scholarly journals The role of peripheral ocular length and peripheral corneal radius of curvature in determining refractive error

2021 ◽  
Author(s):  
Saleh H.A. Alhussain ◽  
Edward A.H. Mallen ◽  
Niall C. Strang ◽  
Sven Jonuscheit
Keyword(s):  
Refractive Error ◽  
Radius Of Curvature ◽  
Corneal Radius

scholarly journals The Role of Axial Length-Corneal Radius of Curvature Ratio in Refractive State Categorization in a Nigerian Population

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Eghosasere Iyamu ◽  
Joy Iyamu ◽  
Christian Izuchukwu Obiakor
Keyword(s):  
Axial Length ◽  
Inverse Correlation ◽  
Radius Of Curvature ◽  
Spherical Equivalent ◽  
Refractive State ◽  
Spherical Equivalent Refraction ◽  
Nigerian Population ◽  
Corneal Radius ◽  
The Mean

The aim of this study was to investigate the association of axial length (AL)/corneal radius of curvature (CRC) ratio (AL/CRC) with spherical equivalent refractive state (SER) in young adults. A total of seventy () subjects consisting of 31 males and 39 females participated in this study. Subjects were categorized into emmetropia, hyperopia and myopia using the spherical equivalent refraction. The axial length was measured with I-2100 A-Scan ultrasonography/Biometer (CIMA Technology, USA), the corneal radius of curvature with Bausch & Lomb H-135A (Bausch & Lomb Corp., USA), and the refractive state by static retinoscopy and subjective refraction. The mean AL, CRC and AL/CRC ratio of all subjects were 23.74 ± 0.70 mm, 7.84 ± 0.19 mm, and 3.03 ± 0.14, respectively. Myopes had significantly longer AL, steeper CRC and higher AL/CRC ratio than the emmetropes and hyperopes. There was statistically significant inverse correlation between AL and CRC (, ), SER (, ), and between SER and AL/CRC (, ). A significant positive correlation was found between CRC and SER (, ). The categorization of the refractive state of an individual is better done by using the AL/CRC ratio index.

scholarly journals Correlation of refractive error with axial length and corneal topography

2016 ◽  
Vol 15 (1) ◽  
pp. 25-33
Author(s):  
Surabhi Ruia ◽  
Poonam Kishore ◽  
Vinita Singh ◽  
Nitin Chaudhary
Keyword(s):  
Negative Correlation ◽  
Refractive Error ◽  
Axial Length ◽  
Corneal Topography ◽  
Radius Of Curvature ◽  
Cross Sectional ◽  
Positive Correlation ◽  
Study Materials ◽  
Group 5 ◽  
Group 2

Purpose: To collect and analyze normative data about corneal topography and axial length in various refractive errors in Indian population.Design: Cross-sectional observational study. Materials and Method: Three hundred eyes (150 patients) of age group 12-35 yrs were arranged in 5 groups according to refractive status; Group 1 (n=44): myopia of SphericalEquivalent (SE) > 6 D; Group 2 (n=67): myopia of SE >0.5 D to 6 D; Group 3 (n=88): nearly emmetropic of SE -0.5 D to +0.5 D; Group 4 (n=59): hypermetropia of SE >0.5 to 6 D; Group 5 (n=42): hypermetropia of SE > 6 D. Axial length(AL), central radius of curvature of cornea (CR), central power of cornea (CK) , Al/CR ratio for each group were documented . Correlation with SE and among each other was studied. Results: Mean AL (in mm) of myopic patients (n=111) was 24.23 ± 1.34, emmetropic (n=88) 22.62 ± 0.94 and hypermetropics (n=101) 20.73 ±0.94. Mean CR (in mm) of myopic patients was 7.55 ± 0.35, emmetropics was 7.70 ±0.32, and hypermetropes was 7.99 ±0.35. Mean CK (in D) of myopics was 44.86±2.59, emmetropes was 43.91±1.76, and hypermetropes was 42.32±1.89. Mean AL/CR ratio of myopics was 3.22 ± 0.29, emmetropics 2.94± 0.07, and hypermetropics 2.60 ± 0.19. AL was negatively correlated with SE(r=-0.91, p<0.0001) and positively with AL/CR(r=0.88, p<0.0001) and CK (r=0.36, p<0.0001). CR was negatively correlated with AL/CR (r=-0.74, p<0.0001) while positively correlated with SE (r=0.62, p<0.0001). CK showed positive correlation with AL/CR (r=0.75, p<0.0001) while negative correlation with SE (r=-0.61, p<0.0001). AL/CR was negatively correlated withSE(r=-0.95, p<0.0001). Conclusion: This study showed a negative correlation between axial length and refractive error and between AL/CR ratio and refractive error with stronger inverse relationship in hypermetropes than myopes. There was a positive correlation of CR with SE with a weaker direct relationship in myopes than hypermetropes. 

scholarly journals Development of Refractive Parameters in 3- to 6-Year-Old Children and Its Application in Myopia Prediction and Intervention Guidance

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Ya Zhang ◽  
Ming Su ◽  
Hua Liu ◽  
Yanxia Song ◽  
Jing Liu ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Clinical Work ◽  
Hebei Province ◽  
Radius Of Curvature ◽  
Spherical Equivalent ◽  
Ocular Biometry ◽  
Refractive Development ◽  
Corneal Radius ◽  
The Mean ◽  
Vision Screener

Objective. To investigate refractive development and prevalence of myopia in children aged 3-6 years in Hebei Province, China, and to explore the developmental law of refraction, so as to clinically guide the prediction and intervention of myopia. Methods. In May 2019, a total of 6120 people were inspected in 68 kindergartens in 11 cities in Hebei Province. Child refractive refraction was checked under noncycloplegia using a handheld binocular vision screener (SW-800, SUOER, Tianjin, China). Axial length (AL) and corneal radius of curvature (CR) were measured using an ocular biometry (IOLMaster 500, Carl Zeiss, Germany). Myopia was defined as spherical equivalent SE ≤ − 0.75   D . Results. A total of 5506 children aged 3-6 years met the criteria and were included in the statistical analysis. The prevalence of myopia was 3.49% (1.93% at age 3, 2.90% at age 4, 3.78% at age 5, and 3.88% at age 6). Overall, the mean SE was + 0.67 ± 1.05   D ( + 0.81 ± 1.00   D at age 3, + 0.79 ± 1.05   D at age 4, + 0.67 ± 1.08   D at age 5, and + 0.13 ± 1.01   D at age 6); the mean CR was 7.76 ± 0.26   mm ( 7.78 ± 0.26   mm at age3, 7.75 ± 0.25   mm at age 4, 7.77 ± 0.26   mm at age 5, and 7.76 ± 0.25   mm at age 6); the mean AL was 22.31 ± 0.73   mm ( 21.98 ± 0.63   mm at age 3, 22.12 ± 0.69   mm at age 4, 22.34 ± 0.73   mm at age 5, and 22.49 ± 0.73   mm at age 6). Conclusions. Prevalence of myopia increases with age in children aged 3-6 years in Hebei, China. With the increase of age, CR is basically stable, and AL increases gradually. AL/CR, which is closely related to SE, can be used as an indicator to predict myopia and guide clinical work.

scholarly journals Genetic Association Study of KCNQ5 Polymorphisms with High Myopia

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Xuan Liao ◽  
Maurice K. H. Yap ◽  
Kim Hung Leung ◽  
Patrick Y. P. Kao ◽  
Long Qian Liu ◽  
...  
Keyword(s):  
Refractive Error ◽  
Odds Ratio ◽  
High Myopia ◽  
Permutation Test ◽  
Minor Allele ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
Association Testing ◽  
Hypersensitive Sites

Identification of genetic variations related to high myopia may advance our knowledge of the etiopathogenesis of refractive error. This study investigated the role of potassium channel gene (KCNQ5) polymorphisms in high myopia. We performed a case-control study of 1563 unrelated Han Chinese subjects (809 cases of high myopia and 754 emmetropic controls). Five tag single-nucleotide polymorphisms (SNPs) of KCNQ5 were genotyped, and association testing with high myopia was conducted using logistic regression analysis adjusted for sex and age to give Pasym values, and multiple comparisons were corrected by permutation test to give Pemp values. All five noncoding SNPs were associated with high myopia. The SNP rs7744813, previously shown to be associated with refractive error and myopia in two GWAS, showed an odds ratio of 0.75 (95% CI 0.63–0.90; Pemp = 0.0058) for the minor allele. The top SNP rs9342979 showed an odds ratio of 0.75 (95% CI 0.64–0.89; Pemp = 0.0045) for the minor allele. Both SNPs are located within enhancer histone marks and DNase-hypersensitive sites. Our data support the involvement of KCNQ5 gene polymorphisms in the genetic susceptibility to high myopia and further exploration of KCNQ5 as a risk factor for high myopia.

The Role of Grain Tip Radius in Fine Grinding

1975 ◽  
Vol 97 (3) ◽  
pp. 1119-1125 ◽  
Author(s):  
G. K. Lal ◽  
M. C. Shaw
Keyword(s):  
Grain Size ◽  
Surface Finish ◽  
Chip Thickness ◽  
Radius Of Curvature ◽  
Undeformed Chip Thickness ◽  
Fine Grinding ◽  
Abrasive Grains ◽  
Grinding Conditions ◽  
Tip Radius

The scratches produced by single abrasive grains in overcut fly milling show that the transverse shape of a grain is closely approximated by an arc of a circle. This radius of curvature is found to be independent of grain type and grinding conditions but varies with the grain size. The equation for undeformed chip thickness for surface grinding is rederived in terms of this radius. The important role that the transverse curvature of the grain plays relative to surface finish is also discussed.

scholarly journals Proportion and characteristic of emmetropia in schoolchildren aged 6-11y: the Shenzhen elementary school eye study

2020 ◽  
Vol 13 (12) ◽  
pp. 1983-1989
Author(s):  
Xian-Ming Jiang ◽  
Xiao Han ◽  
Qian Tan ◽  
Jun-Shu Wu
Keyword(s):  
Elementary School ◽  
Axial Length ◽  
Primary Schools ◽  
Radius Of Curvature ◽  
Special Focus ◽  
School Students ◽  
Normal Value ◽  
Biometric Parameters ◽  
Corneal Radius ◽  
Change Trend

AIM: To investigate the proportion and characteristic of emmetropia in schoolchildren aged 6-11, especially estimate the normal value of ocular biometric parameters of emmetropia. METHODS: A population-based cross-sectional study was conducted on children aged 6-11y in Shenzhen. Totally, 2386 schoolchildren from two primary schools were involved. The axial length (AL) and the corneal radius of curvature (CRC) were measured by partial coherence laser interferometry. Noncycloplegic refraction and refractive astigmatism (RA) was measured using autorefraction. The axial length-to-corneal radius of curvature ratio (AL/CRC), corneal astigmatism (CA) and spherical equivalent refraction (SER) were calculated. RESULTS: The proportion of emmetropia in elementary school students was 41.30%. This percentage decreased gradually from 6 to 11 years of age and decreased rapidly after 9 years of age. The mean and 95%CI of each parameter were provided for boys and girls aged 6 to 11 years of age with emmetropia according to each age group. The change trend of parameters of boys and girls are similar. After 7 years of age, the AL of non-emmetropia started to increase faster than that of emmetropia. The change trend of AL/CRC was the same as that of AL. The other parameters tend to be stable after 7 years of age. CONCLUSION: The age of 7-9 is an important period for the changes of refractive state and ocular biometric parameters of primary school students, and it is a special focus period for children myopia prevention. The normal value and variation of ocular biometric parameters of emmetropia can provide the basis for the clinical judgment of whether or not children’s ocular biometric parameters obtained by single measurement and changes obtained by multiple measurements are abnormal.

CHANGE OF SOME INDICATORS OF EYES BEFORE AND AFTER SURGICAL TREATMENT PHACO CATARACT SENIORS IN HUE UNIVERSITY HOSPITAL

2015 ◽  
pp. 81-85
Author(s):  
Thi Dieu Tram Phan ◽  
Van Nam Phan
Keyword(s):  
Anterior Chamber Depth ◽  
University Hospital ◽  
Radius Of Curvature ◽  
Postoperative Astigmatism ◽  
First Choice ◽  
Before And After ◽  
Corneal Radius ◽  
The Mean ◽  
Phacoemulsification Cataract Surgery ◽  
Cataract Patients

Objective: Phacoemulsification cataract surgery is the method applyied commonly and the first choice of Ophthalmologist. Materials and Method: We study comprised 49 eyes of 42 cataract patients for Phacoemulsification at Hue Hospital University from 5/2013 to 4/2014 with within 3 months after surgery. Result: 3 months after surgery, the visual acuity ≤ 4/10 accounted for 75,5%, corrected vision ≥ 4/10 accounted for 95,9%. The mean postoperative astigmatism was 1,02D ± 0,58, stable and does not change much compared to before surgery. The mean intraocular pressure (IOP) increased to 10,51mmHg ± 1,77 at 3 months postoperatively,the IOP was 3,9mmHg lower at 3 months than preoperative. Anterior chamber depth (ACD) increased by 1,0mm deeper than before surgery. Corneal refractive power increased 0,43D. Corneal radius of curvature decreased 0,11mm by 3 month postoperatively. Key words: Cataract, Phacoemulsification.

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