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Photodynamic Therapy for Retinal Conditions
How Photodynamic Therapy Works
PDT uses a combination of a photosensitive drug and a low-energy laser to selectively close abnormal blood vessels beneath the retina. Understanding the mechanism helps explain why this treatment is well suited to certain conditions and why it is gentler on surrounding tissue than traditional laser treatments.
In the first step, a medication called verteporfin (sold under the brand name Visudyne) is infused through a vein in the arm. Verteporfin travels through the bloodstream and naturally concentrates in the abnormal blood vessels at the back of the eye. Once enough of the drug has collected there, a retina specialist applies a low-energy laser to the targeted area of the retina.
The laser activates the verteporfin, triggering a chemical reaction that produces oxygen molecules inside the abnormal vessels. These molecules damage the vessel walls, causing them to close and stop leaking. Because the drug concentrates in abnormal vessels before the laser is applied, the healthy retinal tissue surrounding the treatment zone is largely protected from harm.
Traditional thermal laser photocoagulation works by generating heat to destroy tissue directly. While effective at sealing leaking vessels, this heat can also damage the healthy retinal cells above and around the treated area, particularly when treatment is needed near the center of vision.
PDT uses what is sometimes called a cold laser because it does not generate heat or burn tissue. Instead, it triggers a targeted chemical reaction within the drug. This makes PDT a better-suited option for treating abnormal vessels located directly beneath the macula, the small central region of the retina responsible for the sharp, detailed vision needed for reading and recognizing faces.
Verteporfin received its first regulatory approval in 1999, and the U.S. Food and Drug Administration approved it in 2000, making it the first pharmacological treatment specifically approved for wet age-related macular degeneration. Early clinical trials confirmed that PDT could slow vision loss in certain patients with wet AMD compared to no treatment.
Subsequent research demonstrated that anti-VEGF injections (medications that block the protein driving abnormal blood vessel growth) produced superior outcomes for most patients with wet AMD. As a result, the role of PDT shifted considerably. Today, PDT holds a well-established place in treating chronic central serous chorioretinopathy and remains a valuable option for some patients with wet AMD who do not respond fully to injections alone.
Conditions PDT Is Used to Treat
PDT is indicated for several retinal conditions involving abnormal or leaking blood vessels beneath the retina. Our retina specialists use detailed imaging to confirm each diagnosis and determine whether PDT is the right approach for that patient's specific situation.
Wet AMD occurs when abnormal blood vessels grow beneath the macula and leak fluid or blood, threatening central vision. Patients typically notice blurred or distorted central vision, difficulty reading, or a dark spot appearing in the center of their visual field. PDT is FDA-approved for a specific pattern of abnormal vessel growth in wet AMD known as predominantly classic subfoveal choroidal neovascularization, meaning vessels growing directly beneath the center of the retina.
Anti-VEGF injections are the standard first-line treatment for most patients with wet AMD today. PDT plays a more targeted role, primarily for patients whose condition has not responded adequately to injections alone or as part of a combination approach designed to reduce how often injections are needed.
Central serous chorioretinopathy, or CSC, is a condition in which fluid accumulates beneath the central retina. Patients may notice blurry central vision, dimmed colors, or a subtle distortion in the appearance of straight lines. Most cases resolve on their own within a few months. When fluid persists beyond that point, the condition is classified as chronic CSC.
For chronic CSC, PDT is widely considered the preferred treatment, according to the American Academy of Ophthalmology. Studies have found that approximately 80% of patients with chronic CSC achieved complete resolution of fluid after a single PDT session. This is one area where PDT consistently outperforms other available therapies, including anti-VEGF injections, which have shown limited effectiveness for this specific condition.
PDT is also FDA-approved for treating choroidal neovascularization (abnormal vessel growth beneath the retina) caused by pathologic myopia, a form of severe nearsightedness that stretches and weakens the eye's internal structure. It may also be used for choroidal neovascularization related to ocular histoplasmosis syndrome, an eye condition associated with prior fungal exposure.
In each of these situations, the goal is the same: to close abnormal vessels that are threatening vision while minimizing damage to the healthy tissue surrounding them.
Who Is at Risk for These Conditions
Understanding the risk factors for conditions treated with PDT helps patients and referring providers recognize when a retina evaluation is warranted. Our specialists see patients with a wide range of backgrounds and risk profiles.
AMD is one of the leading causes of vision loss in older adults. Risk factors for developing the wet form include advancing age, a personal or family history of AMD, cigarette smoking, high blood pressure, and a diet low in leafy greens and antioxidant-rich foods. The risk of wet AMD increases substantially for people over age 75.
When abnormal blood vessels grow beneath the macula and begin to leak, the resulting damage can progress quickly. Early evaluation and prompt treatment are important to preserving as much central vision as possible.
CSC most often affects men between the ages of 20 and 50, though it can also occur in women and older adults. Corticosteroid medications, whether taken by mouth, applied to the skin, or inhaled, are a recognized trigger for CSC. Emotional stress and high-stress personality traits have also been linked to the condition, as the body may produce elevated natural corticosteroids during stressful periods that can trigger fluid buildup in susceptible individuals.
Identifying and addressing contributing factors, such as reducing or discontinuing corticosteroid use when medically appropriate, is an important part of managing CSC alongside direct treatment.
Diagnosing Conditions That May Require PDT
Accurate, detailed imaging is essential before recommending photodynamic therapy. Our retina specialists use several diagnostic tools to map abnormal vessels, assess fluid levels, and plan precise treatment.
Fluorescein angiography is a diagnostic test in which a yellow dye is injected into a vein in the arm. As the dye circulates through the retinal blood vessels, a specialized camera captures rapid photographs of the back of the eye. The resulting images reveal the exact location, size, and pattern of any abnormal vessels, helping confirm the diagnosis and identify precisely where to direct PDT treatment.
Indocyanine green (ICG) angiography uses a different dye that penetrates deeper into the eye, highlighting the choroid, the layer of blood vessels that sits beneath the retina. ICG is particularly useful for diagnosing chronic CSC and for identifying abnormal vessels that may not appear clearly on standard fluorescein angiography. This imaging helps our retina specialists map the precise treatment zone before proceeding with PDT.
Optical coherence tomography, known as OCT, is a noninvasive scan that produces detailed cross-sectional images of the retinal layers. OCT can precisely show fluid accumulation, retinal swelling, and structural changes caused by disease. Our specialists use OCT before treatment to assess the extent of damage and at follow-up visits to evaluate whether fluid has resolved after PDT. This scan is one of the most important tools for tracking treatment response over time.
PDT Treatment Approaches
How PDT is applied depends on the specific condition being treated and how the eye has responded to prior therapy. Our retina specialists tailor every treatment plan to the individual patient based on their imaging findings, symptoms, and clinical history.
For wet AMD, verteporfin is FDA-approved for treating predominantly classic subfoveal choroidal neovascularization. Early clinical trials demonstrated that PDT could significantly slow vision loss in patients with this pattern of disease compared to no treatment. Subsequent research showed that anti-VEGF injections produced better visual outcomes for most patients, and injections are now the standard of care for wet AMD, according to the American Society of Retina Specialists.
PDT plays a more targeted role today, typically for patients who have not responded sufficiently to anti-VEGF therapy or as part of a combination strategy aimed at reducing the burden of ongoing injections over time.
For chronic CSC, PDT has become a well-established first-line treatment. Many retina specialists, including our team, use a modified approach called half-dose PDT, in which the amount of verteporfin is reduced to half the standard dose. This reduction maintains treatment effectiveness while lowering the potential for side effects. Research cited by the American Academy of Ophthalmology found that approximately 80% of chronic CSC patients achieved complete fluid resolution after a single treatment session, and patients who began treatment with significantly reduced vision experienced the most meaningful gains in visual acuity.
For some patients with wet AMD, combining PDT with anti-VEGF injections may offer advantages over either therapy used alone. Anti-VEGF medications, including drugs such as aflibercept, ranibizumab, faricimab, and bevacizumab (used off-label for eye conditions), block the protein that signals abnormal blood vessel growth. When combined with PDT, this approach may help control disease activity while reducing the frequency of injections over time.
Our retina specialists review each patient's imaging and treatment history to determine whether a combination approach makes sense, rather than applying the same protocol to every patient.
PDT technology continues to be refined. Updated laser systems have been cleared by the FDA for use with verteporfin, giving retina specialists improved equipment options for delivering treatment. Ongoing research into dosing protocols, particularly half-dose and half-fluence (reduced light energy) approaches for chronic CSC, continues to refine how PDT is best applied. Our team stays current with these developments through active involvement in clinical research.
What to Expect Before, During, and After PDT
Knowing what happens at each stage of PDT helps patients prepare and recover safely. The procedure is performed in our office and is generally well tolerated by most patients.
Before scheduling PDT, our retina specialist will perform a comprehensive eye examination and review your imaging results. Please inform us about all medications you are currently taking, particularly any that are known to increase sensitivity to light. You will need to arrange a ride home, as vision may be temporarily blurry after the procedure. Prepare dark wraparound sunglasses and protective clothing, including long sleeves, gloves, and a wide-brimmed hat, to have available for the days following treatment.
The full PDT procedure takes approximately 20 to 30 minutes. A nurse or technician places an intravenous line in your arm and infuses verteporfin over roughly 10 minutes. After a brief waiting period to allow the drug to accumulate in the abnormal blood vessels, the retina specialist applies a low-energy laser to the targeted area of the retina for approximately 83 seconds. The laser is completely painless. You will be seated at an instrument similar to what is used during a standard eye examination, and most patients tolerate the procedure comfortably without any form of sedation.
The most important aspect of recovery is strictly avoiding direct sunlight and intense indoor lighting for five full days after the procedure. Verteporfin remains active in the body throughout this period, making both the skin and eyes highly sensitive to light. Exposure during this window can cause severe, sunburn-like reactions on exposed skin and can harm the eyes.
During the five-day light-avoidance period, patients should take the following precautions:
- Stay indoors or remain in deeply shaded areas when outside
- Wear long sleeves, gloves, and a wide-brimmed hat if going outdoors
- Use dark wraparound sunglasses that block light from all angles
- Avoid bright overhead lighting, sunny windows, and any intense light sources indoors
Normal household lighting from lamps is generally considered safe during this period. Patients should also let any other medical or dental providers know about their recent PDT treatment, as examination lights used in those settings can be very bright.
Our retina specialists schedule follow-up visits after PDT to assess treatment response using OCT imaging and, when indicated, repeat angiography. Because the effects of PDT can diminish over time, with abnormal vessels occasionally reopening, additional sessions may be recommended. For wet AMD patients, ongoing anti-VEGF injections are often continued alongside PDT. Many patients with chronic CSC achieve lasting results after a single session, though some require retreatment. Keeping all scheduled appointments is essential for monitoring your progress and catching any recurrence early.
Risks, Side Effects, and Long-Term Considerations
PDT is generally well tolerated, but like any medical procedure, it carries some risks. Our team discusses these with each patient in full detail before moving forward with treatment.
The most significant risk following PDT is photosensitivity during the five-day period after treatment. Skin or eye exposure to bright light during this window can cause serious reactions similar to a severe sunburn. Other less common side effects include temporary visual changes shortly after the procedure, mild back discomfort during the verteporfin infusion, and mild reactions at the intravenous site. In rare cases, swelling within the eye can cause a temporary decrease in vision immediately following treatment. Your retina specialist will explain all potential risks in detail before you decide to proceed.
PDT is designed to stabilize vision by stopping or slowing damage from abnormal or leaking blood vessels. It does not restore vision that has already been lost due to long-standing retinal damage. For patients with chronic CSC, resolution of fluid often leads to meaningful improvement in clarity and a reduction in distortion, though some subtle visual changes may persist. For patients with wet AMD, the primary goal is to preserve as much existing central vision as possible.
Patients can support their retinal health through consistent everyday habits. Eating a balanced diet that includes leafy green vegetables and foods rich in omega-3 fatty acids, avoiding smoking, and managing blood pressure all contribute to long-term retinal health. Using an Amsler grid at home (a simple printed chart with a grid pattern that helps detect changes in central vision such as new distortion or blank spots) is a practical way to monitor your vision between appointments and recognize any changes that need prompt attention.
When to Seek Immediate Care
Some vision changes require urgent evaluation and cannot safely be monitored at home. Knowing which symptoms are emergencies can help protect your sight.
Contact our office immediately or go to an emergency room if you experience any of the following symptoms:
- A sudden increase in floaters (dark spots, strings, or cobwebs drifting across your vision)
- Flashes of light in one or both eyes
- A curtain, shadow, or dark area spreading across part of your visual field
- Sudden loss of vision in one eye
These symptoms can indicate a retinal tear or detachment, conditions that require emergency treatment to prevent permanent vision loss.
Even when vision feels stable, keeping all scheduled follow-up appointments is critical. Conditions like wet AMD and chronic CSC can recur without obvious early symptoms. Regular OCT imaging and clinical evaluation allow our specialists to detect subtle changes before they become more serious, and to adjust your treatment plan accordingly.
Frequently Asked Questions
Below are answers to questions we commonly hear from patients who are preparing for or recovering from photodynamic therapy.
The laser portion of the procedure is completely painless. The verteporfin infusion feels similar to a routine blood draw. Some patients notice mild back discomfort during the infusion, which typically passes quickly. Standard numbing eye drops are used during the laser portion of the treatment, and most patients do not require any sedation. The procedure tends to be much more comfortable than patients expect going in.
This depends on your specific condition and how your eye responds to treatment. For chronic CSC, the majority of patients achieve complete fluid resolution after a single session, based on data cited by the American Academy of Ophthalmology. For wet AMD, additional sessions may be recommended alongside ongoing anti-VEGF injections depending on how the condition responds over time. Your retina specialist will reassess your imaging at each follow-up visit and recommend retreatment only when it is clinically indicated, not on a fixed schedule.
Many patients can return to office-based or indoor work the following day, provided their environment does not involve bright overhead lighting or outdoor sun exposure. The five-day light-avoidance restriction is the key factor in planning your return. If your job involves outdoor work, intense lighting, or significant sun exposure, you may need to modify your duties or arrange time away during that period. We encourage you to discuss your specific work environment with your retina specialist before your appointment so you can plan ahead without disruption.
Clinical trials demonstrated that anti-VEGF injections produced superior visual outcomes for most patients with wet AMD compared to PDT alone, according to the American Society of Retina Specialists. Unlike PDT, which is primarily designed to slow vision loss, anti-VEGF medications can lead to actual vision improvement in many patients by blocking the growth signal driving abnormal vessel formation. PDT remains valuable for patients who have not responded adequately to injections and for those who may benefit from a combination approach that reduces the number of injections required over time.
If you are exposed to direct sunlight or intense light within five days of your procedure, move indoors or into full shade immediately. Verteporfin remains active in the body during this period, and even brief sun exposure can trigger a significant photosensitivity reaction on any exposed skin. Contact our office promptly to report what happened and receive guidance on next steps. The best approach is prevention: have your protective clothing and sunglasses ready before your appointment day and plan your movements carefully for the full five days following treatment.
Yes. Because verteporfin circulates through the entire bloodstream, it makes all skin sensitive to light during the five-day period following treatment, not just the area around the eyes. Any exposed skin on the face, hands, arms, or neck is at risk for a photosensitivity reaction if exposed to bright light. Normal household lighting from lamps is generally safe, but sitting near a sunny window, undergoing bright medical or dental examination lighting, or going outdoors without full protective covering should all be avoided for the complete five-day period.
Visit New England Retina Associates
Our fellowship-trained retina specialists at New England Retina Associates bring extensive experience to the full range of conditions treated with photodynamic therapy, from chronic central serous chorioretinopathy to wet age-related macular degeneration and beyond. We welcome self-referred patients, referred patients, and those in need of urgent retina care at our four office locations serving patients throughout Connecticut. If you have been diagnosed with a retinal condition, noticed a change in your vision, or received a referral from your eye doctor, we encourage you to contact us so we can provide the thorough, individualized evaluation and care you deserve.
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