AMD - Age Related Macular Degeneration
Dry macular degeneration is common in people over 50 though for many people the changes may be subtle and not noticed in everyday life, whilst for others the effect on vision can be much more severe. Dry macular degeneration typically starts with the accumulation of metabolic waste products under the retina (the light-sensitive layer at the back of the eye akin to a film in a camera); collections of such waste products are known as drusen. In time some of the normal structures at the back of the eye can be lost or become thinner (known as atrophy). The changes that develop are irreversible and so accumulate in time, typically having a greater effect on vision. However the extent and rate of progression is very variable. In most people there is some progression over years but many people will never be functionally limited by this. However in others in time there is a more severe loss of central vision, causing inability to read, see faces or drive. With dry macular degeneration progression is slow over many years. If there is a more rapid change in vision, or symptoms of distortion, one should be suspicious of conversion to a different form of macular degeneration known as wet macular degeneration; this is less common but can cause loss of central vision within weeks. Wet macular degeneration is commonly amenable to treatment if applied early and so early diagnosis is required. It is therefore important to know that if ever someone with dry macular degeneration has a sudden deterioration in vision, or new areas of distortion, they should be promptly checked for wet macular degeneration. Amsler charts can be helpful for picking up early changes in vision; of note they must be used one eye at a time (ie with other eye closed) so that subtle changes are noted.
Risk Factors for Progression
Some risk factors for macula degeneration are not modifiable (eg age, caucasian race, family history). However for some people other risk factors are modifiable:
Smoking, or being regularly exposed to smoke
Obesity, high blood pressure and cardiovascular disease
Dietary factors are also potentially relevant, a diet high in saturated fats can increase your risk. In contrast diets rich in fruits and vegetables (and hence antioxidants) and oily fish which contain omega-3 fatty acids may reduce your risk.
Vitamin supplements can have a limited role, 2 large studies (AREDS and AREDS 2), showed a role for vitamin supplements with specific stages of dry macular degeneration. Vitamin supplements matching the preparations used in the AREDS studies are available over the counter.
The medications given by intravitreal injections have been a major advancement in preserving vision. In wet macular degeneration they preserve central vision in over 90% of people, where as without treatment it would be lost; furthermore in 1/3rd of people with wet macular degeneration the vision improves with the treatment. The drugs have similar effects on vision when there is swelling of the retina from diabetes or following retinal vein occlusions. These drugs act on the retina which is at the back of the eye. The drugs can only be given as an injection, using a very fine needle, through the wall of the eye.
You are asked to lie down and local anaesthetic is given. The area around the eye is thoroughly cleaned and a clip is used to help keep your eyelid open. The injection is usually felt as pressure on the eye and a brief sharp sensation, but is not usually nearly as bad as people fear. Following the procedure the eye will be a little red and can feel gritty. This should clear within days.
What are the risks of this procedure?
Unfortunately all procedures have risks. The benefit versus risk ratio is extremely favourable for these injections, and almost all procedures pass without any complication. Nonetheless, although the problems that can occur are uncommon they can have lasting effects as discussed below.
Infection - This occurs after approximately 1 in 2000 procedures but is a sight threatening complication. Urgent attention should be sought after the procedure if the eye became painful, if the vision started to deteriorate or if there was increased swelling around the eye; early treatment of an infection improves the outcomes.
Medication risks - The medications given have been linked with heart attacks and strokes. The amount of the drug used for an injection within the eye is extremely small and there is conflicting evidence as to whether an injection within the eye does or does not have a significant effect on the risk of these events. The drug manufacturers recommend caution when treating people who have had a stroke, mini-stroke or heart attack within the previous 6 months.
Increase in eye pressure - Injections can increase the pressure within the eye and so sometimes it is appropriate to apply an extra eye drop to control the eye pressure.
Bleeding within the eye, cataract, retinal tear or retinal detachment following the injection are possible but very rare. These are estimated to occur after less than 1 in 1000 procedures.
Drying of the front of the eye during the procedure can lead to a corneal abrasion. These are sore but heal rapidly.