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. Dr Hillson will guide you in this decision. Lens types can be divided into four major categories: 1) Standard monofocal lenses; 2) wavefront monofocal lenses; 3) Toric, or astigmatism correcting lenses; and 4) Multifocal/Accommodating Lenses/Extended Depth of Focus lenses.
Standard Monofocal Lenses
Standard monofocal 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 chose 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 Monofocal 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. Dr Hillson uses the Sensar lens, manufactured by Johnson and Johnson, and the SA60AT lens, manufactured by Alcon, as Standard Monofocal Lenses.
Wavefront Monofocal and Monofocal “Plus” Lenses
Wavefront monofocal and monofocal “plus” 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 chose 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. Wavefront Monofocal “Plus” Lenses offer sharp distance vision and some intermediate (arms-length) vision as well. The ideal Wavefront Monofocal Lens patient has no significant astigmatism and wants the best possible vision available, and accepts that glasses will be needed for some activities. Patients that are ideal for Wavefront Monofocal “Plus” Lenses want the best distance vision and want to maximize intermediate vision as well. Wavefront Lenses are not covered by OHIP, and cost between $105 and $205 per lens. Wavefront Monofocal and Monofocal “Plus” Lenses also require Wavefront Analysis, which costs $150 for both eyes. Based on your Wavefront Analysis, Dr Hillson will select a lens 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. They use wavefront technology and are available as a monofocal or monofocal “plus” lens. 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. Monofocal Toric lenses provide good vision for one focal distance only, meaning the patient must chose whether to be more dependent on glasses for either reading or driving. Monofocal “Plus” Toric lenses offer good distance vision and some intermediate (arms-length) vision. The ideal Toric lens patient has 1.0 diopter or more of astigmatism and accepts that glasses will be needed for some activities. Toric lenses are not covered by OHIP, and cost $415 to $490 per lens. Toric Lenses also require Pre-Cataract Corneal Topography testing, which costs $150 for both eyes.
Multifocal/Accommodating Lenses/Extended Depth of Focus Lenses
Multifocal/Accommodating Lenses/Extended Depth of Focus lenses are excellent foldable lenses that are implanted through small self-sealing incisions. These lenses offer the possibility of seeing well at more than one distance, greatly reducing the need for glasses or contacts. Some of these lenses can also correct astigmatism. They 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/Extended Depth of Focus are not the best choice of lens for everyone. 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. Other eye conditions such as Age Related Macular Degeneration, Glaucoma, Diabetic Retinopathy, Pseudoexfoliation, and Epiretinal Membrane may preclude you from having one of these lenses implanted. Dr Hillson will evaluate you and make the most appropriate recommendations based on your specific circumstances. Multifocal/Accommodating Lenses/Extended Depth of Focus lenses require Wavefront Analysis prior to implantation, which costs $150 for both eyes. These lenses are not covered by OHIP and cost between $290 and $1215.
