Accommodative Range Research Articles

Understanding accommodative control in the clinic: Modeling latency and amplitude for uncorrected refractive error, presbyopia and cycloplegia.

Accommodation is the process of adjusting the eye's optical power so as to focus at different distances. Uncorrected refractive error and/or functional presbyopia mean that sharp focus may not be achievable for some distances, so observers experience sustained defocus. Here, we identify a problem with current models of accommodative control: They predict excessive internal responses to stimuli outside accommodative range, leading to unrealistic adaptation effects. Specifically, after prolonged exposure to stimuli outside range, current models predict long latencies in the accommodative response to stimuli within range, as well as unrealistic dynamics and amplitudes of accommodative vergence innervation driven by the accommodative neural controller. These behaviors are not observed empirically. To solve this issue, we propose that the input to blur-driven accommodation is not retinal defocus, but correctable defocus. Predictive models of accommodative control already estimate demand from sensed defocus, using a realistic "virtual plant" to estimate accommodation. Correctable defocus can be obtained by restricting this demand to values physically attainable by the eye. If we further postulate that correctable defocus is computed using an idealized virtual plant that retains a young accommodative range, we can explain why accommodative-convergence responses are observed for stimuli that are too near-but not too far-to focus on. We model cycloplegia as a change in gain, and postulate a form of neural myopia to explain the additional relaxation of accommodation often seen with cycloplegia. This model produces plausible predictions for the accommodative response and accommodative convergence signal in a wide range of clinically relevant situations.

Ocular accommodation and wavelength: The effect of longitudinal chromatic aberration on the stimulus-response curve.

The longitudinal chromatic aberration (LCA) of the eye creates a chromatic blur on the retina that is an important cue for accommodation. Although this mechanism can work optimally in broadband illuminants such as daylight, it is not clear how the system responds to the narrowband illuminants used by many modern displays. Here, we measured pupil and accommodative responses as well as visual acuity under narrowband light-emitting diode (LED) illuminants of different peak wavelengths. Observers were able to accommodate under narrowband light and compensate for the LCA of the eye, with no difference in the variability of the steady-state accommodation response between narrowband and broadband illuminants. Intriguingly, our subjects compensated more fully for LCA at nearer distances. That is, the difference in accommodation to different wavelengths became larger when the object was placed nearer the observer, causing the slope of the accommodation response curve to become shallower for shorter wavelengths and steeper for longer ones. Within the accommodative range of observers, accommodative errors were small and visual acuity normal. When comparing between illuminants, when accommodation was accurate, visual acuity was worst for blue narrowband light. This cannot be due to the sparser spacing for S-cones, as our stimuli had equal luminance and thus activated LM-cones roughly equally. It is likely because ocular LCA changes more rapidly at shorter wavelength and so the finite spectral bandwidth of LEDs corresponds to a greater dioptric range at shorter wavelengths. This effect disappears for larger accommodative errors, due to the increased depth of focus of the eye.

The potential influence of the ligament of Wieger on the crystalline lens shape

This research uses mathematical modelling to evaluate the influence of the ligament of Wieger on the crystalline lens shape at rest, and during accommodation. An axisymmetric model of the anterior segment, including the ligament of Wieger, was created using the finite element method. Different conditions including variations of stiffness and positions of the ligament, with and without the ligament, were tested to see how they affected lens curvature and optical power. Adding the ligament of Wieger to the simulation had a noticeable impact on the optical power of the lens, particularly on the posterior surface power and total power. Ligament stiffness and width significant influenced the accommodative range of the eye by − 0.95D and − 2.39D for ligaments with the same and 3× the stiffness of the capsular bag, respectively. Ligament width and inner diameter had negligible effects on lens thickness but did have significant effects on posterior surface power and accommodation. In this simulation, we found that the ligament of Wieger can significantly affect the lens shape, both at rest and during accommodation, and may need to be considered in lens models.

FIAT: A Device for Objective, Optical Measures of Accommodation in Phakic and Pseudophakic Eyes.

To present FIAT, a novel optical instrument and analysis package that is designed to elicit and optically record accommodation in human eyes. FIAT employs a Shack-Hartmann wavefront sensor and a retro-illumination pupil camera that records from a single eye at video rates. It is effective at eliciting accommodation by offering the subject a full-field binocular view of an alternating distant target and a near-eye display. FIAT analysis software computes wave aberrations for each video frame over full- or subpupil sizes and computes accommodative dynamics and accommodative range. The system is validated by showing accurate refraction measurements in model eyes and human eyes with trial lenses. Robust accommodative responses are shown for young eyes, and a lack of accommodative response is shown for a known presbyopes. Accommodative stimulus-response curves from five phakic subjects over a range of ages show expected results. Results from two individuals with monofocal intraocular lenses are shown. FIAT is an effective instrument for making accurate, objective measures of accommodation in phakic and pseudophakic eyes. We present a device that can play an important role in the development and testing of accommodating intraocular lenses.

Short-Term Vision-Related Ocular Side Effects of Treatment with Dexmethylphenidate for Attention-Deficit/Hyperactivity Disorder.

Objective: To evaluate the short-term effect of dexmethylphenidate (D-MPH) on visual acuity (VA), pupil size, anterior chamber depth, and accommodation-convergence reflex in children treated with D-MPH for attention-deficit/hyperactivity disorder (ADHD). Method: Prospective cohort study including 15 patients aged 8-16 (11.58 ± 2.39) treated with D-MPH for ADHD. Patients were questioned for subjective complaints such as blurred vision and photosensitivity. An ophthalmic evaluation was performed twice; before and 1.5 hours after D-MPH administration. The examination included evaluation of best corrected visual acuity at distance and near, accommodation range, convergence range, 3D vision test (stereopsis), and anterior segment optical coherence tomography. Results: A significant association between change in pupil diameter and D-MPH treatment dose was demonstrated (p = 0.01). In addition, a positive correlation between complaints about blurred vision and pupil's size change was found (p < 0.05). There were no significant changes in VA, convergence range, stereopsis, accommodation range, or anterior chamber measures. Conclusions: Our findings provide support for the effect of stimulants on pupil diameter in a dose-dependent manner. No clinically significant differences in visual functions were found 1.5 hours after consumption of D-MPH. Institutional review board clinical trial refference no. 0122-17-TLV.

Improvement in Accommodation and Dynamic Range of Focus After Laser Scleral Microporation: A Potential Treatment for Presbyopia.

To examine the ocular changes in accommodation, wavefront aberrations, and dynamic range of focus (DROF) after laser scleral microporation (LSM) for treating presbyopia. Four presbyopic aged cynomolgus macaques (>13 years; n = 8 eyes) were included. All eyes received LSM with erbium: yttrium-aluminum-garnet laser. Spherical equivalent, true accommodation, pseudo-accommodation, wavefront aberrations, and extended range of focus (EROF), or collectively known as DROF, were evaluated using a ray tracing aberrometer. True accommodation referred to the difference in spherical equivalent between distance and near vision, whereas EROF (sum of true and pseudo-accommodation) was determined by measuring the difference in diopters (D) between near and distance through-focus curves, at 50% threshold of the visual Strehl ratio of optical transfer function. From before to seven months after surgery, there was a significant increase in true accommodation from 0.6 ± 1.0 D before surgery to 5.9 ± 2.8 D at seven months after surgery (P < 0.001). EROF increased significantly from 3.4 ± 1.0 D before surgery to 11.1 ± 4.6 D at seven months after surgery (P < 0.001). Ocular aberrations did not vary significantly between preoperative and various postoperative timepoints in either disaccommodated or accommodated states (P > 0.05). No adverse event such as scleral perforation or hypotony was noted. This non-human primate study demonstrated that LSM serves as a novel therapy for improving accommodation and DROF function biomechanically, with a positive response observed throughout the seven-month postoperative period. This proof-of-concept study highlights the potential of LSM as a novel treatment for vision recovery in presbyopic eyes.

Virtual reality training improves accommodative facility and accommodative range.

To evaluate the effects of virtual reality (VR) training on different parameters of vision. Sixty individuals ranged 18-60 years old with asthenopia were randomly divided into short-term (n=40) and long-term (n=20) treatment groups. They were given a specially designed VR training device only once for 15min or 3-4 times a day for 15min each time for 1mo. The visual acuity, spherical equivalent, accommodative range, accommodative facility, pupil size, and visual fatigue were evaluated before (control) and after VR training. The visual acuity, accommodative range, and accommodative facility increased in subjects of the short-term treatment group, whereas their pupil size contracted significantly. No significant changes in spherical equivalent and visual fatigue were observed. The changes in distant vision and corrected visual acuity were positively correlated with those in pupil size, but not with spherical equivalent. The accommodative range and accommodative facility improved significantly in subjects of the long-term treatment group. No significant changes in visual acuity, spherical equivalent, pupil size, and visual fatigue were noted. VR training can improve the accommodative range and accommodative facility of human eyes. Although short-term VR training can transiently improve vision, which probably due to bright light adaptation, there is no evidence that it can improve myopia.

A multi-objective stochastic-information gap decision model for soft open points planning considering power fluctuation and growth uncertainty

Recently, soft open points (SOPs) attract much attention due to providing power flow control and voltage regulation to the distribution system (DS). However, multiple uncertainties and expensive capital cost are referred to as thorny issues in the SOPs planning. In this paper, a multi-objective stochastic-information gap decision (MS-IGD) model is presented to alleviate multiple uncertainties with the limited budget. First, a deterministic SOP planning model is built to minimize the comprehensive cost of distributed system operator (DSO). Then, a MS-IGD model is formulated considering power fluctuation and growth uncertainty in distributed generators (DGs) and loads. To solve this model effectively, it is transformed to a mixed integer linear programming (MILP) by the polyhedron linearization technology, linear programming theory and ε constraint algorithm. In case studies, based on a prospective DS from northern China, the SOPs planning scheme with corresponding accommodation range of multiple uncertainties is presented. Numerical results not only authenticate that the worst-case envelope bound should not be decided in advance because of the complicated relationship between multiple uncertainties and investments, but also demonstrate the negative correlation between the deviation of power fluctuation and growth uncertainty under the same budget.

농장비 설계를 위한 한국 척수장애인의 대표 인체모델군 개발

Korea’s agriculture is facing a manpower shortage due to a decrease in the population and an aging workforce. Involving disabled people in agriculture as a solution to the problem of manpower shortage can help both agricultural workers and people with disabilities, and for this purpose, it is necessary to develop agricultural tools that disabled people can use in agricultural tasks. This study was intended to create a representative human body model used in the anthropometric design of agricultural tools for people with spinal cord disabilities. This study used the existing anthropometric data for the spinal cord disabled and created a representative human body model using the method of boundary for the accommodation range of the body size distribution. As a result of factor analysis, 26 body dimensions were reduced to 4 factors, and the representative group had 16 body models to have an accommodation rate of 90% of the distribution. As a result of the evaluation of the accommodation rate of the representative human model group, only 42% of cases satisfied all the ranges of 26 body dimensions for the representative group, but 88% of cases satisfied all the ranges of 23 body dimensions, which is close to the target rate. The representative human model group for spinal cord disabilities was visualized using the Tecnomatix human model module. This can be utilized in identification of problems with existing agricultural tools and anthropometric design for the disabled.

Correcting Presbyopia With Autofocusing Liquid-Lens Eyeglasses.

Presbyopia, an age-related ocular disorder, is characterized by the loss in the accommodative abilities of the human eye. Conventional methods of correcting presbyopia divide the field of view, thereby resulting in significant vision impairment. We demonstrate the design, assembly and evaluation of autofocusing eyeglasses for restoration of accommodation without dividing the field of view. The adaptive optics eyeglasses comprise of two variable-focus liquid lenses, a time-of-flight range sensor and low-power, dual microprocessor control electronics, housed within an ergonomic frame. Subject-specific accommodation deficiency models were utilized to demonstrate high-fidelity accommodative correction. The abilities of this system to reduce accommodation deficiency, its power consumption, response time, optical performance and MTF were evaluated. Average corrected accommodation deficiencies for 5 subjects ranged from -0.021 D to 0.016 D. Each accommodation correction calculation was performed in ∼67 ms which consumed 4.86 mJ of energy. The optical resolution of the system was 10.5 cycles/degree, and featured a restorative accommodative range of 4.3 D. This system was capable of running for up to 19 hours between charge cycles and weighed ∼132 g. The design, assembly and performance of an autofocusing eyeglasses system to restore accommodation in presbyopes has been demonstrated. The new autofocusing eyeglasses system presented in this article has the potential to restore pre-presbyopic levels of accommodation in subjects diagnosed with presbyopia.

Objective changes in astigmatism during accommodation.

Previous studies have shown small but clinically significant changes in the power and axis of astigmatism when the eye accommodates. Monocular objective measurements of the eye during accommodation, when the object approaches the eye without convergence, also reveal small astigmatic changes. Moreover, it is known that the eye exhibits ocular cyclotorsion at different gaze angles. Since accommodation and convergence normally occur simultaneously, we studied the change in the magnitude and axis of astigmatism during accommodation for different convergence angles. The left eye of 15subjects between 20 and 49years old (mean 28.5±9.7years) having ≤1.5D astigmatism was evaluated. Measurements were made using a Shack-Hartmann aberrometer for an accommodation range of +0.50D to -10D in 0.50D steps, and for four monocular convergence demands: 0°, 5°, 10° and 15°. Statistical analysis used power vectors to quantify the change in cylinder power and axis for each accommodation and convergence demand with age. Jackson cross-cylinder component J45 did not change during accommodation for all vergences tested. However, J0 changed by an average of -0.02D per dioptre of accommodation (D/Dacc) for convergence demands of 0°, 5° and 10° and -0.03D/Dacc for the 15° demand. This corresponds to an average cylinder power change of -0.05D/Dacc for convergences of 0°, 5° and 10° and -0.08D/Dacc for 15° of convergence. The cylinder axis always changed towards 90° (against-the-rule), and age did not play a significant role. Except for accommodation demands >4D, we did not find a clinically significant change in astigmatism for convergence angles up to 15º. The small changes in cylinder power and axis may be due to shifts in the position of the crystalline lens during accommodation.

The Light Sword Lens and its usefulness for presbyopia reduction

AbstractPurposeTo evaluate the light sword lens ‐ an optical imaging element with extended depth of focus and angularly varying optical power for compensation of presbyopia.MethodsTwo novel light sword lenses were compared with commercially available intraocular lenses with the help of an optical system for intraocular lens testing certified according to the requirements of the International Organization for Standardization. The point spread function, the modulation transfer function for 50 lines/mm and the modulation transfer function area (MTFa) ratio were measured.ResultsThe light sword lenses exhibit a point spread function with a distinct maximum in the whole designed defocus range (0‐3D or 0‐4D). Contrast transfer ratio maintains higher values than 0.2 for defocus at least up to 2.5 D.ConclusionsUnlike the hitherto known solutions, the light sword lens permits to obtain high uniformity of the contrast transfer function and focusing within a range of defocus extending to the value of 3D. Therefore the proposed concept seems to be very promising for a development of presbyopia‐correcting intraocular lenses capable to restore a high quality functional vision substituting lost accommodation range.

P‐3.4: Hybrid computational near‐eye light field display

We propose a hybrid computational near‐eye light field display based on micro‐lens arrays (MLAs) and structure parameters prioritization method (SPPM) which can render correct accommodation and expand the depth of field (DOF). The proposed display consists two MLAs and two micro‐displays. Two sets of depth‐sliced images are superimposed to reconstruct the object's light field. The system's ray resolution and the spectra difference between the proposed light field and the conventional one are discussed. The DOF of the proposed system is extended without the requiring of high refresh rate display. Furthermore, structure parameters prioritization method is proposed to extend the spatial frequency of the light field. A prototype is demonstrated and the experimental result shows that the depth field of the reconstructed images is significantly increased compared with conventional near‐eye light field display based on single MLA.Schematic of the configuration of the proposed systemfigureThe result of experiment 1: VR modefigureThe result of experiment 2: AR modefigureWe proposed a novel hybrid near‐eye light field display based on MLA to improve the DoF of the reconstructed light field, which is capable of expanding the accommodation range for virtual and augmented reality. The new algorithm for optimizing the structure parameters of hybrid computational neareye light field display is proposed to lessen the ray resolution and the mismatching of the reconstructed light field. We evaluate the capability of extending DOF through optical experiment. It shows that the propose system can effectively expand the depth range in near‐eye displays.

Factors Influencing Pseudo-Accommodation-The Difference between Subjectively Reported Range of Clear Focus and Objectively Measured Accommodation Range.

The key determinants of the range of clear focus in pre-presbyopes and their relative contributions to the difference between subjective range of focus and objective accommodation assessments have not been previously quantified. Fifty participants (aged 33.0 ± 6.4 years) underwent simultaneous monocular subjective (visual acuity measured with an electronic test-chart) and objective (dynamic accommodation measured with an Aston open-field aberrometer) defocus curve testing for lenses between +2.00 to −10.00 DS in +0.50 DS steps in a randomized order. Pupil diameter and ocular aberrations (converted to visual metrics normalized for pupil size) at each level of blur were measured. The difference between objective range over which the power of the crystalline lens changes and the subjective range of clear focus was quantified and the results modelled using pupil size, refractive error, tolerance to blur, and ocular aberrations. The subjective range of clear focus was principally accounted for by age (46.4%) and pupil size (19.3%). The objectively assessed accommodative range was also principally accounted for by age (27.6%) and pupil size (15.4%). Over one-quarter (26.0%) of the difference between objective accommodation and subjective range of clear focus was accounted for by age (14.0%) and spherical aberration at maximum accommodation (12.0%). There was no significant change in the objective accommodative response (F = 1.426, p = 0.229) or pupil size (F = 0.799, p = 0.554) of participants for levels of defocus above their amplitude of accommodation. Pre-presbyopes benefit from an increased subjective range of clear vision beyond their objective accommodation due in part to neural factors, resulting in a measured depth-of-focus of, on average, 1.0 D.

DeepFocus

Addressing vergence-accommodation conflict in head-mounted displays (HMDs) requires resolving two interrelated problems. First, the hardware must support viewing sharp imagery over the full accommodation range of the user. Second, HMDs should accurately reproduce retinal defocus blur to correctly drive accommodation. A multitude of accommodation-supporting HMDs have been proposed, with three architectures receiving particular attention: varifocal, multifocal, and light field displays. These designs all extend depth of focus, but rely on computationally expensive rendering and optimization algorithms to reproduce accurate defocus blur (often limiting content complexity and interactive applications). To date, no unified framework has been proposed to support driving these emerging HMDs using commodity content. In this paper, we introduce DeepFocus , a generic, end-to-end convolutional neural network designed to efficiently solve the full range of computational tasks for accommodation-supporting HMDs. This network is demonstrated to accurately synthesize defocus blur, focal stacks, multilayer decompositions, and multiview imagery using only commonly available RGB-D images, enabling real-time, near-correct depictions of retinal blur with a broad set of accommodation-supporting HMDs.

FocusAR: Auto-focus Augmented Reality Eyeglasses for both Real World and Virtual Imagery.

We describe a system which corrects dynamically for the focus of the real world surrounding the near-eye display of the user and simultaneously the internal display for augmented synthetic imagery, with an aim of completely replacing the user prescription eyeglasses. The ability to adjust focus for both real and virtual stimuli will be useful for a wide variety of users, but especially for users over 40 years of age who have limited accommodation range. Our proposed solution employs a tunable-focus lens for dynamic prescription vision correction, and a varifocal internal display for setting the virtual imagery at appropriate spatially registered depths. We also demonstrate a proof of concept prototype to verify our design and discuss the challenges to building an auto-focus augmented reality eyeglasses for both real and virtual.

Estimation of Spherical Refractive Errors Using Virtual Reality Headset.

Refractive errors are the most common visual defects in humans. They are corrected using lenses whose power is determined using expensive and bulky devices operated by trained professionals. This limits the outreach of eye- health care. We exploit commercial virtual reality (VR) setup to create a portable and inexpensive system for subjective estimation of spherical refractive errors. In doing so, we aim to keep hardware additions simple and to a minimum. We add a plain reflecting mirror in a VR headset to project optotypes on programmable focal planes at varying distances from the subject's eye. An interactive interface uses feedback from the user to estimate accommodation range and spherical refractive errors automatically. We compute the range and precision of our system, and validate them in a user trial study. The proposed setup strongly agrees with clinical subjective refraction.

Visual quality assessment after presbyopic laser in-situ keratomileusis.

To assess visual quality after presbyopia correction using an aspheric ablation profile and a micro-monovision protocol. This is a retrospective interventional study. Fifty-four eyes of 27 patients (mean age, 50.2±7.5y) who underwent presbyopia correction with an aspheric micro-monovision protocol were enrolled. The values of modulation transfer function (MTF) cutoff frequency, Strehl ratio, objective scattering index (OSI) and accommodation range were quantitatively assessed using the HD analyzer. Preoperative and postoperative contrast sensitivity (CS) at far (2.5 m) and near (40 cm) distance and higher-order aberrations (HOAs) were analyzed. Subjective visual satisfaction was evaluated by self-reported questionnaire regarding optical visual symptoms. One year after presbyopia correction, no significant differences were found in the MTF cutoff frequency, Strehl ratio and OSI, however, the HD analyzer accommodation range significantly differed postoperatively (P=0.004). Postoperative CS at 12 and 18 cpd at near showed statistically significant improvement (P=0.020 and 0.008, respectively). Visual performance by self-reported questionnaire revealed satisfactory results in terms of subjective visual quality improvement. Objective optical quality parameters show good visual outcomes. Subjective visual quality assessed by self-reported questionnaire in the presbyopia correction group show satisfactory results.

Lightweight Smart Autofocusing Eyeglasses.

More than 100 million people in the United States of America alone suffer from age-related presbyopia caused by a loss of focal accommodation of the eye crystalline lens as the lens stiffens with age. The resulting accommodative error or lag produces blurred images of objects placed at different distances. Conventional fixed uniform or graded power eyeglasses cannot provide accommodation thus resulting in significant visual impairment. In this paper we will discuss the implementation of lightweight auto-focusing eyeglasses that augment the accommodative range thus partially or fully restoring normal vision function. The paper discusses some aspects of the construction of tunable power eyepieces and the implementation of accommodation correction algorithms.

Fast gaze-contingent optimal decompositions for multifocal displays

As head-mounted displays (HMDs) commonly present a single, fixed-focus display plane, a conflict can be created between the vergence and accommodation responses of the viewer. Multifocal HMDs have long been investigated as a potential solution in which multiple image planes span the viewer's accommodation range. Such displays require a scene decomposition algorithm to distribute the depiction of objects across image planes, and previous work has shown that simple decompositions can be achieved in real-time. However, recent optimal decompositions further improve image quality, particularly with complex content. Such decompositions are more computationally involved and likely require better alignment of the image planes with the viewer's eyes, which are potential barriers to practical applications. Our goal is to enable interactive optimal decomposition algorithms capable of driving a vergence- and accommodation-tracked multifocal testbed. Ultimately, such a testbed is necessary to establish the requirements for the practical use of multifocal displays, in terms of computational demand and hardware accuracy. To this end, we present an efficient algorithm for optimal decompositions, incorporating insights from vision science. Our method is amenable to GPU implementations and achieves a three-orders-of-magnitude speedup over previous work. We further show that eye tracking can be used for adequate plane alignment with efficient image-based deformations, adjusting for both eye rotation and head movement relative to the display. We also build the first binocular multifocal testbed with integrated eye tracking and accommodation measurement, paving the way to establish practical eye tracking and rendering requirements for this promising class of display. Finally, we report preliminary results from a pilot user study utilizing our testbed, investigating the accommodation response of users to dynamic stimuli presented under optimal decomposition.