Changes in Ocular Astigmatism Over the Whole Range of Accommodation

Ukai, Kazuhiko; Ichihashi, Yuichi

doi:10.1097/00006324-199110000-00011

Cited by 54 publications

(21 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Third‐order aberrations (that is, coma and trefoil) may also vary during accommodation, but not systematically, and in many eyes these aberrations remain relatively stable over the range of accommodation demands …”

Section: The Influence Of Aberrations On the Subjective And Objectivementioning

confidence: 99%

Aberrations and accommodation

Águila-Carrasco

Kruger

Lara

et al. 2020

Clinical and Experimental Optometry

View full text Add to dashboard Cite

Modern methods of measuring the refractive state of the eye include wavefront sensors which make it possible to monitor both static and dynamic changes of the ocular wavefront while the eye observes a target positioned at different distances away from the eye. In addition to monitoring the ocular aberrations, wavefront refraction methods allow measurement of the accommodative response while viewing with the eye's habitual chromatic and monochromatic aberrations present, with these aberrations removed, and with specific aberrations added or removed. A large number of experiments describing the effects of accommodation on aberrations and vice versa are reviewed, pointing out the implications for fundamental questions related to the mechanism of accommodation.

show abstract

Section: The Influence Of Aberrations On the Subjective And Objectivementioning

confidence: 99%

Aberrations and accommodation

Águila-Carrasco

Kruger

Lara

et al. 2020

Clinical and Experimental Optometry

View full text Add to dashboard Cite

show abstract

“…This expectation is consistent with the well-known variation of foveal astigmatism with accommodation called sectional astigmia or astigmatic accommodation (Beck, 1965; Brzezinski, 1982; McFadden, 1925) but leaves open the question of which type of astigmatism is responsible. The available evidence suggests that axial astigmatism changes more than oblique astigmatism when the eye accommodates since foveal changes (Cheng et al, 2004; Millodot & Thibault, 1985; Radhakrishnan & Charman, 2007; Ukai & Ichihashi, 1991) are larger than changes in the near peripheral visual field (eccentricity <30°) (Calver, Radhakrishnan, Osuobeni, & O'Leary, 2007; Davies & Mallen, 2009; Lundström, Mira-Agudelo, & Artal, 2009; Mathur, Atchison, & Charman, 2009; Smith, Millodot, & McBrien, 1988; Whatham et al, 2009), although larger changes have been reported in the far periphery (Smith et al, 1988). To help resolve this issue, the present study monitored changes in the axial and oblique components of ocular astigmatism over a range of accommodative states.…”

Section: Introductionmentioning

confidence: 99%

Variation of axial and oblique astigmatism with accommodation across the visual field

Liu

Thibos

2017

Journal of Vision

View full text Add to dashboard Cite

In this study we investigated the impact of accommodation on axial and oblique astigmatism along 12 meridians of the central 30° of visual field and explored the compensation of corneal first-surface astigmatism by the remainder of the eye's optical system. Our experimental evidence revealed no systematic effect of accommodation on either axial or oblique astigmatism for two adult populations (myopic and emmetropic eyes). Although a few subjects exhibited systematic changes in axial astigmatism during accommodation, the dioptric value of these changes was much smaller than the amount of accommodation. For most subjects, axial and oblique astigmatism of the whole eye are both less than for the cornea alone, which indicates a compensatory role for internal optics at all accommodative states in both central and peripheral vision. A new method for determining the eye's optical axis based on visual field maps of oblique astigmatism revealed that, on average, the optical axis is 4.8° temporal and 0.39° superior to the foveal line-of-sight in object space, which agrees with previous results obtained by different methodologies and implies that foveal astigmatism includes a small amount of oblique astigmatism (0.06 D on average). Customized optical models of each eye revealed that oblique astigmatism of the corneal first surface is negligible along the pupillary axis for emmetropic and myopic eyes. Individual variation in the eye's optical axis is due in part to misalignment of the corneal and internal components that is consistent with tilting of the crystalline lens relative to the pupillary axis.

show abstract

“…Although there is debate as to the exact mechanism of accommodation, 1,2 it is generally accepted that contraction of the ciliary muscle occurs, which leads to an alteration in the curvature of the crystalline lens. [3][4][5] As well as leading to changes in the eye's spherical power, accommodation may cause changes in astigmatism [6][7][8][9] and in some of the eye's higher-order aberrations. [10][11][12][13] Due to the anatomical proximity of the cornea to the ciliary muscle, it is conceivable that some small changes in corneal shape occur as a result of accommodation and thus contribute to optical changes accompanying accommodation.…”

mentioning

confidence: 99%