What is a Cataract?
A cataract is a clouding of the lens within the eye.
The lens is just behind the coloured iris and pupil. It helps to bring any light coming into the eye to a focus. This gives a clear image or picture to the layer at the back of the eye called the retina. The lens is normally transparent and clear. Some loss of clarity may be normal or unimportant.
When clouding is more marked it interferes with vision. Patients notice blurring of objects and a loss of brightness in colours. Haloes may be seen around lights. In some cases vision is especially bad in bright light. Often reading vision is more affected than distance vision. Opticians will often find changes in spectacle prescription while a cataract is developing.
About Cataract Surgery
Cataract formation is a normal part of ageing. All people are eventually affected to some extent. Diabetics seem to get cataracts considerably earlier. Also people on certain drugs such as steroids can be affected. Often other diseases of the eye can cause cataract, including eye injuries. Some forms of radiation may even be responsible. Rarely people may be born with a cataract.
The only effective treatment of a cataract is surgical removal of the lens. Before this is recommended, your eye is examined carefully to be sure that the eye is otherwise healthy. If there is nothing else wrong with the eye, the operation has an excellent chance of restoring vision, but if other disease in the eye is found then the result cannot be guaranteed. The most common other disease is age-change of the retina called macular degeneration. Also severe glaucoma (raised pressure in the eye) can reduce the chances of good vision after surgery. If the cataract is so dense that the surgeon cannot see through it, then we cannot predict what the vision will be after the operation and we may even discover a detached retina.
Every patient has to have special measurements taken of the eye to calculate the power of the lens implant that will be used to replace the cataract. This measurement is called biometry and it is a combination of measurement of corneal curvature and measurement of the length of the eyeball.
Contact lenses can cause distortion of the cornea so any patient wearing contact lenses must not have worn them for three weeks before these measurements are taken. In this period you must not wear them even for short periods, as this will spoil the result of your operation.
The 2 sorts of implants, which I currently use for patients with cataracts, are first, the monofocal or standard lens implant, whose cost is covered by the insurance companies and included within the hospital package price. These lenses give the best possible distance vision and reading glasses will almost always be required.
Secondly, multifocal lens implants. These are not the same as bifocal glasses, you do not have to adjust your head position to see distance and near. These lenses are permanently focused both for distance and for near and make you more spectacle independent. No guarantee is ever given that you will never need to wear glasses at all. Some patients with these lenses do note symptoms of halos around lights for some time following surgery up to 4 months. A few patients, who have a degree of astigmatism or who are not perfectly corrected for distance, may even opt for a further laser corneal procedure to get a perfect result eventually.
The operation is usually done under local anaesthesia but may be done under general anaesthesia or with some background sedation. Patients have dilating drops about an hour before the procedure. Local anaesthesia involves an injection of anaesthetic next to the eyeball and this is generally well tolerated, but can be associated with some discomfort. The operation may be done as a day case or an in-patient procedure. Day case patients go home the same day. The procedure itself involves removing the lens and usually replacing it with a plastic lens implant. There are various techniques. The newer technique is called phacoemulsification. In this technique a small incision up to 3mm wide is made into the eye which is self-sealing. This incision is made at the edge of the cornea where the coloured iris changes to the white of the eye. The lens in the eye has an envelope known as the capsule around it. A large circular tear is made in the front of this envelope.
Then the phacoemulsification technique uses an ultrasound tip to break up the lens matter through the small incision. Once this is done the multifocal lens implant is injected through the incision into the envelope space left by removing the cataract. As the incision is self-sealing it should not require a stitch. A microscope is used for this operation as it is delicate and precise.
Video of operation
Whilst you are having the surgery, a bright light is shone into the operated eye and the other eye is covered by some paper. Therefore, you do not see any details of the surgery itself.
Some patients may require their forehead taping to help keep still during the operation.
Immediately after the operation your vision should be improved and colours appear brighter. There should be no pain, only a little discomfort. The eye may be rather red for a few days, and bright light can be uncomfortable. It is usual to go home very soon after surgery. There will be drops to use about four times a day for up to a month. Do not use the drops for longer than recommended as wound healing will be delayed. A protective shield should be taped over the eye at night time for a couple of weeks. The eye must not be rubbed at all. The first follow-up attendance is a week or two after surgery. If the eye becomes painful, increasingly blurred and more sticky before this visit, an urgent examination is necessary. A check will then make sure there is no infection in the eye.
Once the spectacles (if required) are made, vision should be fully recovered. As mentioned, the plastic lens implant is placed into the original lens envelope. This layer can itself become cloudy and thickened in some patients. The timing of this varies from weeks to years. If it does happen, vision will gradually become blurred again. The surgeon can treat this easily by a procedure using a special laser known by the initials YAG. A small hole is cut in the thickened capsule in the middle of the pupil, then a clear path is made for the light to enter the eye. After this treatment a short course of eye drops is given. There is a common misunderstanding that this form of laser treatment can replace the whole cataract operation. This is not true.
Left untreated, a cataract worsens and may make the eye completely blind. In a few patients it may over-ripen (become over-mature). Then it can cause inflammation in the eye or swell up with fluid. Problems of this sort can make the pressure inside the eye too high, and cause discomfort. Permanent damage can also be done to the optic nerve coming into the eye causing irreversible blindness.
What is involved for family and friends?
Following surgery, it is best for someone to help to look after you. You will need to take things quietly for a fortnight, avoiding excess straining. Putting in the drops correctly can be difficult to do alone. Spectacles, if required, should be prescribed after three weeks. (Note: see below).
Patients on glaucoma drops should continue with their drops throughout the cataract treatment.
What problems could there be with cataract surgery?
As with any operative procedure there may be complications in a very small number of cases. The most common problems are:
Up to 2% of patients have some form of setback during or after the cataract operation which is usually reversible.
Around 1 in 500 patients may have a more severe complication relating to cataract surgery resulting in permanent loss of vision.
Most patients who have poor vision after cataract surgery already had a pre-existing eye condition apart from the cataract itself.
Please Note: Many patients have good distance vision without spectacles but some patients who are deliberately left myopic or have astigmatism will need distance spectacles. Also, many patients will require reading spectacles and off the shelf spectacles are often sufficient (try plus 3.0 dioptres). Patients who have elected to have bifocal lens implants should be more spectacle independent.