By Linda Conlin, ABOC, NCLEC
Uncorrected myopia is the leading cause of distance vision impairment globally. Approximately 30 percent of the world is currently myopic, and the number is increasing, projected to affect 50 percent of the world population by 2050, according to the International Myopia Institute. Early intervention and detection in children are key to reducing the impact of myopia on their long-term ocular health and improving their future lives. New developments in spectacle lenses, contact lenses, and orthokeratology have been shown to manage the increased incidence of childhood myopia.
Different types of eyeglass lenses have been shown to slow the progression of myopia. A recent study explored the efficacy of spectacle lenses designed for myopia management versus conventional single-vision spectacle lenses for myopia control. The data revealed that lens designs incorporating both highly aspherical and slightly aspherical lenslets reduced the rate of myopia progression and eye elongation over the course of a two-year period. New spectacle lens designs for myopia control incorporate either “lenslet” or “diffusion” technology. Lenslets can be thought of as tiny 1 mm diameter mini-lenses distributed across the lens surface, helping to send a specific type of signal to the myopic eye to slow down eye growth.
Different lens designs incorporate lenslets. One design features concentric rings of highly aspherical lenslets. Each ring has lenslets of a different power, and within a ring, the lenslets touch. There is a clear central zone and spaces between each ring for sharp distance vision. In another design, lenslets are all of the same power and in a honeycomb array. It also has a clear central zone with spaces between each lenslet for sharp distance vision. A different lens design uses microscopic diffusers and has a smaller central clear zone, creating a diffusion or blur of light around the edges of the lens.
Tip: Become familiar with the different lens designs by working with the prescriber, manufacturers’ reps and product information resources to determine the best lens for the patient.
There is an ever-increasing availability of soft contact lenses that slow myopia progression. A recent study found that contact lenses for children are just as safe for children as they are for adults and may be a good alternative for active children’s lifestyles. One effective method of myopia management includes the use of daily multifocal soft contact lenses. Myopia control soft contact lenses are designed to slow the accelerated eye growth of childhood myopia based on how images are focused on different parts of the retina. When standard vision correction is used, the central part of the image is focused on the retina for clear vision, but the peripheral light rays focus behind the retina, called peripheral hyperopic defocus. Research indicates that this generates a growth signal for the eye, inducing myopia. Specially designed lenses focus light in front of the retina, slowing eye growth and myopia progression.
Contact lens designs for myopia control include simultaneous vision soft lenses, such as aspheric progressive, dual-focus, traditional multifocal, ring focus and extended depth of focus designs. Each design utilizes different zones of power within the lens to focus peripheral light rays in front of the retina to act as a stop signal for myopia progression while also optimizing vision correction.
Tip: Children may prefer the comfort and convenience of contact lenses for active lifestyles. Become familiar with the various lens designs and the basis for the doctor’s lens choice for each patient.
Orthokeratology is a reliable and widely accepted option for myopia management. Special contact lenses are worn during the night to flatten the cornea. Flattening the cornea shortens the distance to the retina, so the light will focus properly. At the same time, peripheral images that focus behind the retina are brought forward. Orthokeratology has the added benefit of freeing the patient from using correction during the daytime. It allows for more parental control and is a great option for athletes, especially swimmers. There are many different contact lens manufacturers making ortho-k lenses and consequently, many different ortho-k lens designs on the market. Moreover, current research shows promising signs that ortho-k lenses can be modified to increase the myopia control effect. Fitting and follow-up for ortho-k lenses are critical to determine the optimum lens design for the individual patient. To monitor efficacy, the doctor will measure myopia and compare it against average expected myopia progression rates.
Tip: The International Myopia Institute recommends checkups every six months when ortho- k is used for myopia control.
Although there’s no cure for myopia, early intervention helps to manage the condition. Research continues, but ECPs currently have a variety of eyeglass and contact lens designs in their toolbox to slow its progression.