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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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Karaca I, Demirkılınç Biler E, Palamar M, Özbaran B, Üretmen Ö. Stereoacuity, Fusional Vergence Amplitudes, and Refractive Errors Prior to Treatment in Patients with Attention-Deficit Hyperactivity Disorder. Turk J Ophthalmol 2020; 50:15-19. [PMID: 32166943 PMCID: PMC7086097 DOI: 10.4274/tjo.galenos.2019.17802] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Objectives: To evaluate stereoacuity, fusional vergence amplitudes, and refractive errors in patients with attention-deficit hyperactivity disorder (ADHD). Materials and Methods: Twenty-three patients who were newly diagnosed as having ADHD and had not started medication, and 48 children without ADHD were included. Retrospective data analysis of comprehensive eye examination, stereoacuity, and fusional vergence amplitudes of the patients were performed. Results: The mean age at ADHD diagnosis was 10.68±2.34 (7-16) years in the ADHD group (14 male, 9 female) and 12.23±2.16 (7-15) years in the control group (25 male, 23 female) patients (p=0.605). The mean stereoacuity was 142.14±152.65 (15-480) sec/arc in patients with ADHD and 46.3±44.11 (15-240) sec/arc in the control group (p<0.001). For ADHD patients, the mean convergence and divergence amplitudes at distance were 19.87±8.40 (6 to 38) prism diopter (PD) and -9.09±-4.34 (-4 to -25) PD, and 37.30±12.81 (14 to 70) PD and -13.13±-3.45 (-4 to -20) PD at near, respectively. The mean cycloplegic spherical equivalent was 1.06±1.13 (-1 to 4.63) diopter in ADHD patients, with 6 patients having significant refractive errors (hyperopia in 4 patients, astigmatism in 2 patients). There were no significant differences between groups in terms of spherical equivalents (p=0.358) or convergence and divergence amplitudes at distance (p=0.289 and p=0.492, respectively) or near (p=0.452 and p=0.127, respectively). Conclusion: Fusional vergence amplitudes did not present significant difference, while the mean value of stereoacuity was significantly lower in newly diagnosed ADHD patients prior to treatment.
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Affiliation(s)
- Irmak Karaca
- Ege University Faculty of Medicine, Department of Ophthalmology, İzmir, Turkey
| | | | - Melis Palamar
- Ege University Faculty of Medicine, Department of Ophthalmology, İzmir, Turkey
| | - Burcu Özbaran
- Ege University Faculty of Medicine, Department of Child and Adolescent Psychiatry, İzmir, Turkey
| | - Önder Üretmen
- Ege University Faculty of Medicine, Department of Ophthalmology, İzmir, Turkey
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Abstract
Background: Fusional amplitudes are important for clinical practice in diagnosing and managing binocular vision anomalies. Several measurement methods can be used to assess fusional amplitudes. However, those methods are not interchangeable, and measurement repeatability has been questioned. Objectives: To compare the normative values of tests for the measurement of fusional vergence and to investigate sources of heterogeneity of diagnostic accuracy including: age, variation in method of assessment, study design and size, type (convergent, divergent, vertical, cyclo) and severity of strabismus (constant/intermittent/latent). Data sources: Bibliographic databases were searched up to March 2018, including Cochrane registers, PubMed, Web of ScienceTM, Google Scholar and Science Citation Index. Trial registers and conference proceedings were hand searched. Review methods: The review observed and reported according to the PRISMA guidelines and was registered with PROSPERO. The I2 was used to show the percentage of observed total variation across studies that is due to real heterogeneity rather than chance. The results of the different studies and the overall effect (meta-analysis under the random effects model) are shown. Results: Eighty-one studies were included in the review. Heterogenous information about break vergence amplitudes is reported for the step vergence method (I2 > 50%; p < 0.05) in children. Four parameters were reported consistently to affect measurements; age, method of assessment, order of testing and target size. For the smooth vergence technique break vergence values heterogeneity was not present in children and adults (I2 = 0%; p > 0.05). Limitations: The results are based on cross-sectional studies that were performed independently of each other, with different examiners, methods of examination and different populations. Conclusions: The source of heterogeneity between studies for vergence break points measured with the step vergence method seems to be linked with age. Normal vergences reported in children had considerable heterogeneity compared with adults. In clinical practice, the population-based vergence ranges measured with the step vergence method in children should not be used as one single criterion. For the smooth vergence technique, normative population data can be used.
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Affiliation(s)
| | - Fiona J Rowe
- b Department of Health Services Research, University of Liverpool , Liverpool
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Przekoracka-Krawczyk A, Michalak KP, Pyżalska P. Deficient vergence prism adaptation in subjects with decompensated heterophoria. PLoS One 2019; 14:e0211039. [PMID: 30657792 PMCID: PMC6338415 DOI: 10.1371/journal.pone.0211039] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Accepted: 01/07/2019] [Indexed: 11/26/2022] Open
Abstract
Vergence prism adaptability was evaluated in subjects with high symptomatic and asymptomatic heterophoria and compared to individuals with a heterophoria within normal range (the control group). A computer haploscope was used to measure phoria values and changes in the eye position after introducing 6 prism diopters base out in front of the right eye. Phoria values were measured with a nonius paradigm every minute for a period of 10 minutes during adaptation. The results showed that subjects with symptomatic heterophoria are characterized by a lower rate of prism adaptation and adapted to a smaller extent with respect to the control group. The group with high but asymptomatic heterophoria showed prolonged adaptation time but after several minutes of binocular viewing the subjects were able to adapt to the prism to a level similar to the control group. These findings suggest that an impairment in the slow vergence control system may be responsible for the inability to fully reduce vergence effort, which results in poor vergence ranges and asthenopic symptoms during prolonged viewing.
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Affiliation(s)
- Anna Przekoracka-Krawczyk
- Laboratory of Vision Science and Optometry, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland
- Vision and Neuroscience Laboratory, NanoBioMedical Centre, Adam Mickiewicz University, Poznań, Poland
- * E-mail:
| | - Krzysztof Piotr Michalak
- Laboratory of Vision Science and Optometry, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland
- Vision and Neuroscience Laboratory, NanoBioMedical Centre, Adam Mickiewicz University, Poznań, Poland
| | - Paulina Pyżalska
- Laboratory of Vision Science and Optometry, Faculty of Physics, Adam Mickiewicz University, Poznań, Poland
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Tannen B, Good K, Ciuffreda KJ, Moore KJ. Prevalence of esophoria in concussed patients. JOURNAL OF OPTOMETRY 2019; 12:64-68. [PMID: 29602686 PMCID: PMC6318546 DOI: 10.1016/j.optom.2018.02.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 02/12/2018] [Accepted: 02/13/2018] [Indexed: 06/02/2023]
Abstract
PURPOSE To assess the prevalence of esophoria at near in concussed patients in a neuro-optometric private practice setting. METHODS A retrospective analysis was performed involving a chart review in a neuro-optometric, private practice setting of consecutive patients with a medical diagnosis of concussion from January 1st 2016 to December 31st 2016. A total of 71 patients were included in the analysis. All received a comprehensive vision examination, with a near vision emphasis. The near horizontal phoria was assessed with the cover test and the von Graefe test. RESULTS Approximately 30% of the patients with a medically based diagnosis of concussion exhibited esophoria at near, with good agreement (95%) between the two tests. Mean esophoria was 5.2 (SD=2.8) prism diopters (pd), with a range from 2pd to 14pd of esophoria. Convergence excess was diagnosed in 23%. DISCUSSION Near esophoria was found in nearly one-third of this practice-based sample of concussed patients. Thus, it was more common than typically believed to be the case. Two proposed oculomotor-based mechanisms related to these symptomatic esophoric patients included phoria decompensation and excessive accommodative vergence.
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Affiliation(s)
- Barry Tannen
- Private Practice, EyeCare Professionals, PC, Hamilton Square, NJ, United States.
| | - Kalynn Good
- Private Practice, Costa Mesa, CA 92626, United States
| | | | - Kelsey J Moore
- Vision Therapy and Neuro-optometric Rehabilitation, EyeCare Professionals, PC, Hamilton Square, NJ, United States
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Santos EM, Yaramothu C, Alvarez TL. Comparison of symmetrical prism adaptation to asymmetrical prism adaptation in those with normal binocular vision. Vision Res 2018; 149:59-65. [PMID: 29940191 DOI: 10.1016/j.visres.2018.06.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2017] [Revised: 06/07/2018] [Accepted: 06/11/2018] [Indexed: 12/16/2022]
Abstract
This study sought to determine whether symmetrical compared to asymmetrical horizontal prisms (base-out or base-in) evoked different rates of phoria adaptation. Sixteen young adults with normal binocular vision participated in a symmetrical phoria adaptation experiment using a 3Δ base-out or 3Δ base-in binocular prism flipper and an asymmetrical phoria adaptation experiment using a 6Δ base-out or 6Δ base-in monocular wedge prism. The experiments were randomized and counterbalanced to reduce the influence of the prism stimulation order. Asymmetrical base-out prism adaptation was significantly faster than symmetrical prism adaptation for subjects with normal binocular vision. Asymmetrical phoria adaptation with base-in prism was not significantly different from symmetrical phoria adaptation implying that there are directional asymmetries (convergent versus divergent eye movements) in the slow fusional component of vergence. Data suggest that a potential interaction between the version system and the slow fusional vergence system may exist. Results have clinical relevance because patients with convergence or divergence insufficiency/excess may potentially show more pronounced differences between symmetrical and asymmetrical phoria adaptation compared to binocularly normal controls. These differences might also be relevant to clinical measurements such as vergence fusional range, which can be measured symmetrically (with Risley prisms in a phoroptor) or asymmetrically (with prism bar).
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Affiliation(s)
- Elio M Santos
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ, USA.
| | - Chang Yaramothu
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ, USA
| | - Tara L Alvarez
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ, USA.
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Mutti DO, Mitchell GL, Jones-Jordan LA, Cotter SA, Kleinstein RN, Manny RE, Twelker JD, Zadnik K. The Response AC/A Ratio Before and After the Onset of Myopia. Invest Ophthalmol Vis Sci 2017; 58:1594-1602. [PMID: 28291868 PMCID: PMC5361580 DOI: 10.1167/iovs.16-19093] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Purpose To investigate the ratio of accommodative convergence per diopter of accommodative response (AC/A ratio) before, during, and after myopia onset. Methods Subjects were 698 children aged 6 to 14 years who became myopic and 430 emmetropic children participating in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error. Refractive error was measured using cycloplegic autorefraction, near work by parent survey, and the AC/A ratio by simultaneously monitoring convergence and accommodative response. The response AC/A ratios of children who became myopic were compared with age-, sex-, and ethnicity-matched model estimates for emmetropic children from 5 years before through 5 years after the onset of myopia. Results The response AC/A ratio was not significantly different between the two groups 5 years before onset, then increased monotonically in children who became myopic until reaching a plateau at myopia onset of about 7 Δ/D compared to about 4 Δ/D for children who remained emmetropic (differences between groups significant at P < 0.01 from 4 years before onset through 5 years after onset). A higher AC/A ratio was associated with greater accommodative lag but not with the rate of myopia progression regardless of the level of near work. Conclusions An increasing AC/A ratio is an early sign of becoming myopic, is related to greater accommodative lag, but does not affect the rate of myopia progression. The association with accommodative lag suggests that the AC/A ratio increase is from greater neural effort needed per diopter of accommodation rather than change in the accommodative convergence crosslink gain relationship.
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Affiliation(s)
- Donald O Mutti
- The Ohio State University College of Optometry, Columbus, Ohio, United States
| | - G Lynn Mitchell
- The Ohio State University College of Optometry, Columbus, Ohio, United States
| | - Lisa A Jones-Jordan
- The Ohio State University College of Optometry, Columbus, Ohio, United States
| | - Susan A Cotter
- Southern California College of Optometry at Marshall B. Ketchum University, Fullerton, California, United States
| | - Robert N Kleinstein
- School of Optometry, University of Alabama, Birmingham, Birmingham, Alabama, United States
| | - Ruth E Manny
- University of Houston College of Optometry, Houston, Texas, United States
| | - J Daniel Twelker
- University of Arizona Department of Ophthalmology and Vision Science, Tucson, Arizona, United States
| | - Karla Zadnik
- The Ohio State University College of Optometry, Columbus, Ohio, United States
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Sreenivasan V, Babinsky EE, Wu Y, Candy TR. Objective Measurement of Fusional Vergence Ranges and Heterophoria in Infants and Preschool Children. Invest Ophthalmol Vis Sci 2017; 57:2678-88. [PMID: 27183054 PMCID: PMC4874477 DOI: 10.1167/iovs.15-17877] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Purpose Binocular alignment typically includes motor fusion compensating for heterophoria. This study evaluated heterophoria and then accommodation and vergence responses during measurement of fusional ranges in infants and preschoolers. Methods Purkinje image eye tracking and eccentric photorefraction (MCS PowerRefractor) were used to record the eye alignment and accommodation of uncorrected infants (n = 17; 3–5 months old), preschoolers (n = 19; 2.5–5 years), and naïve functionally emmetropic adults (n = 14; 20–32 years; spherical equivalent [SE], +1 to −1 diopters [D]). Heterophoria was derived from the difference between monocular and binocular alignments while participants viewed naturalistic images at 80 cm. The presence or absence of fusion was then assessed after base-in (BI) and base-out (BO) prisms (2–40 prism diopters [pd]) were introduced. Results Mean (±SD) SE refractions were hyperopic in infants (+2.4 ± 1.2 D) and preschoolers (+1.1 ± 0.6 D). The average exophoria was similar (P = 0.11) across groups (Infants, −0.79 ± 2.5 pd; Preschool, −2.43 ± 2.0 pd; Adults, −1.0 ± 2.7 pd). Mean fusional vergence range also was similar (P = 0.1) for BI (Infants, 11.2 ± 2.5 pd; Preschool, 8.8 ± 2.8 pd; Adults, 11.8 ± 5.2 pd) and BO (Infants, 14 ± 6.6 pd; Preschool, 15.3 ± 8.3 pd; Adults, 20 ± 9.2 pd). Maximum change in accommodation to the highest fusible prism was positive (increased accommodation) for BO (Infants, 1.69 ± 1.4 D; Preschool, 1.35 ± 1.6 D; Adults, 1.22 ± 1.0 D) and negative for BI (Infants, −0.96 ± 1.0 D; Preschool, −0.78 ± 0.6 D; Adults, −0.62 ± 0.3 D), with a similar magnitude across groups (BO, P = 0.6; BI, P = 0.4). Conclusions Despite typical uncorrected hyperopia, infants and preschoolers exhibited small exophorias at 80 cm, similar to adults. All participants demonstrated substantial fusional ranges, providing evidence that even 3- to 5-month-old infants can respond to a large range of image disparities.
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Talasan H, Scheiman M, Li X, Alvarez TL. Disparity vergence responses before versus after repetitive vergence therapy in binocularly normal controls. J Vis 2016; 16:7. [PMID: 26762276 PMCID: PMC4743712 DOI: 10.1167/16.1.7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
This study sought to determine whether significant changes would be observed between vergence eye movements before and after 12 hr of repetitive vergence therapy (1 hr per day on different days) in subjects with normal binocular vision compared to controls. Disparity vergence responses from 23 subjects were studied. An assessment protocol that minimized the influence of the near dissociated phoria on the disparity vergence system was designed. The following parameters were quantified for the responses: latency, time to peak velocity, settling time, peak velocity, and accuracy (difference between the response and stimulus amplitudes). The following outcomes were observed when comparing the results after vergence therapy to the baseline measurements: (a) near point of convergence and near dissociated phoria did not significantly change (p > 0.15); (b) latency, time to peak velocity, and settling time significantly decreased (p ≤ 0.01); and (c) accuracy significantly improved (p < 0.01). Results support that vergence peak velocity is dependent on the subject's near dissociated phoria. The accuracy and temporal properties of vergence eye movement responses from subjects with normal binocular vision can be improved after vergence therapy. These methods can be utilized within future studies to quantitatively assess vergence therapy techniques for patients with binocular dysfunction.
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Increased onset of vergence adaptation reduces excessive accommodation during the orthoptic treatment of convergence insufficiency. Vision Res 2015; 111:105-13. [PMID: 25891521 DOI: 10.1016/j.visres.2015.04.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 03/31/2015] [Accepted: 04/02/2015] [Indexed: 10/23/2022]
Abstract
This research tested the hypothesis that the successful treatment of convergence insufficiency (CI) with vision-training (VT) procedures, leads to an increased capacity of vergence adaptation (VAdapt) allowing a more rapid downward adjustment of the convergence accommodation cross-link. Nine subjects with CI were recruited from a clinical population, based upon reduced fusional vergence amplitudes, receded near point of convergence or symptomology. VAdapt and the resulting changes to convergence accommodation (CA) were measured at specific intervals over 15 min (pre-training). Separate clinical measures of the accommodative convergence cross link, horizontal fusion limits and near point of convergence were taken and a symptomology questionnaire completed. Subjects then participated in a VT program composed of 2.5h at home and 1h in-office weekly for 12-14 weeks. Clinical testing was done weekly. VAdapt and CA measures were retaken once clinical measures normalized for 2 weeks (mid-training) and then again when symptoms had cleared (post-training). VAdapt and CA responses as well as the clinical measures were taken on a control group showing normal clinical findings. Six subjects provided complete data sets. CI clinical findings reached normal levels between 4 and 7 weeks of training but symptoms, VAdapt, and CA output remained significantly different from the controls until 12-14 weeks. The hypothesis was retained. The reduced VAdapt and excessive CA found in CI were normalized through orthoptic treatment. This time course was underestimated by clinical findings but matched symptom amelioration.
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Abstract
AIM To determine whether the convergence accommodation to convergence (CA/C) ratio during divergence with base-in (BI) prisms is of a similar or different magnitude to that measured during convergence with base-out (BO) prisms. METHODS Eighteen participants with normal binocular single vision were recruited. The participants viewed a pseudo-Gaussian target, which consisted of a light emitting diode (LED) behind a diffusing screen at 40 cm. After 5 minutes of dark adaptation, the refractive status of the eye was measured without any prism using a Shin-Nippon SRW-5000 autorefractor. The participant held the selected prism (5Δ or 10Δ BO or BI, counterbalanced) in front of their right eye and obtained a single, fused image of the target while refractive measures were taken with each. A 30-second rest period was given between measurements. The mean age of the participants was 20.6±3.22 years. RESULTS The mean CA/C ratios for the 5Δ BO, 10Δ BO, 5Δ BI, and 10Δ BI were 0.108 (±0.074) D/Δ, 0.110 (±0.056) D/Δ, 0.100 (±0.090) D/Δ, and 0.089 (±0.055) D/Δ, respectively. A 2-factor repeated measures ANOVA found that the CA/C ratio did not significantly change with differing levels of prism-induced convergence and divergence (p=0.649). CONCLUSIONS Change in accommodation induced by manipulating vergence is similar whether convergence or divergence are induced. The CA/C ratio did not show any change with differing levels of prism-induced convergence and divergence.
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Affiliation(s)
- Joshua M Simmons
- Academic Unit of Ophthalmology and Orthoptics, Faculty of Medicine, Dentistry and Health, University of Sheffield , Beech Hill Road, Sheffield, S10 2RX , UK
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Sreenivasan V, Bobier WR. Reduced vergence adaptation is associated with a prolonged output of convergence accommodation in convergence insufficiency. Vision Res 2014; 100:99-104. [PMID: 24759573 DOI: 10.1016/j.visres.2014.04.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 03/06/2014] [Accepted: 04/07/2014] [Indexed: 10/25/2022]
Abstract
Convergence insufficiency (CI) is a developmental visual anomaly defined clinically by a reduced near point of convergence, a reduced capacity to view through base-out prisms (fusional convergence); coupled with asthenopic symptoms typically blur and diplopia. Experimental studies show reduced vergence parameters and tonic adaptation. Based upon current models of accommodation and vergence, we hypothesize that the reduced vergence adaptation in CI leads to excessive amounts of convergence accommodation (CA). Eleven CI participants (mean age=17.4±2.3 years) were recruited with reduced capacity to view through increasing magnitudes of base out (BO) prisms (mean fusional convergence at 40 cm=12±0.9Δ). Testing followed our previous experimental design for (n=11) binocularly normal adults. Binocular fixation of a difference of Gaussian (DoG) target (0.2 cpd) elicited CA responses during vergence adaptation to a 12Δ BO. Vergence and CA responses were obtained at 3 min intervals over a 15 min period and time course were quantified using exponential decay functions. Results were compared to previously published data on eleven binocular normals. Eight participants completed the study. CI's showed significantly reduced magnitude of vergence adaptation (CI: 2.9Δ vs. normals: 6.6Δ; p=0.01) and CA reduction (CI=0.21 D, Normals=0.55 D; p=0.03). However, the decay time constants for adaptation and CA responses were not significantly different. CA changes were not confounded by changes in tonic accommodation (Change in TA=0.01±0.2D; p=0.8). The reduced magnitude of vergence adaptation found in CI patients resulting in higher levels of CA may potentially explain their clinical findings of reduced positive fusional vergence (PFV) and the common symptom of blur.
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Affiliation(s)
| | - William R Bobier
- School of Optometry and Vision Science, University of Waterloo, Ontario, Canada.
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Momeni-Moghaddam H, Eperjesi F, Kundart J, Mostafavi-Nam K. Stereoacuity as an indicator of prism adaptation. Curr Eye Res 2014; 39:775-9. [PMID: 24559406 DOI: 10.3109/02713683.2014.883410] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE The purpose of this study was to determine whether stereoacuity can be used as an indicator of prism adaptation. In particular, we wanted to know whether the time required for stereoacuity to return to the initial level after viewing through a prism can be used to determine the degree of adaptation. MATERIALS AND METHODS Eighteen subjects participated in this study. Stereoacuity and dissociated phoria were determined using the TNO stereotest and the Maddox rod, respectively. Prism vergences were measured using a prism bar. For each participant, prism power equivalent to the blur point of base-in (BI) and base-out (BO) fusional vergence at 40 cm was divided and placed in front of both eyes. At 0, 3, 6, 9 and 12 min after prism introduction, the stereoacuity was measured, and at 0 and 12 min, the heterophoria was measured. RESULTS The repeated measures ANOVA showed a significant difference between the mean stereoacuity for BI and BO prisms at the different measurement times (p < 0.05). For BO prism, the initial value was different between 0 and 3 min after the prism introduction, whereas for BI prism, a difference in stereoacuity was found between the pre-prism value and the value at 0, 3 and 6 min. The size of the heterophoria with BO and BI prisms was different from 0 to 12 min (p < 0.05). CONCLUSION The time required for stereoacuity to return to baseline level was more than 3 min for BO, and more than 6 min for BI prism. In addition, the time required to return to baseline values was not similar for the stereoacuity and heterophoria. The recovery of stereoacuity is slower when adapting to divergence, as when looking from near to far. This implies that stereopsis responds faster to near targets than to distant one, and may precede complete phoria adaptation.
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Affiliation(s)
- Hamed Momeni-Moghaddam
- Health Promotion Research Center, Zahedan University of Medical Sciences , Zahedan , Iran
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Thiagarajan P, Ciuffreda KJ. Effect of oculomotor rehabilitation on vergence responsivity in mild traumatic brain injury. ACTA ACUST UNITED AC 2013; 50:1223-40. [DOI: 10.1682/jrrd.2012.12.0235] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Revised: 06/11/2013] [Indexed: 11/05/2022]
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Kim EH, Vicci VR, Granger-Donetti B, Alvarez TL. Short-term adaptations of the dynamic disparity vergence and phoria systems. Exp Brain Res 2011; 212:267-78. [PMID: 21594645 DOI: 10.1007/s00221-011-2727-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2011] [Accepted: 05/03/2011] [Indexed: 11/26/2022]
Abstract
The ability to adapt is critical to survival and varies between individuals. Adaptation of one motor system may be related to the ability to adapt another. This study sought to determine whether phoria adaptation was correlated with the ability to modify the dynamics of disparity vergence. Eye movements from ten subjects were recorded during dynamic disparity vergence modification and phoria adaptation experiments. Two different convergent stimuli were presented during the dynamic vergence modification experiment: a test stimulus (4° step) and a conditioning stimulus (4° double step). Dynamic disparity vergence responses were quantified by measuring the peak velocity (°/s). Phoria adaptation experiments measured the changes in phoria over a 5-min period of sustained fixation. The maximum velocity of phoria adaptation was determined from an exponential fit of the phoria data points. Phoria and dynamic disparity vergence peak velocity were both significantly modified (P < 0.001). The maximum velocity of phoria adaptation was significantly correlated with the changes in convergence peak velocity (r > 0.89; P < 0.001). There was a strong correlation between the ability to adaptively adjust two different oculomotor parameters: a tonic and dynamic component. Future studies should investigate additional interactions between these parameters, and the ability to adaptively change other oculomotor systems such as the saccadic or smooth pursuit system. Understanding the ability to modify phoria, dynamic disparity vergence, and other oculomotor parameters can yield insights into the plasticity of short-term adaptation mechanisms.
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Affiliation(s)
- Eun H Kim
- Department of Biomedical Engineering, New Jersey Institute of Technology, University Heights, Newark, NJ 07102, USA
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Sreenivasan V, Bobier WR, Irving E, Lakshminarayanan V. Effect of vergence adaptation on convergence accommodation: model simulations. IEEE Trans Biomed Eng 2010; 57. [PMID: 24712022 DOI: 10.1109/tbme.2010.2061231] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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