Although it is true that there are fewer risks with Canaloplasty than there are with traditional glaucoma surgery (trabeculectomy), it is not without risk. All surgeries (there are no exceptions) have risks associated with them. The important thing to consider when faced with the need for surgery is the relative risk of the procedure compared to going without the procedure. If your glaucoma is not under control then (given enough time) you will lose vision. Glaucoma surgeries offer a method of preventing that loss of vision.

Most Commonly Encountered Risks of Canaloplasty

  1. Bleeding in the eye. Almost 30% of people who have Canaloplasty have some bleeding in the front of the eye. However, as mentioned earlier, this bleeding (called a hyphema or microhyphema) is pretty much to be expected (and may actually be desired)[1]. This resolves with time and rarely causes any permanent reduction in vision.
  2. Intraocular pressure “spikes” during the healing period after surgery. About 5% (one in twenty) people will have a short period after surgery when the IOP is actually higher than it was before surgery. This almost always resolves.
  3. The formation of a bleb (blister) on the surface of the eye in the area of the incision (6%). It is worth noting that with trabeculectomy, the formation of a stable bleb is necessary for success, while with Canaloplasty, it is considered to be an undesireable outcome, or “risk.” These blebs rarely limit the effectiveness of Canaloplasty. However, blebs can be associated with Tear Dysfunctional Syndrome (Dry Eye Syndrome) and could limit your ability to participate in certain activities (such as certain water sports).
  4. Descemet’s Membrane Separation, or Detachment (3%). In order to open Schlemm’s canal, a gel-like substance (called a viscoelastic) is injected into the canal. If the canal is particularly “tight” it is possible for the get to follow the path of least resistance and dissect beneath Descement’s Membrane (the thin film on the back of the cornea). If this happens, the vision could be affected. However, with time (weeks to months) these almost always resolve on their own. If it is not spontaneously improving, it is generally possible for your surgeon to inject a gas bubble in your eye to press this membrane back against the cornea.
  5. The need to perform traditional glaucoma surgery (4%). Less than one in twenty Canaloplasty surgeries “fail” and must be converted to either trabeculectomy or a “shunt.” This may be done either at the time of initial surgery or at a later date. Your surgeon would make this decision as clinically appropriate.
  6. Hypotony (IOP too low). “Too low?” you may be wondering, “I thought the problem was that the pressure was too high?” Well, if the IOP drops below 5mmHg (millimeters of Mercury) and stays there, vision can be lost from a condition known as “hypotony maculopathy.” Fortunately, this condition is pretty rare with Canaloplasty (only one person in 200 would be expected to have prolonged hypotony). Compare this to trabeculectomy in which at least 1 out of every 10 people is likely to experience hypotony.
  7. Infection. To date, vision-threatening infection of the eye (called “endophthalmitis”) has not been documented with Canaloplasty. In theory, however, anytime an incision is made in the eye, an infection could be possible. So, although the risk seems to be less than 1 in 1,000, it’s probably not zero. Compare this to trabeculectomy which carries up to a 5% chance per year of developing an infection called “blebitis” that (if not caught early and treated) can result in endophthalmitis and loss of vision.

In summary, although not without risk, Canaloplasty is associated with significantly fewer risks (both in number and severity) than traditional glaucoma surgeries such as trabeculectomy.


  1. Canaloplasty and Transient Anterior Chamber Haemorrhage: a Prognostic Factor? Koch J, Heiligenhaus A, Heinz C. Klinische Monatsblätter für Augenheilkunde (Clinical Journal of Ophthalmology) 2010 Nov 16. (online ahead of print).

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David Richardson, MD

David Richardson, MD

Medical Director, San Marino Eye

David Richardson, M.D. is recognized as one of the top cataract and glaucoma surgeons in the US and is among an elite group of glaucoma surgeons in the country performing the highly specialized canaloplasty procedure. Morever, Dr. Richardson is one of only a few surgeons in the greater Los Angeles area that performs MicroPulse P3™ "Cyclophotocoagulation" (MP3) glaucoma laser surgery. Dr. Richardson graduated Magna Cum Laude from the University of Southern California and earned his Medical Degree from Harvard Medical School. He completed his ophthalmology residency at the LAC+USC Medical Center/ Doheny Eye Institute. Dr. Richardson is also an Ambassador of Glaucoma Research Foundation.

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