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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 8  |  Issue : 4  |  Page : 370-374

Awareness in the general population about binocular single vision and its importance


Department of Ophthalmology, MGM Medical College and Hospital, Aurangabad, Maharashtra, India

Date of Submission11-Jul-2021
Date of Acceptance21-Oct-2021
Date of Web Publication22-Dec-2021

Correspondence Address:
Prof. Snehal Rhishikesh Thakre
Department of Ophthalmology, MGM Medical College and Hospital, N-6 CIDCO, Aurangabad 431003, Maharashtra.
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mgmj.mgmj_49_21

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  Abstract 

Introduction: Stereo vision adds an extra dimension to aid depth perception and gives a binocular advantage in task completion. Aim: To study the perception of the presence and importance of binocular vision in the general population. Materials and Methods: A standard questionnaire in the local language was circulated amongst 500 people in the outpatient department (OPD). Group 1 had studied < 12th standard, and Group 2 had studied up to 12th standard or more. Results: More participants in Group 2 said that the purpose of having two eyes was to see, for aesthesis, and also for a better quality of vision than those in Group 1 (P = 0.011 s); they knew that it was advantageous to have both eyes work together as one unit than did those in Group 1. (P = 0.010 s) Similarly, Group 2 knew why a squint developed (P = 0.002) and that there was a relationship between a squint and binocular single vision (BSV) (P = 0.000). Group 2 knew that a squint could be treated (P < 0.0001 s). Group 1 did not know the importance of the early treatment of strabismus (P < 0.0001 s). Participants in both groups were aware that they could face difficulty in doing certain jobs due to less vision in one eye (P = 0.201 ns); as well as that visual impairment in children could be prevented in at least some children if vision testing was done during the preschool years. Conclusion: It is important to raise awareness among the general population of the concept of binocular vision and its relationship to strabismus.

Keywords: Awareness, binocular single vision (BSV), functional vision


How to cite this article:
Thakre SR, Nathani KR, Deshmukh PA, Mishrikotkar JP. Awareness in the general population about binocular single vision and its importance. MGM J Med Sci 2021;8:370-4

How to cite this URL:
Thakre SR, Nathani KR, Deshmukh PA, Mishrikotkar JP. Awareness in the general population about binocular single vision and its importance. MGM J Med Sci [serial online] 2021 [cited 2022 Jan 18];8:370-4. Available from: http://www.mgmjms.com/text.asp?2021/8/4/370/333319




  Introduction Top


The advantages of having two eyes in humans with overlapping visual fields are not immediately obvious. Many vision scientists and ophthalmologists have remarked that the sole purpose of having two eyes is so that one can have a “spare.”[1] Though this observation is not untrue, especially when taking into consideration amblyopic individuals, the major advantage of having two eyes working together is the ability to perform stereoscopic depth perception.[1] Stereo vision adds an extra dimension to aid depth perception and gives a binocular advantage in task completion.[2] This makes stereo vision a crucial component of binocular vision, and it is very important; the others are simultaneous perception and fusion. The bifrontal placing of the two eyes provides the benefit of binocular concordance as well as binocular disparity, two partially overlapping views from spatially separated eyes; the two visual fields contain similar (binocular concordance) as well as dissimilar (binocular disparity) information, an important advantage of a BSV.[3]

BSV may be defined as the state of simultaneous vision, which is achieved by the coordinated use of both eyes so that separate and slightly dissimilar images arising in each eye are appreciated as a single image by the process of fusion.[4] In the presence of manifest strabismusm, the patient attempts to regain the advantages of BSV, via abnormal retinal correspondence. Thus, the patient sees binocularly single, despite the presence of a manifest squint. The quality of this BSV varies from patient to patient, ranging from rudimentary to grossly useful stereopsis. Generally, the quality is inversely proportional to the angle of deviation.[4] Such diminished binocular vision can put a person at a disadvantage while performing certain jobs. In recent times, 3D technology has started playing an important role in many aspects of daily living, including surgery. Lack of or reduced stereopsis may have an impact there too.

Many times, there is resistance to the use of spectacles, patching as a form of treatment of amblyopia, and even surgery as a treatment for squint in young children by their parents and caretakers. This is due to the lack of awareness about the causes for the same and more importantly about the consequences of leaving these conditions unattended at the right time. The purpose of this study is to find out the status of awareness about the presence of BSV among the general population and its functional importance.


  Materials and methods Top


A self-designed, nonvalidated questionnaire [Table 1] in the local language was administered by a trained counselor among random 500 people waiting to be examined (patients themselves and/or their relatives) and willing to participate in the Ophthalmology OPD waiting room at a Medical College from December 2018 to February 2019.
Table 1: Questionnaire

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The questionnaire noted the age, educational qualification, and occupation of the respondent along with the specific questions related to the study. The questionnaire was administered in the local language and/or Hindi. The respondents were then divided into two groups: Group 1 had studied < 12th standard, and Group 2 had studied up to 12th standard or more. The results were analyzed as per the responses in the two groups. The procedures followed were by the ethical standards as stated in the Helsinki Declaration of 1975 and revised in 2000.

Statistical Analysis

Data were entered in Microsoft Excel and analyzed using SPSS version 24.0th. Proportions were calculated for categorical variables. The Chi-square test was applied to check the significant association between different attributes. P-Value of <0.05 was considered statistically significant.


  Results Top


The study included 500 respondents, the demographics of whom are described in [Table 2]. The distribution of the responses is described in [Table 3][Table 4][Table 5][Table 6] and summarized in [Table 7].
Table 2: Demographic data

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Table 3: Information regarding two eyes

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Table 4: Information regarding squint

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Table 5: Do you know that if you have less vision or decreased vision in one eye there is difficulty in doing certain jobs?

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Table 6: Do you know that if we test the visual acuity of children in playschool, then we can appropriately treat the child to prevent visual impairment?

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Table 7: Summary of responses from all respondents

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More participants in Group 2 said that the purpose of having two eyes was to see, for aesthesis, and also for a better quality of vision than in Group 1 (P = 0.011 s); they knew that it is advantageous to have both the eyes work together as one unit than did those in Group 1. (P = 0.010 s) [Table 3]. Similarly, Group 2 knew why a squint develops (P = 0.002) and that there was a relationship between a squint and BSV (P = 0.000). Group 2 knew that a squint could be treated (P < 0.0001 s). Group 1 did not know the importance of the early treatment of strabismus (P < 0.0001 s) [Table 4]. Participants in both the groups were aware that they could face difficulty in doing certain jobs due to less vision in one eye; (P = 0.201 ns) as well as that visual impairment in children could be prevented if vision testing was done in children during the preschool years.


  Discussion Top


In this study, we found that the level of awareness about BSV varied with the level of educational status of the respondent, with it being lesser in most aspects among respondents who were educated less than 12th standard.

Besides, providing a spare eye, in case there is decreased vision in one eye due to amblyopia or loss of vision later due to any acquired eye disease such as trauma or any other sight-threatening disease, the most important function served by the two eyes working together is the ability to perform stereoscopic depth discrimination.[1] It has been noted by Birch that children with amblyopia have impaired fine motor skills and this impairment is closely related to binocular dysfunction.[5] Fielder and Moseley concluded that even though humans can function very well without stereopsis, especially tasks performed at a distance, binocularity appears to have an advantage for certain tasks, such as those performed at near, in comprehending complex visual presentations, and those requiring complex hand–eye coordination.[1] It may also be a prerequisite for the development of secondary monocular cues.[1] Binocular disparity cues help us guide our hands precisely and both children and adults with impaired stereo vision perform worse on a range of visuomotor tasks than their peers with normal stereoacuity.[6] Both amblyopia and strabismus affect the planning of visually guided movements.[7]

Awareness about the importance of binocular vision is necessary for not only the general population but also the ophthalmic care providers, as the newer treatments of amblyopia stress dichoptic training even direct stereo training.[5] Along with enabling better visual and motor performance, stereoacuity is also linked to the long-term stability of ocular position after surgical correction.[6]

The most important part of this survey showed that most participants in both groups were aware that they could face difficulty in performing certain tasks or jobs due to poor or decreased vision in one eye. Whether they knew that this was due to related poor binocular vision remains questionable. This awareness carries particular significance now as with the proliferation of 3D technologies, there is also practical interest in individual differences in binocular function, to ensure that the full range of binocular abilities is catered for.[8] 3D viewing is applied to almost all surgical fields, including ophthalmology, called “Heads Up surgery.”[9] In a study designed to compare standardized phantom surgical tasks between 3D HD and 2 D HD visualization techniques, Storz et al. concluded that 3D HD using a state-of-the-art 3D monitor permits superior task efficiency, even as compared with the latest 2D HD video systems.[10] It has been shown that person-to-person variability exists in the ability to perform stereoscopic image fusion and especially people with strabismus are not able to extract the spatial information from the simultaneously perceived images, each with a slightly different angle of view.[10] Hence, people with defective stereoscopic or 3D vision such as strabismic or even anisometropic amblyopic vision may have difficulty in performing these 3D tasks.[10] We would like to share our anecdotal experience in our institute that residents with poor surgical skills on examination were later found to have reduced stereopsis for near. Distance stereopsis could not be evaluated in them due to a lack of infrastructure (nonpublished experience).

O’Connor[11]et al. analyzed the relationship between the performance on motor skills tasks and the level of stereoacuity by making a group of 143 subjects with normal, reduced, or nil stereoacuity, with and without manifest deviation, perform three tasks to assess motor skill function under monocular (the subject chose which eye would be occluded) and binocular conditions. They concluded that, though the performance of those with normal stereoacuity was reduced under monocular conditions, those with reduced stereoacuity were better at the task than those with no stereoacuity. They also determined that even if there is a level of adaptation to the absence of stereoacuity, it is variable depending on the task at hand. Increasing difficulty in performing a task was noted as the difficulty level increased and stereoacuity decreased.[11]

In a study aimed at assessing the prevalence of stereo blindness in medical doctors who were potential users of 3D laparoscopy, Fergo et al. found that 9.7% were stereo blind and 38.7% were stereo deficient.[2] They found that age over 50 years, gender (more males were stereo blind in the study), number of years after finishing postgraduation training, surgical specialty, smoking, motion sickness, and no awareness of having any visual anomaly that was not yet corrected were significantly associated with stereo blindness in their study.[2]

Poor stereopsis has been known to be caused by strabismus, anisometropia, convergence insufficiency, early unilateral cataract, and unilateral retinal damage.[8] Patients with amblyopic vision, if diagnosed and treated on time during the critical period of development of binocular vision in childhood, conventionally considered to be the first seven years of life, can recover visual acuity and stereovision as brain plasticity is at its peak.[5],[12] Young brains are certainly much more plastic than older ones, yet it has been shown that significant plasticity can still be induced beyond the critical period if appropriate input/treatment is provided.[12]

Thus, sufficiently early intervention for the correction of strabismus and amblyopia of any cause can restore stereoacuity to some extent, even if not normal. The later the intervention, the more the stereoacuity may remain subnormal.

Strabismic amblyopia is associated with significant diminution of stereoscopic vision, which also requires more active treatment to recover as compared with anisometropic amblyopia.[5] Early strabismus affects the stereoacuity profoundly, especially fine stereopsis.[6]


  Conclusion Top


Thus, the earlier discussion of BSV, and especially stereopsis, shows that (1) stereopsis affects the performance of tasks, especially fine tasks, and those that are performed at near; (2) the presence of amblyopia that may be anisometropic, strabismic, or a pattern derivational type reduces stereopsis; and (3) most of these causes of amblyopia, especially strabismus and anisometropia, can be treated optimally if diagnosed in time and with the right treatment approach—the plasticity of the brain gives us time. Hence, it is important to increase awareness in the general population (in particular in the less educated ones) about the concept of binocular vision, its relationship to strabismus and amblyopia, and its implications for the growth, development, and future of the child.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Fielder AR, Moseley MJ. Does stereopsis matter in humans? Eye (Lond) 1996;10 (Pt 2):233-8.  Back to cited text no. 1
    
2.
Fergo C, Burcharth J, Pommergaard HC, Rosenberg J. Age is highly associated with stereo blindness among surgeons: A cross-sectional study. Surg Endosc 2016;30:4889-94.  Back to cited text no. 2
    
3.
Jones RK, Lee DN. Why two eyes are better than one: The two views of binocular vision. J Exp Psychol Hum Percept Perform 1981;7:30-40.  Back to cited text no. 3
    
4.
Bhola R. Binocular Vision. EyeRounds.org. Jan 23, 2006. Available from: http://webeye.ophth.uiowa.edu/eyeforum/tutorials/bhola-binocularvision.htm (Last Accessed on 31/7/2020).  Back to cited text no. 4
    
5.
Birch EE. Amblyopia and binocular vision. Prog Retin Eye Res 2013;33:67-84.  Back to cited text no. 5
    
6.
Read JC. Stereo vision and strabismus. Eye (Lond) 2015;29:214-24.  Back to cited text no. 6
    
7.
Niechwiej-Szwedo E, Goltz HC, Chandrakumar M, Wong AM. Effects of strabismic amblyopia on visuomotor behavior: Part II. Visually guided reaching. Invest Ophthalmol Vis Sci 2014;55:3857-65.  Back to cited text no. 7
    
8.
Bosten JM, Goodbourn PT, Lawrance-Owen AJ, Bargary G, Hogg RE, Mollon JD. A population study of binocular function. Vision Res 2015;110:34-50.  Back to cited text no. 8
    
9.
Qian Z, Wang H, Fan H, Lin D, Li W. Three-dimensional digital visualization of phacoemulsification and intraocular lens implantation. Indian J Ophthalmol 2019;67:341-3.  Back to cited text no. 9
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10.
Storz P, Buess GF, Kunert W, Kirschniak A. 3D HD versus 2D HD: Surgical task efficiency in standardised phantom tasks. Surg Endosc 2012;26:1454-60.  Back to cited text no. 10
    
11.
O’Connor AR, Birch EE, Anderson S, Draper H; FSOS Research Group. The functional significance of stereopsis. Invest Ophthalmol Vis Sci 2010;51:2019-23.  Back to cited text no. 11
    
12.
Levi DM, Knill DC, Bavelier D. Stereopsis and amblyopia: A mini-review. Vision Res 2015;114:17-30.  Back to cited text no. 12
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]



 

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