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Toro MD, Bremond-Gignac D, Brézin AP, Cummings AB, Kemer OE, Kermani O, Malyugin BE, Prieto I, Teus MA, Tognetto D, Zweifel S, Rejdak R. COVID-19 outbreak and increased risk of amblyopia and epidemic myopia: Insights from EUROCOVCAT group. Eur J Ophthalmol 2021; 32:17-22. [PMID: 34751045 DOI: 10.1177/11206721211053175] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The most common cause of vision impairment in children is amblyopia. It is defined as impaired visual acuity in one or both eyes that is present with no demonstrable abnormality of the visual pathway and is not immediately resolved by wearing glasses. After the World Health Organization (WHO) recognized COVID-19 as a global pandemic on March 11, 2020, widespread changes and restrictions to social and sanitary practices have presented significant issues in access to eye care during the COVID-19 pandemic. A reduction of more than 80% in pediatric eye care volume up to its total cessation has been observed in different departments. In this scenario, reduced or absent eyesight, due to delay in timely treatment of amblyopic conditions, could create major, long-lasting effects on all aspects of life, including daily personal activities, interacting with the community, school and work opportunities and the ability to access public services. Processes coming out of lockdown should be gradually easing restrictions giving priority to ophthalmology and eye care facilities so that amblyopia does not remain unattended and irreversible as in adults due to lack of timely treatments. If not reversible, this process could lead to a dramatic increase in disability and unsustainable social costs for many governments.
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Affiliation(s)
- Mario Damiano Toro
- Department of General and Pediatric Ophthalmology, 49554Medical University of Lublin, Lublin, Poland.,Department of Ophthalmology, University Hospital of Zurich, Zurich, Switzerland
| | - Dominique Bremond-Gignac
- 246596University Hospital Necker Enfants Malades, APHP, Paris, France.,INSERM 1138, Team 17, Paris Sorbonne University, Cordeliers, Paris, France
| | | | | | | | - Omid Kermani
- Augenklinik am Neumarkt Schildergasse 107 - 109, Köln, Germany
| | - Boris Edvard Malyugin
- 96710Fyodorov Eye Microsurgery Federal State Institution, Moscow, Russian Federation.,A. Yevdokimov Moscow State University of Medicine and Dentistry, Russian Federation
| | | | | | | | - Sandrine Zweifel
- Department of Ophthalmology, University Hospital of Zurich, Zurich, Switzerland
| | - Robert Rejdak
- Department of General and Pediatric Ophthalmology, 49554Medical University of Lublin, Lublin, Poland
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Sangoi A, Scheiman M, Yaramothu C, Santos EM, Gohel S, Alvarez TL. Convergence Insufficiency Neuro-Mechanism Adult Population Study: Phoria Adaptation Results. Invest Ophthalmol Vis Sci 2021; 62:19. [PMID: 34406329 PMCID: PMC8374988 DOI: 10.1167/iovs.62.10.19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The purpose of this study was to compare changes in phoria adaptation between young adult binocularly normal controls (BNCs) and participants with symptomatic convergence insufficiency (CI), who were randomized to either office-based vergence accommodative therapy (OBVAT) or office-based placebo therapy (OBPT). Methods In the double-masked randomized clinical trial, 50 BNC and 50 CI participants were randomized to the following therapeutic interventions: OBVAT or OBPT with home reinforcement for 12 one-hour office sessions. A 6∆ base-out and 6∆ base-in phoria adaptation experiment at near (40 cm) was conducted using the flashed Maddox rod technique at baseline and at outcome. Measurements included the rate and the magnitude of phoria adaptation. Results At baseline, BNC and CI participants had significantly different rates and magnitudes of base-in and base-out phoria adaptation (P < 0.001). When comparing the outcome to baseline measurements, significant main effect differences in longitudinal measurements were observed for the magnitude and the rate of phoria adaptation for both base-out and base-in experiments (P < 0.05). For the magnitude and rate of phoria adaptation, post hoc analyses using paired t-tests revealed that the CI group administered the OBVAT intervention exhibited a significant increase in the magnitude and rate of phoria adaptation compared to baseline for both base-in and base-out phoria adaptation (P < 0.01) but not for those administered OBPT. Conclusions Phoria adaptation is significantly different at baseline between those with normal binocular vision and symptomatic CI participants. OBVAT significantly improves the rate and magnitude of both base-out and base-in phoria adaptation at near compared to OBPT. Results have clinical implications for new therapeutic interventions.
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Affiliation(s)
- Ayushi Sangoi
- Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States
| | - Mitchell Scheiman
- Pennsylvania College of Optometry, Salus University, Philadelphia, Pennsylvania, United States
| | - Chang Yaramothu
- Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States.,School of Applied Engineering and Technology, New Jersey Institute of Technology, Newark, New Jersey, United States
| | - Elio M Santos
- Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States
| | - Suril Gohel
- Department of Health Informatics, Rutgers University School of Health Professions, Newark, New Jersey, United States
| | - Tara L Alvarez
- Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States
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Jayadev C, Sarbajna P, Vinekar A. Commentary: Impact of the COVID-19 pandemic on digital eye strain in children. Indian J Ophthalmol 2020; 68:2383-2384. [PMID: 33120623 PMCID: PMC7774209 DOI: 10.4103/ijo.ijo_3028_20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Affiliation(s)
- Chaitra Jayadev
- Narayana Nethralaya Eye Institute, Bangalore, Karnataka, India
| | - Puja Sarbajna
- Narayana Nethralaya Eye Institute, Bangalore, Karnataka, India
| | - Anand Vinekar
- Narayana Nethralaya Eye Institute, Bangalore, Karnataka, India
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Visio-spatial skills in athletes: comparison of rugby players and non-athletes. SPORT SCIENCES FOR HEALTH 2020. [DOI: 10.1007/s11332-020-00663-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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A Normative Study of Objective Measures of Disparity Vergence and Saccades in Children 9 to 17 Years Old. Optom Vis Sci 2020; 97:416-423. [PMID: 32511163 DOI: 10.1097/opx.0000000000001515] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
SIGNIFICANCE This study establishes normative data for objective outcome measures of vergence and saccade eye movements for the pediatric population. These data should facilitate future clinical trial design. PURPOSE This study was designed to establish normative data for objective measures of disparity vergence and saccades in children between the ages 9 and 17 years using an objective binocular eye movement tracking system. METHODS Participants (aged 9 to 17 years) had a vision examination including refraction, accommodative, and binocular vision testing. Eligibility criteria included 20/25 visual acuity with best correction, normal accommodation, and binocular vision. The ISCAN RK-826PCI binocular tracking system (ISCAN, Woburn, MA) was used to objectively record horizontal, symmetrical disparity vergence, and saccadic eye movements. Parameters assessed included peak velocity, time to peak velocity, latency, and response amplitude for both disparity vergence and saccades. RESULTS One hundred eighteen participants were recruited (54.94% female; mean age, 13.5 years), and 77.1% (91/118) of the participants completed the assessment with usable data. A sample of the normative data included peak velocity (°/s), which had a mean ± standard deviation of 25.4 ± 2.9, 22.0 ± 3.0, 225 ± 16.7, and 332.5 ± 20.5 for 4° convergence, 4° divergence, 5° saccades, and 10° saccades, respectively. The mean ± standard deviation for the latency (seconds) measures were 0.28 ± 0.1, 0.28 ± 0.16, 0.23 ± 0.05, and 0.23 ± 0.05 for 4° convergence, 4° divergence, 5° saccades, and 10° saccades, respectively. CONCLUSIONS Normative data enable researchers to have benchmark results for comparison with patient populations with binocular dysfunction. These objective disparity vergence measures can serve as outcome measures in future clinical trials to assess the effectiveness of therapeutic interventions by determining whether post-treatment results are similar to normal data.
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Abstract
SIGNIFICANCE The effect of predictability in changes of time, magnitude, and direction of the accommodation demand on the accommodation response latency and its magnitude are insignificant, which suggests that repetitive accommodative tasks such as the clinical accommodative facility test may not be influenced by potential anticipation effects. PURPOSE The purpose of this study was to investigate the effect of stimulus' time, magnitude, and direction predictability, as well as their interactions, on accommodation latency and response magnitude. METHODS Monocular accommodative response and latency were measured in 12 young subjects for nine different conditions where the stimulus accommodative demand changed several times in a steplike fashion for a period of 120 seconds. Each change in accommodative demand could have different time duration (i.e., 1, 2, or 3 seconds), magnitude (1, 2, or 3 diopters), and/or direction (i.e., accommodation or disaccommodation). All conditions were created permuting the factors of time, magnitude, and direction with two levels each: random and not random. The baseline condition was a step signal from 0 to 2 diopters persisting for 2 seconds in both accommodative demands. After each condition, subjects were asked to provide a score from 1 to 5 in their perceived predictability. RESULTS Friedman test conducted on the perceived predictability of each condition resulted in statistically significant differences between the nine conditions (χ = 56.57, P < .01). However, repeated-measures analysis of variance applied to latency and accommodative response magnitude did not show significant differences (P > .05). In addition, no correlation was found between the perceived predictability scores and both latency and accommodative response magnitudes between the most predictable and the most unpredictable conditions. CONCLUSIONS Subjects were able to perceptually notice whether the stimulus was predictable or not, although our results indicate no significant effect of stimuli predictability on either the accommodation latency or its magnitude.
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Objective Assessment of Disparity Vergence after Treatment of Symptomatic Convergence Insufficiency in Children. Optom Vis Sci 2018; 96:3-16. [PMID: 30570596 PMCID: PMC6305249 DOI: 10.1097/opx.0000000000001320] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
SIGNIFICANCE This first report of the use of objective measures of disparity vergence as outcome measures for symptomatic convergence insufficiency in children provides additional information that is not accessible with clinical tests. The study results also demonstrate that objective measures of vergence could be used in future randomized clinical trials of binocular vision disorders with children. PURPOSE This study was designed to evaluate changes in objective measures of disparity vergence after office-based vergence/accommodative therapy (OBVAT) for convergence insufficiency in children 12 to 17 years old. METHODS In this prospective trial, we recruited 10 participants with normal binocular vision and 12 with convergence insufficiency. All participants with convergence insufficiency were treated with 12 weeks of OBVAT. The primary outcome measure was average peak velocity for 4° symmetrical convergence steps. Other objective outcome measures of disparity vergence included time to peak velocity, latency, and accuracy. Changes in clinical measures (near point of convergence, positive fusional vergence at near) and symptoms were evaluated. RESULTS There was a statistically significant increase in peak velocity and more accurate response amplitude to 4° symmetrical convergence step stimuli after OBVAT compared with baseline measurements. Near point of convergence, positive fusional vergence, and symptoms also statistically significantly improved after OBVAT. Ten of the 12 participants met clinical success criteria. CONCLUSIONS In this prospective study on the treatment of symptomatic convergence insufficiency in children in which both clinical and objective eye movement measurements were used to evaluate the results of treatment, significant changes were found in symptoms and both clinical and objective measures of disparity vergence after completion of OBVAT in children with symptomatic convergence insufficiency.
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Abstract
OBJECTIVE To compare the odds of sustaining moderate and severe head impacts, rather than mild, between high school football players with high and low visual performance. DESIGN Prospective quasi-experimental. SETTING Clinical Research Center/On-field. PARTICIPANTS Thirty-seven high school varsity football players. INTERVENTIONS Athletes completed the Nike SPARQ Sensory Station visual assessment before the season. Head impact biomechanics were captured at all practices and games using the Head Impact Telemetry System. MAIN OUTCOME MEASURES Each player was classified as either a high or low performer using a median split for each of the following visual performance measures: visual clarity, contrast sensitivity, depth perception, near-far quickness, target capture, perception span, eye-hand coordination, go/no go, and reaction time. We computed the odds of sustaining moderate and severe head impacts against the reference odds of sustaining mild head impacts across groups of high and low performers for each of the visual performance measures. RESULTS Players with better near-far quickness had increased odds of sustaining moderate [odds ratios (ORs), 1.27; 95% confidence intervals (CIs), 1.04-1.56] and severe head impacts (OR, 1.45; 95% CI, 1.05-2.01) as measured by Head Impact Technology severity profile. High and low performers were at equal odds on all other measures. CONCLUSIONS Better visual performance did not reduce the odds of sustaining higher magnitude head impacts. Visual performance may play less of a role than expected for protecting against higher magnitude head impacts among high school football players. Further research is needed to determine whether visual performance influences concussion risk. CLINICAL RELEVANCE Based on our results, we do not recommend using visual training programs at the high school level for the purpose of reducing the odds of sustaining higher magnitude head impacts.
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Mustonen T, Kimmel J, Hakala J, Häkkinen J. Visual Performance With Small Concave and Convex Displays. HUMAN FACTORS 2015; 57:1029-1050. [PMID: 25850112 DOI: 10.1177/0018720815570090] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 12/22/2014] [Indexed: 06/04/2023]
Abstract
OBJECTIVE In this study, we aim to investigate how users' visual performance with a small flexible display changes based on the direction (i.e., convex, concave) and the magnitude (i.e., low, high) of the display curvature. BACKGROUND Despite the wide interest in flexible display materials and deformable displays, the potential effects of nonplanar display surfaces on human perception and performance have received little attention. This study is the first to demonstrate how curving affects visual performance with an actual flexible display (4.5-in. active-matrix organic light-emitting diode). METHOD In a series of three experiments, we compared the performance with a planar display to the performance with concave and convex display surfaces with low and high curvature magnitudes. Two visual search tasks were employed that required the subject to detect target letters based on their contrast (Experiments 1 and 2) and identity (Experiment 3). Performance was measured as the sensitivity of target detection (d') and threshold time of the search, respectively. RESULTS There were similar sensitivities for targets across the curvature variants, but the high-magnitude curvatures resulted in prolonged search times, especially for the convex form. In both of the tasks, performance was dependent on the display location, which was defined as the target's distance from the display center. CONCLUSION High curvature magnitudes should be avoided, even in small displays, because large local changes in visual stimuli decrease processing speed outside the central display. APPLICATION The findings have implications for the development of technologies, applications, and user interfaces for flexible displays and the design of visual display devices.
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Relationship of ocular accommodation and motor skills performance in developmental coordination disorder. Hum Mov Sci 2015; 42:1-14. [DOI: 10.1016/j.humov.2015.04.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 03/29/2015] [Accepted: 04/11/2015] [Indexed: 11/21/2022]
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Alvarez TL. A pilot study of disparity vergence and near dissociated phoria in convergence insufficiency patients before vs. after vergence therapy. Front Hum Neurosci 2015; 9:419. [PMID: 26283944 PMCID: PMC4515554 DOI: 10.3389/fnhum.2015.00419] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 07/06/2015] [Indexed: 11/17/2022] Open
Abstract
Purpose: This study examined the relationship between the near dissociated phoria and disparity vergence eye movements. Convergence insufficiency (CI) patients before vergence therapy were compared to: (1) the same patients after vergence therapy; and (2) binocularly normal controls (BNC). Methods: Sixteen subjects were studied—twelve BNC and four with CI. Measurements from the CI subjects were obtained before and after 18 h of vergence eye movement therapy. The near dissociated phoria was measured using the flashed Maddox rod technique. Vergence responses were stimulated from 4° symmetrical disparity vergence step stimuli. The peak velocity of the vergence response and the magnitude of the fusion initiating component (FIC) from an independent component analysis (ICA) were calculated. A linear regression analysis was conducted studying the vergence peak velocity as a function of the near dissociated phoria where the Pearson correlation coefficient was computed. Results: Before vergence therapy, the average with one standard deviation FIC magnitude of convergence responses from CI subjects was 0.29° ± 0.82 and significantly less than the FIC magnitude of 1.85° ± 0.84 for BNC (p < 0.02). A paired t-test reported that the FIC and near dissociated phoria before vergence therapy for CI subjects significantly increased to 1.49° ± 0.57 (p < 0.04) and became less exophoric to 3.5Δ ± 1.9 exo (p < 0.02) after vergence therapy. A significant correlation (r = 0.87; p < 0.01) was observed between the near dissociated phoria and the vergence ratio of convergence peak velocity divided by divergence peak velocity. Conclusion: The results have clinical translational impact in understanding the mechanism by which vergence therapy may be changing the vergence system leading to a sustained reduction in visual symptoms.
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Affiliation(s)
- Tara L Alvarez
- Department of Biomedical Engineering, New Jersey Institute of Technology University Heights, Newark, NJ, USA
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Sreenivasan V, Irving EL, Bobier WR. Can current models of accommodation and vergence predict accommodative behavior in myopic children? Vision Res 2014; 101:51-61. [DOI: 10.1016/j.visres.2014.05.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 04/23/2014] [Accepted: 05/26/2014] [Indexed: 11/26/2022]
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Horwood AM, Toor SS, Riddell PM. Change in convergence and accommodation after two weeks of eye exercises in typical young adults. J AAPOS 2014; 18:162-8. [PMID: 24582466 PMCID: PMC3991418 DOI: 10.1016/j.jaapos.2013.11.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 10/22/2013] [Accepted: 11/01/2013] [Indexed: 11/17/2022]
Abstract
BACKGROUND Although eye exercises appear to help heterophoria, convergence insufficiency, and intermittent strabismus, results can be confounded by placebo, practice, and encouragement effects. This study assessed objective changes in vergence and accommodation responses in naive young adults after a 2-week period of eye exercises under controlled conditions to determine the extent to which treatment effects occur over other factors. METHODS Asymptomatic young adults were randomly assigned to one of two no-treatment (control) groups or to one of six eye exercise groups: accommodation, vergence, both, convergence in excess of accommodation, accommodation in excess of convergence, and placebo. Subjects were tested and retested under identical conditions, except for the second control group, who were additionally encouraged. Objective accommodation and vergence were assessed to a range of targets moving in depth containing combinations of blur, disparity, and proximity/looming cues. RESULTS A total of 156 subjects were included. Response gain improved more for less naturalistic targets where more improvement was possible. Convergence exercises improved vergence for near across all targets (P = 0.035). Mean accommodation changed similarly but nonsignificantly. No other treatment group differed significantly from the nonencouraged control group, whereas encouraging effort produced significantly increased vergence (P = 0.004) and accommodation (P = 0.005) gains in the second control group. CONCLUSIONS True treatment effects were small, significantly better only after vergence exercises to a nonaccommodative target, and rarely related to the response they were designed to improve. Exercising accommodation without convergence made no difference to accommodation to cues containing detail. Additional effort improved objective responses the most.
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Affiliation(s)
- Anna M Horwood
- Infant Vision Laboratory, School of Psychology & Clinical Language Sciences, University of Reading, United Kingdom; Orthoptic Department, Royal Berkshire Hospital, Reading, United Kingdom.
| | - Sonia S Toor
- Infant Vision Laboratory, School of Psychology & Clinical Language Sciences, University of Reading, United Kingdom
| | - Patricia M Riddell
- Infant Vision Laboratory, School of Psychology & Clinical Language Sciences, University of Reading, United Kingdom
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Horwood A, Toor S. Clinical test responses to different orthoptic exercise regimes in typical young adults. Ophthalmic Physiol Opt 2014; 34:250-62. [PMID: 24471739 PMCID: PMC4238796 DOI: 10.1111/opo.12109] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Accepted: 11/13/2013] [Indexed: 12/02/2022]
Abstract
Purpose The relative efficiency of different eye exercise regimes is unclear, and in particular the influences of practice, placebo and the amount of effort required are rarely considered. This study measured conventional clinical measures following different regimes in typical young adults. Methods A total of 156 asymptomatic young adults were directed to carry out eye exercises three times daily for 2 weeks. Exercises were directed at improving blur responses (accommodation), disparity responses (convergence), both in a naturalistic relationship, convergence in excess of accommodation, accommodation in excess of convergence, and a placebo regime. They were compared to two control groups, neither of which were given exercises, but the second of which were asked to make maximum effort during the second testing. Results Instruction set and participant effort were more effective than many exercises. Convergence exercises independent of accommodation were the most effective treatment, followed by accommodation exercises, and both regimes resulted in changes in both vergence and accommodation test responses. Exercises targeting convergence and accommodation working together were less effective than those where they were separated. Accommodation measures were prone to large instruction/effort effects and monocular accommodation facility was subject to large practice effects. Conclusions Separating convergence and accommodation exercises seemed more effective than exercising both systems concurrently and suggests that stimulation of accommodation and convergence may act in an additive fashion to aid responses. Instruction/effort effects are large and should be carefully controlled if claims for the efficacy of any exercise regime are to be made.
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Affiliation(s)
- Anna Horwood
- School of Psychology & Clinical Language Sciences, University of Reading, Reading, UK
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Horwood AM, Riddell PM. The clinical near gradient stimulus AC/A ratio correlates better with the response CA/C ratio than with the response AC/A ratio. Strabismus 2013; 21:140-4. [PMID: 23713939 DOI: 10.3109/09273972.2013.786741] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AIM To provide evidence that a near clinical gradient AC/A ratio could instead reflect the CA/C relationship (the accommodation driven by response to disparity). DESIGN Case control study. METHODOLOGY 27 emmetropic participants with heterophoria <4 PD, 19 with intermittent distance exotropia, and 17 with near exophoria >6 PD were tested. A remote haploscopic photorefractor, which can measure simultaneous convergence and accommodation to a range of targets containing all combinations of presence or absence of binocular disparity, blur, and proximal (looming) cues, was used to assess response AC/A and CA/C relationships. These were compared with clinical gradient AC/A ratios at near and distance fixation using alternate prism cover test and plus or minus lenses. RESULTS Although the near and distance clinical AC/A ratios correlated weakly with each other (p = 0.03), neither clinical method correlated with the more accurate response AC/A ratio from the laboratory method (p = 0.88 and p = 0.93, respectively). The laboratory CA/C ratio correlated strongly with the near clinical AC/A ratio (p = 0.004) but only very weakly with the distance ratio (p = 0.16). CONCLUSIONS The "near gradient AC/A ratio" may actually reflect the CA/C linkage as the dissociation of the prism cover test disrupts vergence accommodation. If the near deviation diverges more with plus lenses, it may be because the lenses allow clear near vision without needing to recruit convergence accommodation to achieve it.
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Affiliation(s)
- Anna M Horwood
- MRC Clinician Scientist Research Fellow, University of Reading, UK.
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