PRELEX stands for presbyopic lens exchange, and is the name given to the procedure used to replace the natural lens of your eye, which is no longer able to focus on close objects, with a multi-focal or accommodating lens implant. Presbyopia, or the inability to see close objects clearly, often develops at or soon after the age of forty. By replacing your lens with a new lens, which can focus on distant and near objects, it is possible to restore the close vision.
This operation is very similar to cataract surgery; the difference is that advances in lens technology have enabled close vision to be restored, and that in patients undergoing PRELEX surgery, the natural lens of your eye is clear. One advantage of PRELEX is that once your natural lens has been replaced during the operation, you cannot develop a cataract in later life.
During the operation, the natural lens of the eye is gently removed through a tiny incision on the surface of the eye using a machine called a phacoemulsifier. This small probe emits ultrasound waves which break the lens up into fragments which are then washed out of the eye. The new lens is then introduced into the eye to replace the natural lens which has been completely removed. The new lens is made from a flexible material which allows it to be rolled up and so will pass through the very small incision on the surface of the eye. Usually no stitches are needed to seal the eye after the operation and you can return home with minimal discomfort. The operation takes about 20 minutes but you will be in the hospital for at least a few hours in total.
PRELEX is now possible due to the recent advances in lens implant technology. Traditionally, implant lenses have been fixed focus lenses, allowing good distance vision after surgery but not good close vision. With new lens designs, it is now possible to have the best of both worlds with both distance and near vision. The aim of PRELEX is to reduce and if possible eliminate your need for bifocal or reading glasses by the use of multi focal or accommodating implant lenses.
There is always the possibility of a complication with any surgical procedure. PRELEX surgery is technically the same as cataract surgery and so carries the same risks. As an elective procedure, there always exists the option of continuing to wear glasses, bifocals or contact lenses. Risks include infection inside the eye (called endophthalmitis). This is extremely rare and occurs in approximately 1 in every 1000 operations. Other risks are retinal detachment (1 case in every 1000 operations), macular oedema, (1 case in every 250) which is the accumulation of fluid at the back of the eye and results in a more prolonged recovery time after surgery. Floaters may be noticeable immediately after surgery but usually become much less noticeable with time. Posterior capsular opacification is thickening of the membrane which supports the new lens implant. This can happen in about 20% of patients undergoing lens implant surgery and is more common in those having an accommodating lens implant. Other complications include tearing or weakness of the lens capsule which may result in the need to use a monofocal lens and not the multifocal or accommodating lens as had been originally planned.
PRELEX is a great solution to the problems of loss of accommodation which occur later in life. However, it is not suitable for everyone, especially those who have high demands from their eyes and expect the surgery to give them perfect vision at all ranges (distance, computer work and reading) as no lens will work perfectly for all ranges in all people.