OCT and Macular Degeneration

What is Macular Degeneration?

Macular degeneration is a condition in which the centre of the retina (known as the macula) becomes damaged. You may have seen the term "AMD", which stands for age-related macular degeneration. Macular degeneration is rare in younger people, but around 30% of people over 75 have early signs of AMD, and about 7% of those over 75 have more advanced AMD. This is why it's the most common cause of visual impairment in the UK.

Two types

There are two types of AMD; wet and dry. The dry type is more common and develops slowly. In the wet type, blood vessels beneath the macula leak fluid, which can damage the macula relatively quickly. Both types only affect central vision, which means that they don't cause complete blindness. Tasks like reading, however, can be very difficult when there's a blurred patch in the centre. An early symptom of wet AMD is when straight lines suddenly develop a kink in them.

Treatment

Wet AMD can now be treated with injections of new (anti-VEGF) drugs. The key to their success is early detection and treatment.

There's no real treatment for dry AMD at the moment. There's evidence, however, that progression from an intermediate to an advanced stage can be inhibited by taking a supplement of antioxidants and zinc.

OCT

Most of what happens in AMD, at least in the early stages, happens beneath the surface. Often, therefore, the standard eye examination with an ophthalmoscope yields only limited information.

But because the OCT shows a cross-section of the retina, we can see what's going on beneath the surface. This makes it possible to distinguish between wet and dry AMD. When wet AMD is detected, there's a fast track referral system in Surrey to ensure treatment starts quickly.

The OCT can also show other macular problems, such as an epimacular membrane. This is a collagen membrane that damages the surface of the macula and that sometimes requires surgery. Macular oedema is also clearly shown up in an OCT scan, and this is particularly useful when examining diabetics, in whom it's a major cause of loss of vision.

Quite often, people with AMD have cataracts as well. The OCT can give really useful information about whether the vision will be clear or still blurred after cataract surgery.

David Donner