Age-related Macular Degeneration - An Asian Perspective

Introduction: Age-related macular degeneration (AMD) is the top blinding condition in developed countries. Dry AMD progresses slowly. Patients with dry AMD usually retain good vision until geographic atrophy or wet transformation sets in. Wet AMD causes rapid visual loss through chronic progressive or recurrent leakage and haemorrhage. Fundus biomicroscopy provides the clinical diagnosis, confirmed with fundus fluorescein angiogram (FFA). FFA also provides qualitative information on the rate of leakage. However, it does not adequately delineate the offending vascular lesion except in pure classic choroidal neovascularisation (CNV). Advancement in imaging technology employing confocal scanning laser ophthalmoscope indocyanine-green angiography (CSLO-ICGA) allows for accurate identification and delineation of the offending vascular lesion in 95% of cases, and for vascular subtyping into CNV, polypoidal choroidal vasculopathy (PCV) and retinal angiomatous proliferation (RAP). These vascular subtypes have different natural histories, and may respond differently to standard therapies. Methods: In a case series of 158 Asian eyes with wet AMD in Singapore, CNV was found in 85%, PCV in 34% and RAP in 5%. The relative proportion is different from published data involving Caucasian patients. Evidence-based treatment of extrafoveal classic CNV is thermal laser photocoagulation. Evidence-based treatment of subfoveal CNV includes periodic intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) agents such as ranibizumab or pegatanib, and photodynamic therapy (PDT) with verteporfin for suitable lesions. Due to cost considerations, off-label intravitreal injection of bevacizumab, an agent approved for metastatic colorectal cancer, may be considered on a compassionate-use basis. Other treatment modalities include direct thermal photocoagulation of extrafoveal PCV and CSLO-ICGA-guided PDT for occult CNV and PCV. Extrafoveal Stage-1 RAP can be treated with thermal laser photocoagulation. As wet AMD is a chronic recurrent condition, monitoring for treatment response and recurrence is of utmost importance. Optical coherence tomography provides objective measurement of the retinal thickness. Together with serial fundus photographs, it is invaluable for disease monitoring. With optimal treatment, avoidance of moderate visual loss over 24 months can be achieved in over 90% of cases, and a significant visual improvement of 3 lines (LogMAR) can be expected in about a third of cases. Conclusion: Optimal management using new pharmaco-therapies is unfortunately very costly at this juncture, and beyond the means of many Asian patients. Research into alternative cost-effective treatments is urgently needed.