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Photodynamic therapy leads fight against wet age-related macular degeneration
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DULUTH, Ga. — The Food and Drug Administration (FDA) approval of Visudyne (verteporfin, CIBA Vision) on April 13 has brought hope and another treatment option to patients with subfoveal choroidal neovascularization related to the exudative, or “wet,” form of age-related macular degeneration (AMD).
Ophthalmologists as well as optometrists are optimistic about the strides that photodynamic therapy (PDT) will make in treating wet AMD, said William Jones, OD, in private group practice in Albuquerque, N.M. “This will allow better vision and better recovery of vision after treatment,” he said. “It’s a fantastic new way of treating wet AMD, and it has great promise.”
The procedure
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PDT involves intravenously injecting a photosensitizing dye into the arm of a patient in whom a macular lesion has been discovered through fluorescein angiography. While Visudyne is the only agent that has received FDA approval thus far, another dye called Purlytin (tin ethyl etiopurpurin/SnET2, Miravant) is currently undergoing clinical trials.
After the patient is injected with the dye, a low-power laser is applied, said Paul S. Bernstein, MD, PhD, assistant professor of ophthalmology and visual sciences at the Moran Eye Center at the University of Utah. He added that the whole procedure is relatively brief. “The dye is activated by the laser, which is tuned to the correct wavelength for the dye,” explained Dr. Bernstein, who is also one of the participating investigators in the clinical trials for Purlytin. “The infusion takes approximately 10 minutes, and the Visudyne laser treatment takes 83 seconds.”
The unique aspect of the laser used during treatment is that it will destroy the abnormal vessels while not damaging surrounding healthy tissues, said Dr. Jones. As opposed to laser coagulation, which can leave blind spots, the wavelength used during the procedure is much less damaging. “The laser incites the dye itself to release singlet oxygen, or a free radical, which insults the abnormal blood cells of the endothelium to the point that it allows it to actually degenerate and eventually close off,” he said.
The two lasers that are currently approved for use in PDT are the Opal Photoactivator (Coherent Inc., Santa Clara, Calif.) and the Visulas 690s (Zeiss Humphrey Systems, Dublin, Calif.)
Who is a good candidate?
While all patients with wet AMD may be considered for the procedure, not all of them will be good candidates for it, said Dr. Bernstein. Patients who first developed the condition years ago and now exhibit a scar in the area will not benefit from PDT, he said. “The best lesions to treat are those that are classic and of relatively new onset,” he said. “Clearly, the treatment has no role in patients who just have a scar in the macula; it’s not going to reverse or change that process. Of the patients who present with new-onset lesions of wet AMD, probably fewer than 50% will be eligible.”
The FDA has specified that the lesion must be no larger than 5.4 mm across, Dr. Bernstein added, and less than 50% occult.
Potential side effects
Patients should take special care before treatment to bring adequate skin protection to the doctor’s office, such as long-sleeved shirts and wide-brimmed hats, due to the extreme photosensitivity following the treatment, the practitioners said.
“This is the major side effect; patients are susceptible to sunburns the first week after treatment,” said Dr. Bernstein. “They should avoid sunlight during that time.” Bright indoor light should also be avoided.
He said that a less frequent side effect that has occurred is low back pain during the infusion, “but that’s not significant.” Practitioners must ensure that there are no problems with the dye escaping from the vein during the infusion as well, he stressed. “That can cause significant problems, and the infusion should be stopped right away if it seems that it’s not going in properly,” Dr. Bernstein said.
Retreatment often necessary
He added that periodic re-evaluations with fluorescein angiography are needed to check for recurrences, which are common. “It’s very common to need some sort of retreatment with the dye,” Dr. Bernstein said. “In clinical trials, the average retreatment was more than three times in the first year. It does drop in the second year.”
If not covered by the patient’s insurance plan, the procedure and retreatments may be difficult for patients to afford. The dye costs $1,200 per dose, said Dr. Bernstein, and physician fees, facility fees and the cost of fluorescein angiography can drive up the total cost to approximately $2,000. “The insurance companies are still learning about this also,” he said. “Medicare will cover it, so most of the other insurance companies will follow, because it is an FDA-approved treatment.”
Purlytin still in trials
The light-activated compound, tin ethyl etiopurpurin, used in the Purlytin system, originally developed to treat various forms of cancer, is similar to the Visudyne procedure. Following an intravenous injection of the dye, a low-energy laser beam of 664 nm is directed at the leaky blood vessels. The tin ethyl etiopurpurin, which releases the singlet oxygen upon contact with the laser, hones in on the diseased tissue and preserves the healthy eye tissue. The system is currently undergoing phase 3 clinical trials.
Managing a PDT patient
While few optometrists have much experience with the procedure, now that Visudyne has been approved by the FDA the number of PDT patients ODs will see is likely to increase. Checking the patient’s visual acuity is an important part of the follow-up care, said Dr. Jones.
“Observe what kind of visual acuity has actually been maintained, recovered or even lost after the treatment,” he said. “Does the patient have less distortion in his or her vision? Also, just note whether the AMD looks wet or not. Does the retina in the area look boggy, or is it now without fluid edema and a bit drier looking?”
Dr. Bernstein said that, while the treatment should not be considered an absolute resolution to wet AMD, he acknowledges that it is an important move in the right direction. “Clearly, this isn’t a cure for AMD, but it’s an excellent addition to our arsenal of treatments,” he said. “Patients need to understand that there has been a lot of hype that’s a little too optimistic. But it certainly is a big step.”
For Your Information:
- William Jones, OD, is in private group practice and is a member of the Editorial Board of Primary Care Optometry News. He may be reached at 1828 Conestoga, SE, Albuquerque, NM 87123; (505) 265-1711, ext. 4141; fax: (505) 247-2153; e-mail: wm_jones@msn.com. Dr. Jones has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- Paul S. Bernstein, MD, PhD, is the assistant professor of ophthalmology and visual sciences at the Moran Eye Center. He may be reached at the University of Utah, 50 North Medical Drive, Salt Lake City, UT 84132; (801) 581-6078; fax: (801) 581-3357; e-mail: paul.bernstein@hsc.utah.edu. Dr. Bernstein has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.