Displaying all 10 publications

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  1. Chen AH
    PMID: 12152800
    The purpose of this study was to determine if there was any difference between myopes and emmetropes in using blur as a stimulus for accommodation when the chromatic aberration, size and proximal cues were eliminated. Twenty adults (10 myopes and 10 emmetropes) were examined for their accuracy of accommodation response for five different accommodation demands (OD, 1D, 2D, 3D, 4D) under two different light sources: achromatized white light versus monochromatic light. There was no significant difference in using blur stimulus between myopes and emmetropes when the chromatic aberration, size and proximal cues were eliminated.
    Matched MeSH terms: Myopia/physiopathology*
  2. Azemin MZ, Daud NM, Ab Hamid F, Zahari I, Sapuan AH
    ScientificWorldJournal, 2014;2014:783525.
    PMID: 25371914 DOI: 10.1155/2014/783525
    The aim of this study was to compare the retinal vasculature complexity between emmetropia, and myopia in younger subjects.
    Matched MeSH terms: Myopia/physiopathology*
  3. Chung K, Mohidin N, O'Leary DJ
    Vision Res, 2002 Oct;42(22):2555-9.
    PMID: 12445849
    The effect of myopic defocus on myopia progression was assessed in a two-year prospective study on 94 myopes aged 9-14 years, randomly allocated to an undercorrected group or a fully corrected control group. The 47 experimental subjects were blurred by approximately +0.75 D (blurring VA to 6/12), while the controls were fully corrected. Undercorrection produced more rapid myopia progression and axial elongation (ANOVA, F(1,374)=14.32, p<0.01). Contrary to animal studies, myopic defocus speeds up myopia development in already myopic humans. Myopia could be caused by a failure to detect the direction of defocus rather than by a mechanism exhibiting a zero-point error.
    Matched MeSH terms: Myopia/physiopathology
  4. Omar WEW, Singh G, McBain AJ, Cruickshank F, Radhakrishnan H
    Invest Ophthalmol Vis Sci, 2024 May 01;65(5):2.
    PMID: 38691091 DOI: 10.1167/iovs.65.5.2
    PURPOSE: To identify compositional differences in the gut microbiome of nonmyopes (NM) and myopes using 16S ribosomal RNA sequencing and to investigate whether the microbiome may contribute to the onset or progression of the condition.

    METHODS: Faecal samples were collected from 52 adult participants, of whom 23 were NM, 8 were progressive myopes (PM), and 21 were stable myopes (SM). The composition of the gut microbiota in each group was analysed using 16S ribosomal RNA gene sequencing.

    RESULTS: There were no significant differences in alpha and beta diversity between the three groups (NM, PM, and SM). However, the distributions of Bifidobacterium, Bacteroides, Megamonas, Faecalibacterium, Coprococcus, Dorea, Roseburia, and Blautia were significantly higher in the myopes (SM and PM combined) when compared with emmetropes. The myopes exhibited significantly greater abundance of bacteria that are linked to the regulation of dopaminergic signalling, such as Clostridium, Ruminococcus, Bifidobacterium, and Bacteroides. Individuals with stable myopia were found to have a significantly higher proportion of Prevotella copri than those with progressive myopia. Bifidobacterium adolescentis, a gamma-aminobutyric acid (GABA)-producing bacterium, was significantly higher in all myopes than in NM and, in the comparison between SM and PM, it is significantly higher in SM. B. uniformis and B. fragilis, both GABA-producing Bacteroides, were present in relatively high abundance in all myopes and in SM compared with PM, respectively.

    CONCLUSIONS: The presence of bacteria related to dopamine effect and GABA-producing bacteria in the gut microbiome of myopes may suggest a role of these microorganisms in the onset and progression of myopia.

    Matched MeSH terms: Myopia/physiopathology
  5. Price H, Allen PM, Radhakrishnan H, Calver R, Rae S, Theagarayan B, et al.
    Optom Vis Sci, 2013 Nov;90(11):1274-83.
    PMID: 24100478 DOI: 10.1097/OPX.0000000000000067
    To identify variables associated with myopia progression and to identify any interaction between accommodative function, myopia progression, age, and treatment effect in the Cambridge Anti-Myopia Study.
    Matched MeSH terms: Myopia/physiopathology
  6. Morgan IG, Rose KA, Ellwein LB, Refractive Error Study in Children Survey Group
    Acta Ophthalmol, 2010 Dec;88(8):877-84.
    PMID: 19958289 DOI: 10.1111/j.1755-3768.2009.01800.x
    PURPOSE: To determine the natural end-point for refractive development during childhood.

    METHODS: Cycloplegic (1% cyclopentolate) autorefraction was performed on 38, 811 children aged 5 and 15 in population-based samples at eight sites in the Refractive Error Study in Children (RESC). Refractions (right eye) were categorized as myopic (≤-0.5 D), emmetropic (>-0.5 to ≤+0.5 D), mildly hyperopic (>+0.5 to ≤+2.0 D and hyperopic (>+2.0 D).

    RESULTS: At five sites (Jhapa - rural Nepal, New Delhi - urban India, Mahabubnagar - rural India, Durban - semi-urban South Africa and La Florida - urban Chile), there was <20% myopia by age 15. Mild hyperopia was the most prevalent category at all ages, except for Mahabubnagar where emmetropia became the marginally most prevalent category at ages 14 and 15. At the other sites (Gombak - semi-urban Malaysia, Shunyi - semi-rural China and Guangzhou - urban China), there was substantial (>35%) myopia by age 15. At these sites, mild hyperopia was the most prevalent category during early childhood, and myopia became the predominant category later. In Gombak district and Guangzhou, emmetropia was a minor category at all ages, with myopia increasing as mild hyperopia decreased. In Shunyi district, emmetropia was the most prevalent category over the ages 11-14.

    CONCLUSION: Emmetropia was not the predominant outcome for refractive development in children. Instead, populations were predominantly mildly hyperopic or substantial amounts of myopia appeared in them. This suggests that mild hyperopia is the natural state of refractive development in children and that emmetropia during childhood carries the risk of subsequent progression to myopia.

    Matched MeSH terms: Myopia/physiopathology*
  7. Chung KM
    Optom Vis Sci, 1993 Mar;70(3):228-33.
    PMID: 8483585
    Studies of optical defocus on refractive development and ocular growth in animals are presented and discussed in relation to the accommodation hypothesis. None of these studies fully support the accommodation hypothesis. The problems encountered in these studies are also discussed.
    Matched MeSH terms: Myopia/physiopathology*
  8. Deva JP
    J Refract Surg, 1998 Apr;14(2 Suppl):S215-7.
    PMID: 9571558
    PURPOSE: To investigate the accuracy of preoperative optical assessment and other factors that influenced the final visual outcome after photorefractive keratectomy (PRK).

    METHODS: The records of 126 eyes from 54 male and 72 female eyes were studied retrospectively, ranging from 6 months to 3 years post-PRK. Refractive errors ranged from low to high myopia and astigmatism, and proper and careful preoperative selection of patients was made. A single standard ablation zone (AZ) of 6.00 mm and transition zone (TZ) of 7.00 mm was made in all cases.

    RESULTS: The study population showed a high degree of accuracy in visual outcome. In simple myopia, 92.3% of female eyes and 84.1% of male eyes had a visual acuity of more than 6/9 or better. In myopia with astigmatism, 83.05% of female and 65.9% of male eyes had a visual acuity of 6/9 (20/40) or better. However, despite the residual myopia, whether with or induced astigmatism, post PRK visual acuity seemed to be less influenced by it, than as in the pre-PRK status.

    CONCLUSION: This study showed an accuracy in visual outcome of > 90% for females and > 80% for males. The Nidek EC-500 was satisfactory for its purpose.

    Matched MeSH terms: Myopia/physiopathology
  9. Lim KL, Fam HB
    J Refract Surg, 2006 Apr;22(4):406-8.
    PMID: 16629076
    PURPOSE: To evaluate a novel non-surgical method for improving vision in a refractive surgery patient.

    METHODS: A 45-year-old man who had undergone LASIK 5 years previously presented with blurred distance vision. Unaided vision in the right eye was 20/329-2) and 20/20 in the left eye. He enrolled for NeuroVision treatment (NeuroVision Pte Ltd, Singapore), a computer-based interface in which a repetitive set of visual excerises is performed for 10 to 12 weeks.

    RESULTS: After 35 sessions, unaided visual acuity in the right eye was 20/16(-3) and 20/20(-1) in the left eye, representing 2.8 lines of improvement in the right eye and 1.6 lines in the left eye.

    CONCLUSIONS: NeuroVision, a noninvasive treatment based on the concept of perceptual learning, is a benefit in cases in which surgical enhancement is not recommended.

    Matched MeSH terms: Myopia/physiopathology
  10. Radhakrishnan H, Hartwig A, Charman WN, Llorente L
    Clin Exp Optom, 2015 Nov;98(6):527-34.
    PMID: 26450168 DOI: 10.1111/cxo.12296
    BACKGROUND: Differences in accommodation when reading Chinese, as compared to Latin, characters have been suggested to have a role in the higher prevalence of myopia in some Asian countries. Yeo and colleagues (Optom Vis Sci 2013; 90: 156-163) found that, in Chinese-literate children, accommodation was marginally more accurate (by less than 0.05 D), when reading Chinese text. This was attributed to the additional cognitive demand associated with interpreting the more complex Chinese symbols. The present study compared responses to single Chinese and Latin characters, while controlling for cognitive demand.
    METHODS: The monocular accommodative response was measured in Chinese-illiterate adults (10 emmetropes, mean spherical equivalent: -0.07 ± 0.42 D, age: 29.9 ± 4.2 years; 11 myopes, mean spherical equivalent: -4.28 ± 2.84 D, age: 31.7 ± 4.6 years) with an open-field autorefractor. Four Chinese and three Latin characters (approximately 1.15 degrees subtense) were individually presented on a display screen one metre away from the subject, while their vergence was varied over the range zero to 5.00 D using spectacle trial lenses. The slope and the accommodative error index (AEI) were calculated from the accommodative stimulus/response curves (ASRC).
    RESULTS: No statistically significant differences were found between refractive groups or among characters within the same refractive group in ARSC slopes (Latin: 0.87 ± 0.14 for myopes versus 0.81 ± 0.12 for emmetropes; Chinese: 0.84 ± 0.12 for myopes versus 0.85 ± 0.12 for emmetropes). No significant differences were found between characters in accommodative error index either (Latin, 0.78 ± 0.42 D for myopes versus 1.15 ± 0.72 D for emmetropes; Chinese, 0.74 ± 0.37 D for myopes versus 1.17 ± 0.83 D for emmetropes). However, accommodative error indices and accommodative errors were significantly higher for emmetropes.
    CONCLUSION: Under controlled cognitive demand, Chinese and Latin characters elicited similar responses in both individual refractive groups. This study fails to support the hypothesis that development of myopia in some Asian populations is associated with larger lags of accommodation when reading or viewing Chinese characters.
    Study site: Manchester, United Kingdom
    Matched MeSH terms: Myopia/physiopathology*
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