Photodynamic therapy (PDT) offers a non-invasive approach to treating certain eye conditions. This treatment uses a special light-activated medication combined with a specific type of laser light. It aims to target and seal abnormal blood vessels in the eye without requiring surgical incisions, providing an alternative for managing conditions that could otherwise lead to significant vision impairment.
Understanding Photodynamic Therapy (PDT)
Photodynamic therapy works by combining a photosensitizing drug with a non-thermal laser light. The drug, verteporfin, is administered intravenously into a vein in the arm. Once in the bloodstream, verteporfin selectively accumulates in rapidly growing cells, particularly the abnormal blood vessels found in certain eye diseases. This selective uptake helps target the problem areas while minimizing impact on healthy surrounding tissue.
After the drug has circulated and gathered in the target cells, a specific non-thermal laser light is directed at the affected eye. This laser activates the verteporfin, triggering a photochemical reaction. This reaction produces reactive oxygen species within the abnormal cells, which damage the membranes of the endothelial cells lining the abnormal blood vessels, leading to their closure.
Eye Conditions Treated with PDT
Photodynamic therapy is primarily employed for specific types of wet Age-related Macular Degeneration (AMD). This form of AMD involves the growth of abnormal, fragile blood vessels, known as choroidal neovascularization (CNV), beneath the macula. These vessels often leak fluid and blood, causing central vision distortion and loss. PDT is effective because it can selectively target and close these leaking vessels, helping to stabilize vision and prevent further damage.
Beyond wet AMD, PDT also treats other chorioretinal conditions. It is used for central serous retinopathy (CSR), where fluid builds up under the retina, and for ocular histoplasmosis syndrome (OHS), which can also cause abnormal vessel growth. Additionally, the therapy may be considered for polypoidal choroidal vasculopathy (PCV) and choroidal hemangioma, both of which involve abnormal blood vessels in the eye.
The PDT Procedure
Patients undergoing photodynamic therapy have their eyes dilated with drops. A nurse then inserts an intravenous line to administer the photosensitizing drug. The verteporfin drug is infused slowly over approximately 10 minutes.
Following the drug infusion, there is a waiting period to allow the verteporfin to circulate and concentrate within the abnormal blood vessels. An anesthetic eye drop is then applied to the eye, and a specialized contact lens is placed on the eye’s surface to direct the non-thermal laser light to the affected area. The laser light is applied for a precise duration, which activates the drug in the targeted vessels. The procedure itself is generally painless. The entire visit can take up to two to three hours.
Patient Experience and Post-Treatment Care
After a photodynamic therapy session, patients must take strict precautions due to the temporary photosensitivity induced by the verteporfin drug. The drug remains active in the body for approximately 48 hours, making the skin and eyes highly sensitive to light. Patients must avoid direct sunlight and bright indoor lights during this period to prevent severe skin reactions.
To protect themselves, individuals are advised to wear dark sunglasses, a wide-brimmed hat, and protective clothing whenever outdoors during daylight hours. Sunscreen offers no protection against this reaction. It is also recommended to avoid bright halogen lights, sunbeds, and even bright operating lights during dental or surgical procedures for the initial 48 hours. Patients may experience temporary blurred vision or mild visual disturbances.
Follow-up appointments are scheduled to monitor the treatment’s effectiveness and to determine if additional sessions are necessary. Some patients might experience mild side effects such as injection site reactions or temporary back pain during the infusion.