Nearsightedness occurs when a child’s eyeball grows too much – and the level of sharpest vision is therefore in front of the retina. Now, a study with almost 300 children suggests that bifocal contact lenses can slow the progression of myopia. In these lenses, the part actually intended for farsighted people apparently counteracts the excessive growth of the eyeball. After three years, children with multifocal lenses had their myopia worsening 0.45 diopters more slowly than children with normal myopia corrective lenses.
The number of nearsighted people has increased sharply worldwide in the last few decades: in Germany around 40 percent of the population are affected, in Asia even up to 90 percent. Most often, this myopia develops during childhood and gradually worsens because the eyeball grows more than it should during this phase. With severe myopia, the retina is greatly stretched and there is a risk of retinal tears, retinal detachment, and cataracts and glaucoma. In addition to a genetic predisposition, causes of nearsightedness are too frequent reading or focusing on screens and a lack of direct daylight. Studies show that the UVB component of sunlight apparently triggers biochemical processes that slow down eyeball growth.
Multifocal contact lenses against the growth of the eyeball
In order to counteract the increasing myopia, Asia is already experimenting with a “prescribed” free passage for school children. Contact lenses are also said to help slow the growth of the eyeball in teenagers. So far, however, these have only had a limited effect. Jeffrey Walline of Ohio State University and his colleagues may have found a more effective method. In a clinical study with seven to eleven year old myopic children, you investigated whether a multifocal contact lens slows down the growth of the eyeball better than normal lenses used only to correct myopia. “Adults need such multifocal lenses when their eyes can no longer focus well on what is close – they are presbyopic,” explains Walline. In myopic children, the close-focusing areas of the contact lenses should also concentrate the peripheral light in front of the retina to form the image – with monofocal lenses the image plane of this field of view is usually behind the retina. This focusing of all the light in front of the retina is intended to stimulate the eyeball to stop growing.
The researchers tested whether this works with 287 children who had between minus 0.75 and minus 5.00 diopters at the start of the study. Some of the children were then given soft, multifocal contact lenses with 2.50 plus diopters in the marginal area, another group wore lenses with 1.50 plus diopters and the third group wore monofocal lenses that only corrected their myopia. The children wore the contact lenses as often as they could during the day. “About half of seven-year-olds get along very well with the lenses,” reports Walline. “With the eight-year-olds it is almost all.” After three years, the scientists examined how the children’s eyeballs and myopia had developed.
Significant braking effect on myopia
The evaluations showed clear differences between the three study groups: in the children with normal contact lenses, myopia had deteriorated by an average of 1.05 diopters, in those with the weaker farsighted portion by 0.89 and in the group with the 2.50 plus -Dioptres in the lens only by 0.60 dioptres. “Compared to the monofocal lenses, the multifocal lenses have slowed the progression of myopia by up to 43 percent,” says co-author David A. Berntsen of the University of Houston. At the same time, the eyeball of the children with the combination contact lenses also grew less – on average by 0.23 millimeters less than the children with the monofocal lenses.
“So the multifocal lenses have brought a clear advantage over the three years,” says Walline’s colleague Lisa Jones-Jordan. “However, more studies are needed to find out how long the multifocal lenses should ideally be worn. In addition, it has to be determined how long this braking effect will last when the children stop wearing this lens. ” A follow-up study has already started. If the results are positive, this could open up another opportunity to put a stop to the worldwide myopia epidemic.
Source: Jeffrey Walline (Ohio State University, Columbus) et al., JAMA, doi: 10.1001 / jama.2020.10834