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Presbyopic clear lens exchange
What is presbyopia?
The word 'presbyopia' means 'old eye' in Greek. It is a normal part of aging where your eyes gradually loose their ability to see things clearly up close. From around 40 you may find that you hold reading materials farther away to see it clearly.
What causes Presbyopia?
Your lens is just behind the colored iris in your eye. It changes shape to focus light from near and far images onto your retina. In young people the lens soft and flexible and easily changes shape. After 40 the lens becomes more rigid and can not change shape as easily. This causes the difficulty in reading and other close up tasks.
Cornea: Clear, dome-shaped window of the eye that focuses light into your eye.
Lens: Clear part of the eye just behind the colored iris that It helps to focus light on the retina.
Retina: Nerve layer at the back of your eye. It turns light into signals to the brain so that you can see.
There is no way to stop or reverse the normal aging process that causes presbyopia. It can however be corrected with glasses, contact lenses or eye surgery. Speak to your optometrist about reading glasses, bifocal or trifocal glasses or contact lenses. If you do not correct presbyopia you may get headaches due to eye strain.
What are the surgical options for Presbyopia?
Mono-vision with LASIK is when the ophthalmologist uses a laser to reshape the cornea for clear far vision in one eye and close up vision in the other. You will usually try mono-vision contact lenses prior to LASIK surgery. This way you can see if mono-vision is a comfortable option for you prior to surgery. Read more about blade-less LASIK here.
PRELEX (Presbyopic clear lens exchange) is when someone with presbyopia chooses to replace their natural lens with an IOL. This allows them to have an IOL that corrects a refractive error (nearsighted, farsighted, or astigmatism). PRELEX is usually not reimbursed by your medical aid.
What to expect with PRELEX
Your eye surgeon will numb your eye with local anesthetic drops.
In laser PRELEX surgery, an advanced femto-second laser replaces the use of a blade for the 2-3 corneal incisions near the edge of the cornea and opening the bag of the lens. It also breaks up the lens for easy removal. Use of a laser can improve the precision and accuracy, potentially reducing risks of PRELEX surgery.
Using special instruments, your ophthalmologist will break up the eye’s natural lens with ultrasound and gently vacuumed out the pieces through one of the incisions. The “capsular bag” that holds your natural lens in place stays intact.
The Intra ocular lens (IOL) is folded and inserted through the incision. It is placed in the “capsular bag,” where it unfolds. An IOL will refract light properly again, giving you clear vision at certain distances.
The tiny incisions in your eye are “self-sealing,” and you will not need stitches.
It could take 6-8 weeks after surgery to be able to focus fully. Basically, your eye has to heal and relearn how to focus at various distances to see clearly.
Choosing a Multifocal lens
Bifocal, trifical and extended depth IOL's offer different focusing powers within the same lens. These IOL's reduce your dependence on glasses. Based on the scientific literature 90% of individuals do not require spectacles either for distance, intermediate or near vision, you will however still need them for certain tasks like prolonged reading. There are numerous designs that can be considered. You and your ophthalmologist will discuss the best option for you to fit your individual lifestyle and needs.
The lens has several rings or zones set at different powers. With this design, you are actually using both near and far vision at the same time. However, your brain learns to automatically select the right focus for what you want to see.
As yet there are no Multi-focal lens implants which are as good as the natural healthy human lens in a young person. There is no perfect vision. With multi-focal IOL’s there is always a trade-off.
Multi-focal IOL compromises
There are some compromises and differences in the quality of vision that need to be understood.
• It takes time to adapt to seeing through the new multi-focal lenses.
• A multi-focal IOL can reduce the dependency on glasses but some people it might result in generally less sharp vision, which may become worse in dim light.
• Not all patients are completely free of spectacles. About 10% will still require glasses for either distance, intermediate or near vision or a combination of these.
• Reading vision is usually very good but does depend on lighting. Reading may not be as good in dim light.
• The reading distance is typically at a fairly fixed distance so you will need to get used to moving reading material to that position.
• The selection of the correct power of the lens implant is based on very sophisticated equipment and computer formulas but it is not an exact science. Occasionally the focal length of the lens can settle too far in the distance or too close. Usually this is correctable by changing the focal length of the implant used for the second eye, “top-up” LASIK surgery or a implanting a second “piggy-back” IOL.
• Astigmatism (a difference in the curvature of the cornea in different meridians) can be corrected during surgery by using limbal relaxing incisions or Multi-focal lenses with a toric (astigmatic) “in-built” correction.
• Vision typically is far better with the lens implants in both eyes rather than in just one. The improvement in vision after the second eye surgery can be dramatic.
• Visual side-effects such as circles or halos around lights particularly at night are common. It the vast majority of cases these phenomena are regarded as insignificant. If you do a lot of night driving Mono-focal lenses may be a better choice for you.
For more information or questions:
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