Multifocal contact lenses are specially-designed contact lenses that have multiple powers within them. They are sort of like bifocals, but not quite the same. Many adults wear these lenses to correct their distance vision while also getting some plus power to help them see up close. But kids can also benefit from wearing multifocal contact lenses for myopia management, in order to slow the progression of nearsightedness.
How does myopia develop?
The exact mechanism of myopia development is still unclear. The leading thought is that myopia progression is caused in large part by the elongation of the eye. Research suggests that peripheral hyperopic defocus causes elongation of the eye. In English? Light focuses BEHIND the retina in the periphery, as shown in the image below. The periphery can be blurred even if the center is clear (this is the case with traditional, single-vision glasses or contact lens correction), and this peripheral blur is not really something we notice.
in the center, but behind the retina in the periphery
Image via kids orthok
How do multifocal contact lenses slow the progression of myopia?
Single vision glasses and contact lenses induce hyperopic defocus in the peripheral retina. Because center-distance multifocals have more plus power in the periphery, they induce peripheral myopic defocus. This acts like a stop signal to reduce the elongation of the eye (1). Several study results have supported the use of center-distance soft multifocal contact lenses for myopia progression, averaging a 40-50% reduction in myopia progression (2, 3).
Image via Review of Optometry
The CONTROL study found a whopping 72% reduction in progression of myopia over a one year period when compared to wearing single vision soft contact lenses (4), though this study involved myopic children with a specific focusing/postural issue (eso-fixation disparity at near).
One study using Proclear Multifocal D lenses with +2.00D add observed a 50% reduction in myopia and a 29% reduction in axial length in a small group of myopic children age 8 to 11 years over the course of two years (5).
Another study looking at NaturalVue Multifocal 1-Day contact lenses (an extended depth of focus lens) found around 80% of participants ages 6-19 showed slowing of myopia (6).
Most recently, the BLINK study found high add, center-distance multifocal contact lenses to be effective in slowing the progression of myopia in children aged 7 to 11 years old. The study spanned 3 years and compared myopia progression in kids using a high (+2.50D Biofinity Multifocal D lens) add power contact lens and kids using a medium (+1.50D Biofinity Multifocal D lens) add power contact lens to kids using a single vision contact lenses (7). The high add multifocal lens group showed a 43% slowing of refractive error and a 36% slowing of eye elongation when compared to the single vision group. It is worth noting for providers that the medium add lenses produced a smaller though not statistically significant effect, so the add power we use matters! (8)
The MiSight® lens is a dual-focus lens, featuring a concentric ring design with alternating vision correction and treatment zones. The two correction zones correct the child’s vision and provide clear vision, while the two treatment zones create 2 diopters of myopic defocus to slow the progression of myopia. Over a three-year period, comparing MiSight 1 Day to Proclear 1 day (a single vision lens), the MiSight group saw a 59% reduction in refractive error (aka prescription) and a 52% slowing in axial length (9).
Are there any adverse effects to using multifocal contact lenses for myopia management?
The design of multifocal lenses can reduce low-contrast visual acuity (10). Haloes around objects or lights are sometimes reported, especially in dim lighting.
As with any contact lens wear, there is additional risk because contact lenses sit on the eye. That is why they are classified as medical devices by the FDA. Studies have shown that the incidence of corneal infiltrative events related to contact lens wear in kids is no higher than in adults, and actually might be lower in the 8 to 11 year olds (11). Experts estimate that the incidence of microbial keratitis (corneal infection) in those wearing daily disposable contact lenses is about 2 per 10,000 wearers per year (12). So the risk of microbial keratitis is low, and good compliance with contact lens safety and care rules reduces that risk.
Here’s a great resource that goes into more detail: Are contact lenses safe for kids?
| CLIFFSNOTES: Multifocal soft contact lenses are a safe and effective way to slow the progression of nearsightedness (myopia) in children. |