What is the macula?
The retina is the seeing layer of the eye which converts light into electric impulses that can be trasmitted to the brain. It is plastered like wallpaper against the inside wall of the eyeball. The macula is the most important part of your retina – the part responsible for your main central vision.
What is age-related macular degeneration (AMD)?
The macula is susceptible to the wear-and-tear effects of age, like many bodily tissues. AMD describes an age-related decline in the anatomic integrity, and therefore function, of the macula. It is never diagnosed in individuals below the age of 50 years, and it becomes more prevalent with increasing age.
How is AMD diagnosed and investigated?
AMD is usually picked up on clinical examination by an optometrist or ophthalmologist. Investigations to monitor and classify AMD include fundus photography, OCT scanning, and fluorescein angiography. Fluorescein angiography is considered the gold standard for confirming the diagnosis of wet AMD, and the test is generally reported by an ophthalmologist with sub-specialist training in the management of retinal disease.
What are the types of AMD, and what are their symptoms?
There are 2 main types of AMD recognised: dry and wet.
In dry AMD, the changes usually start off with accumulations of debris beneath the retina, called drusen. There may also be areas of loss of the retinal pigment epithelium (RPE) – the layer beneath the retina – this is called geographic atrophy. Drusen and atrophy together can cause slowly progressive distortion, blurring, and/or missing areas in the central vision.
In wet AMD, which usually develops in patients who already have some degree of dry AMD, new and abnormal blood vessels grow in the macula which can either bleed or leak – either way, this usually causes more sudden or marked blurring or distortion of central vision. Unfortunately, some patients don’t notice this happening straight away, especially if the vision in their other eye is very good.
Can AMD affect peripheral vision?
AMD generally only affects the central vision. However if the AMD is severe and affects both eyes, it can lead to complete loss of the central area of vision, meaning that even the largest letters on a test chart cannot be read, and rendering all reading activities virtually impossible. The only way in which AMD can threaten the remaining (peripheral) vision in an eye as well as the central vision, is in the rare scenario where a massive macular haemorrhage is complicated by breakthrough haemorrhage into the vitreous gel of the eye (vitreous haemorrhage). This is quite rare, and if it doesn’t resolve on its own, it can be cleared up with vitrectomy surgery.
How can I monitor my AMD?
I tend to recommend looking at a window frame at home once a week, with either eye occluded in turn. An alternative is to use a formal Amsler chart for this purpose, a copy of which you can obtain from your optometrist or ophthalmologist. When doing this, you should be looking for areas in your vision that are missing (scotoma), distorted (metamorphopsia), or simply blurred. Much of this can be due to dry AMD, and it may very gradually progress. However if you notice a sudden or marked alteration in your central vision, that is markedly different one week from the previous week, you ought to seek prompt attention as this may mean you have developed wet AMD, which needs to be investigated and treated quickly.
How is AMD prevented, delayed or treated?
I tend to advise UV protection (sunglasses), a healthy diet with plenty of spinach and kale in particular, and avoidance of all tobacco smoke (even passive smoke). Many companies sell vitamin supplements for AMD, usually containing the macular pigment lutein. These supplements can help to reduce the rate of progression of dry AMD, although evidence from the AREDS studies only supports their use in certain stages of dry AMD. Interestingly, the beneficial effect of these supplements was found to be lower in patients who already had a diet high in green, leafy vegetables.
There is currently no treatment that reverses the changes of dry AMD, although many drugs are currently being researched. The most promising drug is probably one called lampalizumab, but this is not yet commercially available.
Wet AMD can be effectively treated with intravitreal injections if it is caught early enough. The injections can stabilise or sometimes improve vision, and have revolutionised the treatment of this condition since their widespead adoption in the last decade.
I have been told I have advanced AMD and no further treatment is possible for the AMD. Is there any other treatment that would help me?
Recent attention has been focussed on stem cell treatments to see if retinal pigment epithelium cells can be transplanted beneath the macula in patients with advanced or end-stage AMD. This is still an experimental treatment and the long-term effects remain unknown. Another treatment which has garnered media attention is the artificial retinal prosthesis. This aims to provide some basic vision to patients who have lost all vision, usually due to inherited retinal dystrophies such as retinitis pigmentosa. At present, they provide (at best) fairly crude vision to individuals who previously had no vision whatsoever. However the concepts being explored here are undoubtedly promising and in years to come they may have more of a role in treating patients with end-stage AMD.
Some surgeons have tried implanting miniature telescopes into the eye in an attempt to improve vision (although this approach does not treat the AMD itself). This has the same effect as putting a telescope (or binoculars) in front of your eye. While this can certainly improve central vision and performance on vision test charts, because the implant is permanently fixed inside the eye, it is akin to permanently having a telescope in front of your eyes. Unfortunately this normally entails – by the simple laws of optics – a marked reduction in the peripheral or navigational vision that so many AMD patients find useful for getting around safely. For this reason, the vast majority of surgeons in the UK are not implanting macular telescopes, despite the fact that this technology has been around for almost 20 years. More recently, a magnifying telescope implant was developed which does not reduce peripheral vision too much – but it also doesn’t magnify very much, thereby limiting its utility over and above standard lens implants as used in cataract surgery. A more promising concept, albeit with more modest aims, is the magnifying reading lens implant known as the Scharioth Macula Lens. This is a constantly evolving area however and in the near future there may be better types of lens implant for AMD.
I advise patients with untreatable advanced AMD to contact the Macular Society for support, to try more advanced low vision aids such as CCTV devices, and to start building up their support network, as AMD tends to be a progressive condition. In Jersey, the sight impairment charity EYECAN provide invaluable advice and support to individuals living with sight impairment.
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