Blur thresholds in different refractive groups

Objective To discuss the differences in the response AC/A between progressive myopes,stable myopes and emmetropes,and to try to analyze the causes for the differences.Methods Fifty-one subjects (17 progressive myopes,17 stable myopes and 17 emmetropes) participated in the study.The accommodative response and heterophoria were measured under 9 different stimulus states.And the response AC/A and accommodative error index (AEI) were calculated.A one-way ANOVA was used to analyze the data.Results There was a significant difference in the response AC/A between progressive myopes,stable myopes and emmetropes (F=4.051,P＜0.05).Progressive myopes had a higher AC/A ratio than stable myopes and emmetropes.No significant differences were found in the AEI values for the three refractive groups (F=2.579,P＞0.05).At high stimulus levels (3.21-4.12 D),progressive myopes showed more esophoria than stable myopes and emmetropes,but significant-differences were found between the three refractive groups only at the 4.12 D level (F=3.828,P＜0.05).Conclusion Progressive myopia has a higher response AC/A and more esophoria than stable myopes and emmetropes,which suggests that high AC/A and large esophoria may be the risk factors for myopia progression.And the large esophoria may be the reason for the high AC/A ratio. Key words: Myopia; AC/A ratio; Esophoria; The AEI value

Purpose. Recent work has shown that differences exist in the accommodation response characteristics of myopes and emmetropes, although the exact nature of the differences has yet to be ascertained. This may in part be due to the classification of the refractive error employed in many studies. Previously it has been suggested that inaccuracies in the accommodation response occur predominantly during the progression of myopia. To test this hypothesis we measure nearwork induced transient myopia (NITM) in progressing myopes (PMs), stable myopes (SMs) and emmetropes (EMMs). Methods. A total of 41 young (18–27 years) subjects participated in the study (13 PMs, 14 SMs, 14 EMMs). Following a 10 minute near task (4D) the change in accommodation response back to distance viewing was measured over a two minute time period. Results. Grouped mean data revealed a significant nearwork after-effect in PMs in comparison to SMs and EMMs after 10 seconds (p < 0.01) and 30 seconds (p < 0.01) post-task. Significantly longer time constants were also found in the PMs group. Conclusions. Our results suggest that NITM is manifest during the progressive phase of myopia development.

The purpose of this paper is to review the available evidence concerning the role of the cornea in achieving and maintaining emmetropia, as well as its role in the development and progression of myopia. The role of the cornea in emmetropization is most evident at the two extremes of life. During infancy, when the axial length increases rapidly, both the cornea and the lens become flatter, moving the refractive state of the eye toward emmetropia; during the later years of life, when the axial length remains constant or even shortens, the cornea appears to steepen somewhat. When myopia develops, in some cases the cornea may undergo a "paradoxical" steepening, which accelerates, rather than retards, the development of myopia. The effect of the cornea on the development and progression of myopia is evident when the ratio of axial length to corneal radius--the AL/CR ratio--is considered. Recent studies suggest that a high AL/CR ratio, which has a value of approximately 3.0 in the emmetropic eye, is a risk factor for youth-onset myopia. Several studies have shown that myopic eyes have greater mean corneal powers than emmetropic eyes; this may be mostly due to greater corneal powers being a risk factor for youth-onset myopia.

The impact of computer use in myopia progression: A cohort study in Spain

The choroidal macrophage polarization significantly influences myopia development in murine models.

PurposeThe purpose of this article is to document the rare observation of the development, progression, retinal changes, and results of visual rehabilitation in a young child with unilateral high myopia, as well as additional clinical observations in four very young patients with this condition. We also examine the role of factors such as amount of astigmatism, presence of strabismus, degree of anisometropia, and penalization in the development of optimal vision in these patients.MaterialsA review of patients from 1997–2002 disclosed 33 individuals with a diagnosis of unilateral high myopia. Five children with adequate information on the progression of myopia and/or in whom a final visual outcome could be determined were included in this study. We excluded patients with insufficient follow-up, those who did not comply with occlusion, and those with co-existing ocular conditions such as retinopathy of prematurity.ResultsThree females and two males (four right eyes and one left) were followed for a period of 16 months to 7 years. Myopic fundus changes were present in three patients. Glasses were the preferred method of optical correction in four patients; one patient was prescribed a contact lens. Occlusion therapy was used in four of the five patients. Strabismus was present in four. Ipsilateral astigmatism of +2.00 D or more was present in three of the affected eyes. The difference in the spherical equivalent refraction between both eyes in each patient ranged from 5 to 20 diopters. In one patient, we observed the progressive development of unilateral myopia from an initial hypermetropia of +2.00 at age 2 months to myopia of −9.00 at the age of 5 years.ConclusionsUnilateral high myopia is probably not present at birth. Our observations support its development in the first few years of life. The results of amblyopia therapy depend on the degree of anisometropia, the co-existence of strabismus, the compliance with penalization, and the presence of retinal abnormalities.

To subject a number of areas of contention in the myopia field to evidence-based scrutiny. The 10 topics from our previous review were revisited, and nine new topics were also critiqued with emphasis on the recent peer-reviewed literature. The following observations were made: 0.01% atropine should not be considered a frontline myopia control treatment; the role of relative peripheral hyperopia in myopia development and progression remains unclear; undercorrection probably does not slow myopia progression; treatment efficacy diminishes with time; percentage is a misleading metric of efficacy; handheld digital devices have not been proven to be myopiagenic; more time outdoors may slow myopic shift to a similar extent in children with and without myopia; daylight is responsible for only part of the impact of outdoor time; all myopia, not just high myopia, carries the risk of visually threatening complications; premyopia is a real condition. Furthermore, myopia may be considered a disease; accommodation lag may be a measurement artifact; adult myopia progression is significant; past progression is a flawed indicator to initiate myopia control; fast progression does not mean nonresponse to treatment; single vision soft contact lenses are not myopiagenic; red light therapy may not be safe; contact lens wear in children may be considered safe; rebound cannot be assessed by comparing progression during and following treatment. The myopia field continues to evolve with some conflicts resolved, ongoing areas of confusion, and new uncertainties emerging.

This study compared the ability of myopes and emmetropes to detect subjectively the presence of retinal defocus. Subjects (12 myopes, 12 emmetropes) were cyclopleged and monocularly viewed a bipartite target through an appropriate near addition lens via a 2-mm artificial pupil. One-half of the target remained fixed while the other half was alternatively moved forward or backward until subjects first reported a difference in clarity between the two halves of the target. The mean blur threshold for the emmetropes and myopes was +/-0.11 and +/-0.19 D, respectively (p = 0.0001). These results demonstrate that myopes are less sensitive to the presence of blur, and may at least partially explain why previous reports have demonstrated a larger lag of accommodation in this refractive group. Additionally, the hyperopic retinal defocus resulting from the increased accommodative error may play a significant role in myopia development and progression.

Based on the literature on myopia epidemiology, experiments of basic science, and clinical research, we have identified a number of major characteristics of the myopia problem. It was concluded that the student population of grades 1-12 showed high incidence of myopia and the problem was becoming increasingly more serious. Etiological investigations revealed the aggressive role played by environmental factors. Mature clinical correction methods were available, but there were still a multitude of uncertainties hampering the effort to slow the progression of myopia. Student myopia has become an issue of top concern in China's effort to prevent and control myopia. In order to approach the issue by dealing with problems in the educational environment and to explore for specific measures to prevent and control the onset and development of student myopia, it is important that we gain better understanding of the multiple effects on the onset and development of student myopia caused by the growing demand for education induced by high social development and the rapid changes in the educational environment caused by technological advancement. Approaching the problem from the perspective of the features of the eye and vision in the developmental stages of students of grades 1-12, and the study workload at each stage, this paper retrospectively reviewed the historical literature from the last 90 years and the data from cohort studies done before and after the outbreak of COVID-19. Identifying the education environment as the primary factor causing the onset and progression of student myopia, the paper fully recognizes the scientific rationality of and the specific role served by education-medicine synergy in student myopia prevention and control.

SIGNIFICANCE:There is a lack of knowledge on myopic progression in patients with moderate to high astigmatism, which has been compounded by their exclusion from myopia control studies. This study found increased myopia that was linearly associated with age, emphasizing the importance of understanding myopia control treatments in this population.PURPOSE:Moderate to high amounts of astigmatism cause visual blur and may affect myopic progression. However, there is little information as to the effect of cylinder on change in myopia, and the vast majority of myopia control studies have excluded children with significant astigmatism. The purpose of this study was to assess myopic and cylinder changes in children with moderate to high astigmatism.METHODS:Retrospective review of children (2 to 15 years) who presented with astigmatism (>2.00D) and myopic spherical equivalent refraction (SER) to a tertiary care pediatric hospital. Best corrected visual acuity and cycloplegic refraction changes over at least 2 years of follow-up were analyzed. Patients with confounding ocular disease, history of myopia control, or Trisomy 21 were excluded.RESULTS:Two hundred twenty-seven patients presented at 6.6 years (IQR 5.2, 9.1) with a median 0.00D (IQR −2.00, 0.50) sphere, −3.00D (IQR −4.25, −2.50) cylinder, and −1.75 (IQR −3.75, −0.99) SER. Twenty-four percent of patients had amblyopia and 46% had strabismus. At final exam (4.9 [IQR 3.0, 6.7] years), patients were more myopic and had greater cylinder (p<0.001). Hispanic patients were disproportionately represented (64%) but had no difference in refractive parameters versus non-Hispanic patients. Initial age was linearly associated with sphere and SER, and the rate of change in sphere and SER over 2 to 3 years of follow-up. Initial J0 was linearly associated with myopic and cylindrical progression.CONCLUSIONS:Children with moderate to high levels of astigmatism showed myopic and cylindrical progression at follow-up. Amblyopia and strabismus were common in our cohort, but neither amblyopia nor strabismus affected the rates of myopic or cylindrical progression. Patients with moderate astigmatism (−2.00 to −3.00D) had more myopic and cylindrical progression compared with those with higher levels of astigmatism.

The prevalence of myopia is increasing in Western populations but in East Asian countries, it is increasing to epidemic levels, where there are also markedly increased rates of progression to pathological myopia. Measures to more effectively control the development and progression of myopia are urgently needed. Notwithstanding a large volume of research, especially regarding the different mechanisms for the development of myopia and the efficacy of particular methods of intervention, there is still a great need and scope for improvements in clinical efforts to prevent and/or control myopic progression. Too often clinical efforts may involve only one method of intervention; however, the heterogenous nature of myopia suggests that clinical intervention may be more successful when interventions are employed in combination. The decision to prescribe interventions for the control of myopia in children, especially prior to onset, may be better framed by a comprehensive estimation of the degree of risk for the development and/or progression of myopia. For example, rather than ascribing equal weight to any degree of parental myopia, more accurate estimates may be obtained, if risk is judged to increase with the degree of parental myopia and the extent of any associated degenerative pathology. Risk estimates may be limited to broad mild, moderate and severe classifications due to lack of accurate weighting of risk factors. Nevertheless, comprehensive assessment of risk factors appears likely to better inform a prognosis and discussions with parents. Consideration of numerous environmental influences, for example, such as continuity and intensity of near work and time spent outdoors, may contribute to better risk estimation. Family‐based practice appears to be ideally suited for risk estimation and the clinical application of approaches to control myopia. A proactive approach to estimating risk of developing myopia prior to its onset may be beneficial. Earlier implementation of interventions to control myopia could significantly reduce the chance of progression to pathological myopia.

Purpose: Caucasian children with myopia have elevated response accommodative vergence to accommodation (AC/A) ratios. The purpose of this study was twofold: to determine if response AC/A ratios vary with refractive error and with myopic progression rate in Hong Kong Chinese children, and to determine the effect of beta‐adrenergic antagonism with topical timolol application on AC/A ratios. Methods: Thirty children aged eight to 12 years participated in the study. All refractive errors were corrected with spectacle lenses. Accommodative responses were measured using a Shin‐Nippon autorefractor and concurrent changes in vergence were assessed using a vertical prism and a Howell‐Dwyer card at three metres and 0.33 metre. Accommodative demand was altered using plus or minus two dioptre lenses and lens‐ and distance‐induced response AC/A ratios were calculated. Measurements were repeated 30 minutes after the instillation of topical timolol maleate (0.5 per cent). Results: AC/A ratios appeared higher in progressing myopic children but the difference was not statistically significant. Timolol application reduced accommodative convergence (AC) in the stable myopes (reduction = ‐3 ± 1.14A) but not in the emmetropes (0.69 ± 0.9P) or progressing myopes (0.16 ± 0.43A) and this difference between refractive groups was statistically s ignificant (F2,27= 3.766; P= 0.036). However, timolol did not produce a significant change in the accommodative response to positive or negative lenses or response AC/A ratios. Conclusions: We did not find that AC/A ratios in myopic Chinese children were elevated and therefore, it is unlikely that elevated AC/A ratios are responsible for the high levels of myopia that occur in Hong Kong. The finding that timolol reduced AC in the stable myopes suggests that the autonomic control of accommodative convergence in these children may be different from that in emmetropic children and those with progressing myopia.

BackgroundMyopia has recently emerged as a significant threat to global public health. The high and pathological myopia in children and adolescents could result in irreversible damage to eye tissues and severe impairment of visual function without timely control. Posterior scleral reinforcement (PSR) can effectively control the progression of high myopia by limiting posterior scleral expansion, improving retrobulbar vascular perfusion, thereby stabilizing the axial length and refraction of the eye. Moreover, orthokeratology and low concentrations of atropine are also effective in slowing myopia progression.Case presentationA female child was diagnosed with binocular congenital myopia and amblyopia at the age of 3 and the patient’s vision had never been rectified with spectacles at the first consultation. The patient’s ophthalmological findings suggested, high refractive error with low best corrected visual acuity, longer axial length beyond the standard level of her age, and fundus examination suggesting posterior scleral staphyloma with weakened hemodynamics of the posterior ciliary artery. Thereby, PSR was performed to improve fundus health and the combination of orthokeratology and 0.01% atropine were performed to control the development of myopia. Following up to 8 years of clinical treatment and observations, the progression of myopia could be well controlled and fundus health was stable.ConclusionIn this report, 8-year of clinical observation indicated that PSR could improve choroidal thickness and hemodynamic parameters of the retrobulbar vessels, postoperative orthokeratology combined with 0.01% atropine treatment strategy may be a good choice for myopia control effectively.

PURPOSE. Relative peripheral hyperopia has been associated with central myopia. This study was conducted to determine whether baseline relative peripheral hyperopia is associated with an increased risk of developing myopia or myopia progression in young Singapore Chinese children. METHODS. One hundred eighty-seven children who participated in the Peripheral Refraction in Preschool Children (PREP) Study at baseline underwent a follow-up examination. Autorefraction was performed at five eccentricities with an infrared autorefractor after cycloplegia: central axis and 15° and 30° eccentricities in the nasal and temporal visual fields. The primary outcomes were development of myopia among children who were nonmyopic at baseline, and myopia progression in those who were myopic at baseline. RESULTS. The mean age of the children at baseline was 7.2 ± 3.0 years, and the mean duration of follow-up was 1.26 years. At baseline, 96 children were myopic (mean central spherical equivalent [SE] -2.75 ± 1.72 D) and 91 were nonmyopic (mean central SE 0.76 ± 0.81 D). Baseline relative peripheral hyperopia was not associated with a greater likelihood of becoming myopic or myopia progression. At follow-up, children who remained nonmyopic (n = 24) retained relative peripheral myopia at all eccentricities, whereas those who became myopic (n = 67) developed relative peripheral hyperopia at the nasal (+0.44 ± 0.72 D) and temporal 30° (+0.13 ± 0.74 D). The mean change in central SE was -1.51 ± 0.63 D/y for children who developed myopia, -0.82 ± 0.76 D/y for children who were myopic at baseline, and -1.05 ± 0.80 D/y for all children. CONCLUSIONS. Baseline peripheral refraction did not predict the subsequent onset of myopia or influence the progression of myopia.

Myopia is a significant public health problem, making it important to determine whether a bifocal spectacle treatment involving near prism slows myopia progression in children. To determine whether bifocal and prismatic bifocal spectacles control myopia in children with high rates of myopia progression and to assess whether the treatment effect is dependent on the lag of accommodation and/or near phoria status. This 3-year randomized clinical trial was conducted in a private practice. A total of 135 (73 female and 62 male) Chinese-Canadian children (aged 8-13 years; mean [SE] age, 10.29 [0.15] years; mean [SE] myopia, -3.08 [0.10] D) with myopia progression of at least 0.50 D in the preceding year were randomly assigned to 1 of 3 treatments. A total of 128 (94.8%) completed the trial. Single-vision lenses (control, n = 41), +1.50-D executive bifocals (n = 48), and +1.50-D executive bifocals with 3-Δ base-in prism in the near segment of each lens (n = 46). MAIN OUTCOMES AND MEASURES Myopia progression (primary) measured using an automated refractor following cycloplegia and increase in axial length (secondary) measured using ultrasonography at intervals of 6 months for 36 months. RESULTS Myopia progression over 3 years was an average (SE) of -2.06 (0.13) D for the single-vision lens group, -1.25 (0.10) D for the bifocal group, and -1.01 (0.13) D for the prismatic bifocal group. Axial length increased an average (SE) of 0.82 (0.05) mm, 0.57 (0.07) mm, and 0.54 (0.06) mm, respectively. The treatment effect of bifocals (0.81 D) and prismatic bifocals (1.05 D) was significant (P < .001). Both bifocal groups had less axial elongation (0.25 mm and 0.28 mm, respectively) than the single-vision lens group (P < .001). For children with high lags of accommodation (≥ 1.01 D), the treatment effect of both bifocals and prismatic bifocals was similar (1.1 D) (P < .001). For children with low lags (<1.01 D), the treatment effect of prismatic bifocals (0.99 D) was greater than of bifocals (0.50 D) (P = .03). The treatment effect of both bifocals and prismatic bifocals was independent of the near phoria status. Bifocal spectacles can slow myopia progression in children with an annual progression rate of at least 0.50 D after 3 years. These results suggest that prismatic bifocals are more effective for myopic children with low lags of accommodation. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00787579.