New Technology Removes Cataracts and Improves Vision
Kim Wilson, BSc, MSc
Cataract patients may now choose to have a multifocal implantable lens which corrects for distance, intermediate and near vision. During surgery, the patient's cataract or cloudy crystalline lens is removed and replaced by the foldable multifocal lens which then unfolds once positioned in the eye.
"This lens is significant to the elderly", said Dr. Allan Slomovic, Clinical Director of the Cornea and External Ocular Diseases at the Toronto Hospital (Western Division), and the Program Director in the Department of Ophthalmology at the University of Toronto. Dr. Slomovic is one of eleven ophthalmologists originally performing this surgery in Canada, and he says "this foldable lens allows for a very small incision of about 3.2 mm, which allows the eye to heal faster and the patient recovers their vision quickly."
Other foldable lenses are available, but the multifocal lens has the added advantage of correcting for distance, intermediate and near vision. The multifocal lens has a series of zones with different refractive powers, allowing the patient to see a range of distances. Each zone has different refractive powers, with zones one, three and five allowing the eyes to focus on objects at a distance, while zones two and four allow focusing of near objects.
The multifocal lens was developed by Allergan Inc. in California. Jon Sickle from Allergan Canada said "the multifocal lens was approved for use in Canada in March 1997, when 11 ophthalmologists were originally trained. The launch of this lens occurred in December 1997, since which any ophthalmologist trained in its use can implant the multifocal lens."
Monofocal lenses provide a single plane of focus which requires the patients to be dependent on glasses since distance objects are quite clear, but close-up objects still require glasses. Multifocal lenses provide distance vision similar to monofocal lenses, while also giving the patient better near vision, which reduces the dependency for glasses. However, Dr. Slomovic warns that about half of the patients may still require glasses for either reading or driving, although their dependency on glasses may be greatly reduced.
Dr. Slomovic said that the patient must see their eye care provider to determine their suitability for this lens. An evaluation of the patient's lifestyle, including their activities and hobbies will help in weighing the advantages and disadvantages of this lens. This lens is suitable for cataract patients that have a lifestyle that will improve from the surgery and want to reduce their need for glasses so they can read and see at a distance.
Multifocal lenses provide distance vision similar to monofocal lenses, while also giving the patient better near vision, which reduces the dependency for glasses.
The multifocal lens may not be the right option for a cataract patient that does a lot of night time driving or detailed close work. This type of patient may have difficulties with glare and halos, and may experience reduced vision under poor lighting and visibility conditions. Also, this procedure is not recommended for patients with very near or very far vision, or ocular pathology, such as macular degeneration, advanced optic atrophy or end stage glaucoma.
The operation used in cataract surgery using foldable lenses is phacoemulsification. A small incision is made to allow an ultrasonic tip to soften and break up the cloudy cataract lens, which is then aspirated through a needle before the insertion of the foldable monofocal or multifocal implantable lens. The conventional method of cataract surgery involves extracapsular extraction, where the lens is removed and replaced by an unfoldable implant that is made of rigid material. The insertion of this standard monofocal lens requires a much larger incision.
Currently, this surgery is being used only for cataract patients. The eye care professional will determine if the cataract patient has a medical need for the foldable lens, and the patient will also make a personal lifestyle choice for the type of lens that they require. The lenses are covered differently according to the provincial health insurance and are usually not covered by private insurance plans. The standard monofocal is covered by provincial health insurance, but the patient will have to contribute additional costs for the foldable lenses, with foldable multifocal lenses being the most expensive. The foldable monofocal lens costs about $275 per lens, while the foldable multifocal lens costs $450 per lens.
Current use of implantable contact lenses for patients with myopia and presbyopia is considered cosmetic surgery. Myopic and presbyopic patients who have surgery have an implanted contact lens that is placed behind the cornea, not in the crystalline lens position as is done in cataract surgery. Future research in the area of implantable lenses for myopia and presbyopia patients may result in reducing the need for glasses or contact lenses.