Dr. Rahul A Shroff
Age-related macular degeneration is one of the leading causes of visual impairment in developed nations and may merge as a public health problem in India as life expectancies increase. In this edition, epidemiological data from two centres, Aravind Eye Hospital, Madurai and PGIMER, Chandigarh have been presented. However, no large multicentre population based study has been undertaken in India to estimate the prevalence of this disease.
While fluorescein angiography is still the standard procedure to classify and treat macular degeneration, ICG (Indocyanine green) angiography is considered a good adjunctive procedure in patients with poorly defined membranes. New investigative modalities like scanning laser ophthalmoscopy, where images can be viewed real time, and optical coherence tomography, which gives a cross-sectional image of the macula, give researchers and clinicians a better understanding of the disease process.
Earlier, laser photocoagulation was the only proven treatment available. However, only patients with extrafoveal, juxtafoveal or small subfoveal lesions were eligible for treatment. Moreover, laser photocoagulation of subfoveal choroidal neovascular membranes resulted in an immediate decrease of vision as a result of damage to the overlying retina.
Photodynamic therapy, which relies on photochemical injury to the vessel wall and selective damage to the choroidal neovascular membrane and avoids thermal damage to the retina, was developed as a less damaging treatment for subfoveal choroidal neovascular membranes. The results of the Treatment of Age-related Macular Degeneration (TAP) study and the Verteporfin in Photodynamic Therapy (VIP) study show that patients treated with photodynamic therapy are less likely to have severe vision loss. Both these studies have been discussed.
The limited availability of facilities and the prohibitively high cost of the treatment has put photodynamic therapy out of reach of most of the population. Transpupillary Thermo Therapy is emerging as a cost effective modality especially in the treatment of occult choroidal neovascular membranes. Multicentric, randomised, controlled trials are still required to clarify its role in the management of choroidal neovascular membranes.
The sequence of events leading to disciform scarring and permanent loss of central vision is well recognised. Advances in vitreo-retinal microsurgical methods have made possible surgical procedures to attempt to disrupt this sequence. The Submacular Surgery Trial (SST) has been initiated to define indications and evaluate the visual outcome of subretinal surgery.
Unfortunately, frustration still exists regarding the limited treatment options of proven benefit. Many patients already have significant and permanent loss of central vision. Visual rehabilitation using low vision aids is an important part of their management. The aim of low vision rehabilitation is to enable the patient to perform tasks necessary for survival and for enjoying life. The article on low vision aids outlines the steps of assessment and the devices currently available for visual rehabilitation.
I am grateful to contributing authors for the excellent articles. I specially thank Dr. OP Kapoor, editor, Dr. RJ Mehta and the staff of the Bombay Hospital Journal office for their guidance and support in completing this issue.
DR. RAHUL A SHROFF