Age-related macular degeneration (AMD) is the leading cause of visual acuity loss in Ireland in the over-65s. While only 10 to 15 per cent may comprise the more devastating ‘wet’ or neovascular form, this is the form that causes 90 per cent of blindness.
It is estimated that approximately 7000 people develop this condition every year in Ireland. Wet AMD affects the central point of the retina, the macula, which is responsible for capturing central vision to make our vision sharper. This is the area we use to read and see faces. Progressive damage occurs to the important layer called the retinal pigment epithelium that separates the nourishing blood vessels from the nerve layer.
Early recognition and treatment are critical in reducing the handicap that this loss of central vision may impose on our patients. With the increasingly ageing population, treating this condition places enormous financial and logistical burdens on the healthcare system.
The leaking and bleeding due to blood vessels that have penetrated degenerated parts of the blood retina barrier may be treated with injections given into the eye.
Three different types of injections are currently given by eye specialist to treat this condition to prevent the stimulation of further blood vessel growth and leakage and to limit the scarring that could permanently impair vision. These are called anti-vascular endothelial growth factor therapies (Anti-VEGFs).
Some exciting work is in progress globally in preventing AMD. Unfortunately, most patients with wet AMD still present for the first time with vision loss.
Identifying high-risk patients aged over 60 prior to permanent scarring or even prior to clinical evidence of drusen from the disease is the focus of certain studies and technologies.
Almost all patients initially complain of distorted or fuzzy vision in the centre of their focus. Detail may gradually be lost as the distortion or blurred central spot enlarges and daily tasks become affected. Later, it may become difficult to drive, read and recognise family and friends. In wet AMD, this spot of hazy vision or distortion may appear quite rapidly and should be responded to urgently by seeing an eye-care practitioner.
Most trials support initial monthly injections that are gradually extended up to three-monthly or stopped as required. The vast majority of patients require at least 12 injections in the first two years, improving vision in about 40 per cent of patients and stabilising or decelerating progression in at least 80 per cent. Some patients require switching of their medications if they don’t respond and all require individualisation of their regimens to achieve best results. The results are judged on the basis of their visual acuity and the fluid seen clinically in or under the retina. The injections themselves are done on an outpatient basis and should not be painful if adequate drops are given. Vision after the injections may become blurrier temporarily and floaters may be seen for the first few hours.
These injections must be given to appropriate patients a number of times a year. Do any extended duration treatments exist to reduce the required number of injections? A: There are ongoing early phase trials that use a method of controlled drug delivery aimed at improving outcomes in the future while reducing costs.
Trials are under way that make new vessels more susceptible to anti-VEGFs. Some may be given combined with a less regular but currently used injection.
Some may recruit the immune system to remove the membrane causing the problem. There is also a new anti-VEGF drug on the horizon. Small pumps on or in the eye that deliver sustained medication without the need for injections may also be on the market soon. These would obviously have to be surgically implanted, but then would be refilled periodically.
GPs are the frontline in eye health and vision care. Ill-informed patients are more likely to be registered later with severe visual loss. However, in a recent study in the UK, 40 per cent of GPs admitted that they themselves were ill-informed regarding AMD. This is not surprising given the paucity of exposure our medical students are given to ophthalmology during their training.
Therefore, it is the responsibility and challenge of ophthalmologists to inform and equip their GP colleagues so that they may be more supportive to patients with AMD. Unnecessary loss of visual acuity may be avoided by early referral to their retina specialist or by encouraging regular eye examinations at the local optometrist.
Tests for AMD are part of a standard eye examination and are non-invasive. Those with dry AMD at high risk of wet disease must be encouraged to use their Amsler Grids regularly to identify early distortion in their vision. Those receiving injections are at increased risk of endophthalmitis and retinal detachments and these should be treated as diagnoses of exclusion by GPs and referred promptly.
There are a number of critical things our family practices are already doing to improve eye health, such as smoking cessation, BP control, diabetes detection/control and cholesterol control. They also encourage loss of weight with regular exercise and balanced diets.
Furthermore, UV blocking spectacles — especially those which have brown or yellow lenses — should be encouraged. Poor quality lenses may be worse than none at all so patients should chat with their optometrists in this regard.
GPs also support low vision services in the community so that patients can use affordable technologies to improve their quality of life. They should also be prepared to recognise, support and treat patients who get depressed as a consequence of their diminished sight. Some patients may even hallucinate after severe damage has occurred, requiring reassurance that this a normal reaction and not a sign of dementia.
Should patients with AMD take tablets? The tablets available over the counter for AMD are very important for our patients. These contain the essential carotenoids, zinc, copper, vitamin C and vitamin E. The AREDS 1 and 2 studies — from 2001 to 2006 and 2008 to 2013, respectively — showed that certain formulas proved effective in preventing progression of dry to wet AMD. These may even improve some visual tasks such as those involving dark adaptation. However, a balanced diet remains more essential. There is also no conclusive evidence that the low-dose aspirin used to reduce cardiovascular risk should be stopped in patients with AMD.