The macula is the central part of the retina, the light-sensitive layer in the back of the eye. It's responsible for central vision (what we see straight ahead), our colour vision, and allows us to see the fine details needed for looking at objects, reading and driving. The macula, also referred to as the ‘macula lutea’, contains a very high concentration of rods and cones (photoreceptor cells) that detect light and send signals to the brain1 which are then formed into images.
Several eye problems can affect the macula and lead to loss of central vision if they are not treated. These include macular hole, macular pucker (epiretinal membrane), and macular oedema. Each has its own symptoms and causes, but they can all be detected through an examination called an OCT scan.
A macular hole is a small hole that forms in the macula (at the centre of the retina) and can impact your central vision. This means that people with a macular hole usually experience blurry or distorted vision when reading or performing other visually demanding tasks, while their peripheral (side) vision typically remains unaffected. If left untreated, over time a macular hole can grow, producing a blind spot in your central vision.2
The most common cause of a macular hole is age. As we get older, the vitreous humour (a transparent, gelatinous substance that fills the eye) separates from the retina in a process called vitreous detachment. This process is quite normal, and can occur without any serious symptoms. However, sometimes part of the vitreous humour can remain stuck to the retina, while the rest of it detaches. This causes the macula to stretch and develop a hole.2 This hole can be easily detected and measured with an OCT scan. While this process predominantly happens with age, it can also occur as a result of an eye injury or due to swelling of the macula caused by another eye condition.
The treatment for a macular hole is vitrectomy surgery, which involves removing the piece of vitreous humour that is pulling on the macula.2 A small gas bubble is left in place to flatten the macular hole while the eye heals, which eventually disappears on its own.
Epiretinal membrane or macular pucker
A macular pucker (also known as an epiretinal membrane) is a thin sheet of scar tissue that develops on the surface of the macula, and can impact your central vision as a result. It occurs when the vitreous humour shrinks away from the retina as we age, causing it to pucker and wrinkle. The effect is something like the wrinkling of a sheet of cellophane.3 People with a macular pucker may experience blurred and distorted vision (where straight lines appear wavy). These symptoms are very similar to those caused by a macular hole. An optometrist or ophthalmologist can differentiate between the two with an OCT scan.
In general, a macular pucker does not require any treatment as it doesn't typically affect daily activities such as driving or reading and most people can adjust to the mild distortion of vision.3 In particularly severe cases, however, vitrectomy surgery may be recommended.
Macular oedema is a build-up of fluid in the macula which causes it to swell and thicken. This results in blurred or distorted vision, where colours may appear washed out or faded. Only one eye may be affected by macular oedema and there may be no noticeable vision loss until the condition has reached an advanced stage.4
Macular oedema occurs due to leakage of fluid from damaged blood vessels in the retina. This is quite common in people who have a diabetes-related eye disease.4 Macular oedema may also be caused by eye inflammation or following eye surgery. Oedema of the macula is one of the signs of age-related macular degeneration (AMD), a condition where your macula wears down over time.
Treatment for macular oedema depends on the underlying cause. It can include laser therapy, injection of drugs called anti-VEGF agents into the eye (these are painless), steroid medications, or vitrectomy surgery.4
OCT is very useful in measuring retinal thickness, so it can be used to assess the amount of swelling (oedema) in the macula. An optometrist can check for macular oedema with a thorough eye exam, during which they will look for abnormalities in the retina and macula. An OCT imaging test uses light to create detailed views of the layers in the retina. OCT is also used to assess how you are responding to treatment and to see how well the eye is healing.
How do these macular conditions differ from AMD?
Age-related macular degeneration is the degeneration of the macula in older adults typically caused by the ageing process. There are two forms; dry and wet. The wet form is the less common but more serious form of the condition in which new and abnormal blood vessels grow under the retina and leak fluid, leading to macular oedema. Although symptoms of AMD may be similar to other macular conditions, they are completely unrelated and therefore have different treatment options.
How can a macular OCT scan help?
The OCT scanner creates 3D cross-sectional pictures of the eye, which allows the ophthalmologist to see the eye in even more detail, including the different layers of the retina.
Some people may not realise that they have a macular disease until the condition is advanced, and their central vision becomes distorted or blurry. Regular visits to the optician are therefore essential to detect the early signs of macular conditions – and an OCT scan is a quick and painless test that is an efficient way to detect these conditions.
1. Macular Society. (no date). What is the macula? [Online]. Available at: https://www.macularsociety.org/what-macula [Accessed 22 November 2019].
2. National Eye Insitute. (no date). Macular Hole [Online]. Available at: https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/macular-hole [Accessed 2 April 2020].
3. National Eye Institute. (no date). Macular Pucker. [Online]. Available at: https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/macular-pucker [Accessed 22 November 2019].
4. National Eye Institute. (no date). Macular Edema. [Online]. Available at: https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/macular-edema [Accessed 22 November 2019].