In the initial stages of development, cataracts are mild and may not be noticeable. However, as a cataract grows in size or more develop, the lens of the eye becomes more clouded and light is less able to pass through it and reach the retina. At this stage, vision can become cloudy and blurred and treatment may be necessary.
Glasses can be prescribed to correct mild forms of cataract and the use of brighter lighting when reading, for example, can be helpful. However, the condition worsens with age and eventually surgery may be the only option for resolving more severe cataracts.
Severe visual impairment caused by cataracts can hinder a person’s ability to perform normal day time activities such as driving, reading, watching the television or even being able to see people’s faces clearly during conversations.
The basic principle of cataract surgery is replacement of the natural lens with an artificial, clear plastic lens. The artificial lens is called an intraocular implant or intraocular lens.
For the procedure, a local anaesthetic is administered to numb the eye area and relax the eye muscles. The eye lids are held open and continuously irrigated with fluids to prevent drying.
A small key-hole incision is made at the upper part of the cornea. The natural lens is extracted and replaced by an artificial lens. Cataract surgery does not usually require a hospital stay and the operation is performed as a day care procedure. There is no pain due to the local anaesthetic and the patient is unable to see anything except for a bright light.
Phacoemulsification is a modern form of cataract surgery used to remove the lens from the eye. A tiny probe is inserted into the lens through a small incision made at the upper end of the cornea. This probe is used to break up the cloudy lens into tiny pieces using ultrasound or high frequency sound waves. These pieces are then removed from the eye using suction, a process called aspiration. An artificial lens made of transparent plastic is then inserted. The operation usually takes 15 to 30 minutes.
Traditional cataract surgery
In traditional surgery, a slightly larger incision is made than in phacoemulsification and the lens is removed in one piece rather than being broken down. One form of traditional surgery called intracapsular extraction involves the removal of the lens capsule as well as the lens. A replacement plastic lens would then be inserted and sewn into the eye. This operation is rarely performed today due to the advent of phacoemulsification.
The artificial lens
There are different types of artificial lens available for replacement of the normal lens. These include the monofocal or fixed-strength lense that provides one level of vision, usually distance vision; the multifocal lens which provides two or more different strengths including near and distant vision; and the accommodation lens which enables similar levels of focus to those seen with a real eye lens.
After the operation
The incision that is made during surgery is small enough to heal without stitches. The eyes need to be protected from bright lights and patients should use any eye drops they are given when they leave the hospital. These can help the eye heal and also prevent infection.
Patients should take care to avoid rubbing the eye or getting soap or shampoo in the eye. Swimming should be avoided for a fortnight, as should sports that involve any risk of being knocked in the eye.
Reviewed by Sally Robertson, BSc