Overview

A cataract is a smudge in the lens of the eye. It was originally given this name because the vision through a cataract was equated to looking through a waterfall. There are many causes for cataract but the most common cause is hardening of the lens with age. This is called "sclerosis" and is seen as a yellow brown discolouration of the normally mostly transparent lens.

There is good evidence that cataract is related to excessive sun exposure during life. The other causes of cataract include diabetes, direct injury to the eye, metabolic disorders, inflammation inside the eye, inherited eye disease, genetic defects (you can be born with cataracts), and as a result of other eye surgery.

Often changes in the perception of colours occur due to filtering of some colours by the increasingly brown lens. The photo on the left is the normal, whilst the right one shows washing out of colour saturation. After cataract surgery many people express surprise at how much colour vision returns, as though the whole world has suddenly been washed clean.

What is happening inside the eye to cause all of this?

As the lens develops areas of opacity or discolouration, it causes light to be scattered rather than focussed. This causes the blurring or dimming of vision and can account for glare problems. Certain wavelengths of light are absorbed leading to reduced colour vision. In extreme cases, little or no light passes through the lens to the retina and vision is lost altogether.

How is a cataract treated?

Currently the only way to remove a cataract is using surgery to take out the lens of the eye with the cataractous material included. Cataracts cannot be treated with eyedrops, glasses, or lasers. Typically, a very small cut is made in the cornea and the lens is removed using "phacoemulsification" (high frequency ultrasound) which liquifies the lens and aspirates the liquid material. The surgeon aims to leave behind a thin membrane called the "capsule".

But if the lens of the eye is removed, is the focus of the eye not lost as well?

Certainly. Thus, once the cataract is out, the eye surgeon will insert a small plastic lens implant to refocus the eye (a lens insertion device is picture, right). The size of the lens is normally calculated prior to the operation. There are various styles of lens implants but generally a "foldable" style that fits through the small incision is recommended. Once the lens is in the eye it mostly lasts for life and requires no care from the patient.

There are new lenses emerging on the market including those that correct for astigmatism (where the eye is “out of round”) and those that are multifocal, permitting some reading vision without glasses.

At the end of the operation, stitches may or may not be used. It takes about four weeks for the eye to recover from cataract surgery but sometimes it can take longer. A new lens is then prescribed for the person's existing glasses.

Success Rates and Complications

Cataract surgery is a highly skilled procedure and has a remarkably good success rate. The quality of life returned by cataract surgery is probably not exceeded by any other form of medical therapy. However, There is a small element of risk with any form of eye surgery no matter who carries out the operation. Fortunately most complications in cataract surgery are relatively minor and can be dealt with by your eye surgeon. More serious complications such as dislocation of the cataract or lens implant, retinal tear or detachment, exacerbation of underlying diabetic retinopathy or macular degeneration, and onset of macular oedema can prove more troublesome. In very rare cases, unforseen catastrophic outcomes can occur such as severe infection or bleeding. These can result in blindness or even loss of an eye altogether. A full discussion of predicted outcomes and risks should be given by the eye surgeon prior to operation.