The Visual Impact of Lens-Induced Astigmatism is Linked to Habitual Axis

Hughes, Amy R.; Mallen, Edward A. H.; Elliott, David B.

doi:10.1097/opx.0000000000001000

Cited by 10 publications

(10 citation statements)

References 29 publications

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“…In general, presbyopes wearing presbyopic corrections appear to adapt to the new visual experiences, to both blur in simultaneous vision images (Radhakrishnan et al, 2014) as well as to distortions and to the presence of asymmetric aberrations produced by progressive lenses (Alvarez, Kim and Granger-Donetti, 2017), in consistency with reported mechanisms of spatial neural adaptation (Sawides et al, 2011) In general, understanding how presbyopic lens designs can be improved, and even customized to the patient's refractive profile, requires understanding focus perception in presbyopic patients and to what extent visual perception with a new correction is affected by prior visual experience. Previous studies have shown adaptation to astigmatism (Marcos et al, 2015;Vinas et al, 2013, Hughes, Mallen andElliott, 2016), reflected by a strong bias in the perception of blur orientation.…”

Section: Introductionmentioning

confidence: 93%

“…In addition, young astigmatic subjects appear to be more sensitive to the reduction of visual acuity upon induction of astigmatism than non-astigmats (de Gracia et al, 2011), particularly when astigmatism is induced along the axis of their natural astigmatism (Vinas et al, 2013). Other studies have shown that subjects are not only adapted to their native astigmatism, but also to the magnitude (Sawides et al, 2011) and orientation (Artal, 2004, Sawides et al, 2010b, Hughes, Mallen and Elliott, 2016 of their own aberrations, and that the best perceived focus shifts following adaptation to high order aberrations (Marcos et al, 2015). Achieving optimal best focus is key to providing best optical quality with a correction.…”

Section: Introductionmentioning

confidence: 99%

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Perceptual impact of astigmatism induction in presbyopes

et al. 2019

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We investigated the effect of induced astigmatism on subjective best focus and on visual acuity in 28 subjects of different ages (pre-presbyopic and presbyopic) and with different refractive profiles (emmetropes and astigmats). Measurements were performed using a custom-developed Adaptive Optics system, which allowed correction of high order aberrations and induction of astigmatism (0.5, 1, 1.5 and 2.0 D; axis: 180º, 45º and 22.5º). Upon induction of astigmatism, best focus shifted towards negative values in pre-presbyopic emmetropic eyes (by-0.14 D for 0.5 D and by-0.33 D for 2.0 D), while it shifted towards positive values in presbyopes, both in emmetropic presbyopes (by +0.04 D for 0.50 D and by +0.16 D for 2.0 D) and in astigmatic presbyopes (by +0.23 D for 0.50 D and by +0.40 D for 2.0 D). Also, visual acuity was most sensitive to astigmatism induction in pre-presbyopic emmetropes and least sensitive in presbyopes, particularly when high order aberrations were corrected: visual acuity ratio with/without astigmatism was: 0.74/ 0.85/ 0.98 (for astigmatism induced at 180º) and 0.68/ 0.73/0.86 at 45º, for pre-presbyopic emmetropes/ presbyopic emmetropes/ presbyopic astigmats. These findings may be connected to long term exposure to astigmatism in astigmats and corrected presbyopes.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Perceptual impact of astigmatism induction in presbyopes

et al. 2019

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“…Lens induced astigmatism may affect chartbased visual acuity more than acuity measured with isolated Landolt Cs, because of the potential for the blurred images of adjacent optotypes to interact with each other on charts . It is likely that for isolated letters or for isolated Landolt Cs that doubling will degrade visual acuity less than for our chart‐based measures, because there is no opportunity for adjacent letters to overlap.…”

Section: Discussionmentioning

confidence: 97%

Simulated image doubling and visual acuity: effects of doubling magnitude, orientation, and ghost image intensity

Carkeet

Chang

et al. 2019

Ophthalmic Physiologic Optic

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Purpose The effects of image doubling on logarithmic progression chart visual acuity were investigated by simulating diplopia on a computer monitor. Methods Ten participants (6M, 4F) aged 21–28 years (mean 22.4 ± 2.3) were assessed viewing with their left eye while wearing their best correction. Stimuli were eight rows of five Sloan letters, from 0.4 to −0.3 logMAR (6/15 to 6/3) arranged in logarithmic progression format, generated on an HD monitor. Stimuli were generated with different magnitudes of doubling, different directions of doubling, and different intensity ratios between the ghost image and main images. Results When the ghost image had the same intensity as the main image, there was a significant effect of doubling magnitude on visual acuity, with the mean acuity being −0.11 logMAR (6/4.7) for no doubling. Acuity thresholds (logMAR) increased when doubling exceeded 1 min of arc, reaching a level of 0.12 logMAR (6/7.9) for doubling of 16 min of arc. There were no significant effects of orientation on acuity, nor were there significant orientation‐doubling magnitude interaction effects of visual acuity. Image doubling magnitude level affected visual acuity differently for different ghost image intensities, with the highest acuity elevation occurring when ghost and main images were equal or nearly equal. For faint ghost image intensities (10% and 20%) image doubling did not significantly affect visual acuity. Conclusions Image doubling will degrade visual acuity if doubling is greater than 1 min of arc, and ghost images are sufficiently intense. However, even with very obvious visually‐disturbing image doubling, visual acuity remains only slightly reduced.

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“… 18 A third limitation was the use of optically simulated blur which differs from uncorrected refractive astigmatism, due to magnification effects produced by the defocusing lens and the lack of long-standing neuronal adaptation to the astigmatic error. 54 The sample included in the study did not present significant RA, minimizing the effects of any meridional long-term blur adaptation, 53 , 55 and the effects of blur adaptation on the optical conditions were balanced throughout the sample by randomization.…”

Section: Discussionmentioning

confidence: 99%

The effect of astigmatic axis on visual acuity measured with different alphabets in Roman alphabet readers

Serra¹,

Cox²,

Chisholm³

2018

OPTO

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ObjectiveAstigmatism produces meridional variations in the retinal blur pattern, thus interacting with object spatial detail and altering visual performance as the axis changes. This study investigates the influence of astigmatic axis orientation on visual acuity (VA) for four alphabets used worldwide.MethodsVisual acuity was measured monocularly in 25 Roman alphabet users (mean age: 25.6±7.5 years) using computer-presented logarithm of the minimum angle of resolution (log-MAR) charts with letters from four different alphabets (Arabic, Chinese, Roman, and Tamil). VA was assessed under the effect of four optical conditions: best distance correction and three astigmatic conditions (using a +2.00 cylindrical diopter trial case lens with its axis oriented at 180, 45, or 90 degrees). For each alphabet, single optotypes were presented on a monitor viewed from a distance of 4.0 m, and a matching technique was used to identify the letters.ResultsThe degradation in VA with astigmatic defocus was influenced by the alphabet used (p<0.001) and by the astigmatic axis (p<0.001). Interactions in VA degradation between astigmatic axes and alphabet (p<0.001) showed differences within 0.10 logMAR. These interactions were more pronounced in alphabets with higher dominance of curves and vertical (Tamil) and horizontal (Arabic) detail.ConclusionInteractions between alphabet and type of astigmatism indicate that the effects of meridional blur on letter discrimination differ between alphabets. These findings have relevance in the way VA is assessed in populations using different typographies, and ultimately in the impact of astigmatic axis on their visual performance.

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The Visual Impact of Lens-Induced Astigmatism is Linked to Habitual Axis

Abstract: The impact of lens-induced astigmatism was dependent on the refractive status of the participants. When investigating the impact of lens-induced astigmatism, it is important to consider the participants' habitual axis of astigmatism.

Cited by 10 publications

References 29 publications

Perceptual impact of astigmatism induction in presbyopes

Perceptual impact of astigmatism induction in presbyopes

Simulated image doubling and visual acuity: effects of doubling magnitude, orientation, and ghost image intensity

The effect of astigmatic axis on visual acuity measured with different alphabets in Roman alphabet readers

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