A macular hole is a tiny hole in the centre of the macula, usually less than half a millimetre across. Unfortunately, this part of the macula (the fovea) is the most sensitive part. As a result, patients with a macular hole usually cannot read with the affected eye.
If the other eye is unaffected, this may not be noticeable. All too often, though, the poor vision in the affected eye interferes with the better eye. Many patients with a macular hole close the affected eye when they read or are trying to look at a distant or small object.
Macular holes occur in women more often than men and usually over the age of 60.
OCT scan of a macular hole, showing the vitreous (fine line at the top of the image) still pulling on the edge of the macular hole (black gap in the macular image). The missing central macula means that the patient cannot see anything at all right in the centre of his vision; the edges, swollen with fluid (black cavities), mean that the vision just next to the centre of vision is blurred and distorted.
OCT image of another macular hole after successful surgery with improved vision. There is still a tiny gap in the layer of photoreceptors, which explains the persistent (but much smaller) gap this patient has in the absolute centre of her vision.
How Do Macular Holes Happen?
The cause of a macular hole is unknown, but it is known to be due to a physical pulling open of a hole by the back of the vitreous gel. The vitreous normally fills the back of the eye and is in contact with the whole of the retina, including the macula. The back of the vitreous appears to begin to separate from the macula in a normal pattern but, unlike a normal posterior vitreous detachment (PVD) when the vitreous cleanly separates from the macula, it remains abnormally firmly attached at the fovea but separates from the rest of the macula. The vitreous then ends up pulling on the fovea both outwards and forwards. Over time, this pops a hole open in the centre of the macula (fovea). Dr Chauhan has published peer-reviewed research that has helped to elucidate this process. Click here to read.
How Is The Vision Affected?
Sometimes people notice this happening at the time; others notice it at a later stage, being unaware of a visual problem until they close the better eye or visit an optometrist. The hole progressively gets bigger but rarely progresses to complete loss of vision. Most patients see the top letter on the vision test chart or better.
There are two areas of vision affected by macular holes, which are related to the two areas of abnormality in a macular hole. On an OCT scan (a cross-sectional image of the macula) there is usually an obvious gap in the retina (macular hole) and an area on each side where the macula is thicker than normal. The macular hole itself usually results in a total loss of central vision and the thickened area outside causes vision to be blurred and distorted around the central missing part.
Is Surgery Always Needed?
A small proportion of macular holes, at the earliest stages, close on their own. In most cases however, the macular hole has passed this point by the time the patient is first seen by a vitreoretinal surgeon and vitrectomy surgery is the only realistic option for improving vision. More than 9 out of 10 macular holes are closed with surgery, with almost all seeing less distortion or blurring off-centre; about 8 to 9 out of 10 patients see more in the centre of their vision too.
If left alone, without surgery macular holes do not cause blindness.
When Should The Surgery Be Done?
The longer a macular hole has been present, the lower the chance of the operation being successful and the less the improvement in vision is likely to be. It is not, however, an emergency and can usually wait for a while without making a significant difference to the outcome.