Myopia Control Through Managing Peripheral Refraction - Orthokeratology and Zeiss Myovision Lenses Myopia Control Through Managing Peripheral Refraction - Orthokeratology and Zeiss Myovision Lenses

Myopia Control Through Managing Peripheral Refraction - Orthokeratology and Zeiss Myovision Lenses

One study that measured refraction across the horizontal central visual field in orthokeratology patients before and during treatment found that before treatment, subjects had either a relatively constant mean sphere refraction across the field or a relative farsightedness in the periphery as compared with the central refraction. As a result of treatment, myopia decreased but at reduced rate out into the periphery.  They concluded that Orthokeratology can correct myopia over the central +/- 10 degrees of the visual field but produces only minor changes at field angles larger than 30 degrees . If converting relative peripheral hypermetropia to relative peripheral myopia is a good way of limiting the axial elongation that leads to myopia, orthokeratology is an excellent option for achieving this. (Optom Vis Sci. 2011 Apr;88(4):476-82)

 

Another study investigated the changes in peripheral refraction after orthokeratology (OK) and rigid gas-permeable (GP) lens wear in progressing myopic children and to compare these peripheral defocus changes with reported changes in adults wearing OK.  At baseline, myopic children showed relative peripheral hyperopia compared with central refraction at and beyond 20° in the temporal visual field (VF) and 30° in the nasal VF. Three months of OK lens wear produced hyperopic shifts in refraction between 30° in the temporal VF and 20° in the nasal VF. Peripheral refraction was similar to center at all positions in the temporal VF while remaining significantly myopic at all locations in the nasal VF. No change in either central or peripheral refraction was found after 3 mo in the eye assigned for GP lens wear.  The conclusion was that OK significantly reduced myopia in the central 20° VF in myopic children, converting relative peripheral hyperopia measured at baseline to relative peripheral myopia. These changes in children are similar to changes reported in myopic adults wearing OK lenses. No change in either central or peripheral refraction was found after 3 months of daily GP lens wear. OK lenses can be used to induce myopic defocus in the periphery in myopic children and may thus provide a potential mechanism for myopia control. (Optom Vis Sci. 2010 May;87(5):323-9)

 

Queiros et al,  attempted to characterize the central and peripheral refraction across the horizontal meridian of the visual field before and after myopic corneal refractive therapy (CRT or Orthokeratology) with contact lenses. They concluded that CRT inverts the pattern of peripheral refraction in spherical equivalent refraction, creating a treatment area of myopic reduction within the central 25 degrees of visual field, and a myopic shift beyond the 25 degrees. In peripheral refraction for 30 degrees and 35 degrees, the amount of myopia induced in terms of spherical equivalent has an almost 1:1 relationship with the amount of baseline spherical equivalent refraction to be corrected.

 

Kang et al. studied changes in peripheral refraction after orthokeratology (OK) and rigid gas-permeable (GP) lens wear in progressing myopic children and to compare these peripheral defocus changes with reported changes in adults wearing OK.  They found at baseline, myopic children showed relative peripheral hyperopia compared with central refraction at and beyond 20° in the temporal visual field (VF) and 30° in the nasal VF. Three months of OK lens wear produced hyperopic shifts in refraction between 30° in the temporal VF and 20° in the nasal VF. Peripheral refraction was similar to center at all positions in the temporal VF while remaining significantly myopic at all locations in the nasal VF. No change in either central or peripheral refraction was found after 3 mo in the eye assigned for GP lens wear.  Their conclusion; Orthokeratology significantly reduced myopia in the central 20° VF in myopic children, converting relative peripheral hyperopia measured at baseline to relative peripheral myopia. These changes in children are similar to changes reported in myopic adults wearing OK lenses. No change in either central or peripheral refraction was found after 3 mo of daily GP lens wear. OK lenses can be used to induce myopic defocus in the periphery in myopic children and may thus provide a potential mechanism for myopia control.

 

Although some studies suggest that orthokeratology contact lens wear slows the axial length growth of the eye in children with progressing myopia, some limitations in the methodology employed have been evident. Using a rigorous study design and precise optical measuring instruments, Menicon Co., Ltd. and the Novovision Clinic in Madrid are undertaking the Myopia Control with Orthokeratology contact lenses in Spain (MCOS) study to compare the axial length growth between white European myopic children wearing orthokeratology contact lenses (OK) and distance single-vision spectacles (SP) over a 2-year period. The MCOS study offers a number of notable features: a prospective design; well matched samples and high resolution ocular biometry measures, which collectively should elucidate whether OK contact lens wear is a feasible method of myopia control.

"The MCOS study aims, using a rigorous study design and precise optical measuring instruments, at elucidating whether orthokeratology lens wear slows the axial length growth of the eye in children with progressing myopia. This study is of special relevance taking into account that the prevalence of myopia has increased substantially over recent decades and now is approaching 10-25% and 60-80% in industrialized societies of the West and East, respectively", commented Dr. Jacinto Santodomingo, Global Professional Relations Manager for Menicon Co., Ltd.   We’ll have to wait and see what the results are!
 

LORIC (Long Term Ortho-K Research In Children) Pauline Cho (Curr Eye Res. 2005 Jan;30(1):71-80) showed that axial length increase was 50%of that in Ortho-K patients compared to the control group in glasses. Although OrthoK slowed myopia, the effect couldn't be predicted for individuals.  This 2 year pilot study was conducted to determine whether ortho-k can effectively reduce and control myopia in children.  The conclusion was  Ortho-k can have both a corrective and preventive/control effect in childhood myopia. However, there are substantial variations in changes in eye length among children and there is no way to predict the effect for individual subjects.

The SMART study (Stabilization of Myopia through Accelerated Reshaping Technologies) A five year study where after each year of wear the patient is allowed to normalize without wearing their molding lenses after which they start wearing their lenses again. This 5-year study found that at 2 years the control group was significantly more myopic than the test group undergoing corneal reshaping.

 

The CRAYON study, (Corneal Reshaping and Yearly Observation of Nearsightedness) An update to the LORIC study demonstrated corneal reshaping (CR) slows axial growth over the study length of two years. The final results of this study are not yet published.

 

The COOKI study (Invest Ophthalmol Vis Sci 2003;44), (Children's Overnight Orthokeratology Investigation) essentially proved that CR works overnight for children in the 8-11 year old group.

 

CANDY (Controlling Astigmatism and Nearsightedness in Developing Youth) (Bartels et.al.) showed myopic progression of -.37D per year in normally corrected myopes and -.03D per year in CR patients (corneal refractive).  Patients were allowed to normalize at various times during their CR wear.

 

The last two studies (SMART and CANDY) are attempting to answer the question of whether the stabilization is just a temporary phenomena that would disappear on cessation of lens wear.  It appears that the CR effect is such that patients regress back to their starting point of CR wear, not partially regress or even progress to where they might have been if not wearing CR lenses. The studies are not definitive.  It will be a long time before such data is recognized as clinical fact.  But, the overwhelming evidence at this time is that CR is a very good alternative for young myopes and the only real effective procedure we have of suspending the progress of myopia. Further References

 

Options such as OrthoK, cornea refractive therapy including paragon crt  (vision shaping treatment) are particularly helpful when seeking to  improve  eyesight in children,  and reduce change in vision , specifically myopia in children and may, in some cases reduce the risk of children with myopia advancing to high myopia.  If you are interested in managing  your vision or the vision of a loved one with nearsightedness and concerned about vision changes, please contact the Institute for Control of Eye Myopia in Children (ICEMC) at 1-855-867-8465 or read through our website to learn about other options for improving your eyesight

 

Other  Technologies that Influence Peripheral Refraction - Zeiss MyoVision lens Available Through ICEMC

 

On 25 March 2010,  Scientists from the Vision Cooperative Research Centre (Vision CRC) in Australia announced that myopia, or short-sightedness, can be controlled with new technology. This ground breaking discovery was based on research conducted by Vision CRC partners – the University of Houston College of Optometry and the Brien Holden Vision Institute, located at the University of New South Wales.

 

Myopia affects over 1.6 billion people globally, with two thirds of those affected living in the Asia region. If unchecked, the number is expected to reach 2.5 billion by 2020.

There are 3.5 million people affected in Australia.

 

Successful basic research on the nature and cause of myopia has led to the discovery that the peripheral retinal image plays a major part in stimulating eye growth and myopia. Large scale clinical trials testing both spectacles and contact lenses designed to control the position of the peripheral image and involving over 500 children in China and Australia, have produced promising results.  With myopia, instead of a distant image being focused on the retina, as it needs to be for clear vision, it is focused in front of the retina. Myopia often occurs when children commence school (ages six to seven), and if left undetected the condition progresses and can adversely impact the child’s education and social development.

 

Professor Brien Holden, CEO of the Vision CRC, explained further, “For hundreds of years focusing defects of the eye have been corrected by simply moving the visual image backwards and forwards with spectacle lenses. Professor Earl Smith from the University of Houston College of Optometry, has demonstrated that if we move the central image onto the retina but leave the peripheral image behind the retina, the peripheral image can drive the eye to elongate, causing myopia to increase.The beauty of this new technology is that it addresses this problem by bringing the peripheral image forward, onto or even in front of the retina, and at the same time independently positioning the central image on the retina giving clear vision."

 

“The commercialisation of this technology is a most important outcome for the CRC program because of the potential vision and eye health benefits,” Professor Holden said.

 

Professor Holden announced that the breakthrough technology has been licensed to Carl Zeiss Vision (CZV) and developed into the first spectacle lens of its kind through a joint project with CZV lens designers. This new spectacle lens is called MyoVisoin.  The Vision CRC has also licensed its myopia control technology to CIBA VISION for contact lens applications. Professor Holden added, “Myopia can be a serious eye condition. High myopia significantly increases the risk of cataract, glaucoma, and retinal detachment, all potentially blinding conditions and the public health risk is significant.”  Dr Padmaja Sankaridurg, Head of the Myopia Program at Vision CRC, emphasised the nature of the new technology’s appeal. “Our unique lens designs act to curve or shift the peripheral image forward, thereby removing the stimulus to axial elongation and myopia progression,” she said.  “We are continuing testing in Chinese and Australian children and young adults. So far, trials have found that the first spectacle lens prototypes based on this new technology slow the rate of progress of myopia by 30% in children six to 12 years of age, where the child has a history of parental myopia,” she said.  Professor Smith, from the University of Houston, commented, “Evidence shows that the number of individuals with myopia will dramatically escalate with increasing urbanisation and less outdoor activity”.  “As urbanisation has increased in China, the prevalence and average amount of myopia has also increased. Recent evidence indicates that similar trends are occurring in the US and Australia. This ongoing epidemic of vision loss is associated with spiralling health and social costs, especially in many developing countries where over 80% of children have no correcting spectacles or contact lenses,” he said.  “This new technology is not just for children either. Over 25% of myopes in the Western world are adult-onset myopes, which often begins at University. We believe that this technology has potential benefits for all myopes,” Professor Smith said.

 

Corneal reshaping therapies with gas permeable lens technologies are particularly helpful when seeking to  improve  eyesight in children,  and reduce change in vision , specifically myopia in children and may, in some cases reduce the risk of children with myopia advancing to high myopia.  If you are interested in managing  your vision or the vision of a loved one with nearsightedness and concerned about vision changes, please contact the Institute for Control of Eye Myopia in Children (ICEMC) at 1-855-8ORTHOK (867-8465) or read through our website to learn about other options for improving your eyesight