A macular hole is an actual hole that develops in this highly light sensitive area of the central retina.
It is helpful to know a little about the eye and how it works in order to understand what effect macular hole has on your vision, and how it can be treated.
Anatomy of a normal eye
The retina is the light-sensitive nerve tissue that lines the inside of the eye. Rays of light enter the eye, passing through the cornea, pupil and lens before focusing on the retina. The retina contains photoreceptors 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 as clear, bright, colourful images. The retina can be likened to photographic film in a camera.
The macula is a small area at the centre of the retina. It is very important as it is responsible for our central vision. It allows us to see fine detail for activities such as reading, recognising faces, watching television and driving. It also enables us to see colour.
The choroid is the underlying vascular (blood vessel) layer of the eye, from which the retina receives oxygen and nutrients.
The vitreous is the clear jelly-like substance which fills the hollow space behind the lens.
As we age this vitreous gel opacifies and shrinks away from the retina. This is very common, occurring in about seventy-five per cent of people over the age of sixty-five.
Separation of the vitreous gel from the retina is known as posterior vitreous detachment or “PVD”. It does not itself cause any permanent loss of vision although floaters may be troublesome.
Occasionally when shrinkage of the vitreous jelly within the eye fails to result in separation, the vitreous pulls on the central macular area of the retina, causing swelling and development of a macular hole.
Optical Coherence Tomography (OCT) is a non-invasive imaging technique which provides a cross-sectional image of your retina, as part of your diagnosis.
Fundus images of a normal macula and a macular hole
OCT image of a normal macula
OCT image of a macular hole showing the swollen retina around the hole lifting away from the eye wall.
What causes a macular hole?
Most macular holes occur spontaneously in women around the age of seventy. The actual cause is unknown (idiopathic). It is thought that shrinkage of the vitreous jelly within the eye pulls on the central macular area of retina resulting in an initial swelling followed by the development of a full thickness hole. Occasionally, macular hole is associated with myopia (short-sightedness) or trauma.
Vision worsens as a small disc shaped area of retina around the hole detaches from the eye wall. It is this localised area of detached retina which causes many of the troublesome symptoms and which surgery will address.
How does a macular hole affect your sight?
Common symptoms of a macular hole are:
blurred central vision;
objects appearing “pinched in” and reduced in size;
distortion of straight lines.
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Should you have surgery for a macular hole?
The procedure to treat this condition involves filling the eye with 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. Occasionally, a hole is detected as a chance finding, for example when covering the good eye or when being examined by an optometrist.
Even when few symptoms are present, surgery may be considered to prevent further worsening and to give the best long-term chance of success.
When a macular hole has formed in one eye the fellow eye may also be at risk. In the situation where vitreous gel remains attached to and pulling on the central macula, the chance of a macular hole developing in the fellow eye can be as high as one in six. As cataract is often present along with macular hole, and inevitably worsens following vitrectomy surgery, it is routine for us to offer a combined cataract and vitrectomy procedure.
