The use of multifocal contact lenses in children may reduce the worsening of myopia or nearsightedness, finds a recent study conducted by the NIH. Compared with single vision contact lenses, multifocal lenses slowed myopia progression by about 43% over three years, according to a study published in the journal JAMA.
Myopia occurs when a child’s developing eyes grow too long from front to back. Instead of focusing images on the retina images of distant objects are focused at a point in front of the retina. As a result, people with myopia have a good near vision but a poor distant vision.
Single vision prescription glasses and contact lenses were generally used to correct myopic vision although they fail to treat the underlying problem. The study saw that multifocal contact lenses which are typically used to improve near vision of people over the age of 40 years improved myopic vision in children while simultaneously slowing myopia progression by slowing eye growth during the study.
The soft multifocal contact lenses have two basic portions for focusing light. The center portion of the lens corrects nearsightedness so that distance vision is clear, and it focuses light directly on the retina. The outer portion of the lens added focusing power to bring the peripheral light rays into focus in front of the retina.
By comparison, single vision glasses and standard contact lenses focused peripheral light to a point behind the retina, which prompted the eye to keep growing which progressed myopia.
Animal studies further showed that bringing light to focus in front of the retina cued the eye to slow growth. The higher the power added, the further in front of the retina it focused peripheral light.
The researchers also found that only the high-add power contact lenses produced a meaningful slowing of eye growth.
Study participants involved 287 myopic children, aged 7 to 11 years. At baseline, the children required -0.75 to -5.00 diopters of correction to achieve clear distance vision. The children were randomly assigned to wear single vision contact lenses or multifocal lenses, the outer lens of which were either high-add power (+2.50 diopters) or medium-add power (+1.50 diopters). They wore the lenses during the day as often as they could comfortably do so.
After three years, children in the high-add multifocal contact lens group had the slowest progression of their myopia. Mean myopia progression, as measured by changes in the eye prescription required to correct distance vision, was -0.60 diopters for the high-add group, -0.89 diopters for the medium-add group, and -1.05 diopters for the single vision group.
The multifocal lenses also slowed eye growth. The three-year adjusted eye growth was 0.42 mm for the high add group, 0.58 mm for the medium add group, and 0.66 mm for the single vision group.
Greater amounts of myopia and longer eyes were associated with an increased prevalence of eye conditions that lead to visual impairment. The researchers suggested that eye care practitioners should fit children with high-add power multifocal contact lenses in order to maximise myopia control and the slowing of eye growth.
“There is a clear benefit from multifocal lenses at three years, but further study is needed to determine the ideal duration for wearing the lenses. Researchers will need to determine how permanent the prevention of myopia progression will be once children stop wearing the multifocal lenses,” said Lisa A. Jones-Jordan, Ph.D., principal investigator of the Data Coordinating Center at the Ohio State University. A follow-up study is underway to see if the benefits hold among children in this study when they go off treatment, said the researchers.