An intraocular lens is used to replace the eye's natural lens when cataracts form. After we reach mid-life, the lens may start to develop opacities that block light from entering the eye. Cataracts are progressive and will lead to blindness if nothing is done. Since there is no way these opacities can be removed from the lens, the lens is replaced with an IOL to restore full vision.
Also as we age, the lens becomes gradually less able to provide clear close-up vision - this is a condition called presbyopia. We can now use an IOL as one way of correcting it.
The Eye's Ability to Accommodate
When you look from a far object to one close us, the eyes automatically accommodate to that distance change so that all objects will be in focus. The lens is the structure that accomplishes this – it changes its curvature continually, between a steeper curvature for near vision and a flatter one for far vision. There are two tiny muscles, called ciliary muscles, which tighten and relax to change the curvature.
When the natural lens becomes clouded with cataracts and is removed, the eyes lose that accommodative ability. We now have lens implants that can give us some form of accomodation back.
ReSTOR® IOL
The ReSTOR IOL is not moved by the ciliary muscles. Instead, it has inbuilt concentric rings, creating circular areas that focus light differently. The center step is highest and contributes most to near vision; and as the steps move towards the periphery they become lower and provide distance vision.
Tecnis Multifocal IOL
The Tecnis lens is also not moved by the ciliary muscles. It has concentric areas that interact with light to help you focus at distance and near.
Toric IOLs
If you have a significant degree of astigmatism, a toric IOL would be a good choice. Astigmatism (blurriness at all distances) occurs when the cornea has an oval shape instead of a spherical shape. An oval has two curvatures: a steeper one on the shorter side and a flatter one on the longer side. If you picture a football or the back of a spoon, you will get the idea. The Toric lens has correction built in for astigmatism much the same way as glasses and contact lenses can correct for astigmatism.
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Center For Sight offers this Web site about eye care services for informational purposes only. The content contained here should not be perceived as formal medical advice, nor does the understanding constitute a formal medical relationship with the Center For Sight.
