What is a cataract
The natural lens of the eye is made mostly of water and protein. Sometimes, as the eye ages, some of the proteins undergo changes, causing the eye’s lens to become discolored and clouded. This is called a cataract. When this occurs, light passing through the eye becomes scattered and unfocused. The result is that all objects, near and far become blurry. The only treatment for a cataract is removal of the natural lens and implantation of an intraocular lens (IOL). This restores the eye’s ability to have light pass unobstructed through the retina.
What is the lens?
The lens is a clear part of the eye that helps to focus light, or an image, on the retina. The retina is the light-sensitive tissue at the back of the eye.
HOW DO CATARACTS DEVELOP?
In a normal eye, light passes through the transparent lens to the retina. Once it reaches the retina, light is changed into nerve signals that are sent to the brain.
The lens must be clear for the retina to receive a sharp image. If the lens is cloudy from a cataract, the image you see will be blurred.
Age- related cataracts develop in two ways:
- Clusters of protein reduce the sharpness of the image reaching the retina.
The lens consists mainly of water and protein. When the protein clusters up, it clouds the lens and reduces the light that reaches the retina. The clouding may become severe enough to cause blurred vision. Most age- related cataracts develop from protein clusters.
- The clear lens slowly changes to a yellowish/brownish color, adding a brownish tint to vision.
As the clear lens slowly colors with age, your vision gradually may acquire a brownish shade. At first, the amount of tinting may be small and may not cause a vision problem. Over time, increased tinting may make it more difficult to read and perform other routine activities. This gradual change in the amount of tinting does not affect the sharpness of the image transmitted to the retina.
If you have advanced lens discoloration, you may not be able to identify blues and purples. You may be wearing what you believe to be a pair of black socks, only to find out from friends that you are wearing purple socks.
Are there different types of IOL implants?
Yes, there are a number of different types of intraocular (IOL) implants. The main classifications of implants are the standard spherical monofocal, aspheric (high definition) monofocal, aspheric toric monofocal, aspheric multifocal and aspheric toric multifocal. Different lenses are selected to provide different ranges and qualities of vision based upon the patient’s requirements and ocular health.
The standard spherical monofocal implant is provided by the Ontario Health Insurance Program (OHIP) at no charge. This is a monofocal lens implant that can provide satisfactory vision at one fixed and specified distance. Generally, it requires the aid of glasses to fine tune sight for clear vision at other working distances. Patients opting for this lens should expect to be wearing bifocal glasses after their cataract surgery.
Additional types of implants are not covered by OHIP but can be purchased by the patient through their health care facility. One of the great advantages of these lenses is that the shape of the lens improves the optics of the eye and the overall quality of vision.
Monofocal Lens: The standard IOLs are monofocal. This means that they offer clear vision at one distance only; generally far away. They definitely are an improvement over the cataractous lens that is replaced during surgery, which provides cloudy, blurred vision at all distances. Traditional IOLs mean that you must wear eyeglasses or contact lenses in order to read, use a computer or view objects at arm’s length.
- Aspheric Monofocal Lens: The aspheric monofocal lens implant only corrects distance for far vision, such as that required for driving. The aspheric monofocal lens implant does not usually correct intermediate or “arms length” vision, such as that required for viewing computer screens, and does not correct near vision as required for reading. Patients who wish to have the best quality of distance vision, especially in dim or dusky conditions, should consider an aspheric monofocal lens implant. Please remember that it will still be necessary to wear reading glasses or bifocals to correct for intermediate and near vision tasks.
- Toric Monofocal Lens: Toric monofocal lenses have more power in one specific region in the lens to correct astigmatism as well as distance vision. Due to the difference in lens power in different areas, the correction of astigmatism with a toric monofocal lens requires that the lens be positioned in a very specific configuration. While toric monofocal lenses can improve distance vision and astigmatism, the patient still will require corrective lenses for all near tasks, such as reading or writing.
- Multifocal Lens: Multifocal intraocular lenses are one of the latest advancements in lens technology. These lenses have a variety of regions with different power that allows some individuals to see at a variety of distances, including distance, intermediate, and near. While promising, multifocal lenses are not for everyone. They can cause significantly more glare than monofocal or toric lenses. Multifocal lenses cannot correct astigmatism, and some patients still require spectacles or contact lenses for clearest
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