Increasing prevalence of myopia underscores need for control

The incidence of myopia has increased significantly over the past several decades, according to several researchers and presenters who discussed the topic at the American Academy of Optometry meeting in Denver in November 2014.

Citing a 2009 study from Vitale and colleagues published in the Archives of Ophthalmology, presenters reported that there has been a 17% increase in myopia in 30 years and a prevalence of 42% in the U.S.

Kathryn Richdale, OD, PhD, FAAO, and David Troilo, OD, PhD, FAAO, said during their presentation at the AAO meeting that myopia is a public health concern because “prevalence is increasing much faster than anticipated.”

Patrick Caroline, FAAO, acknowledged the contention over the roles of nature and nurture in myopia, but said that eye care providers need to focus on controlling myopia before preventing it.

“It’s not a debate – children are growing up in a different environment now,” he explained in his presentation. “They are not spending as much time outdoors. When children spend more time outdoors, they are less likely to become myopic.”

Caroline also cited research from Noel A. Brennan, OD, PhD, supporting the increased risk for choroidal neovascularization, glaucoma, cataract and retinal detachment with myopia.

“We in the eye care community have been searching for the Holy Grail – preventing myopia,” he continued. “We have some clinical strategies that have done well and some that have not fared so well.”

Caroline and other presenters discussed various options eye care providers have in treating myopia and where the research is leading.

Undercorrection

Citing studies in Vision Research and Clinical & Experimental Optometry from Chung and colleagues and Adler and colleagues, respectively, Richdale noted that while one might think undercorrection works similarly to adding positive defocus, the method lacks support from clinical studies.

“Studies have shown that undercorrection of myopia enhances rather than inhibits myopia progression,” Richdale explained. “If myopic defocus slows eye growth, why doesn’t undercorrection work? It may not be enough of a stimulus and it can leave hyperopic defocus in the periphery, which may stimulate eye elongation. In addition, the effects may be reduced by changes in viewing behavior.”

Bifocal, progressive addition spectacles

Richdale and Troilo also discussed the Correction of Myopia Evaluation Trial (COMET) and COMET 2 studies, noting that while there were some statistically significant decreases in myopia progression, clinically meaningful differences were found only in children with near esophoria and higher lags.

Another study published in Investigative Ophthalmology and Visual Science by Bernsten and colleagues demonstrated that bifocal glasses may have limited efficacy due to their primary effect on the superior retina, they explained.

“Putting myopic defocus on the retina can slow myopia,” she said, “but it’s limited in its amount and to the area of the retina.”

Multifocal contact lenses

Richdale and Caroline cited several promising studies of multifocal contact lens wear. One study published in Optometry and Vision Science by Walline and colleagues found a 50% reduction in myopia progression with soft multifocal contact lens wear.

“We have to deliver to the eye a significant amount of plus power,” Caroline said. “We can do that very effectively with advanced orthokeratology designs, but we can also do this quite easily with a multifocal soft contact lens.

He continued: “It has to have critical ingredients – center distance multifocal lens design, which rules out 90% to 95% of lenses, which are centered near.”

Caroline explained that, in his experience, the CooperVision center distance multifocal design is a great choice, especially because it comes with add powers up to +4 D. He did note that other manufacturers, including ABB Optical, Advanced Vision Tech, Alden Optical, Art Optical, Metro Optics and Special Eyes also provide good options.

“It’s one of the major obsessions at the university – how to better deliver the optics,” Caroline shared. “The time is now. We’re doing okay with current lens designs, but down the road I think we’ll do a better job.”

Pharmacologic intervention

In two studies evaluating the use of atropine in myopic children, Chia and colleagues reported promising results, Caroline said.

The studies, published in Ophthalmology and the American Journal of Ophthalmology found that atropine 0.01% demonstrated comparable efficacy to stronger concentrations, has fewer side effects and less myopic rebound.

“They looked at lower concentrations of atropine for controlling myopia,” he explained. “They achieved a 59% reduction in myopia with 100 times less concentration. It was a very positive study.

“Lower doses of atropine have less rebound,” Caroline continued. “I see atropine as an adjunct therapy, not a primary therapy. Go with orthokeratology, multifocal soft lenses first. If the child continues to increase, this is where adjunct intervention will play its major role.”

Orthokeratology

In another AAO presentation, Karen Lee, OD, FAAO, FSLS, and colleagues cited several studies, including the Longitudinal Orthokeratology Research in Children (LORIC) study, the Retardation of Myopia in Orthokeratology (ROMIO) study and the Corneal Reshaping And Yearly Observation of Nearsightedness (CRAYON) study, which demonstrated a smaller increase in anterior chamber depth as well as less change in axial length.

Noting that the CRAYON study demonstrated a 50% reduction in myopia, Lee and colleagues shared their specific recommendations for eye care practitioners who wish to prescribe ortho-K.

“I generally recommend to those first starting fitting ortho-K or corneal reshaping to find a design that you understand and you know, but always have a plan B, because it won’t work for all patients,” Harue J. Marsden, OD, MS, FAAO, explained. “You don’t have to know and understand all designs. Understand the basics regarding what changes need to be made if the lens decenters, etc.”

Marsden noted that while practitioners will need to be certified, they can typically do so online.

She continued: “Our recommendation is to start simple. Find a friend or family member, a low myope 2 to 3 D; don’t start with 5 D, the high end of vision shaping treatment lenses, or 6 D, the high end of corneal refractive therapy lenses, and don’t start with a high astigmat.”

Diana Nguyen, OD, explained that one would have the most success with ortho-K candidates who have myopia less than 3 D, and that “central, regular, with-the-rule astigmatism is easier to work with.

“With the progression of myopia, if that patient is really progressing, discuss this method with the parents,” she said. “If the parents are highly myopic, too, and it looks like the child is going to be the same, discuss this option. Good ortho-K candidates are those who do not require perfect vision, because vision may fluctuate throughout the day.”

Lee shared pearls about fitting the lenses.

“In the center, you have the base curve or treatment zone or central optical zone,” she described. “This portion will be flatter than the corneal apex. This portion of the lens is rarely manipulated for centration purposes. The second portion is the reverse curve or the fitting curve, which controls the sagittal depth of the lens. You can get the precise amount of applanation by varying this curve.

“The landing zone is the third portion,” she continued. “It is also known as the alignment curve or zone. Lenses can have multiple alignment zones. The last portion is the edge lift or peripheral zone. It will fit a little steeper than traditional peripheral curves of a normal gas-permeable lens. We don’t want it so steep that it seals off and there’s no tear exchange.”

Nguyen and Marsden also discussed choosing the first lens and how every manufacturer differs in that regard.

“Some manufacturers use an empirical method,” Nguyen said.

“You collect data and send it to a consultant and they suggest an initial lens,” Marsden said. “Computer-based lens selections take topography data. It would be a disservice to not use corneal topography. You then send the data to the lab and they provide the lens to try on the patient. You bring the patient back, take more measurements and send it to the lab for adjustments to the lens.”

Marsden did note a downside to computerized systems.

“You have the responsibility based on your observations on how the lens fits and how the cornea responds,” she acknowledged. “It doesn’t ask about staining or decentration. They are great adjuncts to your ortho-K or corneal shaping armamentarium, but you still need to understand the biomechanics of that lens and how it relates to the cornea.”

What the future holds

Various research regarding myopia control was presented at the AAO meeting, including research combining several traditional myopia treatments in a new way.

Alex Hui, OD, PhD, FAAO, a researcher with the Centre for Contact Lens Research, shared study results that he and colleagues had collected on the combination of atropine and pirenzepine with commercial hydrogel and silicone hydrogel contact lenses.

“None of the currently available studies have been able to arrest the progression of myopia,” he said, noting that their study was designed to evaluate whether a combination device would be effective in doing so.

Researchers evaluated six daily disposable contact lenses and two daily disposable multifocal contact lenses. The lenses were soaked in 1% and 0.1% concentrations of atropine and pirenzepine for 24 hours, Hui described.

“We were able to show that there are various uptakes and releases from these different types of drugs and these commercial materials, but none of them were able to sustain any type of release,” Hui reported. “We could see potential for these commercial lenses that are completely unmodified to be used in this controlled context if we use it in a daily disposable form.”

In the study abstract, the researchers discussed the potential of the drug eluting lenses.

“With recent clinical trials on myopia control demonstrating partial reduction in progression using multifocal contact lenses or pharmacological treatments, a treatment strategy which combines the two techniques is a next logical development,” they wrote. “This work suggests that such an approach is worthy of investigation, if rapid delivery of small amounts of drug are sufficiently synergistic with the impact of lens design. Hydrogel materials appear more promising than silicone hydrogels.”

Hui concluded: “You can envision a child wearing a lens that has been preloaded with this particular drug where they get the doses that they need to control the myopia pharmacologically as well as using the bifocals throughout the course of the day and disposing of them at the end of the night and using a new lens the next day.” – by Chelsea Frajerman