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Biomedical Optics Express May 2024Accommodation is the process by which the eye changes focus. These changes are the result of changes to the shape of the crystalline lens. Few prior studies have...
Accommodation is the process by which the eye changes focus. These changes are the result of changes to the shape of the crystalline lens. Few prior studies have quantified the relation between lens shape and ocular accommodation, primarily at discrete static accommodation states. We present an instrument that enables measurements of the relation between changes in lens shape and changes in optical power continuously during accommodation. The system combines an autorefractor to measure ocular power, a visual fixation target to stimulate accommodation, and an optical coherence tomography (OCT) system to image the anterior segment and measure ocular distances. Measurements of ocular dimensions and refraction acquired dynamically on three human subjects are presented. The individual accommodative responses are analyzed to correlate the ocular power changes with changes in ocular dimensions.
PubMed: 38855690
DOI: 10.1364/BOE.512193 -
Ophthalmic & Physiological Optics : the... Jun 2024Visual function deficits have been reported in adolescents following concussion. We compared vergence and accommodation deficits in paediatric and adolescent patients at...
INTRODUCTION
Visual function deficits have been reported in adolescents following concussion. We compared vergence and accommodation deficits in paediatric and adolescent patients at a tertiary medical centre in the sub-acute (15 days to 12 weeks) and chronic (12 weeks to 1 year) phases of concussion recovery.
METHODS
The study included patients aged 7 to <18 years seen between 2014 and 2021, who had a binocular vision (BV) examination conducted within 15 days and 1 year of their concussion injury. Included patients had to have 0.10 logMAR monocular best-corrected vision or better in both eyes and be wearing a habitual refractive correction. BV examinations at near included measurements of near point of convergence, convergence and divergence amplitudes, vergence facility, monocular accommodative amplitude and monocular accommodative facility. Vergence and accommodation deficits were diagnosed using established clinical criteria. Group differences were assessed using nonparametric statistics and ANCOVA modelling.
RESULTS
A total of 259 patients were included with 111 in the sub-acute phase and 148 in the chronic phase of concussion recovery. There was no significant difference in the rates of vergence deficits between the two phases of concussion recovery (sub-acute = 48.6%; chronic = 49.3%). There was also no significant difference in the rates of accommodation deficits between the two phases of concussion recovery (sub-acute = 82.0%; chronic = 77.0%).
CONCLUSION
Patients in both the sub-acute and chronic phases of concussion recovery exhibited a high frequency of vergence and accommodation deficits, with no significant differences between groups. Results indicate that patients exhibiting vision deficits in the sub-acute phase may not resolve without intervention, though a prospective, longitudinal study is required to test the hypothesis.
PubMed: 38853693
DOI: 10.1111/opo.13346 -
[Zhonghua Yan Ke Za Zhi] Chinese... Jun 2024The increasing incidence of myopia has become a global public health concern. Exploring the mechanisms underlying the onset and progression of myopia is crucial for... (Review)
Review
The increasing incidence of myopia has become a global public health concern. Exploring the mechanisms underlying the onset and progression of myopia is crucial for prevention and control. This paper reviews the role of peripheral retinal defocus mechanisms in the development of myopia, with particular emphasis on the interaction between accommodation lag and peripheral retinal defocus, as well as the impact of optical intervention on myopia control effectiveness. In recent years, researchers have developed various optical tools for myopia prevention and control based on the peripheral retinal defocus theory, such as peripheral defocus spectacle lenses, orthokeratology lenses, and peripheral defocus soft contact lenses. This paper aims to provide clinicians with the latest research findings to deepen their understanding of the mechanisms involved in myopia development and to guide the future development and clinical application of myopia prevention and control products.
Topics: Humans; Myopia; Disease Progression; Retina; Accommodation, Ocular; Eyeglasses; Contact Lenses, Hydrophilic; Orthokeratologic Procedures; Refraction, Ocular
PubMed: 38825954
DOI: 10.3760/cma.j.cn112142-20231024-00173 -
Ophthalmic & Physiological Optics : the... Jun 2024Clinicians measure the near point of convergence (NPC) and the amplitude of accommodation (AA) from the spectacle plane, the bridge of the nose or the lateral canthus...
PURPOSE
Clinicians measure the near point of convergence (NPC) and the amplitude of accommodation (AA) from the spectacle plane, the bridge of the nose or the lateral canthus when assessing visual function. These values are compared to standard clinical criteria to diagnose vergence and accommodation deficits, despite varying reference points. This prospective study explored measuring relative to the spectacle plane and from the lateral canthus for NPC and monocular AA, and the resulting clinical implications of diagnosing visual deficits.
METHODS
Participants were seen by a single clinician for an eye examination. NPC was measured from the forehead and the lateral canthus of the right eye. Monocular AA was measured from the brow and the lateral canthus. Differences between measurements were analysed using non-parametric statistical tests including Wilcoxon Signed Rank, as well as linear regression and a linear mixed effects model to adjust for inter-eye correlation and repeated measures. Chi-square tests were used to assess differences in rates of abnormal findings.
RESULTS
Data were collected from 70 participants (53% female, median age 13 [11-15] years). On average, measuring NPC from the lateral canthus yielded a value 1.8 cm higher than measuring from the forehead. Measuring AA from the lateral canthus resulted in an average difference of 1.5 cm compared to measuring from the brow. A total of 39% and 76% of subjects failed NPC compared to clinical norms when measured from the forehead or the lateral canthus, respectively, while 7% and 40% failed AA when measured from the brow or the lateral canthus, respectively.
CONCLUSION
With the variable anatomy of the eye, it is imperative to account for the measurement point when assessing visual function. Measuring from the lateral canthus greatly increased the failure rates for NPC and AA compared with measuring from the forehead and brow, respectively.
PubMed: 38825806
DOI: 10.1111/opo.13344 -
Journal of Pediatric Ophthalmology and... May 2024To report long-term ocular alignment and sensory outcomes after medial rectus recession for high accommodative convergence/accommodation (AC/A) ratio esotropia.
PURPOSE
To report long-term ocular alignment and sensory outcomes after medial rectus recession for high accommodative convergence/accommodation (AC/A) ratio esotropia.
METHODS
The medical records of consecutive patients who had undergone unilateral or bilateral medial rectus recession for high AC/A ratio esotropia and were observed postoperatively for a minimum of 5 years were reviewed retrospectively.
RESULTS
A total of 34 patients were included. Twenty-three patients (68%) used bifocals preoperatively. The mean age at surgery was 11.5 ± 4.4 years (range: 2.5 to 19.0 years). The mean postoperative follow-up was 7.5 ± 2.3 years (range: 5.0 to 15.25 years). Overall, 21 patients (62%) had surgical success at their last follow-up visit. Age at surgery, preoperative angle of distance and near deviation, distance-near disparity, and preoperative bifocal wear did not predict motor outcome after surgery. Preoperative presence of peripheral binocular single vision was a significant favorable factor for surgical success. At the last follow-up visit, 21% of patients had a recurrence of high AC/A ratio esotropia and 9% each had consecutive exotropia (intermittent [3%] and constant [6%]) and basic esotropia. Peripheral binocular single vision was achieved in 64% of patients and stereopsis in 28%. Bifocal segment was eliminated postoperatively in 70% of patients.
CONCLUSIONS
Nearly two-thirds of patients with high AC/A ratio esotropia achieved a successful long-term motor outcome and peripheral binocular single vision, and nearly one-fourth achieved stereopsis. Recurrence of high AC/A ratio esotropia occurred in some patients, and consecutive exotropia and basic esotropia in a few. Bifocal segment was eliminated postoperatively in 70% of patients. .
PubMed: 38815097
DOI: 10.3928/01913913-20240508-03 -
Contact Lens & Anterior Eye : the... May 2024With over a billion adults worldwide currently affected, presbyopia remains a ubiquitous, global problem. Despite over a century of study, the precise mechanism of...
With over a billion adults worldwide currently affected, presbyopia remains a ubiquitous, global problem. Despite over a century of study, the precise mechanism of ocular accommodation and presbyopia progression remains a topic of debate. Accordingly, this narrative review outlines the lenticular and extralenticular components of accommodation together with the impact of age on the accommodative apparatus, neural control of accommodation, models of accommodation, the impact of presbyopia on retinal image quality, and both historic and contemporary theories of presbyopia.
PubMed: 38796331
DOI: 10.1016/j.clae.2024.102185 -
IEEE Transactions on Visualization and... May 2024Augmented reality (AR) magic-lens (ML) displays, such as handheld devices, offer a convenient and accessible way to enrich our environment using virtual imagery. Several...
Augmented reality (AR) magic-lens (ML) displays, such as handheld devices, offer a convenient and accessible way to enrich our environment using virtual imagery. Several display technologies, including conventional monocular, less common stereoscopic, and varifocal displays, are currently being used. Vergence and accommodation effects on depth perception, as well as vergence-accommodation conflict, have been studied, where users interact only with the content on the display. However, little research exists on how vergence and accommodation influence user performance and cognitive-task load when users interact with the content on a display and its surroundings in a short timeframe. Examples of this are validating augmented instructions before making an incision andperforming general hand-eye coordinated tasks such as grasping augmented objects. To improve interactions with future AR displays in such scenarios, we must improve our understanding of this influence. To this end, we conducted two fundamental visual-acuity user studies with 28 and 27 participants, while investigating eye vergence and accommodation distances on four ML displays. Our findings show that minimizing the accommodation difference between the display and its surroundings is crucial when the gaze between the display and its surroundings shifts rapidly. Minimizing the difference in vergence is more important when viewing the display and its surroundings as a single context without shifting the gaze. Interestingly, the vergence-accommodation conflict did not significantly affect the cognitive-task load nor play a pivotal role in the accuracy of interactions with AR ML content and its physical surroundings.
PubMed: 38771678
DOI: 10.1109/TVCG.2024.3403261 -
Medicine May 2024This study was aimed to analyze ocular biometric changes following cycloplegia in pediatric patients with strabismus and amblyopia. Cycloplegia is routinely used to... (Observational Study)
Observational Study
This study was aimed to analyze ocular biometric changes following cycloplegia in pediatric patients with strabismus and amblyopia. Cycloplegia is routinely used to measure refractive error accurately by paralyzing accommodation. However, effects on axial length (AL), anterior chamber depth (ACD), keratometry (Km), and white-to-white distance (WTW) are not well studied in this population. This retrospective study examined 797 patients (1566 eyes) undergoing cycloplegic refraction at a Samsung Kangbuk hospital pediatric ophthalmology clinic from 2010 to 2023. Ocular biometry was measured before and after instilling 1% cyclopentolate and 0.5% phenylephrine/0.5% tropicamide. Patients were categorized by strabismus diagnosis, age, refractive error and amblyopia status. Differences in AL, ACD, Km, WTW, and refractive error pre- and post-cycloplegia were analyzed using paired t tests. ACD (3.44 ± 0.33 vs 3.58 ± 0.29 mm, P < .05) and WTW (12.09 ± 0.42 vs 12.30 ± 0.60 mm, P < .05) increased significantly after cycloplegia in all groups except other strabismus subgroup (Cs) in both parameters and youngest subgroup (G1) in ACD. Refractive error demonstrated a hyperopic shift from -0.48 ± 3.00 D to -0.06 ± 3.32 D (P < .05) in overall and a myopic shift from -6.97 ± 4.27 to -8.10 ± 2.26 in high myopia (HM). Also, AL and Km did not change significantly. In conclusion, cycloplegia impacts ocular biometrics in children with strabismus and amblyopia, significantly increasing ACD and WTW. Refractive error shifts hyperopically in esotropia subgroup (ET) and myopically in high myopia subgroup (HM), eldest subgroup (G3) relating more to anterior segment changes than AL/Km. Understanding cycloplegic effects on biometry is important for optimizing refractive correction in these patients.
Topics: Humans; Amblyopia; Strabismus; Retrospective Studies; Male; Female; Child; Biometry; Mydriatics; Child, Preschool; Refraction, Ocular; Cyclopentolate; Refractive Errors; Adolescent; Anterior Chamber; Axial Length, Eye
PubMed: 38758890
DOI: 10.1097/MD.0000000000038143 -
The Journal of Manual & Manipulative... May 2024Harlequin syndrome is a rare autonomic condition consisting of unilateral facial flushing and sweating induced by heat, emotion or physical activity. The affected side...
BACKGROUND
Harlequin syndrome is a rare autonomic condition consisting of unilateral facial flushing and sweating induced by heat, emotion or physical activity. The affected side presents anhidrosis and midline facial pallor due to denervation of the sympathetic fibers.
CASE DESCRIPTION
This case describes a patient who reported right-side redness of the face associated with hyperhidrosis during physical activity. She had two previous major motor vehicle accidents. The patient demonstrated difficulties in the visual accommodation of the left eye, but cranial nerve assessment was unremarkable; the patient was then referred to an ophthalmologist, who excluded any autonomic dysfunction as the primary cause of convergence and visual acuity.
OUTCOMES
A left-sided sympathetic dysfunction with Harlequin sign diagnosis was made followed by a progressive compensatory adaptation of the right face. The patient was educated and reassured about the benign nature of her problem.
DISCUSSION
Knowledge of the autonomic nervous system is still limited in clinical practice. Although challenging, physiotherapists should develop the knowledge and ability needed to perform appropriate assessment of autonomic dysfunctions.
CONCLUSION
A dispositional reasoning model should be considered in differential diagnosis.
PubMed: 38757409
DOI: 10.1080/10669817.2024.2349338 -
Journal of Cataract and Refractive... May 2024To determine the effectiveness of the correction of corneal astigmatism utilizing the Alcon Image Guidance system (Ft. Worth, Texas) versus manual marking in the...
PURPOSE
To determine the effectiveness of the correction of corneal astigmatism utilizing the Alcon Image Guidance system (Ft. Worth, Texas) versus manual marking in the orientation of femtosecond laser-assisted astigmatic keratotomy incisions.
SETTING
This study was based in a private practice in Albany, New York, USA.
DESIGN
Retrospective review of patients undergoing FLACS from January 2018 to June 2022.
METHODS
Patients who underwent FLACS with Image Guidance (IG) and without IG were investigated. Variables including pre-operative K values, cylinder, spherical equivalent (SE), and visual acuity (VA) were collected, as well as the cyclorotation angle delta registered by IG, post- operative refractive cylinder, SE, and VA. The primary outcome was post-operative refractive cylinder in patients with IG compared to those without IG.
RESULTS
A total of 160 eyes were included, with 103 eyes who had IG and 57 eyes who did not have IG. Post-operative cylinder was similar in those with IG (0.31 +/- 0.36 D) compared to those without IG (0.31 +/- 0.37 D) (p=0.97). Average cyclorotation in the IG group was 2.82 ± 3.03 degrees. When cyclorotation was stratified into three groups (<2.8 degrees, 2.8-8.5 degrees, >8.5 degrees), no differences were found in post-operative refractive cylinder (p=0.35).
CONCLUSIONS
Patients who underwent FLACS with Image Guidance had similar post-operative cylinder outcomes compared to those without Image Guidance. This study suggests that the accommodation of cyclotorsion using an advanced image guidance system is similar to that obtained with manual marking techniques in patients having 2 diopters or less of astigmatism corrected.
PubMed: 38739530
DOI: 10.1097/j.jcrs.0000000000001477