By Wendy Haaf
I understand there are different types of lenses that can be implanted during cataract surgery. What’s the difference between monofocal and multifocal lenses?
Cataracts are a usually age-related problem with the natural lens of the eye, which becomes clouded or opaque when proteins in the lens have clumped together. In cataract surgery, the faulty lens is removed and replaced with an artificial one.
“These lenses aren’t the same ones we had 20 years ago; the lens technology we have today is incredibly advanced,” says Dr. Guillermo Rocha, an ophthalmologist and professor of ophthalmology at the University of Manitoba’s Max Rady School of Medicine in Winnipeg and past president of the Canadian Ophthalmological Society.
In Canada, “monofocal lenses are the standard of care,” Rocha says, and these are the type covered by your provincial health-care plan. “Focality refers to how sharp the images are going to be on the retina.” Monofocal lenses give you clear vision at a single point of distance. “The majority of the time, we’re talking about distance or driving vision,” he explains. Consequently, glasses are still needed after this type of lens is implanted for activities such as reading and computer work.
However, premium lenses are also available. Unfortunately, these aren’t covered by provincial insurance and patients have to pay out-of-pocket. Costs vary enormously by lens type, jurisdiction, and institution—so much so that it’s not feasible to provide a cost range here.
One extra feature that can be built into any artificial lens is a prescription to correct blurred vision caused by an astigmatism, which is an unevenly shaped or overly curved cornea (the transparent “cover” over the iris and pupil). “All lens options, from the most basic to the most advanced, can have the ability to correct astigmatism,” Rocha says.
You can also choose lenses that give you sharp focus at more than one range of distance. Extended range of vision lenses are like bifocal eyeglasses. “They give us good distance and good intermediate vision,” Rocha says. Full range of vision lenses are essentially trifocals. “The pro of these is that they give us 90 to 95 per cent freedom from glasses.”
There is a potential downside to full range of vision lenses: “They can create glare or halos,” Rocha says, although, he adds, in many cases, the brain will learn to ignore them over time. With extended range of vision lenses, he says, “the con is you still need reading glasses to see up close. The pro is they don’t give as much in terms of glare or halos.”
Deciding which lens is best for you depends on your lifestyle, preference, and the health of your eyes. Full or extended range of vision lenses typically aren’t recommended if you have certain eye diseases or abnormalities. For example, pseudoexfoliation syndrome, a relatively common condition that causes flakes of material to build up in different eye structures, “can be associated with later dislocation of the lens implant,” Rocha says, so the fancier types aren’t recommended.
The bottom line, for Rocha, is that “there’s no perfect option—everything is a compromise.” The key is understanding the limitations of each option. “When patients’ expectations match what we can provide with our technology, it’s a happy interaction.”