MUTIFOCAL INTRAOCULAR LENSES

As we age there is a gradual loss of reading vision. We can start to notice this in our 40’s. This occurs because the eye loses its ability to accommodate. That is to change focus from far to near. When the eye is in focus for distance the eye is at rest. To see close a muscle in the eye contracts allowing the natural lens of the eye to change shape and focus close. As we age the natural lens of the eye loses its elasticity and even tho the muscle is strong our whole lives the natural lens of the eye becomes too stiff or inelastic to change shape.

We now have the ability with cataract surgery to restore our ability to again see both far and close without glasses. Even though the new technology intraocular lens implants are very good and patient satisfaction high, they are not as good as our ability to accommodate that we had in our earlier lives.

TECNIS MULTIFOCAL
www.amo-inc.com
The FDA approved in January 2009 the acrylic Tecnis lens. This lens I feel is the best of the multifocal lenses. In the FDA trial, 94% of patients who had this implant in both eyes had very good uncorrected distance vision of 20/25 or better and 20/15 or better reading vision. Patient satisfaction was very high.

This lens is developed with the front surface being aspheric and the back surface being diffractive. The near vision comes from the rear diffractive surface and this covers the entire rear surface of the lens. This means that reading vision does not change as the pupil size increases or decreases and it will do naturally in changing light conditions.

This lens splits near and far vision approximately 50% for each. This means that there is less light available for near and far that there is with traditional non- multifocal intraocular lenses. This will cause approximately 20% of patients to have nighttime glare and halos. These will become barely noticeable in most users but can be significant in a small number of cases.

CRYSTALENS – Why we don’t recommend this lens
www.crystalens.com
According to the manufacturer this lens acts by moving back and forward in the eye to change power and simulate true accommodation. It is recommended to implant this lens with mild monovision with the non-dominant eye being left mildly nearsighted. The newer version of this lens has actually added a small bifocal to the lens optics.

There have been numerous studies that show that the lens does not more inside the eye or the motion is so small that no accommodation takes place. This lens has the advantage that there is no glare or halo because there is no bifocal in one design and a very small bifocal in the other design. I feel that the optical effect of this lens can be achieved by using a standard intra-ocular lens with a small amount of monovision.

I have implanted this lens in only two patients. One was very happy and one very unhappy. In the patient who was unhappy the lens was implanted first in the nondominant eye and the vision was too poor for distance. There was no accommodation noticed. It seemed as if the lens focused for close and did not move. The other eye was operated on and a standard IOL was used for distance and the patient is very happy with this. She wants to have lasek on the crystalens eye to change this eye for distance.

The other patient is very happy and chose to have a crystalens in the non-dominate eye to see the computer. This did occur but I felt that I could have achieved the same effect with a standard IOL. I could not demonstrate any accommodation in either patient.

TORIC IOL-ASTIGMATISM
Alcon.com
This lens has consistently achieved outstanding results by providing patients with excellent distance visual acuity. 98% of patients with bilateral implants achieved spectacular independence after surgery.

Astigmatism is an optical term. When used to describe the human eye it means that the surface of the eye or the lens of the eye has two different curves instead of one. A spherical surface has a single curve whereas an astigmatic surface has two curves. One can visualize this easily. For example, if you cut a tennis ball in half each half will be round. If you slightly pinch the ball it will then be elliptical instead of round and have two curves. This simulates astigmatism. Most cases of astigmatism occur as we grow and the eye changes slopes. Astigmatism can be correct with glasses, contact lens or both. When undergoing cataract surgery with an intraocular implant any astigmatism that is one the cornea will remain when a standard IOL is used. Glasses, contact lens or lasek would then be used to correct this astigmatism and improve distance vision.

The Toric IOL will correct up to 2.5 diopter of astigmatism and reduce astigmatism if more than this. There is reduce glare also with this correction.