|
|
|
Amblyopia
Age Related Macular Degeneration
Eye Injuries
Glaucoma
Diabetes Eye Disease
New Zealand National Eye Bank Trust
|
|
|
The lens of the human eye is similar to the lens of a camera. Located near the front of the eye, the lens focuses light on the retina at the back of the eye. Light passes through it to produce a sharp image on the retina. When the lens of the eye becomes cloudy or opaque, light is unable to pass through it and the vision is blurred. This condition is known as a cataract.
The cataract forms inside the eye and, contrary to popular misconception, is not a film which is visible on the surface of the eye.
|
|
|
Cataract, the clouding of your lenses, are usually a natural part of aging. They can also exist at birth, be caused by an injury, or be caused by diseases like diabetes. Cataracts usually develop in both eyes, although not always at the same rate.
Cataracts are caused by an alteration of the protein structure within the lens of the eye as a person ages. The vast majority of people with cataracts are healthy and have no other eye disease.
By knowing how a normal eye works and how cataracts develop and affect your vision, you can better understand how cataracts are treated.
|
|
|
Eye with normal lens
In a normal eye the clear cornea allows light to enter. The coloured iris controls the amount of light entering the eye by changing the size of the pupil (opening). Light passes through a clear lens, which is surrounded and supported by a capsule, then through the vitreous (a clear gel that fills the eye). The light is focused by the lens onto the back of the eye, the retina, creating a sharp image. The image is then transmitted to the brain by the optic nerve.
 |
 |
Normal Eye |
Eye With A Cataract |
Eye with cataract
In an eye with a cataract, light passes through a cloudy lens. The lens scatters the light, causing blurring and glare. And because the cataract blocks light less of it is able to enter the eye, making it harder to see in dim light. A cataract on the edge of the lens may not affect the way you see. But a cataract in the middle of the lens may reduce your vision and is likely to interfere with your vision or perception of colour. |
|
|
Cataracts often take a number of years to develop and may not cause problems in their early stages. Cataracts progress at varying rates from individual to individual. But as they develop they can reduce your sight and interfere with your lifestyle. You will notice a blurring of vision, sometimes with some "ghosting". Your eyes may become more sensitive to light and glare.
|
|
|
Because a cataract is a clouding of - not a film over - your lens, surgery is the only way to remove a cataract once it is formed. The operation involves making a small 1/3 of a centimetre opening into the eye, through which is put a small instrument which breaks the cataract up into small pieces so that it can be removed. This is called phacoemulsification. After that, a small clear plastic lens (the implant or IOL - introocular lens) is put into the eye to take the place of the cloudy lens (cataract) which has been removed. The whole operation takes around half to three quarters of an hour. Surgery is done on only one eye at a time. That way you can use the other eye while the eye that has been operated on heals.
 Phacoemulsification
After a small incision is made in the eye, an extremely fine precision tip is inserted into the nucleus (main portion). High-frequency sound vibrations are used to break up the lens material, and the fragments are suctioned out. The posterior (back) capsule is left behind, reducing the risk of complications later on.
Posterior Chamber Lens Implant
Unlike a contact lens that can be removed, the IOL becomes a permanent part of your eye. During the operation an IOL is placed in the posterior chamber (a space behind the iris) and held in place by flexible loops or tabs. The incision may be closed with stitches or with a no-stitch procedure.
Ultrasound Test
Prior to surgery the eye is measured in order to determine what strength your new implant lens will be. This is done by ultrasound waves. The test is painless and performed in the consulting room.
Anaesthesia - What type?
The operation can be done either under local or general anaesthetic. Under local anaesthetic, the anaesthetic is put on and around the eye. The majority of patients prefer this method. If, however, you are apprehensive about being awake during this operation, or have a problem such as an uncontrollable cough, twitch, etc, which would interfere with the operation, it is better for you to have a general anaesthetic. Your surgeon will discuss which is the preferred method for you.
|
|
|
Because a cataract is a clouding of lens, it cannot be removed with a laser. Occasionally, however, a very small amount of cataract can grow back some months after the operation, and this can be removed with a laser. This is a very short outpatient procedure.
|
|
Day of surgery
Shortly after you are admitted to the hospital some eyedrops will be put in your eye to enlarge the pupil, making it easier to operate on the cataract.
Patients having a local anaesthetic need not lie rigidly still during the whole operation. The surgeon will tell you when it's important not to move. If you wish to move to make yourself comfortable please tell your doctor this.
After the operation
A pad may be placed over your eye which should be left in place until the following morning. You will need to come back to see your surgeon the following day. On bright days wear dark glasses. Put the eye drops, which you will be given, into the eye as instructed by the surgeon until they see you again. Pain relief tablets may be needed for a day or two.
You can resume normal activities. There is a misconception that after the operation you should not bend or stoop, cough, etc, but this is not the case. You may take a bath, shower, or wash your hair.
Immediately after the operation objects will look much brighter, but a little out of focus. In view of this you should no drive immediately after the operation. Your glasses will need to be changed, and this is normally done a few weeks after surgery.
Some patients see black spots (called floaters) in the vision. These are usually inconsequential, but inform your doctor when you next visit. You may also notice halos, glare and distortion of lights, particularly at night. You will also experience a little grittiness as the wound heals. All these symptoms recede with time.
After the operation it is most important to report to your surgeon if your eye becomes increasingly painful, or the vision progressively blurred.
Cataract surgery is usually successful with a greater than 95% chance of greatly improved vision. As with any operation, however, there is always some risk of complications, such as infection or haemorrhage. Fortunately, these occur rarely.
Cataracts don't have to interfere with the quality of your life. Your ophthalmologist can work with you to help improve your vision so you can return to the activities you enjoy. |
|
 |
|
