PHOTODYNAMIC THERAPY (PDT)-
A new hope for macular diseases

What is PDT?

Photodynamic therapy is a 2-step procedure, where light-activated drug, the photosensitizer is first to be infused followed by the application of low energy non-thermal laser. This treatment philosophy has been safely used before to treat a wide range of medical conditions including cancers and cardiovascular diseases. Choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD) also involves the abnormal rapid growth of vascular tissues. The photosensitizing drug administered will bind specifically to the abnormal vessel. The drug being activated by the "cold" laser beam subsequently causes a chain of reactions. This will block the abnormal vessel and stop the leakage. The therapeutic effect is not observed until drug and light are combined. So the physico-bio-chemical reaction is a selective one and it reduces the damage on the overlying retina and the normal adjacent tissue.

2-step procedure in Photodynamic Therapy
----Drug infusion & laser projection

When was PDT first used in treating macular diseases?

Controlled trial of PDT for the treatment of AMD in human subjects started in 1996. The Food and Drugs Administration (FDA) of the United States approved PDT for the treatment of choroidal neovascularization due to age-related macular degeneration in April 2000. The Chinese University of Hong Kong started a project to study the efficacy and safety of PDT on patients with CNV secondary to AMD or other causes of choroidal neovascularization such as high myopia in February 2000. It was the first center in Asia to use this new form of treatment.


Fig: A 68-year old gentleman with AMD, decrease in vascular leakage after PDT


Fig: Photos showing a 24-year-old man with myopia of -11.0D, having decrease in vascular leakage after PDT

What are the major advantages of PDT?

Photodynamic therapy for treating choroidal neovascularization is a safe and minimally invasive procedure. A selective non-thermal laser therapy is used to destroy the abnormal new blood vessels without sacrificing or damaging the healthy tissue in the macula.

What is the efficacy in terms of international experiences of the treatment of choroidal neovascularization in AMD and high myopia?
(Please refer to the fact sheet on results for more details)

In a randomized controlled trial in 609 AMD patients with a follow-up of 12 months, AMD patients treated with PDT lost > 3 lines of vision in 39% as compared with the placebo group of 54%. The result of the study was important as the treatment can reduce the risk of moderate or severe loss of vision in many patients, whom in the past had no other proven effective treatment. For details, please refer to the full article published in "Archives of Ophthalmology" (Arch Ophthalmol 1999;117:1329-45).

The result of a 12-month study on 120 high myopia maculopathy patients also showed a treatment benefit. Until now, not much could be offered to this group of patients who are usually young and vision is critical to their works and lives. Patient having received PDT treatment lost > 3 lines of vision in 14% as compared with the control group of 33%. For details, please refer to the full article published in "Ophthalmology" (Ophthalmology 2001;108:841-52).

How safe is the treatment?

In general, it is considered to be a rather safe procedure, but adverse effects have been documented including transient visual disturbance, injection site pain, macular hemorrhage, low back pain and photosensitivity reaction.

What are the precautions after the treatment?

Since the infused drug is a photosensitizing agent, patients are advised to stay away from bright light for about 48 hours after the therapy.


Fact Sheet Main