Photodynamic Therapy (PDT) is a laser-activated ophthalmic procedure that selectively closes abnormal blood vessels in the retina using a photosensitising drug. It is primarily indicated for conditions such as wet age-related macular degeneration (AMD), central serous chorioretinopathy (CSC), and choroidal tumours. PDT offers a precise and minimally invasive alternative to thermal laser treatments by targeting pathological neovascular tissue while sparing surrounding structures.
This article provides a complete overview of Photodynamic Therapy, including its mechanism of action, clinical indications, treatment protocol, essential medications, efficacy rates, cost structure in India, leading treatment centres, associated risks, and therapeutic alternatives such as anti-VEGF injections and laser photocoagulation.
This think-piece aims to deliver a clinically accurate, structured resource for patients, ophthalmologists, and healthcare planners evaluating the use and outcomes of PDT in retinal disease management.
What is Photodynamic Therapy?
Photodynamic therapy (PDT) is a non-thermal, light-based ophthalmic treatment that selectively destroys abnormal subretinal tissues using a combination of a photosensitising drug and laser activation.
PDT involves the intravenous infusion of a light-sensitive medication that selectively accumulates in diseased vascular membranes, such as those found in choroidal neovascularisation.
The drug remains biologically inert until exposed to laser light at a specific wavelength, typically 689 to 694 nanometers. Upon laser activation, the drug undergoes a photochemical transformation that generates reactive oxygen species. These reactive molecules induce oxidative stress, causing endothelial cell damage, platelet activation, and vascular thrombosis in the targeted tissues.
The result is controlled occlusion of abnormal blood vessels without harming adjacent healthy retinal structures. PDT delivers localised therapy with high precision and minimal thermal damage, offering a safer alternative to thermal laser photocoagulation. This targeted approach enables preservation of visual function in patients with retinal disorders characterised by pathological neovascularisation.
What Eye Conditions can be Treated with Photodynamic Therapy?
Photodynamic therapy treats multiple retinal and choroidal conditions by selectively closing abnormal blood vessels and resolving subretinal fluid. These include wet age-related macular degeneration (wet AMD), central serous chorioretinopathy (CSC), choroidal melanomas, choroidal hemangiomas, and idiopathic choroidal neovascularisation (iCNV). Each of these conditions involves distinct pathological mechanisms that are addressed by the targeted vascular occlusion and photochemical effects of PDT, as outlined below:
1. Wet Age-Related Macular Degeneration (wet AMD)
In wet AMD, abnormal choroidal blood vessels grow beneath the macula and leak fluid and blood, damaging central vision. PDT selectively accumulates in these vessels and occludes them upon light activation. This treatment reduces leakage and preserves adjacent retinal tissue. It is most effective in patients with predominantly classic subfoveal lesions.
2. Central Serous Chorioretinopathy (CSC):
CSC is characterised by fluid buildup under the retina due to dysfunction in the retinal pigment epithelium. In chronic CSC, PDT, especially using half-fluence or half-dose protocols, induces choroidal vascular remodelling and resolves subretinal fluid. The treatment avoids the collateral damage associated with thermal laser procedures.
3. Choroidal Tumours:
PDT is a non-invasive treatment for small choroidal melanomas and hemangiomas that are unsuitable for surgery or radiation. Verteporfin accumulates in tumour vasculature and, upon activation, causes ischemia and direct tumour cell death. Multiple sessions may be required depending on the tumour size and location.
4. Idiopathic Choroidal Neovascularisation (iCNV):
iCNV affects younger patients without underlying AMD. These lesions involve abnormal vessel growth beneath the retina. PDT targets the neovascular membrane while sparing the healthy surrounding tissue. Treatment leads to visual stabilisation and resolution of leakage, especially when applied early.
How Does Photodynamic Therapy Work?
Photodynamic therapy (PDT) works through a three-step mechanism: administration of a photosensitiser, selective accumulation in abnormal tissue, and activation by non-thermal laser light to trigger oxidative reactions that selectively occlude abnormal blood vessels.
This therapeutic process is implemented through a structured clinical protocol, which unfolds across three phases: before, during, and after the treatment.
Before the Treatment
Patients undergo a comprehensive pre-treatment assessment, including visual acuity tests, dilated fundus examination, and imaging studies such as optical coherence tomography (OCT), fluorescein angiography, and indocyanine green angiography to define lesion type and treatment area.
Eligibility depends on disease characteristics and clinical history. PDT is recommended for patients with classic subfoveal or juxtafoveal choroidal neovascularisation in wet AMD, and for chronic central serous chorioretinopathy (CSC) persisting beyond three months.
Baseline lab tests evaluate liver function and complete blood count to ensure safe photosensitiser metabolism. The standard verteporfin dose is 6 mg/m² of body surface area. Patients receive guidance on light-avoidance precautions and peri-procedural instructions.
During the Treatment
Verteporfin is infused intravenously over 10 minutes in a monitored clinical setting. After a 15-minute distribution, the ophthalmologist activates the drug using a non-thermal 689 nm laser, precisely directed at the lesion using a magnifying contact lens.
Laser activation excites verteporfin molecules, which transfer energy to surrounding oxygen, producing singlet oxygen and other reactive species. This causes endothelial damage, platelet activation, and thrombosis, leading to selective vascular occlusion.
Topical anaesthesia minimises discomfort. The entire procedure, including preparation and monitoring, takes approximately 20-30 minutes. Adverse reactions are rare under continuous clinical supervision.
After the Treatment
Patients must avoid sunlight and strong indoor lighting for 48 hours post-procedure due to the photosensitive state induced by residual verteporfin. Protective clothing, sunglasses, and high-SPF sunscreen are essential for any brief outdoor exposure.
Recovery typically allows resumption of indoor activities immediately. Side effects may include mild injection site pain, transient visual disturbances, or back pain during infusion, occurring in 2-4% of cases. Severe complications, including vision loss or allergic reactions, are reported in fewer than 1% of patients.
Patients receive written post-care instructions and emergency contact details, ensuring safe recovery and symptom monitoring.
What Medications are Required for Photodynamic Therapy?
Photodynamic therapy (PDT) requires verteporfin (Visudyne) as its primary photosensitising medication. Verteporfin is a benzoporphyrin derivative from the chlorin class, functioning as a light-activated pharmaceutical that selectively targets abnormal blood vessels in ocular tissues. It demonstrates peak light absorption at 689 nanometers.
The drug accumulates in neovascular membranes due to increased low-density lipoprotein (LDL) receptor expression and enhanced vascular permeability in pathological tissues. When activated by non-thermal laser light at a specific wavelength, verteporfin enters an excited state and transfers energy to molecular oxygen. This interaction generates reactive oxygen species, such as singlet oxygen, which induce endothelial damage, platelet activation, and vascular occlusion within the targeted lesion.
Verteporfin is administered intravenously at a standardised dose of 6 milligrams per square meter of body surface area over a 10-minute infusion period. The green-colored solution must be shielded from light during preparation and delivery to maintain drug stability.
Following the procedure, patients must avoid direct sunlight and intense indoor lighting for at least 48 hours. This light-avoidance period is critical because residual verteporfin in the skin can trigger phototoxic reactions upon light exposure. Protective measures such as full-length clothing, sunglasses, and high-SPF sunscreen are mandatory during this time.
Verteporfin is the only approved medication required for ophthalmic photodynamic therapy. Anti-VEGF drugs and other agents may be used alongside PDT in certain cases, but are not part of the core treatment. Adjunctive medications, such as acetaminophen or antihistamines, support patient comfort and safety.
Adjunctive medications may include oral acetaminophen to minimise infusion-related back pain, which occurs in 2-4% of patients and typically resolves without intervention. Premedication does not alter therapeutic efficacy but improves treatment tolerability.
How Effective is Photodynamic Therapy?
Photodynamic therapy (PDT) demonstrates condition-specific effectiveness ranging from 60% to 90%. In central serous chorioretinopathy (CSC), 80-90% of patients achieve complete subretinal fluid resolution within three months following PDT. In polypoidal choroidal vasculopathy (PCV), PDT alone results in polyp regression in 70-80% of cases, improving outcomes to approximately 95% when combined with anti-vascular endothelial growth factor (anti-VEGF) injections.
For wet age-related macular degeneration (AMD), PDT monotherapy stabilises or improves vision in 60-70% of cases. The addition of anti-VEGF agents enhances both anatomical and functional outcomes, particularly in patients with treatment-resistant disease or specific genetic profiles. Long-term benefits of combination therapy include reduced treatment frequency and injection burden.
PDT is most effective in patients with clearly defined lesions, small neovascular complexes, recent symptom onset, and preserved retinal architecture. Conversely, PDT is less effective in chronic AMD with widespread fibrosis, diffuse leakage, or poorly demarcated neovascular membranes.
These outcomes indicate that precise patient selection based on disease subtype, lesion characteristics, and prior treatment response is critical for maximising therapeutic success with PDT.
How much does Photodynamic Therapy Cost in India?
Photodynamic therapy (PDT) in India costs between ₹15,000 and ₹40,000 per treatment session, depending on the hospital type, regional pricing, and diagnostic requirements. The cost of verteporfin (Visudyne), the essential photosensitising medication used in PDT, contributes the largest portion and ranges from ₹12,000 to ₹30,000 per vial.
Most insurance providers in India classify PDT as a specialised procedure that requires preauthorisation. Coverage is limited and varies by insurer, with many policies enforcing reimbursement caps that cover only a portion of the total treatment cost. As a result, 60-70% of patients pay out-of-pocket for PDT sessions.
Additional expenses include ophthalmologist consultation fees (₹800-2,000), diagnostic imaging such as optical coherence tomography and angiography (₹1,500-3,000), and pre-procedure laboratory tests (₹1,000-2,000). The full treatment package, including medication, procedure, and associated diagnostics, typically ranges from ₹18,000 to ₹45,000 per session.
Multiple treatment sessions are often required, depending on the clinical condition, significantly increasing the overall financial burden. Some facilities offer package discounts for follow-up treatments. Financial planning for PDT should incorporate medication costs, diagnostic services, and the probability of multiple sessions with partial insurance reimbursement.
What are the Best Photodynamic Therapy Centres?
The best photodynamic therapy centres in India include Eye7 Eye Hospital, AIIMS Delhi, Sankara Nethralaya, and other government-supported institutions offering PDT under structured clinical frameworks. Below is a brief overview of the key centres:
- AIIMS Delhi offers PDT through its tertiary ophthalmology unit, which is supported by standardised public-sector care pathways and academic infrastructure.
- Sankara Nethralaya (Government-Aided Wing), Chennai, delivers PDT within its public ophthalmology services, offering subsidised access for eligible patients under its charitable care model.
What are the Risks & Side Effects of Photodynamic Therapy?
Photodynamic therapy (PDT) involves temporary side effects such as vision disturbances, light sensitivity, and mild infusion-related discomfort. At the same time, rare complications include retinal damage or allergic reactions that require clinical attention.
Common and Temporary Effects
- Visual disturbances affect 10–15% of patients, including blurred vision, increased floaters, and reduced contrast sensitivity. These symptoms typically resolve within 1-2 weeks.
- Photosensitivity reactions occur in about 20% of individuals who do not follow light-avoidance protocols. Exposure to direct sunlight or bright indoor lighting can trigger skin or eye sensitivity.
- Injection site reactions, including redness, swelling, or discomfort, affect approximately 5% of patients.
- Transient back pain is reported in 2-4% of patients during verteporfin infusion and resolves spontaneously within minutes.
Rare but Serious Complications
- Retinal pigment epithelium (RPE) tears occur in 1-2% of high-risk patients with large or irregular lesions.
- Severe vision loss is reported in fewer than 1% of cases.
- Allergic reactions to verteporfin, including rash, itching, or respiratory difficulty, occur in less than 0.1% of patients and require immediate medical attention.
Patients must avoid direct sunlight and intense indoor lighting for 48 hours following treatment. Protective measures include long-sleeved clothing, sunglasses, and high-SPF sunscreen during unavoidable exposure. Monitoring for unexpected symptoms and adhering to follow-up schedules enhances safety and supports full recovery.
What are the Alternatives to Photodynamic Therapy?
Alternatives to photodynamic therapy (PDT) include anti-VEGF injections, laser photocoagulation, and corticosteroid-based treatments, each offering distinct mechanisms and clinical advantages for managing retinal disorders. Each of them is briefly explained below, along with a quick overview of when you must use this alternative:
Anti-VEGF Injections
Anti-vascular endothelial growth factor (anti-VEGF) therapy involves intravitreal injections of agents like ranibizumab, aflibercept, or bevacizumab that inhibit abnormal blood vessel proliferation and fluid leakage.
This treatment is preferred as first-line management for wet age-related macular degeneration (AMD) and polypoidal choroidal vasculopathy, particularly when long-term visual improvement and continuous disease suppression are required.
Laser Photocoagulation
Laser photocoagulation is a thermal-based treatment that uses focused laser energy to seal leaking retinal vessels and halt disease progression.
It is most appropriate for extrafoveal lesions and proliferative diabetic retinopathy, where lesion precision is less critical and durable closure is prioritised.
Corticosteroid Treatments
Corticosteroid therapy utilises intravitreal steroid injections or slow-release implants to reduce inflammation and control macular oedema.
This option is indicated in retinal vein occlusion or diabetic macular oedema, particularly in cases driven by inflammation or when anti-VEGF response is suboptimal.
Resources
- https://pmc.ncbi.nlm.nih.gov/articles/PMC11508366/