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: using the anterior approach, it is not possible to visualize 360 degrees of the ciliary body. That 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.
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.
The pars plana entry, and what it buys
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 three ports, providing maximal visualization and a 360-degree view. 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, 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.
Kaminsky and Hoffman published the one canine case report as of the article's writing: successful IOP control with vision preservation in a dog that previously underwent phacoemulsification and failed goniovalve implantation in both eyes.
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The procedure itself
After eyelid speculum placement and limbal stay sutures, 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. 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.
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. The three valved cannulas facilitate entry, exit, and rotation of instrumentation throughout the procedure.
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 vitrectomy probe. Traction bands from fibrinous uveitis that led to the glaucoma can be removed the same way.
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.
If indicated, 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. 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.
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 complications that apply to both approaches
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. These complications can also occur with the pars plana approach.
The author believes postoperative uveitis is less likely with the posterior segment approach. The corneal edema is minimized with the pars plana approach, as there is neither a perilimbal incision nor corneal endothelial disruption.
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. 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. 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
Canine glaucoma is often an aggressive disease process. Several dog breeds are 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.
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 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.
Higher success is achieved in patients that have had the fewest number of pressure spikes and the fewest episodes of vision loss. 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
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. She is the only veterinary ophthalmologist to complete a vitreoretinal surgery fellowship and 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.