Role of the Cornea in Emmetropia and Myopia

Grosvenor, Theodore; Goss, David A.

doi:10.1097/00006324-199802000-00017

Cited by 97 publications

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“…Several studies [11] have reported an inverse relationship of AL to refraction (Table 3). The steeper the corneal curvature, the more likely that the resulting refractive error is myopic; eyes with hyperopia are more likely to have flatter corneal curvature readings by means of keratometry [12][13][14]. Heritability estimates for corneal curvature range from 60% to 92%.…”

Section: Discussionmentioning

confidence: 99%

A Survey of the Prevalence of Refractive Errors among Children in Lower Primary Schools in Darnah City, Libya

Elmajri¹

2017

AOVS

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Introduction: Refractive error is a one of the most common problem among children which may lead to blindness. Refractive errors cannot be prevented, but they can be diagnosed early by a routine eye examination and treated with corrective glasses, contact lenses or refractive surgery.Objective: To determine the prevalence of refractive errors among school children attending lower primary school in Darnah city eastern part of Libya and the frequency of the various types of refractive errors, and their associated to selected demographic variables among school children. Materials and Methods:The research design adopted for this study was nonexperimental Descriptive in terms of analysis and Cross Sectional in terms of time frame. The study was conducted at selected school with 10 samples. The samples who met the inclusion criteria were selected by using convenient sampling technique. The tool used for the study was demographic variable and checklist to assess the factors associated with refractive error.Result: A total of 1000 children from 10 schools were randomly selected. However 920 were examined. Mean age of the students was 9.53±1.5. Refractive error was associated with female sex (107) one hundred seven children had a significant refractive error of ±0.50 or worse in one or both eyes, giving a prevalence of 11.6% and the commonest refractive error was hypermetropia which accounted for (57) 53.2% of all errors. This was followed by astigmatism with 34 (31.7%) children and myopia with 16 (14.9%). Conclusion:Refractive error needs careful evaluation and preventive care for children which leads to impaired quality of life and interfere with their daily lifestyle. Assessing the risk factor will help us to prevent and control the problem of refractive error in future generation which is helpful for the students to live a life problem free life. Keywords:

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Section: Discussionmentioning

confidence: 99%

A Survey of the Prevalence of Refractive Errors among Children in Lower Primary Schools in Darnah City, Libya

Elmajri¹

2017

AOVS

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“…10,18,19 Heritability estimates for corneal curvature range from 60% to 92%. 9,[15][16][17] The Sardinian family study 17 noted evidence of modest linkage between corneal curvature and chromosomes 2p25, 3p26, and 7q22, with LOD scores ranging from 2.34 to 2.50.…”

Section: Ocular Refractive Component Geneticsmentioning

confidence: 99%

Complex Trait Genetics of Refractive Error

Young¹

2007

Arch Ophthalmol

182

127

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“…During the first two years of life, the cornea and axial length overcome the initial hyperopia and grow rapidly and in concert as part of the emmetropization process (Scammon and Armstrong, 1925;York and Mandell, 1969;Weale, 1982). Thereafter, corneal power remains relatively stable (Sorsby et al, 1961;Garner et al, 1990;Goss and Jackson, 1993;Fledelius and Stubgaard, 1986), until the adult years, when it may increase slightly (Fledelius and Stubgaard, 1986;Grosvenor and Goss, 1998) Since corneal flattening rather than steepening would be needed to compensate optically for the axial length growth, it is clear that the cornea plays little or no role in the emmetropization process after the first 2 years of life (Sorsby et al, 1961;Goss and Erickson, 1987;Goss and Jackson, 1993;Fledelius and Stubgaard, 1986). Moreover, since there is no evidence that visual feedback plays a role in the growth of the lens (Sorsby et al, 1961;Van Alphen, 1961), emmetropization during this later period involving any large artificially induced retinal-image defocus must be provided only by the rate of change of axial length growth.…”

Section: Resultsmentioning

confidence: 99%

A Unifying Theory of Refractive Error Development

Hung

2000

Bulletin of Mathematical Biology

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While retinal defocus is believed to be myopigenic in nature, the underlying mechanism has remained elusive. We recently constructed a theory of refractive error development to investigate its fundamental properties. Our Incremental RetinalDefocus Theory is based on the principle that the change in retinal-defocus magnitude during an increment of genetically-programmed ocular growth provides the requisite sign for the appropriate alteration in subsequent environmentally-induced ocular growth. This theory was tested under five experimental conditions: lenses, diffusers, occlusion, crystalline lens removal, and prolonged nearwork. Predictions of the theory were consistent with previous animal and human experimental findings. In addition, simulations using a MATLAB/SIMULINK model supported our theory by demonstrating quantitatively the appropriate directional changes in ocular growth rate. Thus, our Incremental Retinal-Defocus Theory provides a simple and logical unifying concept underlying the mechanism for the development of refractive error.

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Role of the Cornea in Emmetropia and Myopia

Cited by 97 publications

References 0 publications

A Survey of the Prevalence of Refractive Errors among Children in Lower Primary Schools in Darnah City, Libya

A Survey of the Prevalence of Refractive Errors among Children in Lower Primary Schools in Darnah City, Libya

Complex Trait Genetics of Refractive Error

A Unifying Theory of Refractive Error Development

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