Causes of Cataracts
Laser Removal of Cataracts
New Developments in Cataract Surgery
Is Vision Always Improved After Cataracts Are Removed?
A cataract is any opacity of the lens of the eye. In the earliest stages you may not even be aware that you are developing cataracts. As time goes on, the medical condition worsens and more symptoms develop from the increased opacity of the lens. There are different ways a cataract can affect your vision:
- Difficulty focusing on objects, like looking through a dirty window
- Glare around lights such as when driving at night
- Reading difficulties
Pain or discomfort
Cataracts do not cause symptoms such as pain, discomfort, or reddening of the eye in the vast majority of patients. Some people can notice eye strain with some associated discomfort.
The most common cause of cataracts is the natural aging changes of the eye. There are other factors that are associated with increased incidence of cataracts. These most commonly include:
- Diabetes Mellitus
- Use of systemic or topically applied steroids such as Prednisone
- Some inborn errors of metabolism
- Chronic exposure to ultra-violet radiation such as sunlight
Generally everyone develops some cataractous changes to their lens with increasing age; this cannot be prevented. Some precautions, however, such as wearing glasses that filter UV rays from the sunlight are helpful. We are also finding new evidence that diet can play a role in preventing cataracts. Some people believe that anti-oxidants can be helpful, but no strong evidence exists.
Cataracts can be congenital; in other words, an infant can be born with them or develop them in early childhood. Current surgical techniques have made remarkable improvement in the lives of these children.
In the early stages cataracts require no treatment at all. At these levels they are usually only detected by an eye doctor during a comprehensive eye and visual system exam. In many cases, there is a shift in the refractive index of the lens, making you more nearsighted. A change of eyeglasses is often helpful. This occurrence is often referred to as “second sight,” as a person who needed glasses for reading (as most people do after the early 40s) may find that they no longer need reading glasses.
Along with this shift in eyesight, there is likely some reduction of the distance vision. There are several techniques that can be used to assess how the vision may be affected. The most common way we record vision is with the Snellen scale. This is what you normally hear referred to as 20/20, 20/40, etc.
A person whose vision is best corrected to 20/40 means that we cannot improve the vision better than 20/40, even with the help of contact lenses or glasses. If your vision is 20/40, another person with normal vision would be able to see at 40 feet what you can first see at 20 feet. Likewise, 20/200 would mean the normal individual could see something at 200 feet that you could see at only 20 feet.
There are newer and more sensitive tests being done on vision. One such technique is called Brightness Acuity Testing (BAT). A light is shown in the eye at a certain level of illumination and then the Snellen Vision is tested. The basis of this test is that in brighter light the pupil becomes smaller and we are required to look through only the central part of the lens of the eye. With certain types of cataract we expect there to be a significant reduction in the visual acuity (VA) as tested by BAT. Another technique is contract sensitivity testing. This test gives the indication of when you are able to detect a subtle difference in the contrast of an object. Eventually, most cataracts require surgical removal to improve the vision.
Cataract surgery is one of the most common operations performed in this country. With modern techniques the recovery is quiet rapid, with generally little pain or discomfort.
The most common type of operation performed presently is referred to as phaco-emulsificaton. In this technique, the major portions of the lens are broken down with ultra-sonic sound waves generated by a small instrument inserted into the eye. It is similar to what dentists now use to remove scale and plaque from teeth. The advantage to using this instrument is that a very small incision is used—generally about three millimeters in length. Following the removal of the eye’s lens, an artificial lens is implanted back into the eye to focus the light rays onto the retina. Older methods of cataract surgery required larger incisions that created astigmatism. Astigmatism is a condition of the eye where the curvature of the cornea, lens, or globe is “out of round,” meaning it is shaped more like a football instead of a basketball. Advantages of the new small-incision surgery include less astigmatism and use of few or no sutures.
Currently, there are lasers being tested for removal of cataracts. At present they do not offer any advantage over phaco-emulsification, but further instrument design and development may improve upon this. We currently use a laser to open what is referred to as a secondary cataract or secondary membrane. The development of a secondary cataract happens fairly commonly after most types of cataract extraction. This laser is used as a separate minor procedure and is not performed in place of the phaco-emulsification type procedure.
We now have multifocal type IOLs (intra-ocular lenses) that are implanted in the eye to give improved near and distance vision so that most people may not need to wear glasses following surgery. There are also now toric IOLs that help correct pre-existing astigmatism by offsetting or neutralizing the astigmatic refractive error that was pre-existing in the eye before surgery. These IOLs have alignment markings and must be oriented carefully at the time of surgery; this also will lessen the need for eyeglasses following surgery.
No. There may be several reasons for this. There may be other pre-existing conditions of the eye or visual system that can affect the outcome. These may include macular degeneration, central nervous system defects following stroke or tumors, glaucoma, or others. There may also be complications associated with the cataract surgery itself or the way the eye heals following the surgery.
You will likely need to change eyeglasses following cataract surgery. This may be done soon after surgery, but it is usually best and more economical to wait at least a month or longer, as the eye may continue to change as it heals.