A macular hole is a small round hole that develops in the centre of the macula, the highly sensitive area of the central retina responsible for detailed central vision. In order to understand the effect a macular hole has on vision, it is helpful to know a little about the eye and how it works.
The eye may be likened to a camera. In the healthy eye, light passes through the lens and vitreous to reach the retina.
The retina is the light-sensitive nerve tissue that lines the inner wall of the eye, like the film in a camera. It contains specialised photoreceptor cells which convert light into electrical impulses. In the healthy eye these impulses are sent via the optic nerve to the brain, where sight is interpreted.
The macula is a tiny area at the centre of the retina. It is responsible for our detailed vision, allowing us to read, recognise faces, drive and see colour.
The vitreous is a clear, gel-like structure which occupies about two thirds of the volume of the eye. It is comprised of over 99% water, but also contains structural elements such as collagen fibres and proteins. As we age, changes occur in the vitreous, and the back surface of the vitreous collapses away from the retina. This is known as posterior vitreous detachment, or “PVD”. A patient may experience flashes of light and new floaters as this process occurs.
Sometimes during vitreous collapse the vitreous fails to completely separate from the retina, and pulls on the macula to form a macular hole.
What causes a macular hole?
It is not clearly understood why macular holes develop, but most occur in women around the age of seventy. Collapse of the vitreous gel within the eye pulls on the central area of the retina resulting in swelling. Eventually a small tear in the macula may form, followed by the development of a full thickness hole. Occasionally, macular hole is associated with high myopia (short-sightedness) or trauma.
Vision worsens as a small disc-shaped area of retina around the hole detaches from the eye wall. Over time, the hole can get bigger, causing the sight to become more blurred and distorted. Straight lines may appear to have a central kink, and eventually a dark area appears in central vision.
Occasionally, a hole is detected as a chance finding, for example when covering the good eye or during a routine examination by an optometrist.
How does a macular hole affect your sight?
Common symptoms of a macular hole include blurred or distorted vision, and a central kink in a straight line or edge.
How can a macular hole be prevented?
There is no known preventive treatment to stop a macular hole from forming. Diet or exercise are not thought to be important, and no medicines or vitamins have been shown to be beneficial. Early diagnosis and prompt treatment offers the best chance of retaining central vision.
Should you have surgery for a macular hole?
Most macular holes require surgery. The procedure used to treat this condition is called a vitrectomy. Microsurgical instruments are inserted through tiny, self-sealing incisions in the wall of the eye and most of the vitreous gel is removed (picture). The vitreous is replaced by a salt solution infused into the eye during surgery. Using microforceps, the surgeon will peel a thin membrane from the surface of the retina around the edges of the macular hole, and the eye is then filled with a temporary bubble of an inert gas to push back the small area of retinal detachment around the macular hole. The hole will effectively “close” with a potential improvement in visual function.
Untreated, nearly all macular holes are progressive and early surgery offers the best chance of long-term visual success.
Over 90% of holes will close after a single surgery. While the gas bubble is in the eye vision will be poor, and will only start to recover once the gas has reabsorbed, over the course of 2-3 weeks.
When a macular hole has formed in one eye the fellow eye may also be at risk, so it is important to monitor both eyes in the postoperative period and beyond. Once the vitreous gel has separated from the retina in the fellow eye (PVD) then a macular hole is most unlikely to develop.
Until recently, patients undergoing macular hole surgery were required to spend up to two weeks after the operation in a face-down position. This is known as “posturing”, and it was thought to be essential for closure of the hole. It was also very unpopular with patients! However, recent research suggests that prolonged posturing is unnecessary, and most surgeons now limit the amount of time a patient is required to spend face down to no more than a few days.
There are two main complications associated with macular hole surgery, the first is common and the second rare.
Cataract: A cataract means that the lens of the eye has become cloudy or opaque. In patients who have not previously undergone cataract surgery, macular hole repair will accelerate the natural process of cataract formation, often within a year of the surgery. This will cause the vision to become generally cloudy and blurred. If this starts to affect the vision then a cataract operation will be necessary to restore vision.
Retinal Detachment: During vitrectomy surgery the instruments inserted into the eye may cause a tear to form in the retina. Usually this is detected during surgery and can be easily treated. However if a tear forms after surgery then the retina may detach from the back of the eye, and further surgery will be required to repair this.