Abstract
Previous research work suggests that predictable target motion such as sinusoidal movement can be anticipated by the visual system, thereby improving the accommodative response. The validity ...of predictable motion for studying human dynamic accommodation is sometimes put into question. The aim of this work was to assess the effect of anticipation along with learning (and motivation, etc.) and fatigue (and boredom, loss of attention, etc.) on dynamic accommodation experiments from a practical perspective. Specifically, changes in amplitude and temporal phase lag were estimated within and between trials as 9 adult observers were instructed to focus on a stimulus that oscillated sinusoidally towards and away from the eye at specific temporal frequencies. On average, amplitude decreased whereas phase increased within trials. No evidence of anticipation or learning was observed either within or between trials. Fatigue consistently dominated anticipation and learning within the course of each trial. Even if the eye is equipped by a
prediction operator
as it is often assumed, fatigue confounds the results from dynamic accommodation experiments more than anticipation or learning.
Aberrations and accommodation Del águila-carrasco, Antonio J; Kruger, Philip B; Lara, Francisco ...
Clinical and experimental optometry,
January 2020, Volume:
103, Issue:
1
Journal Article
Peer reviewed
Open access
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.
Purpose
To compare the optical quality between two intraocular lenses (IOLs): the Mini WELL Ready progressive multifocal (SIFI Medtech, Catania, Italy), and the TECNIS Symfony (Abbott Laboratories, ...Illinois, USA), which both provide a continuous range of vision from far to near positions.
Methods
The in vitro optical quality of each lens was assessed with an instrument conceived for measuring the modulation transfer function (MTF). The optical quality of each lens was described in terms of MTF, through-focus MTF, defocus tolerance, pupil dependence, and Strehl ratio MTF. These metrics were assessed for the best lens far focus, and at four vergences (from −1.5 to −3.0 D in 0.5-D steps), at 3.0 and 4.5 mm apertures.
Results
The through-focus curves of each lens showed two main areas: one corresponding to far-distance vision, and another to intermediate- and near-distance vision. Both lenses showed similar MTF curves and Strehl ratio values at both apertures. The optical quality of both lenses slightly decreased with the aperture for all vergences. Nevertheless, the quality of the progressive multifocal lens increased with the aperture at far-distance vision. This lens also showed the largest defocus tolerance at near-distance vision for both apertures.
Conclusions
The results obtained in the present study suggest that both designs might enlarge the depth of focus. Whereas, the Mini WELL Ready showed better optical quality than the TECNIS Symfony at far vision with 4.5 mm aperture, and larger defocus tolerance than the diffractive lens at near-distance vision.
To compare the optical quality under large apertures among three multifocal intraocular lenses (IOLs): the TECNIS Symfony ZXR00 (Abbott Laboratories, Abbott Park, IL), the AT LISA tri 839MP (Carl ...Zeiss Meditec, Jena, Germany), and the Finevision (PhysIOL, Liège, Belgium).
The in vitro optical quality of each lens was assessed with an instrument that measured the modulation transfer function (MTF). The optical quality of each lens was described in terms of MTF and through focus average MTF. The Strehl ratio, cut-off frequency, area of visibility, and percentage energy were calculated to objectively describe the optical quality of each lens. These metrics were assessed for the best lens distance focus and at four vergences (from -1.50 to -3.00 D in 0.50-D steps) at a 4.5-mm aperture.
The through focus average MTF of the AT LISA and Finevision IOLs showed three mean areas corresponding to distance, intermediate, and near vision. The TECNIS Symfony IOL showed two main areas corresponding to distance and intermediate vision. All metrics revealed that the Finevision IOL showed the best optical quality at distance vision, the TECNIS Symfony IOL at intermediate vision, and the AT LISA IOL at near vision. The TECNIS Symfony IOL showed the most homogeneous light distribution between its best vision foci.
The TECNIS Symfony IOL is less vergence dependent than the AT LISA and Finevision IOLs under dim conditions. These results may help clinicians to choose the proper lens depending on the patient's visual requirements.
To evaluate the optical quality of 3 multifocal intraocular lenses (IOLs): the Mini Well Ready progressive multifocal aspheric IOL, the AT LISA trifocal diffractive IOL, and the Finevision full ...diffractive trifocal IOL.
University of Valencia, Valencia, Spain.
Experimental study.
An instrument designed for measuring real-time modulation transfer function (MTF) and IOL power was used to measure the optical quality of each IOL for 3.0 mm and 4.5 mm apertures. This instrument measures both sagittal and tangential MTFs. The optical quality of each IOL was evaluated with the MTF, through-focus MTF, defocus tolerance, Strehl ratio MTF, and relative percentage of light in each focus. These metrics were evaluated at best focus for each IOL.
Through-focus graphs corresponding to trifocal IOLs showed 3 mean peaks. Nevertheless, the progressive multifocal aspheric IOL showed 2 main areas, 1 corresponding to distance vision focus and the other including both intermediate and near vision foci.
The results obtained in the present study suggest that the progressive multifocal aspheric IOL might be considered for cataract surgery.
None of the authors has a financial or proprietary interest in any method or material mentioned.
To determine the influence of decentration and tilt of a pseudophakic aspheric intraocular lens (IOL) on visual acuity (VA) and higher-order aberrations (HOAs), and to analyze the agreement between ...pupil center/axis and iridocorneal angles center/axis when assessing IOL decentration and tilt.
A prospective interventional case series study including thirty-three patients undergoing Tecnis ZCB00 (Abbott Medical Optics) implantation. IOL decentration and tilt with respect to two reference systems (pupil and iridocorneal angles centers/axes), in cartesian (X,Y) and polar (radius/tilt, polar angle/azimuth) coordinates, were assessed with optical coherence tomography. VA and internal and ocular HOAs were evaluated. Multiple linear regression models and intraclass correlation coefficient (ICC) were computed.
IOL decentration only showed a significant effect on internal HOAs for Formula: see text (R
= 0.20, P = 0.04). IOL decentration with respect to the pupil center showed a significant effect on ocular Formula: see text (R
= 0.18, P = 0.05), Formula: see text (R
= 0.36, P = 0.001) and Formula: see text (R
= 0.24, P = 0.02); and with respect to the center of iridocorneal angles, on ocular Formula: see text (R
= 0.21, P = 0.03), Formula: see text (R
= 0.32, P = 0.003), primary coma (R
= 0.41, P < 0.001), and coma-like (R
= 0.40, P = 0.001). Poor agreement between both reference systems was found for IOL decentration measurements (ICC ≤ 0.41), except for the polar angle coordinate (ICC = 0.83). Tilt measurements showed good agreement (ICC ≥ 0.75).
Tecnis ZCB00 decentration and tilt values after uneventful implantation appear not to have influence on VA, and their effect on HOAs are not high enough to clinically affect quality of vision. Pupil and iridocorneal angles used as reference systems may be interchangeable for IOL tilt measurements, but not for decentration.
The effects of aberrations on image quality and the objectively assessed depth of focus (DoF) were studied. Aberrometry data from 80 young subjects with a range of refractive errors was used for ...computing the visual Strehl ratio based on the optical transfer function (VSOTF), and then, through-focus simulations were performed in order to calculate the objective DoF (using two different relative thresholds of 50% and 80%; and two different pupil diameters) and the image quality (the peak VSOTF). Both lower order astigmatism and higher order aberration (HOA) terms up to the fifth radial order were considered. The results revealed that, of the HOAs, the comatic terms (third and fifth order) explained most of the variations of the DoF and the image quality in this population of subjects. Furthermore, computer simulations demonstrated that the removal of these terms also had a significant impact on both DoF and the peak VSOTF. Knowledge about the relationship between aberrations, DoF, image quality, and their interactions is essential in optical designs aiming to produce large values of DoF while maintaining an acceptable level of image quality. Comatic aberration terms appear to contribute strongly towards the configuration of both of these visually important parameters.
Purpose
To determine if human accommodation uses the eye's own monochromatic aberrations to track dynamic accommodative stimuli.
Methods
Wavefront aberrations were measured while subjects monocularly ...viewed a monochromatic Maltese cross moving sinusoidally around 2D of accommodative demand with 1D amplitude at 0.2 Hz. The amplitude and phase (delay) of the accommodation response were compared to the actual vergence of the stimulus to obtain gain and temporal phase, calculated from wavefront aberrations recorded over time during experimental trials. The tested conditions were as follows: Correction of all the subject's aberrations except defocus (C); Correction of all the subject's aberrations except defocus and habitual second‐order astigmatism (AS); Correction of all the subject's aberrations except defocus and odd higher‐order aberrations (HOAs); Correction of all the subject's aberrations except defocus and even HOAs (E); Natural aberrations of the subject's eye, i.e., the adaptive‐optics system only corrected the optical system's aberrations (N); Correction of all the subject's aberrations except defocus and fourth‐order spherical aberration (SA). The correction was performed at 20 Hz and each condition was repeated six times in randomised order.
Results
Average gain (±2 standard errors of the mean) varied little across conditions; between 0.55 ± 0.06 (SA), and 0.62 ± 0.06 (AS). Average phase (±2 standard errors of the mean) also varied little; between 0.41 ± 0.02 s (E), and 0.47 ± 0.02 s (O). After Bonferroni correction, no statistically significant differences in gain or phase were found in the presence of specific monochromatic aberrations or in their absence.
Conclusions
These results show that the eye's monochromatic aberrations are not necessary for accommodation to track dynamic accommodative stimuli.
To determine whether changes in wavefront spherical curvature (optical vergence) are a directional cue for accommodation.
Nine subjects participated in this experiment. The accommodation response to ...a monochromatic target was measured continuously with a custom-made adaptive optics system while astigmatism and higher-order aberrations were corrected in real time. There were two experimental open-loop conditions: vergence-driven condition, where the deformable mirror provided sinusoidal changes in defocus at the retina between -1 and +1 diopters (D) at 0.2 Hz; and blur-driven condition, in which the level of defocus at the retina was always 0 D, but a sinusoidal defocus blur between -1 and +1 D at 0.2 Hz was simulated in the target. Right before the beginning of each trial, the target was moved to an accommodative demand of 2 D.
Eight out of nine subjects showed sinusoidal responses for the vergence-driven condition but not for the blur-driven condition. Their average (±SD) gain for the vergence-driven condition was 0.50 (±0.28). For the blur-driven condition, average gain was much smaller at 0.07 (±0.03). The ninth subject showed little to no response for both conditions, with average gain <0.08. Vergence-driven condition gain was significantly different from blur-driven condition gain (P = 0.004).
Accommodation responds to optical vergence, even without feedback, and not to changes in defocus blur alone. These results suggest the presence of a retinal mechanism that provides a directional cue for accommodation from optical vergence.
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