Astigmatism – Definition, Etiology, Classification, Diagnosis and Non-Surgical Treatment

Kaimbo, D. Kaimbo Wa

doi:10.5772/18132

Cited by 5 publications

(12 citation statements)

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“… 3 – 6 Refractive astigmatism (that is, total astigmatism) includes both corneal and internal astigmatism and is the type of astigmatism obtained through retinoscopy or subjective refraction. 3 Refractive astigmatism may further be classified as sphero-cylinderical (defined in relation to association with spherical component), magnitude of astigmatism (defined according to magnitude or amount) and axis orientation 3 – 4 (defined based on cylinder axis). Astigmatism is clinically important given its associated symptoms which include asthenopia, blurry vision at various viewing distances, spatial distortion in size, shape or inclination of objects and thus degrades image quality.…”

Section: Introductionmentioning

confidence: 99%

“…Astigmatism is clinically important given its associated symptoms which include asthenopia, blurry vision at various viewing distances, spatial distortion in size, shape or inclination of objects and thus degrades image quality. 3 – 4 Furthermore, astigmatism alters emmetropization and is associated with myopia progression and development of amblyopia. 5 – 7 Therefore, knowledge of the distribution of astigmatism in this population will guide clinical practice, research and epidemiology in records and resource allocation.…”

Section: Introductionmentioning

confidence: 99%

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Characteristics of astigmatism in Black South African high school children.

Wajuihian

2018

Afr H. Sci.

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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.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characteristics of astigmatism in Black South African high school children.

Wajuihian

2018

Afr H. Sci.

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“…Astigmatisms are a commonly encountered refractive error, which account for about 13% of refractive errors of the human eye 6, 7. Astigmatisms are divided into corneal keratometric and internal astigmatisms (a total astigmatism is the sum of keratometric and internal astigmatisms).…”

Section: Introductionmentioning

confidence: 99%

“…Corneal keratometric astigmatisms are a result of unequal curvature along the two principal meridians of the anterior cornea. The ocular astigmatism is attributed to the posterior cornea, unequal curvatures of the front and back surfaces of the crystalline lens, or differing refractive indices across the crystalline lens are referred to as an internal astigmatism 6, 7, 8. Internal astigmatisms are also called residual astigmatisms, which are quantified by magnitude and axis as the vector value of ocular residual astigmatisms 9, 10.…”

Section: Introductionmentioning

confidence: 99%

“… 3 , 6 , 7 Astigmatisms are a commonly encountered refractive error, which account for about 13% of refractive errors of the human eye. 6 , 7 Astigmatisms are divided into corneal keratometric and internal astigmatisms (a total astigmatism is the sum of keratometric and internal astigmatisms). Corneal keratometric astigmatisms are a result of unequal curvature along the two principal meridians of the anterior cornea.…”

Section: Introductionmentioning

confidence: 99%

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Astigmatic treatment with photorefractive keratectomy: Investigations of non-keratometric ocular astigmatism

Peyman

Dastborhan

Peyman

2017

Journal of Current Ophthalmology

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PurposeTo evaluate the effect of non-keratometric ocular astigmatisms on visual and refractive outcomes after photorefractive keratectomy (PRK) for correction of myopic astigmatisms.MethodsSeventy one eyes of 36 subjects were enrolled in this study. Patients underwent PRK for treatment of myopia. Subjects were evaluated for refractive error, keratometry, and visual acuity before and six months after surgery. Pre- and post-op non-keratometric astigmatisms were calculated by vectorial analysis of the difference between the corneal plane refractive astigmatism and keratometric astigmatism. Astigmatic analysis explored the contribution of non-keratometric astigmatisms.ResultsThe pre-op spherical equivalent (SE) was −6.27 ± 1.48 with 1.16 ± 1.02 diopters of corneal plane refractive astigmatism and 1.44 ± 0.47 diopters keratometric astigmatism. Post-op values were −0.60 ± 0.85, 0.56 ± 0.47, and 1.06 ± 0.57, respectively, 6 months after surgery. Pre- and post-op non-keratometric astigmatisms were 0.76 ± 0.41 and 0.76 ± 0.46, respectively, (P = 0.976) with significant correlation (r = 0.37, P = 0.002). Pre-op non-keratometric astigmatisms correlated to the pre-op SE (r = −0.25, P = 0.04). Pre-op non-keratometric astigmatisms had significant correlation with keratometric difference vector of astigmatic correction (r = 0.369, P = 0.002). Post-op non-keratometric astigmatisms correlated to keratometric induced astigmatism (r = 0.334, P = 0.006), keratometric index of success (r = 0.571, P < 0.001), and post-op keratometric astigmatism (r = 0.736, P < 0.001).ConclusionsHigher or lower non-keratometric ocular astigmatisms did not have any effect on refractive and visual outcome after PRK. PRK effectively corrected total refractive astigmatism through correction of keratometric astigmatism and additional adjustment to compensate for non-keratometric ocular astigmatisms.

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Epidemiology and Burden of Astigmatism: A Systematic Literature Review

Zhang¹,

Sharma³

et al. 2023

Optom Vis Sci

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SIGNIFICANCE This is the first literature review to report the epidemiology, patient burden, and economic burden of astigmatism in the general adult population. The unmet needs of astigmatism patients with coexisting ocular conditions (cataract, glaucoma, dry eye, presbyopia, or macular degeneration) and risks associated with untreated astigmatism are also reviewed and reported. PURPOSE This study aimed to identify, report, and summarize the published literature on epidemiology, patient burden, and economic burden of astigmatism using a systematic literature review. METHODS MEDLINE, EMBASE, and Cochrane Library databases were searched (January 1996 to May 2021). Search results were limited to the English language. Proceedings (2018 to 2021) from ophthalmology congresses were searched along with gray literature using the Google Scholar platform. RESULTS The literature search yielded 6804 citations, of which 125 met the inclusion criteria (epidemiology, 68; patient burden, 60; economic burden, 6). Astigmatism prevalence in the general population varied from 8 to 62%, with higher rates in individuals 70 years or older. The prevalence of with-the-rule astigmatism was higher in individuals 40 years or younger, whereas rates of against-the-rule and oblique astigmatism increased with age. Astigmatic patients experienced decreased vision quality, increased glare (53 to 77%), haloes (28 to 80%), night-time driving difficulties (66%), falls, and spectacle dependence (45 to 85%). Astigmatic patients performed vision-related tasks slower (1 D, 9% slower; 2 D, 29% slower) and made more errors (1 D, 38% more errors; 2 D, 370% more errors) compared with fully corrected individuals. In cataract patients with astigmatism, the annual mean per-patient productivity loss costs ranged from €55 ($71) to €84 ($108), and mean informal care costs ranged from €30 ($39) to €55 ($71) with a mean of 2.3 to 4.1 hours spent on informal care. CONCLUSIONS Uncorrected astigmatism decreases patients' vision-related quality of life, decreases productivity among working-age adults, and poses an economic burden on patients and their families.

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Astigmatism – Definition, Etiology, Classification, Diagnosis and Non-Surgical Treatment

Cited by 5 publications

References 65 publications

Characteristics of astigmatism in Black South African high school children.

Characteristics of astigmatism in Black South African high school children.

Astigmatic treatment with photorefractive keratectomy: Investigations of non-keratometric ocular astigmatism

Epidemiology and Burden of Astigmatism: A Systematic Literature Review

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