Macular hole

A macular hole is a full-thickness defect right at the centre of the retina, in the very spot we use to read, recognise faces and pick out fine detail. That spot is the macula, and its centre is the fovea; more of the cells responsible for sharpness are packed in there than in the whole of the rest of the retina. When a hole opens in the fovea, the image at the centre of the visual field first distorts and then drops out altogether. It is painless, the eye looks entirely normal from outside, and many people discover the problem by chance when they happen to cover the good eye. A macular hole does not cause total blindness: side vision is preserved and you continue to find your way about without difficulty. But reading, driving and any close work suffer badly. The hole is closed surgically, and the less time that has passed since the symptoms began, the better the result.

How vision changes

The first thing almost everyone notices is that straight lines stop being straight. A door frame, the join between two tiles, a line of text, the edge of a table all look bent or wavy. Letters in the middle of a line run together, part of a word is missing, and you have to shift your gaze to read it out of the corner of your eye. Objects can look smaller than they are, and the same object may seem a different size to each eye.

Later a grey or black patch appears in the centre. It does not stop you seeing what is around you, but it covers exactly what you are looking at: the face of the person opposite is hard to make out while their outline and the whole room remain perfectly visible.

The other eye covers up the loss for a long while, so symptoms are usually noticed late. Checking is simple: cover one eye with your hand and look at a window frame or a sheet of squared paper. Bent lines or a missing patch in the middle mean a visit to an ophthalmologist, not a change of spectacles.

Why a hole opens at the centre of the retina

The inside of the eye is filled with the vitreous, a clear gel that liquefies with age, shrinks and pulls away from the retina. Usually it separates without leaving a trace. But if it stays stuck at the centre, then as it contracts it drags the retina inwards. The tissue of the fovea is the thinnest in the whole eye, and it gives way. This is vitreomacular traction, the mechanism behind the great majority of macular holes, and there is no external cause behind it.

The main risk factor therefore is age: most holes appear after sixty, and two to three times more often in women than in men. Nothing prevents them in advance, and nobody brings one on themselves.

Less often the hole is secondary. It can follow a blunt injury to the eye, severe short sight with stretched ocular coats, a previous retinal detachment, or persistent swelling of the central retina after cataract surgery, in diabetes or with inflammation inside the eye. A macular hole in a young person with no injury is unusual, and that case is looked into separately: another disease may lie behind it.

What it gets confused with

Complaining that straight lines look bent is not specific to a macular hole, and treatment depends entirely on what is actually found at the macula.

Age-related macular degeneration (AMD) affects the same area but differently: what fails is not the mechanics but the nourishment and metabolism of the tissue. In the wet form, faulty vessels grow under the retina, sight drops over days to weeks, and it is treated with injections into the eye rather than surgery. A hole and AMD can share the same eye, so one does not rule out the other.

An epiretinal membrane is a fine sheet that grows over the surface of the macula and puckers it. The distortion is similar, but there is no full-thickness hole and there is usually no hurry to operate.

There are also partial defects, the lamellar hole and the pseudohole, where an opening is visible on examination but the retina beneath it is intact. These are watched more often than operated on. None of this can be told apart from the symptoms alone: a scan is needed.

How the diagnosis is made

The decisive test is optical coherence tomography (OCT). It is a contact-free cross-sectional scan of the retina, takes a couple of minutes, and shows not only the hole but its width, the state of its edges and whether the vitreous has already separated. Size bears directly on the outlook: small holes close with surgery almost every time, large ones less reliably. Nobody decides to operate today without an OCT.

The doctor also measures visual acuity, puts in drops to widen the pupil and examines the back of the eye, always checking the other eye too. For several hours after dilation everything will look blurred and too bright: it is best not to drive that day, and worth taking sunglasses and, if possible, someone with you.

At home the Amsler grid is useful, a squared sheet with a dot in the middle. Look at it with each eye separately and wearing your reading glasses: distorted squares or a missing patch mean it is time to be seen.

How the hole is closed

A very small, recent defect sometimes closes on its own once the vitreous finishes separating from the retina, so in the first weeks the doctor may suggest watching it and repeating the OCT. Otherwise an operation is needed, and it is called a vitrectomy.

It is done through three tiny incisions in the white of the eye with instruments the thickness of a needle, under a microscope and usually under local anaesthetic: an injection beside the eye takes away both pain and eye movement. The vitreous is removed first, which releases the traction. Then the internal limiting membrane, the very thinnest layer of the retina, is peeled off the surface of the macula with forceps so that the edges of the hole can come together. Finally the eye is filled with gas: the bubble presses the edges from within and is absorbed on its own over two to eight weeks, depending on which gas is used.

The operation takes about an hour and most people go home the same day. Small and medium holes close in roughly nine cases out of ten. With large or long-standing holes the success rate is lower, but even then vision usually stabilises and a second operation often works.

The first weeks after surgery

While the gas is in place the operated eye sees very little: a cloudy, shifting veil sits in front of it, as though you were looking underwater. As the bubble is absorbed it sinks, and a band of normal vision appears above it. Judging distance with one eye is hard, so take extra care on steps and kerbs and with hot pans.

You may be asked to keep your head face down, so that the bubble floats squarely against the macula. For large holes this posture is proven to improve the chance of closure; for small ones it is often unnecessary. How many hours a day and for how many days is for the surgeon to say. If face-down posturing is not prescribed, you will usually still be asked not to sleep on your back.

Until the gas has gone you must not fly or go up into the mountains: at altitude the bubble expands, pressure inside the eye rises steeply and sight can be lost. For the same reason tell any doctor about the gas before an anaesthetic and refuse pain relief with nitrous oxide. Do not drive until the bubble has disappeared. Drops are prescribed for several weeks; at first avoid rubbing the eye, swimming and eye make-up.

What can go wrong with the operation

Vitrectomy is well tolerated, but it is worth knowing the possible complications beforehand.

Cataract is near enough inevitable: the eye's own lens clouds over within a year or two in almost everyone operated on in later life. This is not a failure but an expected consequence; the cataract is removed later in a separate operation, and if it was already there, the two procedures are often combined.

Pressure inside the eye often rises in the first few days as the gas bubble expands. This is usually short-lived and controlled with drops, but a severe or prolonged rise can damage the optic nerve.

Less often, in one or two people in a hundred, the retina detaches: that needs a second operation and cannot wait. Very rarely there is bleeding inside the eye, and rarer still an infection inside the eye, the most dangerous complication of all, where hours matter.

Finally, the hole may fail to close or may reopen. Vision then is usually no worse than before surgery, and reoperating often succeeds.

When urgent help is needed

See an eye specialist the same day, without waiting for a routine appointment, in any of these situations, whether or not you have had surgery:

• a sudden shower of black specks or cobwebs floats in front of the eye, or flashes of light appear;
• a dark curtain or shadow moves in from one side and the field of vision narrows: this is how a retinal detachment starts;
• vision drops sharply over hours or a day;
• after surgery the eye becomes more painful, red or discharging, or vision is worse than it was the day after the operation.

Call an ambulance (in European countries on the single number 112) if severe eye pain and loss of vision come with nausea, vomiting and a bad headache: that is how a dangerous rise in pressure inside the eye presents.

Moderate soreness, a gritty feeling and redness in the first days after surgery are a normal part of healing and are not urgent.

Online consultation

A remote consultation helps at two points. Before any tests, the doctor works out what you are actually seeing: bent lines, a gap in the centre, mist across the whole field or drifting specks belong to different diseases and carry different degrees of urgency. You will be told whether you need to reach an eye specialist today or can book later in the week, and which tests are worth arranging so that you arrive with the scans already done.

Once the diagnosis is settled, online is a good place to work through decisions and practicalities: whether to accept surgery now or watch for a while, what vision to expect afterwards, how to get through the face-down posturing, when flying is safe again, what to tell an anaesthetist before an unrelated operation, how to use the Amsler grid to keep an eye on the other side. And the doctor will spell out the signs that mean going straight to an eye specialist rather than writing a message.

This material is for information only and does not replace medical advice.