Photodynamic Therapy
What Is Photodynamic Therapy for the Eye?
Photodynamic therapy is a two-step treatment that combines a light-sensitive drug with a low-energy laser to close abnormal blood vessels beneath the retina.
PDT works through a process called photoactivation. A medication called verteporfin is injected into a vein in the arm, and it travels through the bloodstream to collect in abnormal blood vessels beneath the retina. A non-thermal laser tuned to a specific wavelength (689 nanometers) is then directed at the affected area, activating the drug. Once activated, verteporfin generates reactive oxygen molecules that damage the walls of the abnormal vessels, causing them to close without harming the healthy retinal tissue above.
PDT was originally developed and FDA-approved for wet age-related macular degeneration (AMD), particularly cases involving predominantly classic choroidal neovascularization, a pattern of abnormal blood vessel growth beneath the macula. Today, our retina specialists also use PDT to treat several other conditions.
- Chronic central serous chorioretinopathy (CSC), a condition where fluid accumulates beneath the retina
- Polypoidal choroidal vasculopathy (PCV), a variant of macular degeneration featuring abnormal branching vessel networks
- Choroidal hemangiomas, benign vascular tumors within the eye
- Select cases of myopic choroidal neovascularization
Traditional thermal laser photocoagulation uses heat to destroy tissue, which can leave permanent scars on the retina and is not suitable for treating vessels directly beneath the center of vision. PDT uses a cold, non-thermal laser that activates the medication without burning surrounding tissue. This distinction makes PDT a viable option for treating abnormalities located in or near the fovea, the part of the macula responsible for sharp central vision.
How Photodynamic Therapy Treats Retinal Conditions
The effectiveness of PDT depends on the specific condition being treated. Our retina specialists tailor treatment parameters, including medication dosage and laser exposure, based on the underlying diagnosis.
In wet AMD, fragile new blood vessels grow beneath the macula and leak fluid or blood, distorting and damaging central vision. PDT seals these vessels by activating verteporfin within the choroidal neovascular membrane. While PDT was once a primary treatment for wet AMD, anti-VEGF injections have since become the first-line therapy for most patients because of their ability to improve, not just stabilize, vision. Anti-VEGF therapy has been the standard of care for wet AMD since 2006 and has reduced rates of legal blindness from AMD by an estimated 50 percent (American Society of Retina Specialists). PDT remains a valuable tool for specific subtypes of wet AMD and for patients who do not respond adequately to injections alone.
Central serous chorioretinopathy (CSC) occurs when fluid leaks beneath the retina, often near the macula, causing blurred or distorted vision. For chronic cases that do not resolve on their own, half-dose PDT (using a reduced concentration of verteporfin at 3 mg/m2 instead of the standard 6 mg/m2) has shown strong results in resolving subretinal fluid and improving visual acuity. Research supports half-dose PDT as an effective treatment that reduces choroidal congestion and abnormal vascular leakage with a favorable safety profile. Patients seeking more information about this condition can learn about central serous retinopathy and the range of available management strategies.
Polypoidal choroidal vasculopathy (PCV) involves abnormal branching blood vessel networks with polyp-like dilations beneath the retina. PDT is particularly effective at closing these polypoidal lesions and is frequently used either alone or in combination with anti-VEGF medications. For many patients with PCV, combining PDT with intravitreal injections produces better outcomes than either treatment alone.
Choroidal hemangiomas are non-cancerous vascular tumors that can cause fluid leakage and vision loss. PDT has demonstrated excellent results in reducing tumor-related exudation and improving visual acuity, with studies showing sustained anatomic improvement and minimal recurrence over long-term follow-up. In many cases, a single treatment session is sufficient to resolve the associated retinal detachment.
Visudyne: The Light-Activated Medication Behind PDT
The success of photodynamic therapy depends on a drug called Visudyne, the brand name for verteporfin. Understanding how this medication works helps explain why PDT can target diseased tissue so precisely.
Verteporfin is a benzoporphyrin derivative, a type of photosensitizing agent that becomes chemically active when exposed to light of a specific wavelength. It was the first drug of its kind approved by the FDA for ophthalmic use. Verteporfin naturally concentrates in areas of rapidly growing or abnormal blood vessels due to the increased presence of low-density lipoprotein receptors on those vessel walls.
After the intravenous infusion, which takes approximately 10 minutes, verteporfin circulates through the bloodstream and binds to plasma lipoproteins. These lipoproteins are preferentially taken up by the endothelial cells lining the abnormal choroidal blood vessels. This selective uptake is what allows PDT to treat diseased vessels while largely sparing healthy tissue nearby.
Once the drug has accumulated in the target vessels, a diode laser delivering 689-nanometer light is applied to the treatment area for approximately 83 seconds. The laser energy activates the verteporfin, which then generates highly reactive forms of oxygen called singlet oxygen. These molecules damage the vessel walls from within, triggering a clotting response that seals the abnormal vessels. Because the laser is non-thermal, there is no heat-related damage to the overlying retina.
Who Is a Candidate for Photodynamic Therapy?
Candidacy for PDT depends on the type and location of the retinal condition, previous treatment history, and overall eye health.
PDT may be recommended for patients with chronic central serous chorioretinopathy that has not resolved after several months of observation. It is also considered for patients with polypoidal choroidal vasculopathy, choroidal hemangiomas, or certain subtypes of wet AMD where the choroidal neovascularization is predominantly classic in type. Patients who have had a limited response to anti-VEGF therapy alone may also benefit from adding PDT to their treatment plan.
PDT may not be appropriate for patients with severe liver disease, as verteporfin is metabolized by the liver. Individuals with porphyria or known hypersensitivity to verteporfin should not undergo this treatment. Patients who are unable to avoid sunlight and bright indoor lighting for 48 hours after treatment may also need to consider alternative options.
Before recommending PDT, our retina specialists perform a thorough evaluation that typically includes optical coherence tomography (OCT), fluorescein angiography, and indocyanine green angiography. These imaging studies reveal the precise location, size, and type of vascular abnormality, allowing us to determine whether PDT is the most appropriate treatment or whether another approach, such as a vitrectomy procedure or injection-based therapy, would better serve the patient.
Frequently Asked Questions
The entire procedure typically takes about 20 to 30 minutes and is performed in our office. You will receive the verteporfin infusion through a vein in your arm over approximately 10 minutes. After a brief waiting period to allow the drug to concentrate in the target vessels, your eye will be dilated and a special contact lens will be placed on the eye. The laser is then applied for about 83 seconds. Most patients experience little to no discomfort during the treatment.
The number of sessions varies by condition. For wet AMD, treatments were historically performed every three months as needed based on imaging results. For chronic CSC, a single half-dose session resolves subretinal fluid in the majority of patients, though some may require a second treatment. Your retina specialist will monitor your response with follow-up imaging and recommend retreatment only when necessary.
The most important precaution after PDT is avoiding direct sunlight and bright indoor light for 48 hours, as the photosensitizing drug remains active in your skin and can cause a severe sunburn-like reaction if exposed to strong light. Other possible side effects include temporary visual changes, mild discomfort at the injection site, and, in rare cases, a transient decrease in vision. Protective sunglasses and covering clothing are recommended after treatment to minimize light exposure risks.
Anti-VEGF injections are currently the first-line treatment for most patients with wet macular degeneration because they can stabilize and often improve vision. PDT works through a different mechanism, physically closing abnormal vessels rather than blocking the growth signal. For conditions like chronic CSC and polypoidal choroidal vasculopathy, PDT may offer advantages over injection therapy alone. In many cases the two treatments complement each other and may be used together for optimal results.
Yes, combination therapy is a well-established approach in retinal care. PDT is frequently paired with anti-VEGF injections, particularly for polypoidal choroidal vasculopathy and resistant wet AMD. Combining the two can reduce the total number of injections needed over time while maintaining strong visual outcomes. Depending on the full scope of your retinal condition, your treatment plan may also involve other procedures such as scleral buckle surgery or pneumatic retinopexy for associated retinal detachment.
Results depend on the condition being treated and its severity. For chronic CSC, studies show that the majority of patients experience complete resolution of subretinal fluid, with many achieving meaningful improvements in visual acuity. In wet AMD, PDT has been shown to help slow vision loss when used as part of a tailored treatment plan. Our retina specialists will discuss realistic expectations for your specific situation during your consultation.
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