Photodynamic Therapy for Retinal Conditions
Understanding Photodynamic Therapy
Photodynamic therapy is a two-step procedure used to treat abnormal blood vessels growing beneath the retina. In the first step, a light-sensitive medication called Visudyne (verteporfin) is injected into a vein in the arm. The drug travels through the bloodstream and collects in the abnormal blood vessels at the back of the eye. In the second step, a retina specialist shines a low-energy laser into the eye to activate the drug.
Once the laser activates Visudyne, the drug produces reactive oxygen molecules inside the abnormal vessels. These molecules damage the walls of the leaking blood vessels, causing them to close. Because the laser targets only the area where the drug has collected, surrounding healthy retinal tissue is largely spared.
Traditional thermal laser photocoagulation uses heat to destroy tissue directly. This can seal leaking vessels but also damages the healthy retina above and around the treated area. PDT uses a 'cold laser' that does not burn tissue. Instead, it triggers a chemical reaction within the drug that selectively closes abnormal vessels. This makes PDT a gentler option for treating blood vessels located directly beneath the center of vision.
Visudyne (verteporfin) received its first approval in Switzerland in December 1999. The United States Food and Drug Administration approved it in April 2000, making it the first pharmacological treatment for wet AMD (ASRS). Two landmark clinical trials, known as the TAP and VIP studies, established that PDT could slow vision loss in certain patients with wet AMD. Later, the ANCHOR and MARINA trials showed that anti-VEGF injections (medications that block abnormal blood vessel growth) were more effective for most patients with wet AMD. Today, PDT plays a more targeted role in retina care.
Who Is Affected and Risk Factors
PDT is used to treat several retinal conditions involving abnormal or leaking blood vessels. The most common conditions include:
- Wet age-related macular degeneration, particularly subfoveal choroidal neovascularization with a classic pattern on imaging
- Chronic central serous chorioretinopathy, a condition where fluid builds up beneath the central retina
- Choroidal neovascularization caused by pathologic myopia (severe nearsightedness)
- Choroidal neovascularization related to ocular histoplasmosis syndrome
About 11 million people in the United States have some degree of age-related macular degeneration (BrightFocus Foundation). AMD affects more than one-fourth of Americans over age 75. Risk factors for developing the wet form of AMD include advancing age, family history, smoking, high blood pressure, and a diet low in leafy green vegetables. Wet AMD occurs when abnormal blood vessels grow beneath the macula and leak fluid or blood, threatening central vision.
Central serous chorioretinopathy, known as CSC, most commonly affects men between the ages of 20 and 50. Exposure to corticosteroid medications, whether taken by mouth, applied to the skin, or inhaled, can bring on or worsen CSC. Emotional stress and personality factors associated with high stress levels have also been linked to this condition. The body may produce natural corticosteroids during periods of stress, which could trigger CSC in people who are prone to it.
Signs and Symptoms
Patients with wet AMD typically notice blurred or distorted central vision, difficulty reading, or dark spots in the center of their visual field. PDT may be considered when vision loss develops gradually rather than suddenly. A retina specialist may recommend PDT for patients whose wet AMD has not responded adequately to anti-VEGF injections, or as a combination treatment alongside anti-VEGF therapy to reduce the number of injections needed.
Chronic CSC causes a persistent buildup of fluid under the central retina. Patients may notice blurry central vision, a dimming of colors, or a subtle distortion in straight lines. When CSC lasts for several months or keeps returning, a retina specialist may recommend PDT. Research has shown that half-dose or half-fluence PDT is widely considered the first-line and preferred therapy for chronic CSC (AAO).
Diagnosis and Testing
Before recommending PDT, a retina specialist typically performs fluorescein angiography. In this test, a yellow dye is injected into a vein in the arm. As the dye circulates through the blood vessels in the retina, a specialized camera takes rapid photographs. The images reveal the exact location, size, and type of abnormal blood vessels. This information helps the specialist determine whether PDT is appropriate and where to aim the laser.
Indocyanine green angiography, or ICG, uses a different dye that highlights deeper blood vessel layers beneath the retina called the choroid. ICG is especially useful for diagnosing conditions like CSC and for identifying abnormal vessels that may not show up clearly on fluorescein angiography. It helps the retina specialist map the precise treatment area for PDT.
Optical coherence tomography, known as OCT, is a noninvasive imaging scan that creates detailed cross-sectional pictures of the retina. OCT shows fluid buildup, swelling, and structural changes within the retinal layers. Retina specialists use OCT before treatment to assess the extent of damage and after treatment to monitor whether fluid has resolved. Approximately 80% of chronic CSC patients achieved complete resolution of fluid after PDT in clinical studies (AAO).
Treatment Options
Visudyne (verteporfin) is FDA-approved for the treatment of predominantly classic subfoveal choroidal neovascularization caused by wet AMD, pathologic myopia, and ocular histoplasmosis. In the TAP study, 61% of patients with subfoveal choroidal neovascularization lost fewer than three lines of vision at 12 months of follow-up (ASRS). While these results were significant at the time, anti-VEGF injections have since become the primary treatment for most patients with wet AMD.
Today, PDT for wet AMD is generally reserved for cases that do not respond well to anti-VEGF therapy alone. It may also be used in combination with anti-VEGF injections such as Eylea (aflibercept), Lucentis (ranibizumab), Avastin (bevacizumab, used off-label for eye conditions), or Vabysmo (faricimab). Combination therapy may help reduce the frequency of injections while maintaining treatment effectiveness.
For chronic central serous chorioretinopathy, PDT has become a well-established treatment. Many retina specialists use a modified approach called half-dose PDT, where the amount of Visudyne is reduced to half the standard dose to lower the risk of side effects while still closing the source of fluid leakage. Studies have found that approximately 80% of chronic CSC patients required only one PDT treatment to achieve resolution of fluid (AAO). Patients with worse baseline vision experienced the greatest improvement, with 50% of those starting with 20/100 or worse vision gaining two or more lines of visual acuity (AAO).
Anti-VEGF injections work by blocking vascular endothelial growth factor, a protein that drives abnormal blood vessel growth and leakage. These medications, including Eylea (aflibercept), Lucentis (ranibizumab), Avastin (bevacizumab, used off-label for eye conditions), and Vabysmo (faricimab), require repeated injections every four to sixteen weeks depending on the specific drug and the patient's response. PDT works through a different mechanism, using a photochemical reaction to physically close abnormal vessels rather than blocking a growth signal.
For wet AMD, anti-VEGF injections produce better visual outcomes for most patients and have become the standard of care. For chronic CSC, PDT is often preferred because anti-VEGF injections have shown limited effectiveness for that condition. A retina specialist will recommend the approach best suited to the specific diagnosis and clinical situation.
In 2023, the FDA approved the ML6710i photodynamic laser, manufactured by Modulight, for use with Visudyne (verteporfin) in PDT treatment (FDA, 2023). This updated laser system provides retina specialists with newer equipment options for performing PDT. Research also continues into optimizing PDT dosing protocols, particularly half-dose and half-fluence approaches for chronic CSC, to maximize effectiveness while reducing potential side effects.
What to Expect
A retina specialist will perform a thorough eye examination and imaging tests before scheduling PDT. Patients should inform the specialist about all medications they are taking, especially any drugs that increase sensitivity to light. It is important to arrange transportation home because vision may be slightly blurry after the procedure. Patients should also plan to have dark sunglasses and protective clothing available for the days following treatment.
The PDT procedure is performed in the retina specialist's office and typically takes about 20 to 30 minutes total. First, a nurse or technician places an intravenous line in the arm and infuses Visudyne (verteporfin) over approximately 10 minutes. The specialist then waits a short period for the drug to accumulate in the abnormal blood vessels. Next, the specialist applies a low-energy laser to the targeted area of the retina for about 83 seconds. The laser is painless. Patients are seated at a specialized instrument similar to what is used during routine eye exams.
After treatment, patients must avoid direct sunlight and bright indoor lighting for five days. The Visudyne drug remains in the body and makes the skin and eyes highly sensitive to light during this period. Exposure to sunlight or bright light can cause serious skin burns and eye damage. Patients who need to go outdoors during this time should wear long sleeves, gloves, a wide-brimmed hat, and dark sunglasses that block light from all angles. Normal indoor lighting from lamps is generally considered safe.
A retina specialist will schedule follow-up visits to monitor the response to treatment using OCT and possibly repeat angiography. Because the effects of PDT can be temporary, with abnormal blood vessels sometimes reopening over time, additional treatments may be needed. For wet AMD patients, the specialist may recommend ongoing anti-VEGF injections alongside PDT. For chronic CSC patients, many achieve lasting results after a single session, though some require retreatment.
Living With a Condition Treated by PDT
PDT is designed to slow or stop vision loss and, in some cases, improve vision. It does not restore vision that has been lost from long-standing damage to the retina. For patients with wet AMD, the primary goal is to preserve as much vision as possible. For patients with chronic CSC, resolution of fluid often leads to noticeable improvement in clarity and reduced distortion, though some subtle visual changes may persist.
PDT is generally well tolerated, but it does carry some risks. The most important precaution involves photosensitivity. Failing to avoid bright light for five days after treatment can result in severe sunburn-like reactions on any exposed skin. In rare cases, Visudyne can cause immediate swelling in the eye that leads to a temporary decrease in vision. Other uncommon side effects include back pain during the infusion, injection site reactions, and temporary visual disturbances. A retina specialist will explain all risks before the procedure.
Patients undergoing PDT should plan their schedules around the five-day light-avoidance period. This may mean adjusting work commitments, especially for those who spend time outdoors. Wearing UV-protective eyewear and using the Amsler grid, a simple chart that detects changes in central vision, at home can help patients monitor their condition between appointments. Eating a balanced diet rich in leafy greens and omega-3 fatty acids, not smoking, and managing blood pressure support overall retinal health.
When to See a Retina Specialist
Certain vision changes require immediate medical attention. See a retina specialist or go to the emergency room immediately if you experience any of the following:
- A sudden increase in floaters (dark spots or strands drifting across your vision)
- Flashes of light in one or both eyes
- A curtain, shadow, or dark area spreading across your field of vision
- Sudden loss of vision in one eye
Even if vision seems stable, regular follow-up appointments with a retina specialist are essential for anyone who has received PDT. Conditions like wet AMD and chronic CSC can recur without obvious symptoms at first. OCT imaging and clinical examination allow the specialist to detect subtle changes early and adjust the treatment plan. Patients should keep all scheduled appointments and report any new visual symptoms promptly.
Questions and Answers
The laser portion of PDT does not cause pain. The intravenous infusion of Visudyne (verteporfin) feels similar to a standard blood draw. Some patients experience mild back pain during the infusion, which usually resolves quickly. Overall, most patients tolerate the procedure comfortably without the need for sedation or anesthesia beyond standard numbing eye drops.
The number of treatments varies depending on the condition being treated and how the eye responds. For chronic central serous chorioretinopathy, approximately 80% of patients need only one session to achieve resolution of fluid (AAO). For wet AMD, multiple sessions may be needed, often in combination with anti-VEGF injections. A retina specialist will develop a treatment plan based on imaging results and individual response.
Many patients can return to indoor work the next day, provided the workspace does not involve bright overhead lighting or outdoor exposure. The critical restriction is avoiding direct sunlight and intense light for five days after treatment. If your job requires time outdoors or involves exposure to bright light, you may need to take time off or modify your duties during the light-avoidance period. Discuss your specific situation with your retina specialist before the procedure.
After the ANCHOR and MARINA clinical trials demonstrated that anti-VEGF injections such as Lucentis (ranibizumab) produced superior visual outcomes for wet AMD, those injections became the standard of care (ASRS). Anti-VEGF medications block the growth signal that drives abnormal blood vessels, and they can improve vision in many patients rather than simply slowing vision loss. PDT remains a useful option for patients who do not respond adequately to anti-VEGF treatment alone or who may benefit from combination therapy to reduce the number of injections needed.
Accidental sun exposure within five days of PDT can cause a photosensitivity reaction because Visudyne (verteporfin) remains active in the body. This can result in severe sunburn-like skin damage on any exposed area. If accidental exposure occurs, move indoors or into shade immediately and contact your retina specialist for guidance. Wearing protective clothing, a wide-brimmed hat, and wraparound dark sunglasses during the entire five-day period is the best way to prevent this complication.