This blog will talk about the difference between multifocal contacts/glasses and peripheral defocus contacts/glasses. The reason we need these treatment options is the fact that regular glasses and contacts actually encourage myopia to increase. This happens because the central vision is placed correctly in the front central retina but the peripheral vision is placed behind the peripheral retina. The peripheral retina will then compensate by encouraging the eye to grow and increase in axial length. Axial length simply refers to the length of the eye. At this point, your eye prescription becomes a basic physics equation. The longer the eye – the bigger the prescription. A good link for additional information is below:
Progressive Addition Lenses (PALs) have been shown to help eliminate the peripheral defocus but they were not designed specifically for that purpose. Specific peripheral defocus lenses and contacts do provide slightly better results that than the PALs. Zeiss (from the link above) and Essilor both offer defocus lenses for spectacles. Coopervision is making peripheral defocus contacts called MiSight. MiSight is a daily spherical contact lens that has completed a 4-year study to show that it does indeed reduce myopic progression. MiSight is not approved by the FDA for the US yet, but it has been approved for most other major markets in the world. I imagine CooperVision is doing their best to get it available here very soon.
At this time though, contacts in the US will be PALs and patients can have the option of defocus lenses for glasses. For cost-effective purposes, PALs may still be your best option until the defocus lenses become more popular and available. On a side note, patients with high astigmatism may find the PAL contacts difficult, and glasses will be their best option for myopic control. Of course, the toric (astigmatism) lenses can still be used for sports, special events, etc., but we would encourage the use of glasses for the primary myopia correction.
On the flow sheet from Brien Holden in entry #1, you may have noticed time outdoors as a factor for controlling myopia. We will explore things that don’t involve your wallet next time. Again, don’t forget to schedule your eye exam.