Photodynamic therapy (PDT) for wet age-related macular degeneration is already changing ophthalmology practices. Since the drug Visudyne and the Zeiss Humphrey and Coherent lasers used to activate the drug received FDA approval in April, more doctors are incorporating this procedure into their routines.

In March, we took a comprehensive look at how to add PDT into your schedule. Here we'll take that one step further and concentrate on the PDT lasers, providing preparation and utilization tips for a smooth procedure.

The Coherent Opal Photoactivator and the Zeiss Visulas 690s Laser system have basic similarities. (See chart on next page.) Both are small, diode 689-nm lasers with slit-lamp delivery. There are differences in features, such as beam tracking and screens. The Coherent model has audible tracking. The Zeiss currently comes with a slit lamp.

Whichever one you choose for performing PDT with Visudyne (verteporfin for injection), you have a limited window to use it, so you want to ensure that everything is prepared for your patients. As you know, you infuse Visudyne over a 10-minute period, and you must perform the laser treatment exactly 15 minutes after the start of the infusion. The expense of the drug and that limited 5-minute window demand careful preparation for you and your patient.

"Don't wait until the last minute to put the lens on and to adequately position the patient comfortably," says David Boyer, M.D., who was part of the Visudyne clinical trials. "If you wait until the last minute, you're rushing to do it."

Both Dr. Boyer and Philip Rosenfeld, M.D., Ph.D., who also participated in the clinical trials, have a dedicated room for PDT in their practices. Although this might not be economically viable in smaller practices, it's proved efficient for both. PDT patients don't have to hurry to another room for laser treatment after infusion, which in some cases is difficult at best for elderly, infirm patients.

And although these lasers are portable, having a dedicated PDT room also keeps the lasers calibrated and limits potential damage to the units.

Dr. Rosenfeld, who has a bustling PDT practice at the Bascom Palmer Eye Institute in Miami, says it's probably more cost-effective to use a separate room for infusion because you're not tying up the laser chair. However, he still prefers using a dedicated room and chair.

"I always infuse in the same chair. With older patients it's so much harder to move them quickly," Dr. Rosenfeld says. "The biggest problem you don't want to get into is being rushed -- that's the worst situation to be in."

Dr. Rosenfeld carefully preps his equipment before the infusion begins. These checks ensure that all the equipment is working properly and eliminate most unwelcome surprises.

First, the patient enters the treatment room and signs the procedure consent form. Dr. Rosenfeld puts anesthetic drops and then the contact lens on the patient's eye. He also visualizes the lesion at the spot size setting.

Choosing the correct lens for the lesion is a critical part of the process. "It's important that you pick lenses that you're comfortable with," says Dr. Boyer, who's performed 125 treatments in his California office. He prefers a larger lens. "With the 1.50 magnification, the advantage is that in larger lesions you need that lens to treat it adequately."

Dr. Rosenfeld gives patients who are receiving the treatment for the first time a 10- to 15-second "preview" of the laser treatment. The required 83 seconds of beam is much longer than the milliseconds of other laser treatments, Dr. Rosenfeld says. His patients say the laser prep helps them focus and stay still for the actual treatment.

"It's essential to educate the patients about the importance of keeping their eyes still. I give them a short burst of the nonthermal laser just to get them used to it," Dr. Rosenfeld says. "Most patients are nervous at the time of their first treatment, and this helps them know what to expect."

The next step is crucial -- measuring the laser's output. Dr. Rosenfeld uses a handheld power meter and quickly double-checks the output.

"You want to make sure you're not undertreating. It's always better to confirm it. With technology we assume a lot of things. Checking the output doesn't take very long and it's easily accomplished," Dr. Rosenfeld says.

Some of his handheld readings have found a 10% to 15% difference between the laser's power and what it's supposed to be. "The lasers will fall out of calibration, just as any laser can," he says. "That's why you need to check regularly."

After he tests the output, the nurse infuses the Visudyne. The procedure begins.

The PDT preparations involve more than just the equipment. Both Dr. Boyer and Dr. Rosenfeld agree that a challenging aspect of the PDT laser procedure is the lack of visual outcome. When you're finished with the treatment, the lesion looks the same.

"There's no endpoint, so that's one of the problems at the beginning. For most retinal surgeons, it's not a good feeling," Dr. Boyer says. "In every other treatment you always see the endpoint of what you've done."

"This kind of laser treatment is really different than any other; you really see no treatment effect," Dr. Rosenfeld says.

Dr. Rosenfeld likens the treatment to radiation therapy for cancer patients. The patients are receiving the advantages of the procedure, but there's no visible immediate result, only long-term benefits.

Occasionally problems do occur with the lasers, some due to operator error. These are easily remedied by making careful preparations. For instance, Dr. Boyer says beginners can switch the command screens easily, but then can't find their way back to the correct screen in time to adjust the parameters.

"They somehow get to a different screen, then they say 'how do I get back to the treatment screen?' Others find they can't see the lesion very well. It's important not to wait until the last minute to make a change.

"Make sure your staff alerts you in enough time. You don't want to be left with just a few minutes, and then find out the laser won't fire. You've got a limited window," Dr. Boyer says.

Dr. Rosenfeld agrees that preparation can prevent common errors. But if everything checked out OK and the laser stops in the middle of treatment, Dr. Rosenfeld says turning the laser off and then turning it back on usually works. If not, he keeps the company's toll-free emergency phone number handy.

Whichever laser you choose, be aware that this is a different type of procedure, with new requirements of you and your patient. Preparation will help ease you both through the learning curve of photodynamic therapy, and as a result you'll both reap the benefits.

As you can see from the sampling below, the Coherent Opal Photoactivator and the Zeiss Visulas 690s lasers share many of the same features.