Cyclophotocoagulation (CPC) is a kind of laser therapy for glaucoma that reduces the amount of fluid that your eye produces. Here, ophthalmologist Yvonne Ou, M.D. of the University of California, San Francisco Medical Center explains how CPC works, who may be eligible, and what benefits and risks you can expect. 

How CPC works

In glaucoma, the eye’s natural drainage system is compromised. Improving the outflow of aqueous humor—the fluid that nourishes the eye and helps to retain its shape—in order to lower internal eye pressure is often the goal of treatment. There are other treatments, however, that target fluid inflow to reduce eye pressure. One such target is the source of fluid production, a ring-shaped structure called the ciliary processes.

CPC reduces fluid production and pressure by shrinking the ciliary processes. Ou explains that, because the ciliary processes can regenerate, the procedure sometimes needs repeating. The procedure can also destroy the ciliary processes, which is why CPC typically hasn’t been used until other options have been tried. 

A number of clinicians have recently begun using CPC earlier in treatment, however, as newer laser methods are able to target specific tissue and cause less inflammation.

Current CPC options

There are several types of CPC currently available.

• Transscleral diode cyclophotocoagulation is the standard CPC treatment, in which a tiny laser probe is applied to spots on the surface of the sclera (white part of the eye). There are no incisions (so no infection risk), and it is an outpatient procedure.
  
• Micropulse transscleral cyclophotocoagulation is a newer type of CPC. It is similar to transscleral diode CPC, but the laser energy is sectioned into “micropulses” for less inflammation, and potentially less damage to neighboring tissues.
  
• Endocyclophotocoagulation also uses a tiny laser probe, but instead involves making an incision and inserting the probe into the eye with a camera, for direct visualization and targeting of the ciliary processes.

Who’s a candidate for CPC?

Ou says that people with all forms of glaucoma can potentially have CPC treatment, though there are special concerns with some forms of the disease.

• CPC may not be appropriate for people with uveitic glaucoma, due to the risk of added inflammation.
• CPC may be a good choice for people with plateau iris syndrome, however, since reducing fluid production may also open the angle of the eye where fluid drains out.

For any surgery that’s suggested, Ou says a good question to pose to your ophthalmologist is, “Why are you recommending this procedure specifically for my eye?”

What to expect from CPC

Regardless of which type of CPC is advised, the goal is to lower eye pressure. Ou says a decrease of 20%-30% in eye pressure can generally be expected. 

What’s more, the treatment may be purposefully left incomplete to avoid hypotony, where eye pressure drops too low. Surgeons may choose to break up CPC treatment into several stages.

What are the risks?

Potential risks commonly associated with CPC include:

• Inflammation, which can happen in the front of the eye or, less commonly, causes swelling in the retina
• Bleeding, especially if you have neovascular glaucoma

Less common risks include:

• Vision loss
• Hypotony
• Sympathetic ophthalmia (a rare condition in which the untreated eye becomes inflamed)

Discuss your options

Ou says that CPC can be “very effective” at lowering eye pressure. The newer procedures are less invasive than conventional CPC, she adds, though the laser settings in conventional CPC can be adjusted to reduce inflammation. Discuss your options with your doctor.

*Ou, Y. (2021, August 23). Glaucoma Surgery Series: Cyclophotocoagulation. BrightFocus Foundation. https://www.brightfocus.org/glaucoma/article/glaucoma-surgery-series-cyclophotocoagulation