If you have any concerns about your eye health, call us or drop in at the practice. An early professional examination offers you peace-of-mind and can ensure the most effective treatment if needed.
This is a scan of an eye with a healthy macula
The retina is the photo sensitive layer at the back of the eye, similar to the photographic film in an older fashioned camera. Light lands on it on a photoreceptor layer where it triggers a nervous impulse that is transferred to the brain where we recognise the image seen. These photoreceptors are not spread evenly across the retina but have a greater density in the central area, the macula, and this is the area of the eye where we have high discrimination vision due to having more receptors triggered. This macula area, due to its high density of receptors, therefore has considerably more traffic passing through than the rest of the retina and is the reason that it tends to ‘wear’ more than the rest of the retina, and explains why AMD only affects the central part of the retina, never causing loss of peripheral vision.
Why does AMD happen?
Thinking back to the analogy of the film in a camera. Light would land on the film, made with a coating of photo-chemicals, and alter the chemicals. We would then have used that chemical and need to roll in another piece of film with another fresh set of chemicals on before we could take another picture. The retina is different in that it regenerates the pigment so that the same area can keep responding time and time again. Think of it as a battery that keeps discharging and then recharging itself.
Whenever the body does any work it creates waste material that needs taking away, creating free radicals (damaging elements that cause changes as we age). The body combats this by using anti-oxidants which act like blotting paper mopping up these free radicals. If the balance between the two is lost there is a build up of the damaging changes, making the recharging of the battery less efficient and preventing the photo-receptors refreshing themselves as quickly. Everybody notices that as the eye gets older that it takes longer to recover from a bright light (coming inside from a sunny day to a dark room) compared to when we were young. This is because our ‘battery’ is naturally becoming less efficient at recharging and this is very normal.
Our natural source of anti-oxidants is from vitamins, found in fruit and vegetables and is the reason that we are told to eat our ‘five a day’. However healthy our diet, we will probably eat less as we get older, and so this provision can drop at exactly the time when we seem to require ‘support’ more. For this reason some people will take vitamin supplements to enhance supply of anti-oxidants. What has been shown very clearly is that smoking has a marked effect on this balance and is the greatest single risk factor for making things worse. Stopping smoking is the biggest favour you can do for your eyes and the rest of your body too.
How does AMD show itself?
To the patient it will normally just seem as if there is a gradual diminishing of their vision and a greater reliance on optimised lighting, trying to increase contrast on what we are looking at. We notice glare more when viewing an object that has bright light behind it.
These sorts of changes are typical of dry AMD.
Wet AMD will normally exhibit a distortion to the central vision with sufferers often describing the appearance of a kink, or bulge, forming in the vision of one eye.
Whilst dry changes tend to happen gradually, wet changes happen suddenly and it is always best to have an urgent review, within a couple of days, if any distortion is noted. It is possible to have distortion to the vision with dry AMD but this is generally more subtle and slow in formation.
Wet and Dry AMD – what is the difference?
The layer just below the receptors on the retina is called the Retinal Pigment Epithelium (RPE) and is responsible for supplying the nutrition and oxygen to keep the receptors functioning well. Between the RPE and the receptors is a limiting layer called Bowman’s membrane.
With dry AMD there are two main types. There can be a collection of waste material that can’t be transported away and limits the efficiency of the system as it acts as a partial barrier. These are called colloid deposits or drusen. (see scan 1) The other form is where the RPE starts to break down, or atrophy, and so cannot support the receptors as well as before (see scan 2). The effect of both of these is that the efficiency of the receptors drops and the vision is limited,. Normally this would progress slowly or very slowly. If the drusen become larger they can cause a slight distortion to the vision but this change would be very gradual.
Wet AMD occurs when there has been leakage of fluid into the retinal layers. This has a much more damaging effect to the vision and needs reviewing urgently to optimise any help that is possible. The fluid come from vessels that have breached the limiting layer of Bowman’s membrane. The fluid tends to spread, splitting the retinal layers and acting as a barrier stopping supply of nutrition to the retina. The distortion of the vision is seen because the retina has been lifted out of place and happens quickly as it is due to a new layer being caused by the seepage of fluid.
What help is available?
Wet AMD needs urgent treatment from a hospital department. For certain cases, treatment by injection into the eye of a drug called anti-VegF can help. The aim is to shut down the leaking vessels, stopping new ones forming and trying to optimise the re-absorption of the leaked fluid. This is generally an ongoing process for a minimum of 6 months but can be long term in some cases. Treatment generally seems more efficient the earlier it is started and is normally thought to be needed to start within two weeks of initial symptoms. Laser treatment to the back of the eye (not at all like the laser advertised to change the power of the eye) is sometimes used instead, or as well as the injections. The set of scans below show images of the same eye before and during management for Wet AMD.
Dry AMD is best thought of as a general ageing change and as such there is little proven help available. Lifestyle changes are important. Stopping smoking is absolutely critical and a healthy diet is thought to be helpful. The question of vitamin supplements is a more difficult area.
There was a medical study conducted in the USA that suggested that at times supplements with the inclusion of a mineral ‘lutien’ may prove beneficial to some AMD cases where there are appreciable drusen present. There did not seem to be a specific sub group that benefitted but they quote figures of approximately 20% benefitting. We stock various brands of supplements but do not feel they are necessarily better than other suppliers. We are aware that some people already use other suppliers for multi-vitamins and most of these will have their own brand of multivitamin with lutein. As long as they are a reputable supplier with appropriate controls, we do not suggest that ‘ours’ are better. If you feel that you want to take a multivitamin, and you have AMD, then we suggest using one with lutein.
How can I monitor my macula health?
You check yourself by looking with each eye separately. Cover one eye at a time to see if you notice any distortion or change in the vision. It is common for perfectly healthy eyes to have one that performs better than the other. And remember that a poorer vision may be caused by nothing more serious than an out of date spectacle prescription.
There is a specific test used to monitor central distortion, called an Amsler chart. These can be provided at no charge if you wish. But a very simple method is always available to you. Using one eye at a time, look at a straight line (door frame, window sill, mantelpiece etc) and see if there seems to be any ‘kinking’ or deviation of the line. If there is and you move your eye along the line, does the distortion move as well? If so, seek an urgent review. If not, repeat in a week’s time or thereabouts.
An optometrist will view the macula area as part of a routine eye examination and will flag up any concerns they may have. In our practice we have been taking images of the retina for over 14 years to enable us to monitor more accurately any changes. We now have taken that a leap forward. We have a new 3D imaging system (Ocular Coherence Tomography- OCT). This equipment is very rarely found in opticians. Instead of just looking at the surface of the eye, we can now see the different layers of the retina; nerves, receptors, and RPE. This shows if there is a build up of drusen, or if the RPE is looking thin, and if it changes over time. If there are any areas of oedema or fluid these are shown much more obviously than can be seen using traditional techniques and particularly when otherwise using a 2D image rather than the depth of a 3D image.
Imaging with the OCT takes just a few seconds and involves looking at the reflection of infra-red light from the posterior areas of the eye. As the patient we ask you to keep a steady fixation, without blinking, on a green target and a dim red line appears to drift across your vision for about 3 seconds, taking 128 scans in the 3 seconds. This is the scanning infra-red light. Using a technique similar to ultrasound we can build up a series of images that the computer then processes to give a 3D representation of the retinal area. After that there is a small flash of light, like with normal retinal cameras, and an image of the eye is taken which can be used to reference areas of interest in the scan. The image taken there is the same as the image taken with a standard retinal camera, so the OCT scans and photographs. The resulting scans can seem similar in presentation to the sections people may have seen of the rest of the body after an MRI scan, but this is achieved using just a dim, completely safe, low brightness light.
Please view our video showing more details about the OCT
We charge an extra £40.00 for this scanning procedure when it is incorporated into our OCT enhanced examination. If you are eligible for an NHS examination the cost to you is £40 and if you are paying privately for your examination the total cost of the appointment including OCT is £60.