Reduce Myopia Progression Research Articles

The Effect of Dynamic and Isometric Exercise on Refractive State, Accommodation and Intra-Ocular Pressure

Introduction: Several studies have demonstrated that an increase in the number of hours children spend outdoors is associated with reduced myopia progression One suggestion is that physical exercise could affect refractive development, either through a change in the accommodative response or IOP. This study evaluated the effect of both isotonic and isometric exercise on these ocular parameters. Methods: 20 young, healthy subjects participated in 3 trials. In the first trial, subjects spent 10 minutes exercising on a stair climbing machine while in the second session, they were required to maintain an unsupported squat position for a continuous 2 minute period. In a control condition, subjects watched television in a seated position for 10 minutes. Before and immediately after each trial, the following parameters were measured: (i) systolic and diastolic BP, (ii) heart rate, (iii) distance refractive state, (iv) accommodative response to 3, 4 and 5D stimuli and (v) IOP. In a second study, IOP was assessed both before and during (while the subject was still in the squatting position) 1 minute of isotonic exercise in 14 young, healthy subjects. Results: A significant increase of 32 mmHg in systolic BP was observed following the stair climbing exercise while significant increases in heart rate were recorded following both the stair climbing and squatting trials. However, no significant changes in IOP, distance refractive state or accommodative response were noted following any of the 3 conditions. In the second study, mean IOP before and during the squatting exercise was 14.6 and 19.1 mm Hg, respectively (p < 0.0001). Conclusions: Brief periods of exercise do not produce significant changes in refractive state, accommodation or IOP. Although a significant change in IOP was observed during the course of isometric exercise, this effect dissipated rapidly. While a cumulative effect may exist following longer or multiple exercise sessions, there is no support for the proposal that physical exercise will alter refractive state development or progression.

Peripheral refraction in a range of commonly available soft contact lenses

Purpose: The potential role of peripheral retinal defocus in the development of myopia has prompted interest in the manipulation of peripheral refraction. Soft contact lenses designed to reduce myopia progression are being trialled but are not yet available in many countries. The aim of this study was to investigate the impact of a range of currently available soft lenses on peripheral refraction.

Hard Times

The prevalence of myopia has increased substantially in recent decades and has approached 20–50% and 60–80% in the West and far East Asia, respectively. Worldwide, the condition is considered to be the leading cause of visual impairment. Therefore, finding effective treatment options for the control of myopia progression in children is both appealing and demanding. Several treatment therapies, including pharmaceutical agents; bifocal & multifocal spectacle lenses, and conventional, single vision GP & soft contact lenses have been used with relatively modest success to reduce myopia progression. Overall, most therapies have either limited treatment benefits or there are professional issues with regard to long-term prescribing of pharmaceutical agents. Recently, modern orthokeratology has been shown to be effective in slowing myopia progression in children.

The Effect of Multifocal Soft Contact Lenses on Peripheral Refraction

To compare changes in peripheral refraction with single-vision (SV) and multifocal (MF) correction of distance central refraction with commercially available SV and MF soft contact lenses (SCLs) in young myopic adults. Thirty-four myopic adult subjects were fitted with Proclear Sphere and Proclear Multifocal SCLs to correct their manifest central refractive error. Central and peripheral refraction were measured with no lens wear and subsequently with the two different types of SCL correction. At baseline, refraction was myopic at all locations along the horizontal meridian. Peripheral refraction was relatively hyperopic compared with center at 30 and 35 degrees in the temporal visual field (VF) in low myopes, and at 30 and 35 degrees in the temporal VF, and 10, 30, and 35 degrees in the nasal VF in moderate myopes. Single-vision and MF distance correction with Proclear Sphere and Proclear Multifocal SCLs, respectively, caused a hyperopic shift in refraction at all locations in the horizontal VF. Compared with SV correction, MF SCL correction caused a significant relative myopic shift at all locations in the nasal VF in both low and moderate myopes and also at 35 degrees in the temporal VF in moderate myopes. Correction of central refractive error with SV and MF SCLs caused a hyperopic shift in both central and peripheral refraction at all positions in the horizontal meridian. Single-vision SCL correction caused the peripheral retina, which initially experienced absolute myopic defocus at baseline with no correction to experience an absolute hyperopic defocus. Multifocal SCL correction resulted in a relative myopic shift in peripheral refraction compared with SV SCL correction. This myopic shift may explain recent reports of reduced myopia progression rates with MF SCL correction.

Optical treatment strategies to slow myopia progression: Effects of the visual extent of the optical treatment zone

In order to develop effective optical treatment strategies for myopia, it is important to understand how visual experience influences refractive development. Beginning with the discovery of the phenomenon of form deprivation myopia, research involving many animal species has demonstrated that refractive development is regulated by visual feedback. In particular, animal studies have shown that optically imposed myopic defocus slows axial elongation, that the effects of vision are dominated by local retinal mechanisms, and that peripheral vision can dominate central refractive development. In this review, the results obtained from clinical trials of traditional optical treatment strategies employed in efforts to slow myopia progression in children are interpreted in light of the results from animal studies and are compared to the emerging results from preliminary clinical studies of optical treatment strategies that manipulate the effective focus of the peripheral retina. Overall, the results suggest that imposed myopic defocus can slow myopia progression in children and that the effectiveness of an optical treatment strategy in reducing myopia progression is influenced by the extent of the visual field that is manipulated.

Peripheral Refraction in High Myopia with Spherical Soft Contact Lenses

Previous studies suggest that the refractive status of the peripheral retina may influence the progression of myopia. Our aim was to investigate peripheral refractions in human eyes with high myopia when corrected with a conventional soft spherical contact lens (CL). Ten young adults with high myopia (over -6.00 D) were investigated. An open-field auto-refractor was used to measure on- and off-axis refractions in primary gaze, with and without a CL, every 5° out to 20° horizontally in nasal and temporal retina. Results were analyzed as mean sphere (M) and astigmatic (J(0) and J(45)) vector components. Partial coherence interferometry measures of eye size were also made on- and off-axis at 10 and 20° in nasal and temporal retina. Subjects (mean age, 22 years; range, 20 to 26 years) had an average on-axis spherical refractive error of -8.31 ± 2.10 D and an average on-axis eye length of 27.39 ± 1.18 mm. Mean sphere exhibited a significant shift from hyperopic relative peripheral refraction (RPR) in the uncorrected state to myopic RPR on correction, in both nasal and temporal retina. Mean RPR of all subjects across all eccentricities was hyperopic when uncorrected (M = +0.20 ± 0.49 D: mean ± 1 SEM) becoming myopic when corrected (M = -0.45 ± 0.56 D: p = 0.0003, reaching -1.21 ± 0.82 D at 20° in the temporal retina). Peripheral J(0) astigmatism also became significantly more negative on correction (p = 0.002), whereas J(45) astigmatism remained unchanged. On- and off-axis measures of eye length indicated a relatively prolate retinal contour. Uncorrected off-axis mean sphere refractive error reduced with eccentricity, and this was accurately predicted (R > 0.98) by the measured retinal contour. Correcting the foveal refractive error in high myopia with standard spherical soft CLs can result in significant absolute myopic defocus in the peripheral retina. If peripheral refraction does indeed influence myopia progression, then our results suggest that in high myopia, standard soft CLs may be beneficial in reducing myopia progression.

Prentice Award Lecture 2010: A case for peripheral optical treatment strategies for myopia.

It is well established that refractive development is regulated by visual feedback. However, most optical treatment strategies designed to reduce myopia progression have not produced the desired results, primarily because some of our assumptions concerning the operating characteristics of the vision-dependent mechanisms that regulate refractive development have been incorrect. In particular, because of the prominence of central vision in primates, it has generally been assumed that signals from the fovea determine the effects of vision on refractive development. However, experiments in laboratory animals demonstrate that ocular growth and emmetropization are mediated by local retinal mechanisms and that foveal vision is not essential for many vision-dependent aspects of refractive development. However, the peripheral retina, in isolation, can effectively regulate emmetropization and mediate many of the effects of vision on the eye's refractive status. Moreover, when there are conflicting visual signals between the fovea and the periphery, peripheral vision can dominate refractive development. The overall pattern of results suggests that optical treatment strategies for myopia that take into account the effects of peripheral vision are likely to be more successful than strategies that effectively manipulate only central vision.

Myopia and defocus: the current understanding

The current theories relating to the development and progression of myopia are related to exposure of the eye to hyperopic defocus. This paper discusses these theories and the large body of recent research investigating the evidence behind them. As both human and animal studies demonstrate, when considering the potential influence of defocus on eye growth, the duration of exposure as well as the type and magnitude of the blur are important. In addition, we must understand the defocus threshold over which an eye growth signal can be made. Investigations with respect to central defocus alone have been unable to find a unified theory due to (1) insufficient evidence showing refractive group differences in the amount of central defocus actually present and (2) unsuccessful attempts to wholely reduce myopia progression using corrective lenses. Recent research measuring peripheral blur is summarised in this paper and modelled together with previous measurements of peripheral defocus thresholds, providing an up-to-date perspective on myopia.

Peripheral Refraction Profiles in Subjects with Low Foveal Refractive Errors

To study the variability of peripheral refraction in a population of 43 subjects with low foveal refractive errors. A scan of the refractive error in the vertical pupil meridian of the right eye of 43 subjects (age range, 18 to 80 years, foveal spherical equivalent, < ± 2.5 diopter) over the central ± 45° of the visual field was performed using a recently developed angular scanning photorefractor. Refraction profiles across the visual field were fitted with four different models: (1) "flat model" (refractions about constant across the visual field), (2) "parabolic model" (refractions follow about a parabolic function), (3) "bi-linear model" (linear change of refractions with eccentricity from the fovea to the periphery), and (4) "box model" ("flat" central area with a linear change in refraction from a certain peripheral angle). Based on the minimal residuals of each fit, the subjects were classified into one of the four models. The "box model" accurately described the peripheral refractions in about 50% of the subjects. Peripheral refractions in six subjects were better characterized by a "linear model," in eight subjects by a "flat model," and in eight by the "parabolic model." Even after assignment to one of the models, the variability remained strikingly large, ranging from -0.75 to 6 diopter in the temporal retina at 45° eccentricity. The most common peripheral refraction profile (observed in nearly 50% of our population) was best described by the "box model." The high variability among subjects may limit attempts to reduce myopia progression with a uniform lens design and may rather call for a customized approach.

Effect of Dual-Focus Soft Contact Lens Wear on Axial Myopia Progression in Children

To test the efficacy of an experimental Dual-Focus (DF) soft contact lens in reducing myopia progression. Prospective, randomized, paired-eye control, investigator-masked trial with cross-over. Forty children, 11-14 years old, with mean spherical equivalent refraction (SER) of -2.71 ± 1.10 diopters (D). Dual-Focus lenses had a central zone that corrected refractive error and concentric treatment zones that created 2.00 D of simultaneous myopic retinal defocus during distance and near viewing. Control was a single vision distance (SVD) lens with the same parameters but without treatment zones. Children wore a DF lens in 1 randomly assigned eye and an SVD lens in the fellow eye for 10 months (period 1). Lens assignment was then swapped between eyes, and lenses were worn for a further 10 months (period 2). Primary outcome was change in SER measured by cycloplegic autorefraction over 10 months. Secondary outcome was a change in axial eye length (AXL) measured by partial coherence interferometry over 10 months. Accommodation wearing DF lenses was assessed using an open-field autorefractor. In period 1, the mean change in SER with DF lenses (-0.44 ± 0.33 D) was less than with SVD lenses (-0.69 ± 0.38 D; P < 0.001); mean increase in AXL was also less with DF lenses (0.11 ± 0.09 mm) than with SVD lenses (0.22 ± 0.10 mm; P < 0.001). In 70% of the children, myopia progression was reduced by 30% or more in the eye wearing the DF lens relative to that wearing the SVD lens. Similar reductions in myopia progression and axial eye elongation were also observed with DF lens wear during period 2. Visual acuity and contrast sensitivity with DF lenses were not significantly different than with SVD lenses. Accommodation to a target at 40 cm was driven through the central distance-correction zone of the DF lens. Dual-Focus lenses provided normal acuity and contrast sensitivity and allowed accommodation to near targets. Myopia progression and eye elongation were reduced significantly in eyes wearing DF lenses. The data suggest that sustained myopic defocus, even when presented to the retina simultaneously with a clear image, can act to slow myopia progression without compromising visual function. Proprietary or commercial disclosure may be found after the references.

Attempts to Reduce the Progression of Myopia and Spectacle Prescriptions during Childhood: A Survey of Eye Specialists

PurposeTo determine methods tried in clinical trials to reduce the progression of myopia in children, and spectacle prescribing patterns of hospital ophthalmologists.MethodsA multi-sectioned survey composed of Likert items relating to the methods of reducing myopia progression (orthokeratology lenses [O-K lenses], undercorrected glasses, and topical atropine) and the patterns of prescribing spectacles for children (including two cases involving a 5-year-old girl and an 8-year-old boy) were distributed to members of the Korean Ophthalmological Society, and the collected data was statistically analyzed.ResultsA total of 78 out of 130 ophthalmologists returned the survey. On a scale of 1 to 5, the mean rates of whether the ophthalmologists think O-K lenses arrest myopia progression, and whether they recommend their patients to wear O-K lenses if indicative, were 3.06 and 2.75, respectively. Moreover, the mean rates of whether they consider that wearing glasses which are undercorrected would slow down the progression of the myopia, or if they think topical atropine helps in arresting myopia progression in children, were 2.34 and 1.27, respectively. In response to the case studies, the majority of practitioners preferred to prescribe the full amount found in cycloplegic refraction to pediatric patients with myopia.ConclusionsOphthalmologists in clinical practice encouraged children to wear O-K lenses more than undercorrected glasses as a way to retard myopia progression. However, the application of atropine is rarely tried in clinical trials. In managing pediatric patients with myopia (case specific), the majority of the practitioners chose to prescribe glasses with full cycloplegic correction.

Myopia: its prevalence, origins and control

Myopia: its prevalence, origins and control

Adenosine receptor protein changes in guinea pigs with form deprivation myopia

Recent results have shown that treatment with the non-selective adenosine antagonist 7-methylxanthine (7-MX) reduces the development of form deprivation myopia (FDM) in guinea pigs. The aims of this study were to identify the presence of adenosine receptors (AdoRs) in the eye wall of the guinea pig and to determine their possible changes during form deprivation. Three-week-old guinea pigs were monocularly treated with a translucent lens to induce FDM. After 21 days, samples were taken from the posterior eye wall and examined with immunofluorescence confocal microscopy for the presence of AdoRA1, AdoRA2A, AdoRA2B and AdoRA3 proteins. Western blot analysis was used to quantitate AdoRs in samples from the retina, choroids and sclera. All four subtypes of AdoR were expressed in the posterior wall of the guinea pig eye, although AdoRA3 only weakly. Twenty-one days after the induction of myopia, we observed a significant decrease in protein expression for AdoRA1 (- 25.5%) and an increase in protein expression for AdoRA2B (+ 66.7%) in the retina of FDM eyes. AdoRs of all subtypes are expressed in the retina, choroids and sclera in guinea pigs and may play a role in the regulation of eye growth. The changed pattern of AdoR expression during form deprivation confirms that pharmaceutical intervention targeting AdoRs may reduce myopia progression.

Visual symptoms and compliance with spectacle wear in myopic children: double-masked comparison between progressive addition lenses and single vision lenses.

The aim of this study is to clarify visual symptoms and compliance with spectacle wear in children kusing progressive addition lenses (PALs). Ninety-two children, participating in a randomized, doublemasked, crossover trial to determine whether PALs reduce myopia progression (mean+/-SD age: 11.0+/-1.6 years; refractive errors: 3.11+/-1.34 D), wore PALs (1.50 D near addition) or single vision lenses (SVLs) for 18 months, alternately. A questionnaire survey was performed 6 and 12 months after the beginning of the use of the lenses (6-month survey), and the results were compared between PAL- and SVL-wearing periods. In the PAL-wearing period, the children reported difficulty in adapting to newly provided spectacles (36%), disturbances in distance vision (22%), vertigo in the lateral gaze (11%), and difficulty in ascending and descending stairs (9%). However, the frequency of these symptoms was not significantly different from that reported in the SVL-wearing period. There was no difference in compliance with spectacle wear between the PAL- and SVL-wearing periods, and 98% of the children wearing PALs reported excellent compliance. The results of this study indicate that, compared with SVLs, the PALs provide a similar level of comfort and compliance with spectacle wear for myopic children.