Now composed of silicone, acrylic and hydrogel, intraocular lenses (IOLs) are commonly implanted to treat cataracts. (LifeART)

Doctors are starting to look beyond simply using intraocular lenses (IOLs) for cataracts - the latest technology can be used to correct nearsightedness, far-sightedness and astigmatism. (LifeART)

Kim Edwards is a freelance writer and the editor of Optical Prism magazine.

Wish you could kiss your glasses goodbye? While laser eye surgery garners a lot of attention, it cannot correct presbyopia, a change in the lens of the eye that commonly occurs as people age and which makes it difficult to focus on nearby objects.. But new hope may be in sight in the form of surgery that uses intraocular lenses (IOLs).

IOLs were invented by accident by British ophthalmologist Dr. Harold Ridley during the Second World War. While treating injured aviators, he noticed that little pieces of plastic from airplane cockpits sometimes became embedded in the eyes of Spitfire pilots, but did not seem to irritate the tissue. He hit on the idea that acrylic might be used to manufacture artificial lenses that could be inserted into a human eye permanently without rejection.

Ridley's artificial acrylic lenses were soon used to replace the lenses in the eyes of patients who had developed cataracts — a procedure that has become the most common type of eye surgery in the world.

"The first IOLs were made of a plastic called polymethyl methacrylate, a material which is stiff and not bendable," says David Tak Wah Wong, assistant professor in the department of ophthalmology at the University of Toronto.

IOLs did not find widespread acceptance in cataract surgery until the 1970s, when advancements in lens design and surgical techniques were made. Now composed of silicone, acrylic and hydrogel, IOLs are commonly implanted to treat cataracts and less than a week of recovery time is typically necessary after surgery.

New uses for IOLs

Doctors are now starting to look beyond simply using IOLs for cataracts — the latest technology can be used to correct nearsightedness, far-sightedness and astigmatism. And IOLs can make your sunglasses obsolete, since most now contain an ultra-violet (UV) filter, ideal protection for the eyes in light of today's concerns about the thinning ozone layer and increasing levels of eye-damaging UV radiation.

"The lenses are no longer just being used for cataracts, they can be used for monofocal or bifocal vision, and there are UV filtering and blue light filtering lenses as well," says Wong. The latest IOLs "have added chromophores allowing filtering of harmful light to the retina that may reduce macular degeneration," he adds.

Monofocal lenses usually correct distance vision but do not provide good focus for near vision. Aspheric lenses allow superior perception of contrast and distance vision, but also do not correct near vision. However, for people who need bifocals or multifocal lenses, newer multifocal IOLs can correct both near and far vision problems, giving patients close to perfect vision without glasses or contacts.

The vision corrections made by IOLs are said to be as effective as ophthalmic or contact lenses.

"The new technologies are taking into account various optical aberrations in the eye," says Dr. Alan Cruess, head of the Dalhousie University department of ophthalmology. "By getting rid of these aberrations the focus can be sharper, the vision that can be achieved can be much sharper. The multifocal lens is attracting a lot of attention. Since most cataract patients are in the presbyotic age group [people over 40, the age group where far-sightedness generally develops], they can benefit from these lenses."

Slow adoption

Despite the technological advances, few people today are opting to have IOLs put in electively.

"Sometimes people will do elective clear lens extraction," says Dr. Sherif El-Defrawy, associate professor and chair of the department of ophthalmology at Queen's University. "[But] that's not a common thing. This is predominantly for people who have cataract surgery. Most of these people are very used to wearing glasses and bifocals. When they find out they don't need glasses for distance, they are ecstatic."

But for those who do go the IOL route, either to treat cataracts or improve vision, it can be difficult to find a doctor in Canada who will do a multifocal IOL implant.

The reason is that the cost for basic foldable single-vision IOL implants is covered by most provinces, but multifocal lenses and lenses with other features can have costs to the patient that go as high as $1,000.

Some provinces also won't pay doctors for the additional costs related to surgery involving multifocal intraocular lenses, so they are often reluctant to do the surgery, El-Defawy says.

"The problem is in Ontario, for example, if someone needs a multifocal lens, there's a lot more testing, more physician education, a lot more of the physician's time is taken up by this lens. But they are not [compensated], because the government says there can't be any additional physician's cost. In Ontario, I know some doctors are shying away from [multifocal lenses] even though their patients want them."

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