<<Press Conference on May 22, 2001>>
Photodynamic
Therapy Brings Hope to
Patients with Macular Diseases
Degeneration arising from both old age (age-related macular degeneration, AMD) and high myopia (600 degree or more) can cause choroidal neovascularization (CNV). CNV consists of abnormal vessels that bleed and lead readily and blindness is a common result. Photodynamic Therapy (PDT) can treat and seal off these abnormal vessels and therefore bring hope to patients suffering from AMD and high myopia macular degeneration, whom could have gone blind.
The Chinese University of Hong Kong (CUHK) was the first center in Asia to use PDT on patients with CNV secondary to AMD or high myopia. The clinical trial started in February 2000 and over 90 patients have received PDT. In the AMD group, 32% of patients have visual acuity gain of 1 line or more while 16% have visual acuity loss of 3 lines or more. The respective figures for the high myopia group are 60% and 0%.
"The results are encouraging. We have less patients experiencing moderate to severe visual loss and more patients achieving visual gain, when compared to international studies," remarked by Dr. Wai-man Chan, Assistant Professor of the Department of Ophthalmology and Visual Sciences, the CUHK.
Professor Dennis Shun-chiu Lam, Chairman of the Department of Ophthalmology and Visual Sciences, the CUHK commented that, "since most patients with macular CNV are not suitable candidates for current treatment modalities like laser treatment or surgery, PDT is a viable new option in which it could limit the progression of macular diseases with CNV especially when used at the early stage of the diseases."
"Nevertheless, PDT is not a magic treatment and it cannot restore vision already permanently lost," Professor Lam cautioned. "The drug is also relatively expensive. The drug cost per treatment is around $10,000 and an average of 3 treatments are needed in the first year."
PDT is a selective non-thermal laser therapy to destroy the abnormal new blood vessels on the retina of patients suffering from CNV. Controlled trial of PDT for the treatment of AMD in human subjects started in 1996, though it has been used safely to treat a wide range of medical conditions including cancers and cardiovascular diseases long before that. The Food and Drugs Administration (FDA) of the United States approved PDT for the treatment of CNV due to AMD in April 2000.
Professor Lam warned that with an ageing population and a rising prevalence of high myopia in Hong Kong, the number of patients suffering from macular diseases would be on the rise.
"AMD is the leading cause of blindness in elderly over 60 in western countries and unfortunately there are signs that Hong Kong is following the footsteps of western countries," Professor Lam remarked.
Professor Lam said that age was the most important factor and had shown to be strongly linked to AMD. Other risk factors are cigarette smoking, diet with saturated fat and cholesterol, excessive sunlight exposure, family member with AMD and one eye already suffered from AMD.
High myopia is the seventh leading cause of blindness in the US. As the estimated percentage of high myopia in the general population in Hong Kong is 4%, compared to only 2% in the US, Professor Lam envisaged that the local situation could be worse.
There is also a higher possibility of macular diseases in the younger generation in Hong Kong, since a recent study by the CUHK revealed that 6% of secondary students in Hong Kong are suffering from high myopia.
Professor Lam pointed out that once the photosensitive retinal cells in the macular region have been damaged, the vision is, in general, not recoverable. "Early detection and treatment is crucial for keeping the vision."
Professor Lam recommended people over the age of 50 or with higher risk for AMD, as well as those suffering from high myopia, to do self-check daily with an Amsler chart and to have regular check-up by eye doctor.