A Cataract is the gradual opacification, and yellowing of the natural lens in the eye. The most common type is called Senile, or Nuclear type, and results from the absorption of high energy light over a period of years. The natural lens is made of an Alpha protein which is clear. High energy light causes a chemical reaction that transforms this Alpha protein to a Beta protein which is yellow. Over time, as the lens becomes more and more yellow, it diffracts light as it travels through the lens. Ultimately, it prevents light transmission and vision decreases. It is at this point that people seek out the eye doctor to consider a Cataract operation. Additional types of cataracts are those induced by trauma, drugs and some are even congenital.
Todays cataract surgery is far superior to that done even 10 years ago. Today a small incision is made in the temporal aspect of the cornea, the natural lens is removed. An implant is introduced into the eye through this opening. Complications to this point may be a poor incision resulting in excess aqueous fluid leaking out and rupture of the natural lens. This will results in lens protein floating around the eye causing an Iritis which is an internal inflammatory response. This is treated with steroid eye drops. While the healing period will be longer, the long term prognosis is unchanged.
The newest intraocular implants, unlike the older ones, are multifocal. That is to say, they let the patient see both distance and near just as they did when they were younger. The Rezoom lens, and the Restore are commonly used implants. They work on the principle of multiple images being projected on to the retina, and allows the patient to see at all distances. They are very similar to old style bifocal contact lenses like the Echelon. The Rezoom has a center zone for near surrounded by distance zones. The Restore has the opposite. The center area is for far while the surrounding zones are for near. Clinical practice has not shown either one better then the other for the average patient.
However, the same problems arise as did with the Echelon bifocal lens. The first is that glare, especially at night, is bothersome. The second is that there is usually some sacrifice for vision at near. The third complication is that the implant must be PERFECTLY placed in the center of the pupil. Many times the implant may shift as the eye heals, and if the sac that hold the lens brakes, the implant will also move. Any of these movements will result in decreased vision and on occasion, double vision. Some surgeons have started sewing the implant in place to prevent movement.
In short, the concept is acceptable for these implants, but in practice I have found that most patients with them complain about glare and poor vision requiring eye glasses for either distance, near or both. It is the side effect of double vision, and glare that disturb most people. Keeping in mind that most cataract patients are seniors, and are less tolerant of these visual affects, one must think long and hard if they are willing to take a chance on these multifocal implants. As a side note, the best results with them have been to use a Rezoom in one eye and a Restore in the other.
With cataract surgery so far advanced, the best results seem to still be using a single vision distance implant and using reading glasses after surgery.