PDT for Eye Health: Overcoming Myopia and Macular Degeneration
Eye or vision problems are common around the world, especially with advancing age. In this vein, the primary benefit of photodynamic therapy (PDT) has been to eliminate the early signs of age-related macular degeneration, or ARMD, the third leading cause of blindness worldwide (after cataract and glaucoma). The treatment is performed with red laser light after intravenous injection of the photosensitizer (such as a porphyrin), which leads to accumulation of the porphyrin in cells involved in the progression of ARMD.
PDT was introduced in the late 1990s as a novel treatment for ARMD and for a condition called choroidal neovascularization (CNV), which can be associated with both ARMD and myopia (nearsightedness). The term neovascularization refers to proliferation of blood vessels in tissues not normally containing them, such as the eyes. Abnormal or excessive formation of blood vessels in the eye can be related to vision problems such as myopia and ARMD.
Researchers from the National Healthcare Group Eye Institute in Singapore recently assessed the effects of PDT in 18 consecutive cases of pathological myopia. About 72% avoided moderate visual loss and 28% improved by at least 1 line after 1 year. Of those individuals who were treated within 2 weeks of visual symptoms, 89% avoided the loss of 3 or more lines compared to about 57% for those who presented later. There was a statistically significant improvement in vision as a result of PDT, and this was associated with younger age, smaller lesion size and earlier initiation of treatment.
Meanwhile, a clinical study at the VMR Institute in Huntington Beach, California, focused on the use of PDT in patients with neovascular ARMD after at least three courses of standard treatment, which entails anti-VEGF injections. Visual acuity was checked at regular intervals for six months following a combination of PDT with the standard treamtent. The researchers found that the combined PDT/anti-VEGF therapy resulted in a significant improvement in vision and other favorable outcomes, as reported in the 25 May 2013 issue of Opthalmology.
Ophthalmologists should therefore consider PDT as a treatment option for both ARMD and myopia. Larger clinical trials are being planned and expected to provide a clearer picture of how exactly this important modality can help individuals who are suffering from an age-related decline in their vision.
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Tan CS, Chew MC, Lim KH, Lim TH. Factors affecting visual outcome of myopic choroidal neovascularization treated with verteporfin photodynamic therapy. Int J Ophthalmol. 2013 Jun 18;6(3):327-30.
Tozer K, Roller AB, Chong LP, Sadda S, Folk JC, Mahajan VB, Russell SR, Boldt HC, Sohn EH. Combination Therapy for Neovascular Age-Related Macular Degeneration Refractory to Anti-Vascular Endothelial Growth Factor Agents. Ophthalmology. 2013 May 25. [Epub ahead of print]
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