The short-term accommodation response to aniso-accommodative stimuli in isometropia

Bilateral Femtosecond Laser-Assisted Clear Lens Extraction with Trifocal Intraocular Lens Implantation for Presbyopia Correction: A Short-Term Observational Study in Chinese Adults

Purpose

To observe the outcome of bilateral femtosecond laser-assisted clear lens extraction with trifocal intraocular lens (IOL) implantation for presbyopia correction and evaluate its feasibility in early presbyopic adults.

Methods

Prospective case series of eyes with clear crystalline lenses that underwent femtosecond laser-assisted lens extraction and trifocal IOL (Acrysof IQ PanOptix, Model TFNT00, Alcon) implantation between 2021 and 2023 were followed up for at least 3 months after surgery. Outcome measures included monocular uncorrected visual acuity at near (UNVA, 40 cm), intermediate (UIVA, 60 cm), and distance (UDVA, 5 m), monocular manifest refraction, corrected distance visual acuity (CDVA), defocus curve assessment, and spectacle independence at both near and distance.

Results

A total of 60 eyes from 30 consecutive patients were included, and their mean age was 50.4±6.5 years. After surgery, the mean UNVA (LogMAR) increased from 0.28±0.16 to 0.08±0.07, UIVA increased from 0.25±0.12 to 0.09±0.06, and UDVA increased from 0.27±0.21 to 0.01±0.08. The enhancements of UNVA, UIVA and UDVA were all significant (P < 0.05). The optometric results showed that the mean postoperative spherical equivalent (SE) was -0.21±0.24 D, and the mean postoperative CDVA (LogMAR) was -0.00±0.06. The preoperative spectacle independences at near and distance were 46.7% (14/30) and 56.7% (17/30), respectively, and both increased to 100% at 3 months after surgery.

Conclusion

Satisfactory visual outcomes and safe surgical procedures were observed in this study, which demonstrate that bilateral femtosecond laser-assisted clear lens extraction with PanOptix IOL implantation could be a feasible approach for presbyopia correction in working-age Chinese patients.

Efficacy of contact lenses for myopia control: Insights from a randomised, contralateral study design

PURPOSE

To determine the efficacy of two myopia control contact lenses (CL) compared with a single-vision (SV) CL.

METHODS

Ninety-five Chinese children with myopia, aged 7-13 years in a 1-year prospective, randomised, contralateral, cross-over clinical trial with 3 groups; bilateral SVCL (Group I); randomised, contralateral wear of an extended depth of focus (EDOF) CL and SVCL (Group II) and MiSight® CL and SVCL (Group III). In Groups II and III, CL were crossed over at the 6-month point (Stage 1) and worn for a further 6 months (Stage 2). Group I wore SVCL during both stages. At baseline and the end of each stage, cycloplegic spherical equivalent refractive error (SE) and axial length (AL) were measured. Six-monthly ΔSE/ΔAL across groups was analysed using a linear mixed model (CL type, stage, eye and eye* stage included as factors). Intra-group paired differences between eyes were determined.

RESULTS

In Group I, mean (SD) ΔSE/ΔAL with SVCL was -0.41 (0.28) D/0.13 (0.09) mm and -0.25 (0.27) D/0.16 (0.09) mm for stages 1 and 2, with a mean paired difference between eyes of 0.01 D/0.01 mm and 0.05 D/-0.01 mm, respectively. ΔSE/ΔAL with SVCL was similar across Groups I to III (Stage 1: p = 0.89/0.44, Stage 2: p = 0.70/ 0.64). In Groups II and III, ΔSE/ΔAL was lower with the EDOF and MiSight® CL than the contralateral SVCL in 68% to 94% of participants, and adjusted 6-month ΔSE/ΔAL with EDOF was similar to MiSight® (p = 0.49/0.56 for ΔSE/ΔAL, respectively). Discontinuations across the three groups were high, but not different between the groups (33.3%, 48.4% and 50% for Groups I to III, respectively [p = 0.19]) and most discontinuations occurred immediately after baseline.

CONCLUSIONS

Extended depth of focus and MiSight® CL demonstrated similar efficacy in slowing myopia. When switched from a myopia control CL to SVCL, myopia progression was similar to that observed with age-matched wearers in SVCL and not suggestive of rebound.

Lags and leads of accommodation in humans: Fact or fiction?

The focusing response of the human eye — accommodation — exhibits errors known as lags and leads. Lags occur when the stimulus is near and the eye appears to focus farther than the stimulus. Leads occur with far stimuli where the eye appears to focus nearer than the stimulus. We used objective and subjective measures simultaneously to determine where the eye is best focused. The objective measures were made with a wavefront sensor and an autorefractor, both of which analyze light reflected from the retina. These measures exhibited typical accommodative errors, mostly lags. The subjective measure was visual acuity, which of course depends not only on the eye's optics but also on photoreception and neural processing of the retinal image. The subjective measure revealed much smaller errors. Acuity was maximized at or very close to the distance of the accommodative stimulus. Thus, accommodation is accurate in terms of maximizing visual performance.

Accommodation and binocular vision changes after wearing orthokeratology lens in 8- to 14-year-old myopic children

PURPOSE

The study aimed to observe and analyze the dynamic accommodation and binocular vision changes in myopic children after they switched from spectacles to orthokeratology (ortho-k) lenses.

METHODS

Thirty-six myopic children aged 8-14 years were enrolled in this prospective, self-controlled study from West China Hospital. General information was gathered, and examinations were performed at baseline and at 1, 3, 6, and 12 months after switching to ortho-k lenses. The examination included assessments of distance/near visual acuity, distance/near horizontal and vertical ocular alignment, distance/near horizontal vergence range, accommodative amplitude, monocular/binocular accommodative facility, accommodative response, positive and negative relative accommodation (PRA/NRA), accommodation convergence/accommodation (AC/A), stereopsis, and reading ability.

RESULTS

After the children switched to ortho-k lenses, distance and near ocular alignment showed an exophoric shift (distance: p = 0.001, near: p = 0.002), and the horizontal vergence range decreased by different degrees (convergence: distance blur point (p = 0.002), distance break point (p = 0.005), near blur point (p = 0.011), near break point (p = 0.043); divergence: distance break point (p < 0.001), distance recover point (p < 0.001), near recover point (p = 0.005)). The stereopsis ability (p < 0.001), monocular/binocular accommodative facility (p < 0.001), and PRA (p = 0.010) increased. The accommodative lag (p < 0.001), accommodative amplitude (p < 0.001), and calculated and gradient AC/A (calculated: p = 0.001, gradient: p = 0.025) decreased. The adjusted horizontal and vertical reading times and their ratio decreased (all p < 0.001).

CONCLUSION

The subjects showed distance and near exophoric shifts after switching to ortho-k lenses; improvements in accommodative function, stereopsis, and ocular motility; and a decrease in the binocular horizontal vergence range. The relationships between these changes and the ortho-k myopic control effects require further investigation.

Accommodative Exercises to Lower Intraocular Pressure

Purpose

This study investigated how a conscious change in ocular accommodation affects intraocular pressure (IOP) and ocular biometrics in healthy adult volunteers of different ages.

Methods

Thirty-five healthy volunteers without ocular disease or past ocular surgery, and with refractive error between −3.50 and +2.50 diopters, were stratified into 20, 40, and 60 year old (y.o.) age groups. Baseline measurements of central cornea thickness, anterior chamber depth, anterior chamber angle, cornea diameter, pupil size, and ciliary muscle thickness were made by autorefraction and optical coherence tomography (OCT), while IOP was measured by pneumotonometry. Each subject's right eye focused on a target 40 cm away. Three different tests were performed in random order: (1) 10 minutes of nonaccommodation (gazing at the target through lenses that allowed clear vision without accommodating), (2) 10 minutes of accommodation (addition of a minus 3 diopter lens), and (3) 10 minutes of alternating between accommodation and nonaccommodation (1-minute intervals). IOP was measured immediately after each test. A 20-minute rest period was provided between tests. Data from 31 subjects were included in the study. ANOVA and paired t-tests were used for statistical analyses.

Results

Following alternating accommodation, IOP decreased by 0.7 mmHg in the right eye when all age groups were combined (p = 0.029). Accommodation or nonaccommodation alone did not decrease IOP. Compared to the 20 y.o. group, the 60 y.o. group had a thicker ciliary muscle within 75 μm of the scleral spur, a thinner ciliary muscle at 125–300 μm from the scleral spur, narrower anterior chamber angles, shallower anterior chambers, and smaller pupils during accommodation and nonaccommodation (p's < 0.01).

Conclusion

Alternating accommodation, but not constant accommodation, significantly decreased IOP. This effect was not lost with aging despite physical changes to the aging eye. A greater accommodative workload and/or longer test period may improve the effect.

Assessment of eye fatigue caused by head-mounted displays using eye-tracking

BACKGROUND

Head-mounted displays (HMDs) and virtual reality (VR) have been frequently used in recent years, and a user's experience and computation efficiency could be assessed by mounting eye-trackers. However, in addition to visually induced motion sickness (VIMS), eye fatigue has increasingly emerged during and after the viewing experience, highlighting the necessity of quantitatively assessment of the detrimental effects. As no measurement method for the eye fatigue caused by HMDs has been widely accepted, we detected parameters related to optometry test. We proposed a novel computational approach for estimation of eye fatigue by providing various verifiable models.

RESULTS

We implemented three classifications and two regressions to investigate different feature sets, which led to present two valid assessment models for eye fatigue by employing blinking features and eye movement features with the ground truth of indicators for optometry test. Three graded results and one continuous result were provided by each model, respectively, which caused the whole result to be repeatable and comparable.

CONCLUSION

We showed differences between VIMS and eye fatigue, and we also presented a new scheme to assess eye fatigue of HMDs users by analysis of parameters of the eye tracker.

Objective Verification of Physiologic Changes during Accommodation under Binocular, Monocular, and Pinhole Conditions

BACKGROUND

To objectively investigate accommodative response to various refractive stimuli in subjects with normal accommodation.

METHODS

This prospective, non-randomized clinical trial included 64 eyes of 32 subjects with a mean spherical equivalent -1.4 diopters (D). We evaluated changes in accommodative power, pupil diameter, astigmatic value, and axis when visual stimuli were applied to binocular, monocular (dominant eye, non-dominant eye, ipsilateral, and contralateral), and pinhole conditions. Visual stimuli were given at 0.25 D (4 m), 2 D (50 cm), 3 D (33 cm), and 4 D (25 cm) and accommodative response was evaluated using open view binocular autorefractor/keratometer.

RESULTS

The accommodative response to binocular stimulus was 90.9% of the actual refractive stimulus, while that of the monocular stimulus was 84.6%. The binocular stimulus induced a smaller pupil diameter than did the monocular stimulus. There was no difference in accommodative response between the dominant eye and non-dominant eye or between ipsilateral and contralateral stimuli. As the refractive stimuli became stronger, the absolute astigmatic value increased and the direction of the astigmatism axis became more horizontal. Pinhole glasses required 10%-15% less accommodative power compared with the monocular condition.

CONCLUSION

Binocular stimuli enable more precise and effective accommodation than do monocular stimuli. Accommodative response is composed of 90% true accommodation and 10% pseudo-accommodation, and the refractive stimulus in one eye affects the contralateral eye to the same extent. This should be taken into account when developing guidelines for wearing smart glasses while driving, as visual stimulation is applied to only one eye, but far distance attention is constantly needed.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03557346.

Comparison of three monocular methods for measuring accommodative stimulus-response curves

PURPOSE

The aim was to evaluate the repeatability of dynamic measurement of the accommodative stimulus-response curve (ASRC) at three different dioptric speeds using a modified instrument and its agreement with two other methods.

METHODS

Twenty-nine adults (23.5 ± 2.0 years) were enrolled in the study. ASRC was measured monocularly using three methods: dynamic and static measurement using a motorised Badal system mounted on an open-field auto-refractor (WAM-5500, Grand Seiko Co., Ltd, Japan) and the minus lens technique. Dynamic measurements were conducted at three dioptric stimulus speeds to simulate continuous stimuli for ASRC (0.25, 0.40 and 0.55 D/s), with three repetitions for each speed. All three types of ASRCs were fitted with third-degree polynomial equations. The slope and objective accommodative amplitude of the ASRC were analysed.

RESULTS

The repeatability of objective accommodative amplitude worsened as the speed of the stimuli increased. The repeatability of the slope was best at a speed of 0.40 D/s and worst at 0.55 D/s. The measurement method significantly influenced the objective accommodative amplitude values and slope (both, p < 0.001). The minus lens technique yielded the highest amplitude of accommodation (6.21 ± 0.84 D) and steepest slope (1.11 ± 0.14), followed by the static Badal method (5.60 ± 0.83 D and 0.89 ± 0.09 D). The objective accommodative amplitude decreased with increasing speed during dynamic measurements. There was no difference between the slopes at 0.25 D and 0.40 D/s (p > 0.05) and the slope was lowest at 0.55 D/s.

CONCLUSION

The accommodative stimulus-response curve values are method-dependent and the significant differences between three methods used to determine the ASRC based on slope and accommodative amplitude indicate that these methods are non-interchangeable. Using dynamic measurements, accommodative behaviour varies with the speed of dioptric-change of the stimulus. A speed of 0.40 D/s appears to be the best compromise in terms of time, results and repeatability for dynamic ASRC measurement.

Dominant Eye and Visual Evoked Potential of Patients with Myopic Anisometropia

A prospective nonrandomized controlled study was conducted to explore the association between ocular dominance and degree of myopia in patients with anisometropia and to investigate the character of visual evoked potential (VEP) in high anisometropias. 1771 young myopia cases including 790 anisometropias were recruited. We found no significant relation between ocular dominance and spherical equivalent (SE) refraction in all subjects. On average for subjects with anisometropia 1.0–1.75 D, there was no significant difference in SE power between dominant and nondominant eyes, while, in SE anisometropia ≥1.75 D group, the degree of myopia was significantly higher in nondominant eyes than in dominant eyes. The trend was more significant in SE anisometropia ≥2.5 D group. There was no significant difference in higher-order aberrations between dominant eye and nondominant eye either in the whole study candidates or in any anisometropia groups. In anisometropias >2.0 D, the N75 latency of nondominant eye was longer than that of dominant eye. Our results suggested that, with the increase of anisometropia, nondominant eye had a tendency of higher refraction and N75 wave latency of nondominant eye was longer than that of dominant eye in high anisometropias.

The Impact of Visual Guided Order Picking on Ocular Comfort, Ocular Surface and Tear Function

Purpose

We investigated the effects of a visual picking system on ocular comfort, the ocular surface and tear function compared to those of a voice guided picking solution.

Design

Prospective, observational, cohort study.

Method

Setting: Institutional. Study Population: A total of 25 young asymptomatic volunteers performed commissioning over 10 hours on two consecutive days. Main Outcome Measures: The operators were guided in the picking process by two different picking solutions, either visually or by voice while their subjective symptoms and ocular surface and tear function parameters were recorded.

Results

The visual analogue scale (VAS) values, according to subjective dry eye symptoms, in the visual condition were significantly higher at the end of the commissioning than the baseline measurements. In the voice condition, the VAS values remained stable during the commissioning. The tear break-up time (BUT) values declined significantly in the visual condition (pre-task: 16.6 sec and post-task: 9.6 sec) in the right eyes, that were exposed to the displays, the left eyes in the visual condition showed only a minor decline, whereas the BUT values in the voice condition remained constant (right eyes) or even increased (left eyes) over the time. No significant differences in the tear meniscus height values before and after the commissioning were observed in either condition.

Conclusion

In our study, the use of visually guided picking solutions was correlated with post-task subjective symptoms and tear film instability.