Photodynamic Therapy
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Photodynamic therapy (PDT) is a technique to treat outer retinal or choroidal disorders without damaging the surrounding retinal structures. First, blood vessels are made sensitive to a specific wavelength of light (689nm) by intravenous infusion of Verteporfin (Visudyne). Then a non-thermal (cold) laser is applied to the treatment area. Verteporfin reacts with laser light to produce singlet oxygen and free radicals interacting with blood vessel endothelium. Unlike traditional laser therapy, PDT can be used close to the fovea without causing structural damage due to thermal effects.
Conditions treated by PDT
Central serous chorioretinopathy
Half dose or half fluence PDT is the treatment of choice for chronic central serous chorioretinopathy. Treatment speeds up recovery and also lowers the risk of recurrence. Usually, one would consider PDT if there has been no improvement in the subretinal fluid four months after onset. However, this can be performed earlier if specific indications exist (e.g., recurrent central serous chorioretinopathy or occupational requirement).
Polypoidal choroidal vasculopathy
Full dose full fluence PDT is used in polypoidal choroidal vasculopathy to induce polyp closure. The likelihood of polyp closure is around 70% in patients treated with combination PDT and anti-VEGF therapy, compared to about 30% with anti-VEGF therapy alone (EVEREST I, EVEREST II and PLANET studies). This can translate to fewer injections or, in some cases, cessation of injection therapy.
Choroidal haemagioma
Multiple studies have examined using full fluence, full dose PDT in treating choroidal haemangioma. PDT has resulted in haemangioma regression and elimination of subretinal and intraretinal fluid.
PDT has also been used in patients with pachychoroid neovasculopathy and to treat intraocular tumours with exudation.
How is PDT performed?
First, Dr Sheck will discuss if PDT is a suitable treatment for your condition. An OCT scan and often fluorescein and indocyanine green angiograms are required for treatment planning.
If PDT is deemed appropriate, your height and weight will be measured (as the dosage of Verteporfin is based on your height and weight), and an intravenous line will be inserted. Dr Sheck will double-check the dosage calculation. The appropriate dosage of Verteporfin will be infused over 10 minutes, and 15 minutes after the start of the infusion, the actual treatment will start.
Dr Sheck will place you in front of the PDT laser machine. The treated eye will be numbed using eye drops. He will insert a small lens in front of your eye to see the treatment area. You will be asked to be steady and focus on one point to stop your eyes from moving. Dr Sheck will activate the laser for precisely 83 seconds in the treatment area. Occasionally more than one area will have to be treated.
The laser light is invisible to you, and there is no pain associated with the procedure.
Side effects
Most patients tolerate Verteporfin well, and the risk of severe allergic reaction is infrequent (well less than 1 in 10000). Some patients report back pain during the infusion, but this is transient. Your skin and eyes will be more sensitive to sunlight for 48 hours after the procedure, and you will be asked to avoid sunlight and wear dark glasses. We will supply a pair of dark glasses to wear after the procedure.
The risk of serious ocular problems from PDT is rare. These can include bleeding, RPE rupture, or foveal damage if repeated treatments are performed over the fovea. Uncommonly, patients can develop acute exudative maculopathy, where there is significant fluid leakage in the treated area after PDT. This can result in worsening of vision and even exudative retinal detachment. Fortunately, this condition tends to be self-limiting and resolves over 2-6 weeks. Dr Sheck may give you systemic prednisone to take or perform intravitreal anti-VEGF injections if the condition is severe.
Funding for PDT and availability of Verteporfin
Most private insurance companies fund the procedure, but the medication Verteporfin is unfunded. In most cases, private patients for PDT will have to pay for the Verteporfin themselves. Please get in touch with our team regarding pricing.
Verteporfin has been out of stock during the COVID era, but the supply of this medication is stabilising now.
About Dr Leo Sheck
Dr Sheck is a RANZCO-qualified, internationally trained ophthalmologist. He combined his initial training in New Zealand with a two-year advanced fellowship in Moorfield Eye Hospital, London. He also holds a Doctorate in Ocular Genetics from the University of Auckland and a Master of Business Administration from the University of Cambridge. He specialises in medical retina diseases (injection therapy), cataract surgery, ocular genetics, uveitis and electrodiagnostics.
