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Peli E, Jung JH. Review: Binocular double vision in the presence of visual field loss. J Vis 2024; 24:13. [PMID: 38899959 PMCID: PMC11193068 DOI: 10.1167/jov.24.6.13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Accepted: 03/13/2024] [Indexed: 06/21/2024] Open
Abstract
Binocular double vision in strabismus is marked by diplopia (seeing the same object in two different directions) and visual confusion (seeing two different objects in the same direction). In strabismus with full visual field, the diplopia coexists with visual confusion across most of the binocular field. With visual field loss, or with use of partial prism segments for field expansion, the two phenomena may be separable. This separability is the focus of this review and offers new insights into binocular function. We show that confusion is necessary but is not sufficient for field expansion. Diplopia plays no role in field expansion but is necessary for clinical testing of strabismus, making such testing difficult in field loss conditions with confusion without diplopia. The roles of the three-dimensional structure of the real world and the dynamic of eye movements within that structure are considered as well. Suppression of one eye's partial view under binocular vision that develops in early-onset (childhood) strabismus is assumed to be a sensory adaption to diplopia. This assumption can be tested using the separation of diplopia and confusion.
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Affiliation(s)
- Eli Peli
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
| | - Jae-Hyun Jung
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
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Benhaim-Sitbon L, Lev M, Polat U. Abnormal basic visual processing functions in binocular fusion disorders. Sci Rep 2023; 13:19301. [PMID: 37935803 PMCID: PMC10630403 DOI: 10.1038/s41598-023-46291-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 10/30/2023] [Indexed: 11/09/2023] Open
Abstract
Heterophoria is a common type of binocular fusion disorder that consists of a latent eye misalignment with potential consequences on daily activities such as reading or working on a computer (with CVS). Crowding, a type of contextual modulation, can also impair reading. Our recent studies found an abnormal pattern of low-level visual processing with larger perceptive fields (PF) in heterophoria. The PF is the fundamental processing unit of human vision and both masking and crowding depend on its size. We investigated how heterophoria would impact the PF's size via a lateral masking experiment and consequently affect the foveal crowding at different letter-spacings (the crowding zone). More specifically, we explored the relationship between crowding, lateral masking, the PF's size, and the amount of heterophoria. The binocular horizontal PF's size was larger with heterophoric subjects, in agreement with our previous study. We found a stronger crowding and an extended crowding zone associated with slower response times; this shows that the processing of letter identification under both crowded and uncrowded conditions requires more processing effort in heterophoric individuals. In agreement with previous studies, we found a correlation between the crowding zone and the PF's size; each was strongly correlated with the amount of phoria. These findings resemble those involving the PF size and the extended crowding found at the fovea in amblyopia and young children. We suggest that these findings could help explain the inter-observers' variability found in the masking literature, and the reading difficulties often encountered in subjects with high heterophoria.
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Affiliation(s)
- Laura Benhaim-Sitbon
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, Israel
| | - Maria Lev
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, Israel
| | - Uri Polat
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, Israel.
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Laughton SC, Hagen MM, Yang W, von Bartheld CS. Gender differences in horizontal strabismus: Systematic review and meta-analysis shows no difference in prevalence, but gender bias towards females in the clinic. J Glob Health 2023; 13:04085. [PMID: 37651634 PMCID: PMC10471156 DOI: 10.7189/jogh.13.04085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/02/2023] Open
Abstract
Background Strabismus is a misalignment of the visual axis that affects 2-3% of the population and can lead to loss of binocular vision. It is currently controversial whether there is a gender difference in the most common form of visual misalignment: horizontal strabismus. Some studies claimed that more females than males have an outward deviation (exotropia), while others concluded that there is no significant gender difference. No previous work has systematically explored gender differences in horizontal strabismus or has compared the results of population-based studies with those of clinic-based studies. Methods We conducted a systematic review and meta-analysis of studies reporting the prevalence of horizontal strabismus. We included 73 population-based studies and compared their disclosed gender population with that in 141 comparable clinical-based studies. We analysed the data according to gender, strabismus type (esotropia, exotropia), and geographic region/ethnicity. Results Summary statistics showed a nearly identical prevalence of horizontal strabismus (2.558% for males, 2.582% for females), esotropia (1.386% males vs. 1.377% females), and of exotropia (1.035% males vs. 1.043% females). Meta-analysis results showed that these differences between males and females were not statistically significant (odds ratio (OR) = 1.01; 95% confidence interval (CI) = 0.97-1.10), but that females were significantly more frequent (by 7.50%) in clinic-based studies than males, with 5.00% more females for esotropia, and 12.20% more females for exotropia when adjusted for the population's sex ratio. The extent of the female gender bias differed between geographic regions/societies, with Asians having the lowest bias towards females and Latin American countries having the strongest bias. Conclusions Males and females have the same prevalence of horizontal strabismus, including exotropia. Females with strabismus seek health care or are brought to clinics significantly more often than males. This is an example of gender bias in health care in favour of females rather than males, apparently because parents - erroneously fearing only cosmetic consequences - are more concerned about strabismus in their daughters than their sons. Societal attitudes towards females, as well as economic factors (insurance status), appear to be relevant factors that determine the magnitude of the gender bias in horizontal strabismus.
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Affiliation(s)
- Sydney C Laughton
- Center of Biomedical Research Excellence in Cell Biology, University of Nevada, Reno School of Medicine, Reno, Nevada, USA
| | - Molly M Hagen
- School of Public Health, University of Nevada, Reno, Nevada, USA
| | - Wei Yang
- School of Public Health, University of Nevada, Reno, Nevada, USA
| | - Christopher S von Bartheld
- Center of Biomedical Research Excellence in Cell Biology, University of Nevada, Reno School of Medicine, Reno, Nevada, USA
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, Nevada, USA
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Benhaim-Sitbon L, Lev M, Polat U. Extended perceptive field revealed in humans with binocular fusion disorders. Sci Rep 2023; 13:6584. [PMID: 37085571 PMCID: PMC10121568 DOI: 10.1038/s41598-023-33429-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 04/12/2023] [Indexed: 04/23/2023] Open
Abstract
Binocular vision disorders or dysfunctions have considerable impact on daily visual activities such as reading. Heterophoria (phoria) is a latent eye misalignment (with a prevalence of up to 35%) that appears in conditions that disrupt binocular vision and it may affect the quality of binocular fusion. Our recent study, which used lateral masking (LM), suggests that subjects with binocular fusion disorders (horizontal phoria) exhibit an asymmetry and an abnormal pattern of both binocular and monocular lateral interactions, but only for the horizontal meridian (HM). The perceptive field (PF) is the fundamental processing unit of human vision and both masking and crowding depend on its size. An increased PF size is found in amblyopic populations or in young children. We hypothesized that the PF's size would be asymmetric only for the phoric group (larger along the HM). We estimated the PF's size using two different methods (LM with equal-phase and opposite-phase flankers). Phoric subjects exhibited a larger binocular PF size, only for the HM, confirming our hypothesis of an asymmetric PF size. However, the monocular PF size of phoric and control subjects was similar. Phoria affects the PF's size similarly to meridional amblyopia but without being attributed to abnormal refraction. We suggest that these findings could help explain the inter-observer variability found in the masking literature and the reading difficulties often encountered in subjects with high heterophoria. Since perceptual learning can reduce the PF's size, further investigation of training may provide a novel therapy to reduce some symptoms related to heterophoria.
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Affiliation(s)
- Laura Benhaim-Sitbon
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Maria Lev
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Uri Polat
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.
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Binocular fusion disorders impair basic visual processing. Sci Rep 2022; 12:12564. [PMID: 35869104 PMCID: PMC9307628 DOI: 10.1038/s41598-022-16458-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 07/11/2022] [Indexed: 11/18/2022] Open
Abstract
In an era of increasing screen consumption, the requirement for binocular vision is demanding, leading to the emergence of syndromes such as the computer vision syndrome (CVS) or visual discomfort reported by virtual reality (VR) users. Heterophoria (phoria) is a latent eye misalignment (with a prevalence up to 35%) that appears in conditions that disrupt binocular vision and may affect the quality of binocular fusion. Collinear facilitation (CF), the mechanism for grouping contour elements, is a process that reveals lateral interactions by improving the visibility of a target by flankers placed collinearly. An abnormal pattern of CF has been observed in strabismic amblyopia. We hypothesize that phoria may affect CF in the horizontal meridian (HM) due to latent eye misalignment and its impact on binocular fusion. Fully corrected participants (phoria group and controls) completed a standard CF experiment for horizontal and vertical meridians during binocular and monocular viewing. Phoric observers exhibited (1) an asymmetry and an abnormal pattern of CF only for the HM, during both monocular and binocular viewing, (2) poor binocular summation between the monocular inputs, and (3) no binocular advantage of the CF. Phoria affects the CF in a way that is reminiscent of meridional amblyopia without being attributed to abnormal refraction. The abnormal pattern of CF in monocular viewing suggests that phoria could be a binocular developmental disorder that affects monocular spatial interactions. We suggest that the results could contribute to explain the visual discomfort experienced with VR users or symptoms when presenting CVS.
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Armarnik S, Kozlov Y, Yahalomi T, Ekshtein A, Levian L, Gurfinkel Y, Tehori O, Ben-Ari O, Kinori M. The influence of refractive state and heterophorias on visual acuity and stereoacuity in healthy young adults. J AAPOS 2022; 26:181.e1-181.e6. [PMID: 35863607 DOI: 10.1016/j.jaapos.2022.04.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/25/2021] [Revised: 04/21/2022] [Accepted: 04/24/2022] [Indexed: 10/17/2022]
Abstract
PURPOSE To evaluate associations of refractive error and heterophoria with best-corrected visual acuity and stereoacuity in a population of healthy young adults. METHODS Data extracted from the Israeli Defense Forces Air Force candidates database was analyzed retrospectively. Myopia and hyperopia were defined as spherical equivalent of ≤ -0.50 D and ≥ +0.50 D. Cylinder of ≥0.75 D was considered astigmatism. Oblique astigmatism was defined as axis between 30°-60° and 120°-150°. Heterophoria of ≥8Δ for near was considered exo- or esophoria. RESULTS The study population included 5,491 subjects (75.8% male), with a mean age of 17.6 ± 0.9 years: 2,355 (42.9%) had myopia, 640 (11.6%) had hyperopia, and the rest were emmetropic. Astigmatism was present in 2,006 participants (36.5%), and of those, 619 (30.9%) had oblique astigmatism. Emmetropia was correlated with better best-corrected visual acuity; astigmatism and high hyperopia, with poorer best-corrected visual acuity. A total of 331 subjects (6%) had heterophoria of ≥8Δ; of those, 300 (90.6%) had exophoria and 31 (9.4%) had esophoria. The prevalence of exophoria was higher in the myopic group, and exophoria was not associated with stereoacuity. Esophoria and anisometropia were associated with worse stereoacuity. The best stereopsis was achieved by emmetropic subjects with no astigmatism. CONCLUSIONS Emmetropia is associated with better best-corrected visual acuity and stereoacuity. Astigmatism and high hyperopia are correlated with poorer best-corrected visual acuity. Exophoria does not interfere with stereopsis, but both esophoria and anisometropia do.
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Affiliation(s)
- Sharon Armarnik
- Goldschleger Eye Institute, Sheba Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Tel Hashomer, Israel
| | - Yuval Kozlov
- Israeli Air Force Aeromedical Center, Tel Hashomer, Ramat Gan, Israel; Israeli Defense Forces Medical Corps, Tel Hashomer, Ramat Gan, Israel; Department of Military Medicine and "Tzameret," Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Tal Yahalomi
- Department of ophthalmology, Assuta Medical Center Ashdod, Israel and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Aya Ekshtein
- Israeli Air Force Aeromedical Center, Tel Hashomer, Ramat Gan, Israel
| | - Leora Levian
- Israeli Air Force Aeromedical Center, Tel Hashomer, Ramat Gan, Israel
| | - Yoav Gurfinkel
- Israeli Air Force Aeromedical Center, Tel Hashomer, Ramat Gan, Israel
| | - Omer Tehori
- Israeli Air Force Aeromedical Center, Tel Hashomer, Ramat Gan, Israel; Israeli Defense Forces Medical Corps, Tel Hashomer, Ramat Gan, Israel; Department of Military Medicine and "Tzameret," Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Oded Ben-Ari
- Israeli Air Force Aeromedical Center, Tel Hashomer, Ramat Gan, Israel; Israeli Defense Forces Medical Corps, Tel Hashomer, Ramat Gan, Israel; Department of Military Medicine and "Tzameret," Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel; Adelson School of Medicine, Ariel University, Ariel, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Michael Kinori
- Department of ophthalmology, Assuta Medical Center Ashdod, Israel and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
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Zhu B, Wang X, Fu L, Yan J. Pattern Strabismus in a Tertiary Hospital in Southern China: A Retrospective Review. MEDICINA (KAUNAS, LITHUANIA) 2022; 58:medicina58081018. [PMID: 36013485 PMCID: PMC9414984 DOI: 10.3390/medicina58081018] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 06/12/2022] [Revised: 07/23/2022] [Accepted: 07/25/2022] [Indexed: 11/18/2022]
Abstract
Background and objectives: To analyze demographic and clinical features of pattern strabismus patients and assess the relationship among these clinical variables and risk factors. Materials and Methods: Medical records of pattern strabismus patients who had undergone strabismus surgery at our center between 2014 and 2019 were retrospectively reviewed. Data collected included gender, age at onset, age at surgery, refraction, Cobb angle, pre- and post-operative deviations in the primary position, up- and downgaze, angle of ocular torsion, type/amount of pattern, grade of oblique muscle function and presence/grade of binocular function. To verify the clinical significance of the Cobb angle, 666 patients who had undergone surgery within one week after ocular trauma between 2015 and 2021 were enrolled as controls. Results: Of the 8738 patients with horizontal strabismus, 905 (507 males and 398 females) had pattern strabismus, accounting for 10.36%. Among these 905 patients, 313 showed an A-pattern and 592 showed a V-pattern. The predominant subtype was V-exotropia, followed by A-exotropia, V-esotropia and A-esotropia. Over half of these patients (54.6%) manifested an A- or V-pattern in childhood. The overall mean ± SD Cobb angle was 5.03 ± 4.06° and the prevalence of thoracic scoliosis was 12.4%, both of which were higher than that observed in normal controls (4.26 ± 3.36° and 7.8%). Within A-pattern patients, 80.2% had SOOA and 81.5% an intorsion, while in V-pattern patients, 81.5% had IOOA and 73.4% an extorsion. Patients with binocular function showed decreases in all of these percent values. Only 126 (13.9%) had binocular function, while 11.8% of A-pattern and 15.1% of V-pattern patients still maintained binocular function. Pre-operative horizontal deviation was negatively correlated with binocular function (r = −0.223, p < 0.0001), while the grade of oblique muscle overaction was positively correlated with the amount of pattern (r = 0.768, p < 0.0001) and ocular torsion (r = 0.794, p < 0.0001). There were no significant correlations between the Cobb angle and any of the other clinical variables. There were 724 patients (80.0%) who had received an oblique muscle procedure and 181 (20.0%) who received horizontal rectus muscle surgery. The most commonly used procedure consisted of horizontal rectus surgery plus inferior oblique myectomy (n = 293, 32.4%), followed by isolated horizontal rectus surgery (n = 122, 13.4%). Reductions of pattern were 14.67 ± 6.93 PD in response to horizontal rectus surgery and 18.26 ± 7.49 PD following oblique muscle surgery. Post-operative deviations were less in V- versus A-pattern strabismus. Post-operative binocular function was obtained in 276 of these patients (30.5%), which represented a 16.6% increase over that of pre-operative levels. The number of patients with binocular function in V-pattern strabismus was greater than that of A-pattern strabismus (p = 0.048). Conclusions: Of patients receiving horizontal strabismus surgery, 10.36% showed pattern strabismus. In these patients, 54.6% manifested an A- or V-pattern in childhood, and V-exotropia was the most frequent subtype. Pattern strabismus patients showed a high risk for developing scoliosis. Cyclovertical muscle surgery was performed in 724 of these patients (80.0%), and horizontal rectus surgery was effective in correcting relatively small levels of patterns. Binocular function represented an important factor as being involved with affecting the occurrence and development of pattern strabismus.
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Hashemi H, Nabovati P, Yekta AA, Agha Mirsalim M, Rafati S, Ostadimoghaddam H, Khabazkhoob M. Binocular vision disorders in a geriatric population. Clin Exp Optom 2021; 105:539-545. [PMID: 34016028 DOI: 10.1080/08164622.2021.1922065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Clinical relevance: A population-based epidemiological survey is important to help establish the frequency of binocular vision disorders in a geriatric population. Such data will be useful to clinicians and help guide diagnostic testing for this age group.Background: To determine the prevalence of binocular vision disorders and their associations with age and sex in the geriatric population.Methods: This report is a part of the Tehran Geriatric Eye study (TGES); a population-based cross-sectional study conducted on residents over 60 years of age in Tehran, Iran, using random stratified cluster sampling. A total of 165 clusters were selected (proportionally to size) from 22 strata of Tehran city. All participants underwent a complete ocular examination including the measurement of visual acuity, refraction, unilateral and alternating cover tests, and the Worth 4-dot suppression test. Strabismus was defined as the presence of constant unilateral or alternating esotropia or exotropia at either near (40 cm) or far (6 m). Distance and near exophoria were defined as more than 3Δ and 9Δ of exophoria at 6 m and 40 cm, respectively. Distance and near esophoria were defined as more than 1Δ and any amount of esophoria at 6 m and 40 cm, respectively.Results: Statistical analysis was performed on the data of 2,227 participants. The mean age of the participants was 66.6 ± 5.4 years and 59.4% were female. The prevalence of distance exophoria, esophoria, and hyperphoria was 8.9%, 0.34%, and 0.29%, respectively. The prevalence of near exophoria, esophoria, and hyperphoria was 32.4%, 0.61%, and 0.37%, respectively. The prevalence of distance exotropia and esotropia was 1.3% and 0.63%, respectively. The prevalence of near exotropia and esotropia was 4.6% and 0.59%, respectively.Conclusion: Non-strabismic binocular vision disorders were prevalent in an elderly population. Exo deviations were more prevalent than eso deviations.
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Affiliation(s)
- Hassan Hashemi
- Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran
| | - Payam Nabovati
- Rehabilitation Research Center, Department of Optometry, Iran University of Medical Sciences, Tehran, Iran
| | - Abbas Ali Yekta
- Department of Optometry, Mashhad University of Medical Sciences, Mashhad, Iran.,Translational Ophthalmology Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | | | - Shokoofeh Rafati
- Rehabilitation Research Center, Department of Optometry, Iran University of Medical Sciences, Tehran, Iran
| | - Hadi Ostadimoghaddam
- Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mehdi Khabazkhoob
- Department of Medical Surgical Nursing, School of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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