Orientation-specific long-term neural adaptation of the visual system in keratoconus

Hastings, Gareth D; Schill, Alexander; Hu, Chuan; Coates, Daniel R.; Applegate, Raymond A.; Marsack, Jason D

doi:10.1016/j.visres.2020.10.002

Cited by 13 publications

(20 citation statements)

References 70 publications

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“…The present analysis of six keratoconic eyes suggests that there may be ceiling and floor limits to this adaptability: when disease severity is relatively mild and aberrations are not much worse than regular levels, then the visual system might not experience sufficient gain from adaptation to motivate its development. Most control eyes measured in this manner did not show synergistic tuning of neural processing to their optics, 14 although this might be possible if the aberrations of healthy eyes have pronounced rotational asymmetry 37 . On the other end of the spectrum, chronic aberrations in keratoconus might be so detrimental to vision that they exceed the ability of the neural component to compensate, and so no adaptation is attempted or maintained.…”

Section: Introductionmentioning

confidence: 97%

“…The system used was similar to those of Williams, 17,18 and Coletta and Sharma 19 but was modified with the capability to test neural contrast sensitivity along multiple orientations. The interferometry system is described in detail elsewhere 14 …”

Section: Introductionmentioning

confidence: 99%

“…After the beams were recombined, a dove prism was electronically rotated to change the orientation of the fringes; this did not affect the contrast or spatial frequency 14 …”

Section: Introductionmentioning

confidence: 99%

“…The optical aberrations of the keratoconic eyes show marked rotational asymmetry and cause orientation‐specific blur 34,35 – this is equally captured by the optical PSFs, before applying the neural weighting function, in both versions of the metric. After adaptation to these optical patterns, the neural sensitivities of these individuals become tuned to emphasise meridians that are better in focus, while suppressing sensitivity in meridians that are more habitually blurred 14,15 …”

Section: Introductionmentioning

confidence: 99%

“…A successful clinical application of the VSX metric has been to optimise objective refraction, where the metric has identified spherocylindrical corrections that performed at an equivalent level or better than subjective refraction in myopic eyes 3 . Subsequently, similar methods have assisted the refraction of two other populations, namely: (1) individuals with keratoconus, 5 where elevated levels of higher‐order aberrations and neural adaptation 14 confound the subjective discernment of best focus and cause greater variability in refraction than found in typical myopic eyes 42 and (2) individuals with Down syndrome, 6 where high levels of aberrations are compounded by cognitive deficits. In both of these groups, the same generic photopic neural weighting function from typical healthy eyes was used in the metrics.…”

Section: Introductionmentioning

confidence: 99%

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Clinical applications of personalising the neural components of visual image quality metrics for individual eyes

Hastings

Applegate

Schill

et al. 2022

Ophthalmic Physiologic Optic

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Purpose: Eyecare is evolving increasingly personalised corrections and increasingly personalised evaluations of corrections on-eye. This report describes individualising optical and neural components of the VSX (visual Strehl) metric and evaluates personalisation using two clinical applications. (1) Better understanding visual experience: While VSX tracks visual performance in typical eyes, non-individualised metrics underestimated visual performance in highly aberrated eyes -could this be understood by personalising metrics? (2) Metric-optimised objective spherocylindrical refractions in typical and atypical eyes have used neural weighting functions of typical eyes -will personalisation affect the outcome in clinical 0.25D steps? Methods: Orientation-specific neural contrast sensitivity was measured in four typical myopic and astigmatic eyes and six eyes with keratoconus. Wavefront error was measured in all eyes while uncorrected and when the keratoconic eyes wore wavefront-guided scleral lenses. Total experiment duration was 24-28 h per subject. Two versions of VSX were calculated for each application: one weighted ocular optics with measured neural contrast sensitivity data from that eye, another weighted optics with a representative neural function of typical eyes. Wavefrontguided corrections were evaluated using the two metric values. Spherocylindrical corrections that optimised each metric were identified.Results: Metric values for keratoconic eyes improved by a mean factor of 1.99 (~0.3 log units) when personalised. Applying this factor to a larger sample of eyes from a previous keratoconus study reconciled dissonances between the percentage of eyes reaching normative best-corrected metric levels and the percentages of eyes reaching normative levels of visual acuity and contrast sensitivity. Spherocylindrical corrections that optimised both versions of VSX were clinically equivalent (mean ± SD Euclidean dioptric difference 0.13 ± 0.18 D). Conclusions:Personalising visual image quality metrics is beneficial when actual metric values are used (evaluating ophthalmic corrections on-eye against norms) and when fine increments in visual quality are imparted (wavefront-guided corrections). However, partially individualised metrics appear adequate when metrics relatively rank spherocylindrical corrections in 0.25 D steps.

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Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

“…After the beams were recombined, a dove prism was electronically rotated to change the orientation of the fringes; this did not affect the contrast or spatial frequency 14 …”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Clinical applications of personalising the neural components of visual image quality metrics for individual eyes

Hastings

Applegate

Schill

et al. 2022

Ophthalmic Physiologic Optic

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show abstract

Special issue: Calibrating the visual system

et al. 2022

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Automatic compensation enhances the orientation perception in chronic astigmatism

Son

Shim

Kang

et al. 2022

Sci Rep

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Astigmatism is a prevalent optical problem in which two or more focal points blur the retinal image at a particular meridian. Although many features of astigmatic vision, including orientation perception, are impaired at the retinal image level, the visual system appears to partly restore perceptual impairment after an extended period of astigmatism. However, the mechanism of orientation perception restoration in chronic astigmatism has not yet been clarified. We investigated the notable reduction of perceptual error in chronic astigmatism by comparing the orientation perception of a chronic astigmatism group with the perception of a normal-vision group, in which astigmatism was transiently induced. We found that orientation perception in the chronic group was more accurate than in the normal vision group. Interestingly, the reduction of perceptual errors was automatic; it remained even after the optical refractive errors were fully corrected, and the orientation perception was much more stable across different orientations, despite the uneven noise levels of the retinal images across meridians. We provide here a mechanistic explanation for how the compensation of astigmatic orientation perception occurred, using neural adaptation to the biased distribution of orientations.

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Orientation-specific long-term neural adaptation of the visual system in keratoconus

Cited by 13 publications

References 70 publications

Clinical applications of personalising the neural components of visual image quality metrics for individual eyes

Clinical applications of personalising the neural components of visual image quality metrics for individual eyes

Special issue: Calibrating the visual system

Automatic compensation enhances the orientation perception in chronic astigmatism

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