes through a limbal incision. The eye's shape and pressure must be maintained with viscoelastic substances, and visualization can be cumbersome due to variable intraocular pressure.

The limitation that matters for IOP control: according to Veterinary Practice News, "using the anterior approach, it is not possible to visualize 360 degrees of the ciliary body," which can "result in an inadequate IOP drop or the need for" repeat surgery. The author's opinion is that the anterior approach also produces greater postoperative inflammation due to iris chafing, probe placement in the anterior chamber, and "the multidirectional forces required through a limbal-based incision," according to the article.

An abstract presented at the 2013 American College of Veterinary Ophthalmologists conference "reported a success rate of 80 percent in IOP reduction and 70 percent in vision preservation at one year following ECP by an anterior approach for primary and secondary glaucoma in canine" patients, according to Veterinary Practice News.

The pars plana entry, and what it buys

According to the article, "the pars plana approach involves inserting a laser endoscope through a fixed scleral port into the pars plana" in pseudophakic or aphakic eyes. "The endoscope has a camera, a light source, and a laser. The pars plana is considered the safest entry point for eye surgery because it lacks critical blood vessels and sensory retina." A smooth flat band sits wide enough to accommodate the endoscope between the iris and retina.

The endoscope can be placed "through each of the three ports, providing maximal visualization and a 360-degree view," according to Veterinary Practice News. The author describes this as "a more thorough treatment, especially in aggressive cases of glaucoma notoriously found in dogs."

In a human study with a two-year follow-up, according to the article, "pars plana ECP combined with phacoemulsification and IOL placement achieved superior IOP control, and patients were maintained on fewer glaucoma medications compared to those" who underwent an anterior ECP approach. A separate human study "observed an IOP decrease of 61-66 percent with a pars plana approach after being refractory to other glaucoma surgical interventions, compared to those who had an anterior ECP with an IOP decrease of approximately 31" percent, Veterinary Practice News reports.

Kaminsky and Hoffman published the one canine case report as of the article's writing: "successful IOP control with vision preservation" was achieved "in a dog that previously underwent phacoemulsification and failed goniovalve implantation in both" eyes, according to the article.

We write one of these every week for veterinarians navigating the gap between what the literature says works and what's available locally. Subscribe to VeterinaryPracticeNow.

The procedure itself

After eyelid speculum placement and limbal stay sutures, according to Veterinary Practice News, "a small conjunctivectomy is performed over the sclerotomy sites." Bipolar cautery coagulates "the intrascleral venous plexus in preparation for three-port sclerotomy sites and valved cannula placement." The article describes how "a 23-gauge trocar and valved cannula one-step device" makes an inferolateral stab incision "through the pars plana 6 mm posterior to the limbus." An infusion of balanced salt solution "is placed, and IOP control is fixed at the vitreoretinal console at 30 mmHg to maintain the shape of the globe," according to the article.

With constant infusion in place, no viscoelastic substances are needed to maintain eye pressure. The same technique places 23-gauge valved cannulas superolaterally and superomedially to house the endoscope and other instruments. According to Veterinary Practice News, the three valved cannulas "facilitate entry, exit, and rotation of instrumentation throughout the procedure."

The article notes that "patients that have had previous cataract surgery can occasionally present with white fibrinous webs that" obstruct "visualization of the ciliary processes. These can be" removed by a vitrectory probe. Traction bands from "fibrinous uveitis that led to the glaucoma can be" removed the same way, according to Veterinary Practice News.

According to the article, "a 23-gauge straight endoscope is inserted and alternated among all three valved cannulas to achieve 360-degree cyclophotocoagulation of the ciliary processes. The power setting ranges from 90 to 150 mW, with" continuous duration "to treat the entire ciliary processes" (head, tails, and valleys) "until shrinkage and whitening occur, indicating effective photocoagulation," Veterinary Practice News reports.

If indicated, according to the article, "a laser retinopexy is performed upon completion of the ECP to decrease the possibility of retinal detachment," particularly for "predisposed breeds or when a small retinal tear is noted." The article states that "prior to closure, silicone oil can be infused into the eye" to "act as an emollient on the acutely lasered ciliary processes, which reduces" postoperative inflammation.

According to Veterinary Practice News, "patients are maintained on glaucoma medications until a successful reduction in" IOP is noted. Typically, patients "show a stable reduction in IOP by 10-14 days postoperatively," the article reports.

The complications that apply to both approaches

Veterinary Practice News reports that "complications of ECP by the anterior approach include intraocular inflammation with or without fibrin, cataract formation from lens touch, uncontrolled IOP, corneal ulceration, corneal edema, and phthisis bulbi." According to the article, "these complications can also occur with the pars plana approach."

The author believes postoperative uveitis is less likely with the posterior segment approach. According to Veterinary Practice News, "the corneal edema is minimized with the" pars plana "approach, as there is neither a perilimbal incision nor corneal endothelial disruption."

The article states that "an advantage of the pars plana approach includes enhanced direct visualization and 360-degree access to perform cyclophotocoagulation more effectively with less energy required, thereby reducing the risk of postoperative inflammation." According to Veterinary Practice News, "a disadvantage" is "the need for additional surgical steps before endoscope placement; however, because eye pressure is static, the view is improved, which" speeds "up surgical cyclophotoablation time." The article adds that "another disadvantage is that more equipment and a more advanced skill set are required."

The breeds you see this in, and when the procedure applies

According to Veterinary Practice News, "canine glaucoma is often an aggressive disease process." The article lists "several dog breeds commonly seen in veterinary practice for glaucoma, including the cocker spaniel, Boston terrier," basset "hound, Labrador, Siberian husky, chow chow, French bulldog, and shiba inu" (due to goniodysgenesis). "Other breeds, as well as mixed-breed dogs, can also present with the disease. Medical therapy may work initially, but then ultimately fail, leading to ocular pain, lethargy, and blindness," Veterinary Practice News reports.

According to the article, "pars plana ECP may benefit canine patients with glaucoma refractory to medical therapy, dogs predisposed to glaucoma, or cataract candidates with a glaucoma risk." The author suggests that "pars plana ECP can be considered as a first-line surgical treatment for dogs undergoing cataract surgery that are predisposed to glaucoma" or "those dogs that have a history of glaucoma in the fellow eye," according to Veterinary Practice News.

The article states that "higher success is achieved in patients that have had the fewest number of pressure spikes and the fewest episodes of vision loss." According to Veterinary Practice News, "good candidates are dogs developing a modest rise in pressure while still maintaining vision. The goal of surgery is vision preservation with minimal or no indication for" postoperative glaucoma medication.

Higher success is achieved in patients that have had the fewest number of pressure spikes and the fewest episodes of vision loss.

What to watch

According to Veterinary Practice News, "a larger-scale study of 50 dogs will be presented at the annual ACVO Conference in October 2026." That will be the first multi-case dataset in the veterinary literature. Until then, the pars plana approach in dogs rests on one published case report and the human data showing a 30-percentage-point IOP-reduction advantage over the anterior approach in refractory cases.

The author of the Veterinary Practice News spotlight is Dr. Allison Hoffman, "a board-certified veterinary ophthalmologist and vitreoretinal surgeon at Eye Care for Animals in Pasadena," California, according to the article. Veterinary Practice News reports that "she is the only veterinary ophthalmologist to complete a vitreoretinal surgery fellowship and" is "one of only three veterinarians worldwide elected to membership in the American Society of Retinal Specialists."

The skill set and equipment required for pars plana ECP remain the limiting factors. The technique exists. The training pipeline that would make it available beyond a handful of practices does not yet.

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