Types of Myopia Control Treatments
Myopia, or nearsightedness, is a signiﬁcant public health concern in many countries around the world. It is estimated that in 30 years, approximately 50% of the world population will be affected by myopia.
There are four clinically accepted methods of myopia control therapies: the most common and most studied method is Orthokeratology or Ortho-K, low dose atropine eye drops, peripheral defocus multifocal soft contact lenses and in some cases specialized multifocal eyeglasses. Eye doctors throughout the world use various methods based on patient age, prescription and severity of disease, sometimes combining methods for maximum effect.
Myopia Control Methods //
Orthokeratology (ortho-k), when used for partial or full correction of myopia (nearsightedness), has been shown to slow myopic progression in children by 36-56% as compared to their spectacle or contact-lens wearing peers.
The typical ortho-k treatment consists of fitting a specialized contact lens (retainer lens) that is worn during sleep, that reshapes the cornea to correct for the myopia. This is similiar to the way LASIK works except it is done at a more superficial layer of the cornea and as such is reversible and adjustable. There are additional effects induced by the ortho-k treatment which are outlined in more detail below.
The most commonly accepted theory on how ortho-k decreases axial elongation (myopia progression) relies on the peripheral "defocus" created on the retina by the corneal changes made by the rigid lens. Studies have shown that those at greatest risk for myopic progression were those whose peripheral refraction was hyperopic (far-sighted) - that is, they had a hyperopic peripheral 'defocus'.
A number of studies have since suggested that treatment approaches to myopia correction should address this peripheral refraction as a means of slowing further axial elongation. When looking at subjects treated with ortho k, we see that the lenses do in fact introduce a peripheral myopic defocus while leaving the central refraction close to plano or zero (no prescription).
This effect is achieved by limiting the axial elongation of the eye which is of particular concern in high myopes (>6.00D) and children, where myopic progression has been shown to proceed at a faster rate than average. As early intervention is considered beneficial if not essential.
LOW DOSE ATROPINE THERAPY
Atropine for the treatment of childhood myopia has in recent times been extensively researched. An early study from 2006 was the first randomized, double-masked, placebo-controlled trial designed primarily to study whether topical (eyedrop) 1% Atropine can prevent the progression of low and moderate myopia effectively and safely in children between 6 and 12 years of age over two years study duration.
The results of numerous studies have shown that Atropine 1% did in fact slow the progression of low to moderate myopia by 77% with no serious adverse events. It was also found that lower dose atropine (0.01%) was just about as efficacious as the higher dose with less side effects, such as light sensitivity, than the higher dose regimen.
NATURAL LIGHT THERAPY
Things that protect against nearsightedness or slow the worsening of nearsightedness of particularly important, as they can be
implemented at the population level and would not involve
pharmaceutical interventions in children.
Comparisons of children with and without myopia have identiﬁed time spent outdoors as a significant factor for both the presence of nearsightedness and the progression of nearsightedness. The ﬁrst study to identify this correlation analyzed myopia progression of school children and found increased time outdoors correlated with decreased progression.
Further studies on this issue have suggested that natural light exposure such as when spending time outdoors, much more than other factors like exercise for instance, was the most likely providing the protection against myopia.
These results changed our approach and we now realize how environ-
mental conditions during the growth years could change the rate and severity of myopia.
The increasing rates of myopia seen today were once thought to be solely due to prolonged near work. As we have already mentioned new research has strongly suggested that a leading cause of myopia is lower exposures to certain wavelengths in sunlight and their beneficial effects beginning at the retinal level.
Research and studies on myopia progression now suggest that the “dopamine reaction" to certain light wavelengths in the retina (dopamine is instrumental in controlling eye growth and therefore the development of myopia) is therefore a significant factor for myopia progression. Therefore a beneficial therapy is likely to be found in those strategically beneficial wavelengths of sunlight.
Specialized LED illumination for indoor use offers a helpful solution that can be prescribed to help maintain contact with those beneficial wavelengths of light particularly in the winter months when light deprivation is most significant.
MYOPIC MULTIFOCAL EYEGLASSES
Regular multifocal eyeglasses have long been prescribed for myopia control. The theory behind it stemmed from the idea that near point stress such as with reading and other near tasks, can induce myopia from accommodative (neaar focusing) induced stress and changes to accommodative tone. The results were not super promising clinically until the development of the Defocus Incorporated Multiple Segments (DIMS) eyeglass lens.
In a clinical trial, children wearing the DIMS Eyeglass Lens had significantly less 59% myopic progression, compared with those wearing single vision lenses, according to the release.
The study also showed that wearing the DIMS Spectacle Lens stops the progression of myopia in some children; 21.5% of children in the treatment group had no myopic progression whereas only 7.4% in the control group had no myopic progression.
This lens will be available to us in the US (hopefully) soon.
PERIPHERAL DEFOCUS CONTACT LENSES
The U.S. Food and Drug Administration approved the first contact lens in late 2019 indicated to slow the progression of myopia (nearsightedness) in children between the ages of 8 and 12 years old at the initiation of treatment.
The MiSight contact lens is a single use, disposable, soft contact lens that is discarded at the end of each day, and is not intended to be worn overnight.Soft multifocal contact lens wear resulted in a 50% reduction in the progression of myopia and a 29% reduction in axial elongation during the 2-year treatment period compared to a historical control group.
Other soft multifocal contact lenses with similar designs are also emplolyed for myopia control such as the NaturalVue 1-Day and the C-VUE Monthly Lens. Which lens design is best employed are determined by the fitting characteristics needed as well as the best optics to match the fitting and visual situation for any one patient. That determination is made by the fitting doctor at the time of consult and may be adjusted as treatment needs change.
NEW THERAPIES BEING CURRENTLY STUDIED
Research suggests a link between myopia and the brain chemical dopamine. All-natural sunlight may be the key.
Research has looked into the direct effects of dopamine on eyeball development. A survey of the most current research has suggested strongly that low dopamine levels in the retina was associated with elongated eyeballs and thus high and progressive myopia in animal studies. This suggests a possible therapeutic target for future clinical use so that adequate dopamine levels can be attained and that can help normalize proccess and attain the correct length of the eye necessary to obtain normal vision.