Your eye’s natural lens plays an important role in focusing images on the retina. When a cataract develops, the lens loses its clarity. Light rays cannot focus clearly, and the image you see is blurry. Eyeglasses or contact lenses usually can correct slight refractive errors caused by early cataracts, but they cannot sharpen your vision if an advanced cataract is present.
The only treatment for a severe cataract is to remove the eye’s natural lens and replace it with an artificial intraocular lens (IOL). An IOL is a tiny, lightweight, clear plastic or silicone disc placed in the eye during cataract surgery. An IOL replaces the focusing power of the eye’s natural lens. Most are about as big as a small button. Intraocular lenses offer many advantages. Unlike contact lenses, which must be removed, cleaned, and reinserted, the IOL remains in the eye after surgery.
An IOL may be implanted either in front of or behind the iris. Behind the iris is the most frequent placement site. IOLs can be made of hard plastic, soft plastic, or soft silicone. Soft, foldable lenses can be inserted through a small incision, which shortens recovery time following surgery.
The rapid evolution of IOL designs, materials, and implant techniques has made them a safe and practical way to restore normal vision after cataract surgery. Today’s patients are faced with a wide range of choices regarding which IOL to have placed in their eyes. Your ophthalmologist can help guide you in this decision. Lens types can be divided into four major categories: 1) Standard lenses; 2) Wavefront lenses; 3) Toric, or astigmatism correcting lenses; and 4) Multifocal/Accommodating lenses.
Standard intraocular lenses are excellent foldable lenses that are implanted through small self-sealing incisions. They provide good vision for one focal distance only, meaning the patient must choose whether to be more dependent on glasses for either reading or driving. Patients with significant astigmatism before surgery will probably require glasses for most activities. Standard lenses make use of conventional spherical optics technology, meaning when the pupil is large as would occur with night-driving, dim lighting or in fog, some visual distortion and reduced contrast sensitivity will occur. The ideal Standard Lens patient wants improved vision but does not want to pay for a premium lens, and accepts that night vision and vision in low-contrast lighting will be slightly reduced. Patients selecting a Standard Lens must also accept that glasses will be needed for some or all activities. Standard Lenses are covered by OHIP and are provided to cataract surgery patients at no cost.
Wavefront intraocular lenses are excellent foldable lenses that are implanted through small self-sealing incisions. They provide good vision for one focal distance only, meaning the patient must choose whether to be more dependent on glasses for either reading or driving. Patients with significant astigmatism before surgery who select a Wavefront Lens will probably require glasses for most activities. Wavefront lenses use advanced aspheric optics and are designed to correct spherical aberration, thereby increasing contrast sensitivity, which is especially useful under low-light or foggy conditions. Investigators comparing traditional lenses to wavefront lenses reported that wavefront-corrected IOLs permit better reaction times than standard IOLs when elderly subjects were tested in a night-driving simulator. The ideal Wavefront Lens patient has no significant astigmatism and wants the best possible vision available, and accepts that glasses will be needed for some activities.Wavefront Lenses also require Wavefront Analysis, which costs $127 for both eyes. Based on your Wavefront Analysis, your ophthalmologist will select one of three different Wavefront Lenses (the AMO Tecnis lens, the Akreos AO lens by Bausch and Lomb, and the Acrysof IQ lens by Alcon) to complement your unique degree of spherical aberration.
Toric (Astigmatism Correcting) Lenses
Toric, or astigmatism lenses are excellent foldable lenses that are implanted through small self-sealing incisions. Toric lens reduce or eliminate astigmatism, which is an asymmetric curvature to the cornea that increases the need for glasses at all distances. Many patients receiving Toric lens implants no longer need glasses for distance vision. Toric lenses provide good vision for one focal distance only, meaning the patient must choose whether to be more dependent on glasses for either reading or driving. Toric lenses use conventional spherical optics technology, meaning when the pupil is large as would occur with night-driving, dim lighting or in fog, some visual distortion and reduced contrast sensitivity will occur. The ideal Toric lens patient has 1.5 diopters or more of astigmatism and accepts that glasses will be needed for some activities. Toric lenses are not covered by OHIP. Toric Lenses also require Pre-Cataract Corneal Topography testing.
Multifocal/Accommodating Lenses are excellent foldable lenses that are implanted through small self-sealing incisions. Multifocal/Accommodating Lenses offer the possibility of seeing well at more than one distance, greatly reducing the need for glasses or contacts. Multifocal Lenses accomplish this feat by assigning some light that enters the eye to near vision, and some light to distance vision. Accommodating Lenses reduce the need for glasses by changing their position in the eye, which changes the focal length of the eye to match the task being performed at that time. It is important to note that Multifocal/Accommodating Lenses are not the best choice of lens for everyone. The nature of the way in which light is handled by Multifocal Lenses can decrease contrast sensitivity and create visual abberations like glare and haloes around lights. Accommodating Lenses are not suitable for patients with previous eye trauma, or who have unstable support structures for the intraocular lens. Multifocal/Accommodating Lenses are not suitable for patients with significant astigmatism unless additional surgery is performed. Other eye conditions such as Age Related Macular Degeneration, Glaucoma, Diabetic Retinopathy, Pseudoexfoliation, and Epiretinal Membrane may preclude you from having a Multifocal/Accommodating Lens implanted and achieving the best possible results. Your ophthalmologist will evaluate you and make the most appropriate recommendations based on your specific circumstances.