glaucoma
The Evolution of Cyclophotocoagulation
Examining the differences between TCP and ECP for the
treatment of glaucoma.
ROBERT J. NOECKER, M.D.
Over the past several years there have been many changes in the technology of cyclophotocoagulation. The top two forms of cyclophotocoagulation that come to mind are transscleral cyclophotocoagulation (TCP) and endoscopic cyclophotocoagulation (ECP). ECP is actually a much more refined laser procedure that is often associated with TCP. Although the methods of the treatment may be similar, ECP is quite different from TCP. We'll address those differences and when each is appropriate. I believe there is still a need for both procedures for the treatment of glaucoma.
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The surgeon positions the G-probe 1.2mm behind the limbus for transscleral or contact retrobulbar block. |
Using TCP
With the studies, data and images at our disposal, TCP is a relatively uncontrolled, tissue non- specific procedure. TCP may be more destructive than ECP, but I still find it useful for end-stage glaucoma. The typical patient already has very poor visual potential and any damage TCP might cause will not make a big difference in the outcome at this stage.
Every patient and situation is different and the truth is, not all procedures work the same on every person. Therefore, when a given patient needs IOP-lowering treatment, there is always a chance that it will not be as successful or as safe as intended. For extremely bad cases that fail other surgical procedures, it may still be worth using TCP as a last resort to lower IOP.
There are additional situations for which TCP is indicated, for example if a patient is not a candidate for incisional surgery, or if poor visual acuity and excessive conjunctival scarring limit the possibility of successful filtering or seton surgery.
Using ECP
ECP is a much more targeted and refined treatment compared with TCP. It's extremely hard to over-treat the ciliary processes, unlike with TCP. The surgeon is also able to visualize the target tissue with the ECP laser. The inability to see what you are shooting at with TCP is what makes it so easy to over- or under-treat the ciliary body. In addition, with ECP the endoscope allows an incredible view of the eye. This lowers the learning curve a bit. And knowing over-treatment will not be an issue if the procedure is perform-ed correctly is very reassuring.
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Limbal approach demonstrates the incision placement of a curved endoscope. |
In my opinion, ECP is reasonable as a first-line surgical procedure before attempting trabecu- lectomy or shunts. ECP does not leave an external entry space from the eye versus these other procedures. Other surgical procedures also are effective but may not be as safe. My patients are more agreeable to a procedure that is very gentle and has low risk of complications, which is how I describe ECP.
Other situations for which I opt to use ECP include corneal transplants, congenital glaucomas, aphakic/vitrectomized eyes, replacement medical therapy in conjunction with other surgery, or any patient who has had TCP treatment.
Technique
ECP is performed in the operating room through a typical clear cornea incision. ECP is best performed when the surgeon "paints" the ciliary body over 270� to 360� in a continuous mode. The endpoint is whitening and shrinkage of the ciliary body.
When performing a transscleral procedure, I begin with a setting of 2,000 mW for 2,000 msec. While applying the laser, I continually listen for popping sounds, which signifies excessive heat that will produce gas bubbles. I adjust the laser setting to an amount below the patient's vaporization threshold. Typically, I apply six spots per quadrant, totally about 18 to 24 applications for 270� to 360�.
A "pop" is dangerous because it means the tissue has been boiled to the point of explosion, which signifies over-treatment. Complications and inflammation are likely to arise as a result. With this evolution in technology, many physicians are finding techniques with ECP that are compatible with their own methods or styles of treatment.
There are several different incision methods for ECP that surgeons can use through cornea or pars plana. I find it best when surgeons use the incision type that they are most familiar with. I recommend surgeons who use scleral tunnels use them and those who are comfortable with pars plans incisions with an MVR blade, use those.
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Image taken with three port probe and lens with 70� field of view that enables direct visualization of th ciliary body. |
Post-op
My typical post-operative management includes a topical steroid to treat the inflammation and atropine to decrease ciliary spasm. The patient follows-up the next day, then at two weeks, one month and at two to four months post-op to monitor IOP.
Thorough viscoelastic removal is important for post-operative treatment. Administer the same post-operative eye drops used for cataract surgery and restart glaucoma medications, then discontinue as needed. The patient's IOP may not drop as quickly as it does with trabeculectomy, and IOP may fluctuate during the first two weeks. You will be able to identify the ultimate post-ECP pressure between the second and sixth week post-treatment. Then you can consider retreatments.
Commonly seen complications for both ECP and TCP include inflammation, IOP spike, transient hemorrhage, vitreous prolapse and pupil irregularity. Any complication associated with anterior segment surgery can arise as a result of these procedures. The rates for all of these complications are much lower with ECP.
Where we are today
TCP is a lot harsher than ECP. Through the evolution of cyclophotocoagulation, procedures are safer with less risk of hitting other crucial parts of the eye, blood vessels, muscles and tissues. You can also perform ECP in conjunction with phacoemulsification. These newer procedures are less destructive and more targeted to ciliary body epithelium. The mode of delivery of laser energy is a trade-off between efficacy, safety and side effects.
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Tailoring treatment to each patient |
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We
have been fortunate to have ECP available in our group
practice for several years. And we've learned a few
things about the procedure, including it's good safety
profile. The biggest limitation is that it may not be
effective enough and may need to be repeated later.
We've also learned that ECP really does work. Some patients have a lower pressure on the same medications and some can maintain their pressure on fewer medications. However, the majority of our patients both experience lower pressures and require fewer medications. Case-by-case Here are some common clinical situations and how we approach them: � Cataract and uncontrolled glaucoma. Because the ECP safety profile is so positive compared with trabeculectomy, and the postoperative management is so much simpler, we find it hard to find any indication for combined phacoemulsification/trabeculectomy procedures. Patients with a cataract and uncontrolled glaucoma who previously would have undergone phacoemulsification/trabeculectomy now have a much safer option with phacoemulsification/ECP. If the ECP does not provide the desired reduction in pressure, it can be repeated. A trabeculectomy can always be performed later if necessary, so that door is not closed. � Cataract and controlled glaucoma. The important thing to remember about ECP is that the indications for use are the same as any other therapeutic adjustment: efficacy and compliance. If a patient has a pressure that is controlled with medications, but further lowering is required, an ECP can provide a drop in pressure, continuing with either the same number medications or fewer. If eye drops adequately maintain a patient's pressure, we ask about compliance and whether the cost of the drugs is an impediment to their use. We are always surprised by how many patients use their medications only half as often as instructed due to cost limitations. We never promise to get them off the medications completely, but for many, having to buy or use fewer of them helps with compliance and long-term vision preservation. � Cataract and borderline glaucoma. The question to ask is whether this patient would be put on medication regardless of the need for cataract surgery. Because some eyes get a lower pressure from cataract surgery alone, we usually do not suggest ECP in these cases. Occasionally, however, we find a patient with open angles, IOP over 30mm Hg, cupping, and a history of missing office visits. In this case, we might recommend ECP as primary therapy in order to improve the chance of long-term success. � Inadequate glaucoma control in an aphakic or pseudophakic patient. We recommend stand-alone ECP, especially if a trabeculectomy is the next best option. � Inadequate glaucoma control in a phakic patient. We do not recommend stand-alone ECP for these patients. If the laser probe touches the lens, it may create a cataract. Management pearls Post-op, some patients develop more iritis than you might typically expect after cataract surgery alone. These cases are controllable with topical steroids and, if necessary, cycloplegics. Some patients have an immediate post-op pressure spike due to incomplete removal of viscoelastic tissue, and may require an anterior chamber tap and additional pressure medications for a day or two. Usually we begin reducing glaucoma medications about six to eight weeks post-op, and adjust each month until we are happy with the pressure and need for medicines. |
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