Researchers work to address increasing incidence of myopia

Currently, more than 1.6 billion people in the world are myopic, and this number is expected to increase. Although today’s conventional contact lenses and spectacles correct this refractive error, they do not slow the progression of the condition. Because myopia can progress rapidly in childhood and adolescence, some practitioners feel that more proactive anti-myopia strategies should be undertaken as early as possible.

Brien A. Holden, PhD, DSc, LOSc, said he believes that future myopia interventions will address the problem across a variety of therapeutic approaches. Image: International Centre for Eyecare

“Parents are very disturbed about their children progressing in myopia year after year,” Brien A. Holden, PhD, DSc, LOSc, chief executive officer of the Brien Holden Vision Institute, Kensington, New South Wales, Australia, told Primary Care Optometry News. “I remember vividly a very research-conscious, academic mother saying to me, ‘My husband and I are both quite myopic, and we’ve watched our children grow in myopia by 1, 2, 3, 4 and 5 D in 8 or 9 years.’ She said she felt like a very bad parent.”

The limitation of many current myopia correction methods has led to a great deal of research into new optical approaches to slowing myopia progression. In particular, clinicians are studying the use of lenses that address peripheral defocus, such as orthokeratology (ortho-K) and anti-myopia contact lenses.

“It is not possible at this stage of our knowledge to predict which anti-myopia approach is best for an individual child,” Helen Swarbrick, PhD, FAAO, professor at the School of Optometry and Vision Science, University of New South Wales, said in an interview. “Studies are still being conducted to see which approaches are the most efficacious.”

The goal of peripheral defocus

A state of defocus on the peripheral rather than central retina is thought to be an important mechanism in controlling the myopia progression. Children with myopia are thought to have peripheral hyperopic defocus, which causes the eyeball to grow in an elongated shape.

“The key thing a lens needs to do is impose a certain kind of defocus on the retina,” Earl Smith III, OD, PhD, dean of the University of Houston College of Optometry and prominent myopia researcher, told PCON. “Our goal is to impose the defocus on the periphery of the retina in order to maintain good central vision.”

Dr. Smith said it is important that a lens induce this defocus on the peripheral retina without diminishing central vision.

“What we want is a lens that optimizes the image in the central retina,” he said, “but then we want to incorporate power profiles in the periphery of the lens without compromising vision in the central retina.”

Ortho-K research

A study conducted by Dr. Swarbrick and colleagues published in Optometry and Vision Science indicated that ortho-K is an effective approach to manipulating peripheral defocus.

Helen Swarbrick

The study of 16 myopic children found that overnight wear with an ortho-K lens in one eye for 3 months significantly reduced myopia in the central 20-degree visual field, leaving the peripheral visual field with relative myopic defocus.

Ortho-K lens wear was found to reduce central myopia from an average of -2.37 D to -0.54 D after 3 months of wear, with no significant change in astigmatism.

“Ortho-K has been shown to slow the progress of myopia through its effect on corneal shape and, indeed, by affecting the peripheral image and the actual elongation associated with peripheral hyperopia,” Dr. Holden said. “So ortho-K is definitely a viable option.”

In a more recent study presented at the 2011 Association for Research in Vision and Ophthalmology meeting, Dr. Swarbrick and colleagues found that overnight ortho-K suppressed axial length growth and slowed myopia progression over a 12-month period.

In this study, 26 myopic children (ages 10.5 years to 16.7 years) wore an overnight ortho-K lens in one eye and a gas permeable (GP) lens for daily wear in the other eye for 1 year. At 6- and 12-month follow-up, the ortho-K eyes showed no axial length growth and a slight reduction in myopia from baseline. The GP eyes showed axial length growth and myopia progression.

Opinions on ortho-K

According to Dr. Smith, ortho-K is definitely effective, but it is best suited to patients with high myopia.

“With ortho-K, the amount of anti-myopia therapeutic effect is proportional to the area you are trying to correct,” he said. “The therapeutic effect increases with the amount of myopia you have, so if you have more myopia, you get more effect.”

Earl Smith

He added that for patients with lower levels of myopia, ortho-K may be unnecessarily invasive.

“Ortho-K lenses are more complicated and intrusive than regular contact lenses,” he said.

Dr. Swarbrick said the fact that ortho-K lenses do not need to be worn during the day might reduce some of the issues connected to full-time lens regimens.

“Orthokeratology lenses are worn during sleep, which carries its own risks, but these lenses do not need to be worn during the day. This reduces the overall risk associated with full-time contact lens wear.”

Dr. Holden said although ortho-K’s availability is largely “confined to developed countries,” he considers it a good approach to myopia control.

“If I had high myopia and my partner also had high myopia, I would definitely seek ortho-K for my children,” he said.

Anti-myopia contact lenses

Another approach to myopia control is the use of a new type of contact lens specifically designed to decrease peripheral hyperopia. One-year results from a 3-year study of these lenses were published in the December 2011 issue of Investigative Ophthalmology & Visual Science.

For this study, in which both Dr. Holden and Dr. Smith are involved, about 85 Chinese children between the ages of 7 and 14 are being evaluated. These children, who had baseline myopia from sphere -0.75 to -3.50 D and cylinder =1.00 D, were divided into two groups. One group of 45 children was fitted with the new contact lens, and a second group of 40 children wore normal, single-vision, spherocylindrical glasses. The two groups were matched for age, sex, parental myopia, refractive error and axial length.

At the 1-year follow up, after adjusting for parental myopia, age, sex, spherical equivalent values and compliance, the estimated progression in spherical equivalence was 34% less (-0.57 D) with the novel contact lenses than in the spectacle group (-0.86). The estimated axial length increase was 33% less in the contact lens group (0.27 mm) than in the spectacle group (0.40 mm).

These 1-year results suggest that manipulating peripheral hyperopia can change refractive development and slow myopia progression.

Although the subsequent 2 years of follow-up have not yet been published, Dr. Holden said they were consistent with the findings reported in 2011.

“The trends in that research project continued as reported for another 2 years,” he said. “So the peripheral plus lenses do slow the progress of myopia and axial length by 35% to 40%, and it lasts.”

Dr. Smith said anti-myopia contact lenses are a good choice for patients with normal levels of myopia and do not appear to have significant drawbacks.

“An interesting advantage is that they actually improve peripheral vision,” he said. “And as far as I can tell, there is no disadvantage to wearing them.”

He said he would recommend that such lenses be worn as soon as myopia is diagnosed.

“The therapeutic effect is only one that slows the development of myopia, it doesn’t stop it,” he said. “So the earlier you can intervene, the more likely you are to have a larger effect.”

Other studies

According to a study published online in Optometry and Vision Science, standard spherical soft contact lenses can produce “significant absolute myopic defocus” in the peripheral retina and may, therefore, be useful in reducing the progression of myopia.

In the study by Kwok and colleagues, 10 young adults with high myopia (-6.00 D) were treated with soft spherical contact lenses. The researchers used an open-field autorefractor to measure on- and off-axis refractions in primary gaze, with or without a contact lens, every five degrees out to 20 degrees horizontally in the nasal and temporal retina. The results were evaluated as mean sphere and astigmatic vector components.

The study found that the mean sphere showed a significant shift from hyperopic relative peripheral refraction without contact lenses to myopic relative peripheral refraction upon correction.

“If peripheral refraction does indeed influence myopia progression,” the researchers noted in the abstract, “then our results suggest that in high myopia, standard soft contact lenses may be beneficial in reducing myopia progression.”

Bifocal contact lenses

Another approach currently used to slow myopia is treatment with bifocal contact lenses. Dr. Holden said these lenses have definite advantages but are not necessarily ideal for this purpose.

“In many circumstances, bifocal contact lenses can slow the progress of myopia by around 40%,” he said. “However, it depends on the level of visual compromise those bifocal contact lenses produce in children and, indeed, they are intended to produce visual compromise by having both distance and near foci created for the bifocal effect.”

Dr. Smith said bifocal lenses “work, but are not optimal,” but added that currently there are few commercially available alternatives.

“If, for example, it was my son or daughter, bifocal lenses might be a good option,” he said. “You just have to be judicious in how you fit them. But you still get a lens that doesn’t decrease central vision.”

Pharmaceutical agents

Anti-muscarinic medications such as atropine and pirenzepine have also been used to slow myopia progression. According to a study published in 2004 in Archives of Ophthalmology, 0.5% atropine used on a daily basis could almost arrest myopic progression in children who used the drug for a year.

However, follow-up data has shown that atropine has a significant “rebound effect,” wherein the treated eyes become more myopic after the medication was discontinued.

Dr. Holden said that while medications such as atropine may be effective, they might ultimately be unhealthy for children.

“It is quite clear that agents such as atropine can have a dramatic effect on the rate of progress of myopia, but they are neither healthy nor synergistic with a good vision lifestyle,” he said. “However, very low dose forms of this therapy are being tested, and it may be a visual proposition as an initial treatment for high myopia in young children.”

Dr. Holden does predict, however, that pharmacological treatment will probably play some future role in managing myopia in children.

“I suspect that drugs will be used in cases of high myopic parents with children who are becoming myopic at an early age and are progressing rapidly,” he said. “I think these drugs will be used for a period of time, and in as mild a form as possible.”

Commercialization efforts

Within the ophthalmic industry, companies are working to address the problem of myopia progression from several different angles. Glen Moro, global head of innovation for Alcon’s Vision Care Group, said the company is dedicated to addressing this pervasive visual problem.

“Alcon is actively involved in myopia intervention,” Mr. Moro said in an interview. “We are exploring several avenues, both optical and pharmaceutical, with the goal of slowing the progression of myopia.”

Mr. Moro said Alcon’s research efforts are currently in various stages of investigation.

“We are looking at some technologies that are proprietary,” he said.

“Alcon intends to be a key contributor to this new frontier of myopia intervention,” he said.

Representatives from Bausch + Lomb, Vistakon and CooperVision had no comment on this topic for Primary Care Optometry News.

What does the future hold?

Dr. Holden said he believes that future myopia interventions will address the problem across a variety of therapeutic approaches.

“I believe it will be a combination of visual and ocular hygiene approaches, in other words, choosing a healthy lifestyle for children so that they spend much time outdoors, which seems to have a significant effect on reducing the risk of myopia,” he said. “I think children will wear anti-myopia spectacles when they need to and anti-myopia contact lenses when they can.”

He said he feels that Asian children, in particular, should be treated in a proactive manner, due to their increased risk of myopia.

“If I’m to take an extreme view, I would say anti-myopia treatment is indicated for every Asian child, because the rate of myopia progression is now of epidemic proportions, with more than 50% of the population being myopic. In some places, like Taiwan, more than 80% of 18-year-old girls are myopic.”

He said children with highly myopic parents might also be considered for automatic intervention.

“You could say it would make sense for all children who are likely to become myopic to be wearing contact lenses from the age of 7 or older,” Dr. Holden continued. “It will be a long time before such an approach is taken; however, any child born of myopic parents should be using an anti-myopia strategy across the range of more outdoor exposure, anti-myopia spectacles and anti-myopia contact lenses.”

Dr. Swarbrick maintained that each child should be considered for myopia treatment on an individual basis.

“None of these approaches has been shown to work for all children, and we cannot predict for which individual child a particular option will work,” she said. “All have their advantages and disadvantages, so at this stage of our clinical knowledge, my best advice is to discuss the pros and cons with the parents and try whatever option might suit the child based on considerations such as wearing schedule, contraindications and other similar factors.”

A clear need

Dr. Holden said despite the clear demand for a solution to myopia progression, the industry has been slow in developing anti-myopia contact lenses.

“The industry has not been aggressive in its timelines related to the provision of anti-myopia lenses,” he said. “The companies have not taken a very proactive attitude toward the studies necessary to produce regulatory approvals. But I am sure this will change as the first myopia control lens gets on the market and has a significant effect.”

Dr. Holden said, until then, he fears this unmet need will continue to be handled by well-intended parents in unorthodox, improvisational ways.

“I’ve spoken to parents who have taken extraordinary steps to reduce the rate of myopia progress in their children,” he said. “One parent virtually kept the children from reading, and read everything to them. Another parent used atropine for 10 years on his children.”

Dr. Holden said for this reason, he feels it is crucial that the development of anti-myopia products continues to move forward. He said contact lenses are currently the best prospect.

“There is a tremendous demand and a tremendous benefit to this approach to controlling myopia,” he said. “I think if anti-myopia contact lenses can be made safe, comfortable and adverse event-free, they are the best way of controlling the progress of myopia.” – By Jennifer Byrne

References:

• Kang P, Swarbrick H. Peripheral refraction in myopic children wearing orthokeratology and gas-permeable lenses. Optom Vis Sci. 2011;88(4):476-482.
• Kwok E, Patel B, Backhouse S, Phillips JR. Peripheral refraction in high myopia with spherical soft contact lenses [published online ahead of print January 26, 2012]. Optom Vis Sci. doi: 10.1097/OPX.0b013e318242dfbf.
• Sankaridurg P, Holden B, Smith E, et al. Decrease in rate of myopia progression with a contact lens designed to reduce relative peripheral hyperopia: One-year results. Invest Ophthalmol Vis Sci. 2011;52(13):9362-9367.
• Siatkowski RM, Cotter S, Miller JM, Scher CA, Crockett Rs, Novack GD, US Pirenzepine Study Group. Safety and efficacy of 2% pirenzepine ophthalmic gel in children with myopia: a 1-year, multicenter, double-masked, placebo-controlled parallel study. Arch Ophthalmol. 2004;122(11):1667-1674.
• Swarbrick HA, Alharbi A, Lum E, Watt K. Changes in axial length and refractive error during overnight orthokeratology for myopia control. Paper presented at: ARVO; May 2011; Fort Lauderdale, FL.

• Brien A. Holden, PhD, DSc, LOSc, is a professor at the University of New South Wales and head of the Institute for Eye Research. He can be reached at Level 4, Rupert Myer Bldg., University of New South Wales, NSW Sydney 2052 Australia; (61) 2-9385-7418; fax: (61) 2-9385-740; B.Holden@brienholdenvision.org.
• Glenn Moro is global head of innovation at Alcon Vision Care. He can be reached at 6201 South Freeway, Fort Worth, TX 76134; (817) 615-2340; glenn.moro@alconlabs.com.
• Earl L. Smith III, OD, PhD, is dean of the University of Houston, College of Optometry. He can be reached at University of Houston, College of Optometry, 505 J Davis Armistead Bldg., Houston, TX 77204-2020; (713) 743-1899; (713) 743-0965; esmith@uh.edu.
• Helen A. Swarbrick, PhD, FAAO, is a professor at the school of optometry and Vision Science, University of New South Wales. She can be reached at School of Optometry and Vision Science, University of New South Wales, Sydney, Australia; (61) 2 9385 4373; h.swarbrick@unsw.edu.
• Disclosures: Dr. Holden and Dr. Swarbrick have no relevant financial interests to disclose. Dr. Smith holds patents related to peripheral anti-myopia lens designs but no financial interests in any currently available contact lenses.