Multimeridional Refraction: Dependence of the Measurement Accuracy on the Number of Meridians Refracted

Oechsner, Ulrich; Kusel, R.

doi:10.1097/00006324-199706000-00027

Cited by 13 publications

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“…According to this theory the cylinder axis of the astigmatism should have no influence on the expected VA. This hypothesis was supported by Oechsner and Kusel using numerical simulations 18 and later experimentally in different studies 19, 20, 21, 22, 23. On the contrary, Miller et al 10 and Wolffsohn et al 24 suggested that with-the-rule astigmatism (WTR) has a less negative influence on VA compared with against-the-rule (ATR) or oblique astigmatism.…”

Section: Introductionmentioning

confidence: 88%

Influence of different types of astigmatism on visual acuity

Remón

Monsoriu

Furlan

2017

Journal of Optometry

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PurposeTo investigate the change in visual acuity (VA) produced by different types of astigmatism (on the basis of the refractive power and position of the principal meridians) on normal accommodating eyes.MethodsThe lens induced method was employed to simulate a set of 28 astigmatic blur conditions on different healthy emmetropic eyes. Additionally, 24 values of spherical defocus were also simulated on the same eyes for comparison. VA was measured in each case and the results, expressed in logMAR units, were represented against of the modulus of the dioptric power vector (blur strength).ResultsLogMAR VA varies in a linear fashion with increasing astigmatic blur, being the slope of the line dependent on the accommodative demand in each type of astigmatism. However, in each case, we found no statistically significant differences between the three axes investigated (0°, 45°, 90°). Non-statistically significant differences were found either for the VA achieved with spherical myopic defocus (MD) and mixed astigmatism (MA). VA with simple hyperopic astigmatism (SHA) was higher than with simple myopic astigmatism (SMA), however, in this case non conclusive results were obtained in terms of statistical significance. The VA achieved with imposed compound hyperopic astigmatism (CHA) was highly influenced by the eye's accommodative response.ConclusionsVA is correlated with the blur strength in a different way for each type of astigmatism, depending on the accommodative demand. VA is better when one of the focal lines lie on the retina irrespective of the axis orientation; accommodation favors this situation.

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Section: Introductionmentioning

confidence: 88%

Influence of different types of astigmatism on visual acuity

Remón

Monsoriu

Furlan

2017

Journal of Optometry

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“…This result was later supported by Oechsner and Kusel using numeric simulations. 11 More recently, Rubin and Harris 12 also explored the relation between VA and defocused refractive state in the context of a symmetric dioptric power space. For a single stimulus size (20/60 computer-generated letter O), they obtained the associated refractions simulated in healthy eyes by means of spheres and Jackson's crosscylinders.…”

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confidence: 99%

“…This assertion creates a discrepancy with previous results. 10,11 The purpose of this work is to analyze additional empiric results to elucidate whether the simulated cylindrical axis changes influence the expected VA and, if so, to what extent. To this end, astigmatism of several degrees with variable axis orientations were simulated on compensated eyes and the maximum VA achieved in each case recorded.…”

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confidence: 99%

Visual Acuity in Simple Myopic Astigmatism: Influence of Cylinder Axis

Remón

Tornel

Furlan

2006

Optometry and Vision Science

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“…In Snell's law and first order optics both the incident and refracted rays and the normal to the point of incidence are assumed to lie in one plane. The power of a lens or a refraction is defined as the reciprocal of the reduced focal length or far point, respectively 50 (p.8), 51 . Some of the difficulties in calculating SIA are related to the continued use of the simplified model of first order optics XII .…”

Section: Basic Conceptsmentioning

confidence: 99%

Assessment and Statistics of Surgically Induced Astigmatism

Næser

2008

Acta Ophthalmologica

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The aim of the thesis was to develop methods for assessment of surgically induced astigmatism (SIA) in individual eyes, and in groups of eyes. The thesis is based on 12 peer-reviewed publications, published over a period of 16 years. In these publications older and contemporary literature was reviewed(1). A new method (the polar system) for analysis of SIA was developed. Multivariate statistical analysis of refractive data was described(2-4). Clinical validation studies were performed. The description of a cylinder surface with polar values and differential geometry was compared. The main results were: refractive data in the form of sphere, cylinder and axis may define an individual patient or data set, but are unsuited for mathematical and statistical analyses(1). The polar value system converts net astigmatisms to orthonormal components in dioptric space. A polar value is the difference in meridional power between two orthogonal meridians(5,6). Any pair of polar values, separated by an arch of 45 degrees, characterizes a net astigmatism completely(7). The two polar values represent the net curvital and net torsional power over the chosen meridian(8). The spherical component is described by the spherical equivalent power. Several clinical studies demonstrated the efficiency of multivariate statistical analysis of refractive data(4,9-11). Polar values and formal differential geometry describe astigmatic surfaces with similar concepts and mathematical functions(8). Other contemporary methods, such as Long's power matrix, Holladay's and Alpins' methods, Zernike(12) and Fourier analyses(8), are correlated to the polar value system. In conclusion, analysis of SIA should be performed with polar values or other contemporary component systems. The study was supported by Statens Sundhedsvidenskabeligt Forskningsråd, Cykelhandler P. Th. Rasmussen og Hustrus Mindelegat, Hotelejer Carl Larsen og Hustru Nicoline Larsens Mindelegat, Landsforeningen til Vaern om Synet, Forskningsinitiativet for Arhus Amt, Alcon Denmark, and Desirée and Niels Ydes Fond.

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Multimeridional Refraction: Dependence of the Measurement Accuracy on the Number of Meridians Refracted

Cited by 13 publications

References 0 publications

Influence of different types of astigmatism on visual acuity

Influence of different types of astigmatism on visual acuity

Visual Acuity in Simple Myopic Astigmatism: Influence of Cylinder Axis

Assessment and Statistics of Surgically Induced Astigmatism

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