When Will We Eliminate Reading Glasses?

Laser surgery is freeing more and more people from eyeglasses and contact lenses, but no matter how successful the surgery, their liberation is only temporary. Sooner or later the need for reading glasses descends on all adults -- and from those devices there is still no quick escape.

Human bodies age at enormously different rates with one single exception: the fine-focus mechanism of the human eye. The lens of the eye and the muscle that surrounds it tick away the passage of time, slowly deteriorating with a precision so predictable that ophthalmologists say they can accurately estimate patients ages to within a few years by measuring their ability to focus close up.

The loss of close-up focus is known as presbyopia, from the Greek for elderly vision.” By the age of 50 or so, when the eyes can focus no closer than a yard or two away, almost all adults in the world need glasses to read newspapers or thread needles. Those who claim they do not, researchers say, are simply unusually skilled at blur interpretation, fooled by good guesswork into thinking they are exceptions to a universal biological rule.

Many scientists think that the most important factors leading to presbyopia are age-related changes to the proteins within the lens of the eye, making the lens harder and less elastic with the years. Age-related changes also take place in the muscle fibers surrounding the lens.

Some people find that a satisfactory solution is the creation of monovision, in which one eye is manipulated to focus well at reading distances (usually with a contact lens or an intraocular lens placed after cataract surgery), while the other focuses for distance. People instinctively grow to favor one eye or the other for different tasks. But while some people are delighted with this solution, others are plagued by dizziness or nausea, or miss the depth of vision they once had.

For the last five years, researchers have been arguing over the risks and benefits of an experimental surgical procedure, scleral expansion surgery, that, despite a host of scientific objections, appears to fix it.

Scleral expansion surgery was devised by Dr. Ronald Schachar, a Texas ophthalmologist and physicist, in the early 1990 s. A maverick who has argued that much of what scientists think they know about the focusing mechanism of the eye is actually untrue, Dr. Schachar believes that presbyopia develops as the lens of the eye swells with age, the muscles and fibers surrounding it grow lax, and the visual system can no longer work effectively.

By stretching the system out again, Dr. Schachar says, presbyopia can be easily and permanently reversed. He claims to restore tension to the muscle and fibers by surgically implanting four small curved pieces of plastic in the white of the eye a few millimeters from the iris, which, he says, re-establish an effective working distance between the lens muscles and the lens.

His technique has evoked howls of protest from physiologists who point out that it ignores decades of solid experimental evidence implicating age-related changes within the lens itself as key causes of presbyopia. But a few hundred patients who have volunteered for the surgery over the last decade in Mexico, Canada and Europe have stymied the procedure s critics with reports that the surgery does indeed seem to restore their ability to see up close.

In March, the Food and Drug Administration approved preliminary trials of the operation at six sites in the United States. Dr. Stephan D. Plager, 60, an ophthalmologist in Santa Cruz, Calif., is also among the investigators who are to take part in the evaluation of surgical expansion surgery. In early May, Dr. Plager himself underwent the procedure in both eyes.

Two days later, he said, he was performing cataract surgery in his office, and 10 days later, vision still a little blurry but getting clearer every day.” Familiar with all the reasons that his surgery should not work, Dr. Plager said only that while the theory behind the procedure might be flawed, the end result was hard to ignore.

The proof that it works will ultimately be in the scientific studies, he said, but the proof as far as I m concerned is already on the table.”

Judith Lee