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Night Vision
August 01, 2000

Instead of dreaming of better eyesight, you could be improving your eyesight while you dream.

Researchers at Ohio State University are studying the effects of a type of hard contact lens, designed to be worn only at night, which reshapes the cornea of the eye so that people with mild nearsightedness can see normally again during the day.

Visionary treatment

If the technique, called orthokeratology, meets with the approval of eye doctors, the nighttime contacts could provide an alternative to vision correction surgery for people who do not want to wear glasses or ordinary contacts.

The cornea of a myopic eye is more rounded than that of a normal eye.
image: AAO

The contacts restore vision by exploiting the flexibility of the cornea—the tough, transparent layer at the front of the eye. In people who are nearsighted (who have trouble focusing on objects that are far away, aka myopia), the cornea is too rounded and light rays entering it get bent before they reach the lens of the eye, which is responsible for focusing the images that our eyes see. The special nighttime contacts, called reverse geometry lenses, work by reshaping the curve of the cornea.

Instead of being bowl-shaped like regular contact lenses, reverse geometry lenses are shaped more like dinner plates. Custom-fit to correct the amount of myopia in each of the wearer’s eyes, the nighttime contacts are sculpted so that they flatten the cornea under the pressure of the eyelid of the sleeping wearer. "I like to use the analogy that it’s kind of like molding Jell-O," says Joseph Barr, professor of ophthalmology at Ohio State University in Columbus, who is leading the research.

Seeing is believing

Test subjects in Barr’s study experienced some improvement in vision after just one night of wearing the lenses, but it took up to four weeks of nightly wear for the contacts to have their full effect in all patients. According to Barr, patients who have a prescription of two diopters or less can benefit from the treatment and can expect near-perfect vision as a result of orthokeratology. "We don’t think this is good for very high myopia," says Barr, "but most of the people in the population who have myopia have the lower kind that we believe this treatment would correct."

Each patient is custom-fit for reverse geometry lenses

For patients in Barr’s study, the vision restoring effect of wearing the lenses lasted for about eight hours in most wearers, after which the effects began to wear off as their corneas returned to their natural shape. Based on this initial research it seems that people using the night contacts will have to wear them regularly, "I think we’ll find in the long run is that people will have to wear the lenses overnight about every other night, or every third night to retain the effect," says Barr.

There are some drawbacks to sleeping your way to better vision. According to Barr, some people he has treated have failed to respond to the lenses at all and, because each lens must be custom made for each eye, they cost four to five times more than regular hard lenses. Moreover, the technique represents a temporary fix to a problem which can be repaired

Other options

Refractive surgery with lasers is similar but permanent.
image: AAO

Refractive surgery also works by flattening the cornea just like reverse geometry contact lenses do. Critics of Barr’s work say that a temporary fix for nearsightedness isn’t needed, because refractive surgery–especially widely advertised "LASIK" laser eye surgery–is safe, effective and permanent. "Orthokeratology isn’t a procedure I would endorse," says Sandra Belmont, MD, an ophthalmologist at New York Presbyterian Hospital in New York, NY. According to Belmont, the procedure’s effects are too temporary to be beneficial, and even could be dangerous. "What if the effects of it were to wear off while driving?" Belmont says.

Barr—who is investigating the feasibility of the technique but isn’t working on getting it approved for use in clinics—accepts the criticism: "We feel it’s advisable for people to keep their glasses with them, or keep their contact lenses... if they’re on the road or away from home, especially."

But Barr thinks that reverse geometry contacts could be ideal for those who don’t want to opt for surgery. "Refractive surgery has been very successful for over well over 95 percent of the people who’ve had it, but there are those people who have a very low prescription, who may not feel it’s worth the expense, or perhaps don’t want to permanently alter their body," says Barr. He hopes that the nighttime contacts will most benefit active, young people the most. "Athletes, people who enjoy outdoor sports, especially swimmers, who don’t want to have a permanent change in their vision like refractive surgery, but are willing to try an alternative," he says.

So for some people at least, nighttime contact lenses may an idea worth sleeping on.

Elsewhere on the web:

A history of vision correction

EyeNet from the American Academy of Opthalmology

Anatomy of the eye

by Tom Clarke

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