Age-related Macular Degeneration (AMD)

Background

The inner membrane in the eyeball is called the retina. The retina is the factory that transforms the light rays reaching it to electric signal and send it to the brain for interpretation.

The central part of the retina is called the macula. The macula is responsible for the sharpness and colour vision – central vision. It helps us seeing the details of the targets we look at.

Ag-related macular degeneration is a disease that causes damage to the macula. This might cause mild effect on the quality of vision in the early stages but the more the disease is advanced, the more effect it has on central vision.

The exact cause/causes of AMD are not known. There are risk factors like age above 65 (By definition, people above age of 50 might develop AMD), smoking, diet, sunlight and genetic factors but unfortunately it is not clear their role in the development of AMD.

Symptoms

• Blurred vision: this could be struggling seeing small print that you could read before. Later you might notice deterioration of vision in general, for distance or reading. Some patients notice missing some details of the target they are looking at
• Distortion of vision: Straight lines The edge of the door, neighbours’ windows may look wavy.
• Increased sensitivity to bright light.

Type of Age-related macular degenerations (AMD)

• • Dry AMD: That is when the macula becomes weak due to the damage of the disease. As all forms of AMD, dry AMD is a progressive disease however, this type of AMD progresses slowly usually over years. The worst case scenario in advanced dry AMD is called geographic atrophy where you lose significant proportion of your central vision but the peripheral vision remained fine

• • Wet AMD: There are different forms of wet AMD – that is when some abnormal blood vessels start growing under the retina or less commonly within it, leaking, bleeding and causing quick damage to the structures of the macula and hence much faster deterioration of vision compared to dry AMD. In general, wet AMD is the same as dry AMD in terms of damaging the macula which is the central part of the retina but the peripheral vision remains unaffected. That means you will not become completely blind from this disease.

• • The end stage of wet AMD is either large scar in the macula or significant atrophy in it or both

Treatment

• Dry AMD: There no treatment for dry AMD. The Age-Related Eye Disease Study 2 (AREDS2) found that oral supplementation of macular pigment – Lutein and Zeaxanthin in addition to Zinc, Cupper vitamin C and E help slowing down the disease and reduction in the rate of development of advanced AMD in minority of patients. This was helping up to 25% of patients from progressing to an advanced stage. However, that was in people who already have advance disease in one eye and the AREDS2 supplementation helped slowing down the development of advanced stage of AMD in only 25% of cases. That means 75% of patients did not benefit from the formula. If you have mild to moderate dry AMD then the benefit was even much less.
• Wet AMD: There is no cure for wet AMD however there is a group of medication called Anti-vascular endothelial growth factor (anti-VEGF) that helps stabilising the disease and limiting the damage from the growing vessels.Anti-VEGF are antibodies (particles produced by the blood’s white cells) that neutralises the substances that stimulate blood vessels growth. By shrinking theses growing vessels, they limit the damage of the disease. Unfortunately, they act for a short period of time and hence many patients need many injections into the eye (intra-vitreal injections). At the present time, there are 3 drugs used widely for wet AMD: Lucentis and Eylea, both are licensed by the producing company for intra-vitreal injection (i.e. to be injected inside the eye) and Avastin which is a bowl cancer drug that was found to help in wet AMD and that what triggered the same company to develop Lucentis for intra-vitreal injections. Avastin is not licenced to be injected into the eye, but it is widely used around the word for the treatment of wet AMD as it is far cheaper than the first two drugs. AREDS2 tablets formula has no effect on wet AMD.

Intravitreal injections

The risks specific to anti-VEGF drugs include, a very small increase in risk of strokes and heart attacks due to thrombosis (about 0.4%). It is important to remember that the mean age group that gets AMD is the same group that is more prone to developing strokes and heart attacks and therefore if this unfortunate event occurs after an injection, it is very difficult to say that it wouldn’t have occurred without the injections.

In the UK, 1 in 4000 patients develops sight- threatening infection in the eye due to intra-vitreal injections of anti-VEGF.

The injection

Before the injection, both you and your eye doctor will need to sign a consent form. The procedure takes a few minutes but the injection itself is done in a few seconds. It is given in a clean room while lying on a couch. The eyelids and surface of the eye are cleaned first to reduce the risk of infection.

The eye is first made numb with eye drops. During the injection, you will feel a prickle or a pressure type sensation similar to taking blood from your arm.

 

Risks that are common to all injections treatment options

1. Conjunctival bleeding on the surface of the eye – often painless, and resolves with no treatment within 1-2 weeks.
2. Corneal abrasion that gives you pain shortly after the injection for about 24-48 hours until it heals completely.
3. Infection inside the eye that might cause loss of vision (endophthalmitis) – very rare.
4. Bleeding into the gel of the eye.
5. Lens touch causing cataract (clouding of the lens within the eye).
6. Raised intraocular pressure leading to glaucoma.
7. Retinal detachment.
8. Hypotony (reduced pressure in the eye).

  

How often will you require treatment with anti-VEGF?

Initially, you should prepare yourself to see your eye doctor every 4 weeks. Later, the management and the intervals between visits will be tailored individually to yourself for as long as the wet AMD shows signs of active disease. The first three visits will require you to have an injection on a monthly basis, then you will be offered an injection if there is evidence that the leakage is still active.

Recently, a protocol called “Treat and Extend” became popular in treating some forms of wet AMD. The idea is that every time you get a bleed or swelling in the macula due to AMD, damage to the cells of the macula is inevitable. Hence, rather than waiting for the leakage/bleed to happen and then treat it, the injections are given on a two-weekly extended intervals despite not having leakage/bleed on that visits. The idea is to try and prevent the leakage and bleeding from happening and causing damage to the macula. Should leakage or bleeding happen after a particular interval, then you go back two weeks in terms of the next appointment for an injection.

For example, if you come 4 weeks after an injection and your retina is dry, you get an injection and you will be given an appointment in 6 weeks. When you come in 6 weeks, if the macula scan is dry, then despite that good scan, you get an injection and you get an appointment in 8 weeks and so on. Now, if you come in 10 weeks with leakage on the macula, then you will get an injection but an appointment for another injection will be given in 8 weeks and so on.