Common Eye Conditions
Cataracts
Briefly:
The description given to a condition where the lens in the eye becomes less transparent, classically this is an ageing change.
Fuller Explanation:
The lens at the front of the eye acts as a window letting
light into the eye. As we get older the lens gets thicker and starts to lose its transparency. The actual layers of the lens can become slightly opaque and water or other materials can form between the layers. The end result of this ageing is that not as much light enters the eye and what gets through the lens is sometimes scattered. Instead of looking out through a clear window we now look through something more like a misted-up window with condensation or dirt on it, its lets you still see things but not with the clarity that you did.
The literal definition of a cataract is when there is any obstruction
to the clear passage of light through the lens but most people would use the term when there has been sufficient ‘misting’ to make vision seem difficult. Everyone has some element of misting as the eye ages but it can vary markedly on when it starts and how quickly it deteriorates.
These images of a pair of retinas were taken with the same camera
but whilst we can see one image clearly because the eye’s lens is clear the other eye has some cataract present in the lens and the light has been diffused giving an indistinct picture. When we are looking out of the eye through a cataract a similar hazing is created of whatever we are looking at
When a cataract is developed to the extent that it limits the vision to an unacceptable amount, despite correcting as well as possible with lenses, the way to improve things is to consider cataract surgery. With this surgery the ‘dirty’ lens is removed from the eye and a clean artificial lens (implant) is put in its place. This is an operation that is generally done as a day case patient, it can be done under local or general anaesthetic and it is common to find that after surgery spectacles are often not needed for distance vision as the consultant can in many cases choose the power of the implant to match the length of the eye.
The latest form of surgery called ‘phako’ will normally result in a good vision within a day.
Phako emulsification surgery
Very small incisions are made in the cornea and a probe is introduced into the eye. The front surface of the capsule holding the lens / cataract is removed and ultrasound is used to break up the cataract, the remains being sucked out of the eye via the probe. This leaves an empty sac, which is used to hold the new replacement lens. This is introduced into the eye, in a rolled up form, through the same hole as the original probe and it unfurls in the capsule to be held in place where the eye’s original lens was. When the probes are removed the wounds created are so small that they normally self seal without the need for stitches. Most operations are done under local anaesthetic althought general anaesthetic is also possible dependant on other health considerations. It is common for the patient to attend as an out patient going home the same day.
Can a cataract re-grow?
Effectively what has taken place is like replacement double glazing the surgeon has reached in, taken out the dirty window (cataract) and replaced it with a clean one (implant). Just behind this new clean lens there is the posterior capsular remnant and this acts like a clear curtain.
Occasionally this capsular remnant can after time fibrose and become thicker. It then acts more like a net curtain rather than a clear curtain and this causes the vision to deteriorate as it did with the original cataract. As the capsular remnant is so thin it can often be targeted with a laser, which creates a hole in it, just as if a hole was cut in the net curtain in your window at home, giving a clear path again for the light to shine through. It can’t grow again and a long term clear view is achieved.
The laser takes seconds, is painless, done as an outpatient and gives an improved vision straight away. Capsular fibrosing is becoming less common all the time as new implant materials are used and operating techniques are honed further still.
If this fibrosing happens it is not always able to be rectified with a laser,
particularly if there is some retinal / macular damage present in the eye and your consultant will be able to advise best.
When should an operation be done?
One of the most important things to remember about a cataract is that it is not a disease and does not damage the eye in any way. Leaving a cataract alone is very unlikely to ever cause problems in the eye, however it may well frustrate you. I generally say that the time to consider surgery is when the frustration of the poor vision caused by the cataract is greater than you are happy with.
This leaves us with a balance to consider and it will vary from person to person.
Any operation has an element of risk attached and although the incidence of problems in cataract surgery is very small some people will find that a very daunting prospect, leaving them happy to accept a poorer standard of vision than others may be happy with. Cataract surgery is nearly always performed on more elderly members of society and so over the years has evolved in a form which causes least problems to people who are of age where they least like disruption, I am sure that is why so many people are very happy with the outcome.
As cataracts are nearly always found in older eyes we often find other changes
can be present. As a general rule when we are older the retina is not as efficient at using light as it once was and a cataract operation will help to give a better light supply helping the vision. If the retina is compromised (for example by macula degeneration) then it can limit the benefits. Unfortunately we are only as good as our weakest link and if there is a damaged retina and a cataract, removing the cataract is going to give a limited improvement. This is just one of the reasons that I earlier said that poorer vision is why you should consider surgery.
It is only when you have had a full assessment of your eye by an appropriate professional that you can be guided and make up your mind based on knowledge rather than pure emotion and possibly hearsay.
When you are examined at the hospital, or opticians, do ask questions and tell the person what you consider to be problems.