New scientific evidence on how feedback from the eye affects visual development may lead to more effective approaches to treating myopia (nearsightedness) in children, reports a paper in the September issue of Optometry and Vision Science, official journal of the American Academy of Optometry. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.
In particular, optical treatment strategies to correct peripheral vision may be effective in slowing the progression of myopia in children. The new discoveries and their clinical implications are the subject of the Charles F. Prentice Award Lecture by Earl L. Smith III, O.D., Ph.D., of University of Houston.
Evidence Builds Case for Treatments Addressing Peripheral Vision
Dr. Smith summarizes recent studies of the vision-dependent mechanisms regulating visual development. Myopia is a common problem in children, making it difficult for them to see objects clearly. Over time, myopia can get steadily worse, potentially leading to permanent vision loss if the extent of the myopia is severe. Vision correction (glasses or contact lenses) are needed to improve vision, and possibly to prevent progressive myopia.
The eye grows and develops in response to visual feedback from the eye. In the past, optical treatment strategies for myopia have emphasized the correction of central, or foveal, vision. (The fovea is the central pit of the retina, where visual acuity is sharpest.) Optometrists have generally assumed that signals from the fovea have the greatest impact on normal visual refractive development.
However, recent experiments in laboratory animals have suggested that visual development is affected by "local retinal mechanisms"—and not by central vision, according to according to Dr. Smith. Some studies have even suggested that "foveal vision is not essential for many vision-dependent aspects of refractive development."
Instead, much of the feedback affecting eye growth and visual development seems to come from the peripheral retina—areas away from the center, which make up most of the retina. There's even evidence to suggest that when there are conflicting visual signals between the central and peripheral retina, the peripheral signals predominate.
Taken together, the new evidence suggests that optical strategies to improve peripheral vision may have a greater impact on visual development than strategies addressing central vision. Based on the data, optometrists may want to reconsider their vision prescriptions for children with myopia, Dr Smith believes.
More Research Needed to Evaluate New Optical Strategies
"We are on the verge of having a number of optical treatment options that do effectively slow myopia progression," Dr. Smith writes. Clinical studies have shown that strategies specifically targeting peripheral vision can reduce the rate of worsening myopia. However, Dr. Smith notes that most of these trials are only preliminary. Larger and longer-term studies will be needed to assess the new lens designs and answer other questions about the effects of peripheral strategies.
Dr. Smith emphasizes that the new strategies won't eliminate existing myopia—to maximize the impact on the developing eye, treatment should begin as early as possible. He concludes, "Given the increasing prevalence of myopia, having an optical treatment strategy that produces a clinically meaningful reduction in myopia progression would have huge public health benefits."
For his paper, Dr. Smith was named winner of the American Academy of Optometry's Charles F. Prentice Medal for 2010. Established in 1958, the Charles F. Prentice Medal is awarded annually to an outstanding scientist who has contributed significantly to the advancement of knowledge in the visual sciences.
Source Optometry and Vision Science