Clinicians have numerous options to consider in patients in whom myopia control may be needed.
The prevalence of myopia differs throughout the world, Dr. Ruskiewicz explained. In the Sherpa of Nepal, the prevalence is the lowest, at only 2%. In Israel, myopia has a prevalence rate of 18%; in the United States, 25%. But Taiwan has the highest prevalence of myopia in the world, at a rate of 84%. Singapore is not far behind, with a prevalence of 76%.
"In China, Singapore, and Taiwan, myopia is no longer a problem-it's an epidemic with very high prevalence rates, where the vast majority of people are myopic, and a lot of that myopia is high," he noted.
Several pharmaceutical interventions have been shown to delay or halt the progression of myopia, including atropine, pirenzepine, tropicamine, cyclopentolate, and levodopa, Dr. Ruskiewicz said.
Atropine is one of the oldest pharmaceutical interventions for myopia. It is a muscarinic antagonist that binds with M3 and M1. M3 controls accommodation and mydriasis.
"Atropine is used rather extensively in Taiwan. I personally do not keep atropine in the office, because the packaging is similar to other mydriatic products," he said, adding that atropine has an extensive potential for reactions. These include hallucinations, photophobia, and cycloplegia. Atropine, however, works well to control myopia, and is available at a low-cost.
Pirenzepine 2% gel has been evaluated by some clinical trials in the United States for treatment of myopia. It has better patient acceptance and is easy to use, but myopia control is not as good as that achieved with atropine. The cost of pirenzepine is unknown because it has not completed U.S. clinical trials.
Levodopa, indicated for the treatment of Parkinson's disease, has been shown to be helpful in inhibiting form-deprivation myopia in animal studies. The theory behind the use of levodopa to control myopia is that both D1 and D2 dopamine receptors are widely present in the retina and may play a role in emmetropization.