Epiretinal membrane and vitreomacular traction

The macula is the centre of the retina, the part you use to read and recognise faces. Here we are talking about two different problems that cause very similar symptoms, and that often go together.

When the vitreous is still attached to the macula but does not distort it, it is called vitreomacular adhesion. This is a normal stage in the ageing of the vitreous, it causes no symptoms and is not treated.

The word "idiopathic" that you will see in some reports just means there is no specific cause. That is the most common situation.

Many people have a membrane and don't know it: it is found at a check-up. When it does cause symptoms, the typical ones are:

• Straight lines looking bent: a door frame, floor tiles, lines of text.
• Blurred or less sharp vision in that eye.
• One eye seeing things at a different size from the other, making it hard for both eyes to work together.
• Double vision in some cases.
• Difficulty reading or driving. Some people end up closing the affected eye to read better.

It usually progresses slowly, over months or years. With vitreomacular traction the symptoms can come on more suddenly.

It is a common problem, and more so the older you are. An OCT scan finds it in a significant proportion of older people, although most have very mild forms. In some people it appears in both eyes.

As well as age, it is more common in people who have had:

• A vitreous detachment, which is when the gel comes away from the retina.
• Retinal tears or a retinal detachment.
• Inflammation inside the eye (uveitis).
• A retinal vein occlusion or diabetic retinopathy.
• Cataract surgery or other eye operations.

Other factors, such as short-sightedness or smoking, have been studied, but it is not clear that they play a part. There is nothing specific you can do to prevent it.

I examine the back of the eye with the pupil dilated, including the outer edge of the retina to rule out tears. And I do an OCT scan, which is the key test: in a few seconds, without touching the eye, it shows me a cross-section of the retina. It shows the membrane, whether the vitreous is pulling, how much the macula has thickened and whether there is fluid or a hole.

The OCT also lets you see it for yourself. Putting your scan next to a normal retina helps a lot in understanding what is happening and why I suggest one option or another.

If I suspect the membrane is caused by another retinal condition, I may add other imaging tests.

Here is the reassuring news: most membranes do not change much over the years. In population studies, only a little under a third got worse in five years, and some even improved. Waiting until there are symptoms does not worsen the result of an operation later on.

With vitreomacular traction, especially when the attached area is small, the vitreous lets go by itself in quite a few cases, roughly a third within one or two years. When that happens, vision usually improves.

In the meantime:

• Check-ups with OCT to compare with the previous one.
• Check each eye separately from time to time, covering the other one. The Amsler grid or the lines of a door frame will do.
• There are no drops or tablets that get rid of a membrane.

Overall, about 8 in 10 people who have the operation clearly gain vision. The distortion usually improves a lot, and sometimes disappears. Some people don't gain many letters on the eye chart and are still happy, because lines have stopped looking bent.

It is worth having realistic expectations: improvement is slow, takes months, and is not always complete. Between 1 and 2 in 10 patients stay the same or are slightly worse. If the deeper layers of the retina look well preserved on OCT, the outlook is better.

The risks I explain to you before surgery:

• Cataract: the most common consequence, almost certain over time if you haven't already had cataract surgery.
• Retinal tear or detachment: uncommon with modern surgery, around 1 in 100.
• The membrane coming back, less likely if the internal limiting membrane is removed.
• Changes in eye pressure in the first few days, especially if you have glaucoma.
• Serious infection inside the eye (endophthalmitis): very rare, fewer than 1 in 2000 operations.

I'll see you the next day and again after one or two weeks, sooner if needed. I'll give you some drops and explain how to put them in.

If I leave a gas bubble in the eye at the end, your vision will be blurred until it is absorbed and you will need to take precautions while it lasts: no flying, no going up into the mountains, and telling the team you have it if you need a general anaesthetic. I'll give you the specific instructions for your case.

If after the operation you still see double or find it hard to use both eyes together, there is specific help available from binocular vision specialists.