CATARACT

The lens of the eye is normally clear. When we become older most of us get small?opacities?in the peripheral parts of the lens. As long as they do not disturb vision they are called opacities. If they start interfering with vision, the doctors talk about?cataracts. Cataract means opacities, cloudiness of the lens. It is not a layer that grows inside the eye or on the eye preventing clear vision.

Peripheral opacities of the lens do not usually disturb vision during the day when the pupil is small. They may disturb night driving. The lights of the advancing cars become large halos and it is difficult to see in twilight and dark.?Photophobia, increased light sensitivity is perhaps the most common symptom of small opacities that do not yet reduce visual acuity notably. Then it is important to use a hat or a visor so the light does not fall directly on the eyes. It is also much easier to see when walking on the shadow side of the street. Yellow tint in spectacles may decrease light sensitivity both outside and when reading.

Figure 14 shows different types of lens opacities. The opacities may look like thin lace, small bubbles, or as frosted glass. The center of the lens may become yellowish. Then the person often becomes nearsighted and may be able to read without reading glasses.

14. Lens opacities occur in different parts of the lens.

A. Opacities resembling lace on the central posterior surface of the lens.

B. The central?nucleus?of the lens is yellowish.

C. Small bubble-like changes in the anterior part of the lens.

D. Peripheral opacities are often behind the iris (in this picture the pupil is dilated).

E. Small changes in the anterior part of the lens may remain unchanged for several years.

If the lens opacities disturb too much, it is usually possible to remove the cloudy lens. In most cases it is possible to replace the removed lens with a clear plastic lens. If it is not possible, the patient has to use catarcat spectacles or a contact lens after the operation. Cataract spectacles make everything look larger than normal and straight lines seem to be curved. These disturbances disappear in a few weeks.

Fig.15. Cataract surgery.

A. In western countries the cloudy lens is now removed piece by piece through a very small opening in the cornea by sucking the pieces through a thick needle like instrument.

B. A plastic lens is put into the eye to replace the removed lens. To see the original pictures in colour, click the picture.

After the cataract surgery many patients see nearly as well as they saw in their younger years, some other patients see only a little bit better than before the operation. If there are changes in the retina or the optic nerve the vision will not be clear even if the cloudy lens has been removed.

Cataract surgery is usually uneventful. Since the person with cataract is often elderly and may have several diseases, it is wise to ask the medical doctor whether an examination before the surgery is needed to make sure that there is nothing that might cause problems during the surgery. After the surgery the eye should not be touched or rubbed. Therefore it is good to cover it with a shield for the night.