A contact lens worn each night could remove the need for reading glasses
- Lenses work by gently pressing on the eye to restore it to the shape of someone with normal vision
- Worn at night so vision is corrected during the day
- Already used for people who are short-sighted, but now also suitable for age-related sight loss
A contact lens worn each night could remove the need for reading glasses in middle age.
The technique – which experts liken to braces for the teeth – alters the shape of the eye to correct vision, without needing glasses or surgery.
The lenses work by gently pressing on the eye to restore it to the shape of someone with normal vision.
Because they are worn while asleep, the wearer no longer needs their vision corrected during the day with reading glasses.
And because the lenses aren’t worn in the day, the eyes still get sufficient oxygen.
Most middle-aged people experience some age related decline in near vision, known as presbyopia.
Typical symptoms include having to hold a menu further away to get the text in focus – and many people require bifocals or reading glasses.
But the new technique – known as hyperopic orthokeratology – offers an alternative, according to Dr Paul Gifford of Australia’s University of New South Wales.
As a technique, orthokeratology has existed for centuries. It’s thought the Chinese slept with small weights or sandbags on their eyelids to reduce short-sightedness.
But until recently,’ says Dr Susan Blakeney, optometric adviser to the College of Optometrists, ‘it has been considered unreliable, as there was never any guarantee the lenses would work.
‘Since then, techniques such as corneal topography - where the curve of the cornea is measured - have developed. This means lenses can be made to fit the curve of each person’s eye very accurately.’
Presbyopia is caused by age-related loss of flexibility in the cornea-the transparent front part that lets light into the eye.
Dr Gifford and his colleague Dr Helen Swarbick studied a ‘monocular’ technique, with patients wearing a custom-made lens in one eye overnight for one week.
To preserve normal distance vision, the other eye was left untreated.
In all patients, the orthokeratology technique was successful in restoring near vision in the treated eye.
The improvement was apparent on the first day after overnight lens wear, and increased further during the treatment week.
Eye examination confirmed that the lenses altered the shape of the cornea, as they were designed to do.
Vision in the untreated eye was unaffected, and all patients retained normal distance in that eye.
The reshaping is temporary, however, because the cornea will gradually spring back to its original shape, so the lenses must be worn every night.
So to retain the correction in near vision, patients had to continue wearing their lenses every night.
Dr Anthony Adams, editor of Optometry and Vision Science, likened this ongoing treatment to the ‘retainer’ that orthodontic patients have to wear nightly.
He said: ‘The authors have shown the feasibility of correcting one eye for near vision through orthokeratology, in which overnight contact lens wear shapes the cornea of one eye to allow in-focus near vision for reading.
‘This study demonstrates that orthokeratology is quite viable as a nonsurgical option for monovision that does not require wearing contact lenses during the day, although it does require ‘retainer’ orthokeratology contact lenses to be worn overnight.
‘This possibility will certainly appeal to many people, especially since the changes in the corneal curvature of the treated eye are fully reversible.’
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