Multifocal and Accommodative IOLs

How we see the world around us

For us to see clearly, light rays enter our eyes through the clear cornea, pupil and lens. These light rays are focused directly onto the retina, the light-sensitive tissue lining the back of our eyes.

The retina converts light rays into impulses that are sent through the optic nerve to our brain, where they are recognized as images. Seventy percent of the eye’s focusing power comes from the cornea and 30 percent from the lens. While problems with the cornea (the clear front window of your eye) or the lens may prevent light from focusing properly on the retina, a refractive error may prevent us from seeing clearly in certain situations, despite having a clear cornea and lens.

Today, many people are choosing to correct their refractive errors with options other than eyeglasses or contacts.

Various forms of refractive surgery – such as LASIK – improve vision by permanently changing the shape of the cornea to redirect how light is focused onto the retina. In some cases, instead of reshaping the cornea, the eye’s natural lens is either replaced or enhanced by an implanted intraocular lens (IOL) that helps correct vision.

The role of multifocal and accommodative IOLs in clearer vision

The eye’s lens, which contributes to your focusing power, has four primary functions:

  1. Transparency: To provide a clear medium through which light rays from an object can reach your retina.
  2. Optical: To focus a sharp image of an object onto the retina.
  3. Anatomic: To create a functional barrier between the front (anterior) and back (posterior) segments of the eye.
  4. Accommodation: To vary the eye’s refractive power, providing clear images of objects over a wide range of near, far and intermediate distances.

For people with cataracts, the lens of the eye becomes cloudy. Light cannot pass through it easily, and their vision is blurred. Cataract surgery is used to remove the cloudy lens and replace it with a clear IOL.

In some cases, people without cataracts who want to reduce or eliminate their need for glasses and who may not be candidates of LASIK may choose to have an IOL implanted in a procedure called refractive lens exchange (RLE). This procedure may be used to correct moderate to high degrees of myopia (nearsightedness), hyperopia (farsightedness) and presbyopia (the inability to focus at near distances with age).

When the natural lens is removed during cataract surgery, or removed as a form of refractive surgery, IOLs are inserted to take the place of the natural lens. IOLs are artificial lenses surgically implanted in the eye, replacing the eye’s natural lens. These lenses help your eye to regain its focusing and refractive ability.

The most common type of implantable lens is the monofocal, or fixed-focus lens, which is intended to give clear vision at one distance. In order to see clearly at all ranges of distances, one is required to wear glasses or contact lenses.

Other types of lenses which are gaining in popularity are the multifocal and accommodative lenses. These IOLs may be used to treat myopia, hyperopia and presbyopia, and may allow less reliance on glasses, contact lenses, or both to see clearly at a distance and near.

A multifocal IOL has several rings of different powers built into the lens. The part of the lens (ring) you look through will determine if you see clearly at a far, near, or intermediate distance (this is sometimes called pseudoaccommodation).

An accommodative IOL is hinged to work in coordination with the eye muscles. The design allows the accommodative lens to move forward as the eye focuses on near objects, and move backward as it focuses on distant objects.


Different Lenses:



                                                     
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