How overnight corrective lenses lend clear vision

CLEAR SIGHT: Overnight corrective lens remains a less explored option. A patient being helped to wear the lens, at the Government Eye Hospital, Egmore. Photo: R. Ragu

V. Nitin is looking forward to the Interschool Sri Lankan Academy cricket tournament as he would be the vice captain of the team from India. If he has come this far then it is thanks to the overnight corrective contact lens that he has been wearing for the past three years.

The corrective contact lenses are much smaller than the regular contact lenses which extend beyond the cornea. “Since the lenses are smaller they allow the cornea to absorb nutrients and oxygen. Patients sleep with the lenses and during the day they can do without glasses,” explains K.Vasantha, director, Government Eye Hospital, Egmore.

Nitin, who dreams of becoming a professional cricketer, inherited his mother's high myopia. “When his scores dropped, his teacher advised me to have his eyes checked. In UKG he wore glasses with minus 1 power. By the time he came to II Standard it was minus 3.5,” recalls his mother Nalini, who has been wearing contact lenses for 20 years.

The young boy remembers making mistakes, slowing down in class and losing marks. He could not play cricket because of the “glare” on field due to his glasses. It was then his ophthalmologist Dr.Vasantha suggested overnight corrective lens.

R.Suraj, 18, an engineering student of Anna University, opted for overnight corrective lens last year as he “was not comfortable with glasses and had to remove the regular contact lenses on returning from college.”

Some patients have noticed that their vision has improved with corrective contact lenses. B.Athiba, a standard XII student, says: “The [corrective] lenses were suggested as an alternative. When I started wearing them my power was minus 3.75 and now it has reduced. I have been wearing these lenses for three years,” he adds.

Nitin, Suraj and Athiba inherited short-sightedness from their parents and are among the youngsters being treated for myopia at the Government Eye Hospital in Egmore. In persons with myopia, light rays fall in front of the retina instead of on it, resulting in poor vision.

Dr. Vasantha says: “Usually children develop myopia at the age of eight and until recently there was no way to arrest the progression of myopia.” By the time myopic children turned 19, they would be wearing thick glasses to correct refractive errors. “We began by prescribing overnight corrective lenses to half a dozen children. In some, the rise in power has been arrested. These patients can opt for laser correction or could move to wearing regular contact lenses when they are older,” she adds. According to K. Mohan, who is in charge of the patients using these orthokeratology lenses (as the corrective overnight lenses are known) at the hospital, in the intervening years some of the patients have gone abroad to pursue higher studies.

Despite the benefits the lenses are not prescribed for all. “The cost is prohibitive as each pair costs Rs.15,000. The lenses are imported from the U.S. At our hospital expensive investigations such as topography are done free of cost. And we suggest lenses only when we are sure that the patient will take care of the lenses well and handle them hygienically,” Dr. Vasantha says.

Protocols such as cleaning the lenses and not wearing them in case of allergic reactions must also be followed assiduously.

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Printable version | May 9, 2022 5:49:53 am | https://www.thehindu.com/sci-tech/health/rx/how-overnight-corrective-lenses-lend-clear-vision/article2517182.ece