The Aging Eye: Preventing and treating eye disease

The new focus: Specialized replacement lenses

Starting around age 40, the lens in your eye becomes less flexible—a normal part of aging that makes near vision more difficult, especially in low light. Eventually, everyone develops this problem, known as presbyopia, and most people (even those without cataracts) need reading glasses to see well close-up. But several new types of intraocular lenses (IOLs) may reduce or eliminate the need for glasses after cataract surgery for people who have presbyopia, as well as those with astigmatism.

Accommodating. When you switch from gazing at something far away to something nearby (or vice versa), the tiny ciliary muscles in your eye tug on your lenses so they change shape ever so slightly, enabling you to focus near, far, or in-between. This capability, called accommodation, diminishes as the lens stiffens with age. But the ciliary muscles retain their ability to contract and relax. Accommodating IOLs have hinges on the sides, enabling them to change focus, just like the lens in a younger eye. The first accommodating IOL, the Crystalens, gained FDA approval in 2003, and several similar types of accommodating lenses are under development. Overall, these IOLs offer excellent distance and middle vision, but aren’t as reliable for near vision. Eye exercises can help people get used to them, but about half of people who receive them still end up needing reading glasses.

Multifocal. Like bifocals or progressive lenses used in glasses, these IOLs include different areas designed for distance, intermediate, and near vision. But unlike the lenses in glasses, the areas are organized in concentric circles, rather than from top to bottom. The brain and eye figure out which part of the lens to use. One example, the Restor IOL, uses a type of refractive technology to provide focus for multiple distances. The lens has small, concentric circular ridges that permit the eye to change its range of focus. Another lens, called the ReZoom, has five broad zones to provide distance, intermediate, and near vision. The main drawback of multifocal lenses is difficulty in seeing well at night. The tiny ridges can distort bright light, creating more glare and halos.

Toric. These are monofocal IOLs that have been altered to correct for astigmatism. Instead of making limbal relaxing incisions, the surgeon may implant this IOL. The first one, the STAAR Toric IOL, won FDA approval in 1998; a second one, the AcrySof IQ Toric IOL, was approved in 2005. One drawback to these IOLs is the risk that they will rotate out of position, which may require further surgery to reposition or replace the lens.

Companies that make IOLs are refining several other modifications designed to enhance vision. One new category is aspheric IOLs. Unlike traditional IOLs, which are spherical (meaning the front surface is uniformly curved), aspheric IOLs are slightly flatter around the edges. These lenses are supposed to improve contrast sensitivity (the ability to distinguish an object from its background) or to reduce visual aberrations, such as glare and halos. One aspheric IOL, the Tecnis Z9000, is advertised as improving the ability to see in varying light conditions such as rain, snow, fog, twilight, and nighttime darkness.

Many IOLs include filters that block ultraviolet (UV) light, which is known to increase the risk of cataracts and other vision problems. At least one new IOL, the AcrySof Natural, also filters high-energy blue light, which is present in both natural and artificial light and may damage the retina, possibly playing a role in age-related macular degeneration.

What to consider

Only a small percentage—about 6%—of people who have cataract surgery receive one of these specialized lenses. Not everyone is a good candidate; for instance, people with severe macular degeneration, glaucoma, or diabetic retinopathy are not the best candidates. If you have had LASIK surgery (see page XX), choosing the correct IOL can be a challenge, although the newer lenses aren’t out of the question. 

Anther consideration is cost: these so-called premium lenses are not covered by Medicaid or most insurance plans, so you will likely pay between $1,500 to $2,500 extra for each eye if you chose a specialized lens. Because there are so many different lenses on the market, it’s difficult to find comprehensive, reliable data about the magnitude of the benefits and risks associated with each. The most common problems with the newer lenses are glare and halos and the continued need for eyeglasses. Discuss your options with your own cataract surgeon.