Characteristics of astigmatism in Black South African high school children.

Abstract

BackgroundAstigmatism impairs vision at various distances and causes symptoms of asthenopia which negatively impacts reading efficiency.ObjectiveThe aim of conducting this study was to determine the prevalence and distribution of astigmatism and its relationship to gender, age, school grade levels and spherical ametropia.MethodsUsing a multi-stage random cluster sampling, 1589 children who included 635 (40%), males, and 954 (60%), females were selected from 13 out of a sample frame of 60 schools. Their ages ranged between 13 and 18 years with a mean of 15.81±1.56 years. The parameters evaluated included visual acuity using the LogMAR chart and refractive errors measured using an autorefractor and then refined subjectively. Axis of astigmatism was presented in the vector method where positive values of J0 indicated with-the-rule, negative values described against-the-rule and J45 represented oblique astigmatism.ResultsThe mean cylinder power was −0.09 ± 0.27 and mainly with-the-rule, J0 = 0.01 ± 0.11. The overall prevalence of clinically significant astigmatism (≤ − 0.75 cylinder) in the sample was 3.1% [(95% Confidence interval = 2.1–4.1%)]. Cylinder of at least − 0.25 power was considered to classify astigmatism types. Thus, the estimated distributions of types of astigmatism were: axis- 11.5%, sphero-astigmatism 10.1% and magnitude-astigmatism 11.2% while 67.2% had no cylinder of any magnitude.ConclusionThe prevalence of astigmatism is relatively low in this population studied. Older children and those in high school grade levels were more likely to have with-the-rule or against-the-rule astigmatism. The prevalence of astigmatism were comparable within but not across regions.

Axial length shortening after orthokeratology and its relationship with myopic control

“…The traditional clinical representations of refraction using sphere, cylinder, and axis, are not adequate for quantitative analysis of astigmatism. Therefore, the transformations, J0 and J45 in the vector notation was used to analyze axis-astigmatism according to the formula: J0 = − 1/2 C cos (2 α) and J45 = −½ C sin (2 α), Where C = negative cylinder power and α = cylinder axis in degrees [ 17 , 18 ]. Significant difference between the two groups was found in J0 component of astigmatism ( p <0.05) and no significant difference was found in J45 component of astigmatism ( p = 0.81).…”

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“…The prevalence of this refractive error differs depending on race [48,51], sex and age [52]. It is also influenced by genetic factors, with a higher prevalence than myopia and hyperopia, between 30% and 77% [52].…”

Astigmat Kornea Pada Penderita Katarak

“…Sedangkan astigmat derajat sangat berat lebih banyak pada WTR. Hasil penelitian ini berbeda dengan hasil penelitian Wajuihian 24 di Afrika pada tahun 2017 yang melaporkan pasien terbanyak yaitu pasien astigmat WTR dengan derajat ringan dengan persentase sebesar 42,4%.…”