Binocular Vision: Why it is so important

Binocular vision should form a fundamental part of every visual assessment, especially when looking after children’s vision, for three main reasons:

Binocularity

• Having two eyes that work together, enables us to have three-dimensional vision, depth perception, distance judgement and eye-hand coordination.  Without binocular vision, catching a ball, driving a car or even a simple task like walking becomes difficult.
• Binocular vision problems could have a significant effect on quality of life, and have the best prognosis if diagnosed and treated early when the visual system is still developing.¹

Comfortable vision when Reading and Learning

• Children spent at least 60% of their time in the classroom looking at near objects and digital screens, with fixations from distance-to-near occurring 10 times a minute. This requires a stable and accurate visual system to ensure comfort and comprehension.²
• An insufficient accommodation reserve affects our ability to focus on near work for sustained periods, while accommodation infacility would make changing focus form distance-to-near slow and tedious.
• Alignment issues, like reduced vergence facility and esophoria, are known to affect not only our visual comfort, but also speed and accuracy during reading. ³
• Convergence insufficiency (CI) becomes so uncomfortable, that it is linked to behavioral issues like attention deficit and avoidance of schoolwork. Many children have been diagnosed with attention deficit hyperactivity disorder (ADHD), when in fact, they actually had CI.⁴

Myopia Onset, Progression and Management

• Myopia is affected by inaccurate binocular vision – including near esophoria, higher AC/A ratios, accommodative lag and greater variability in accommodative responses.^5-8
• Intermittent exotropia (IXT) has also been associated with a higher prevalence of myopia, with 47% of children with IXT becoming myopic by age 10 and 91% by age 20.⁹
• Binocular vision is therefore a very important consideration when deciding on treatment options for a myopic patient.
• Myopia management, when esophoria, accommodation issues and higher AC/A ratios are present, have shown better efficacy with progressive addition or bifocal (BF) spectacle lenses, as supposed to peripheral defocus spectacle or contact lenses.¹⁰
• Fitting exo myopic children from spectacles to contact lenses, can increase their exo deviation which could affect visual comfort and myopia control efficacy.¹¹

References

1. Marianne EF, Simmers AJ. ‘‘It’s too late’. Is it really? Considerations for amblyopia treatment in older children.’ Ther Adv Ophthamol 2019;11:1-8
2. Narayanasamy S. ‘Visual demands in modern Australian primary school classrooms.’ Clin Exp Optom 2016; 99:233-240
3. Quaid P, Simpson T. ‘Association between reading speed, cycloplegic refractive error, and oculomotor function in reading disabled children versus controls.’ Graefes Arch Clin Ophthalmol 2013;251:169-187
4. Granet DB, Gomi CF, Ventura R, Miller-Scholte A. ‘The relationship between convergence insufficiency and ADHD.’ Strabismus 2005;4:163-8
5. Ciuffreda KJ, Vasudevan B. ‘Nearwork-induced transient myopia (NITM) and Permanent myopia – is there a link?’ Ophthal Physiol Opt 2008;28:103-114
6. Seidemann A, Schaeffel F. ‘An evaluation of the lag of accommodation using photorefraction.’ Vision Research 2003;43:419-430
7. Chung KM, Chong E. ‘Near esoporia is associated with high myopia.’ Clin Exp Optom 2000;83:2:71-75
8. Gwiazda J, Grice K, Thorn F. ‘Response AC/A ratios are elevated in myopic children.’ Ophthal Physiol Opt 2002;19:2:173-179
9. Ekdawi NS, Nusz KJ, Diehl NN, Mohney BG. ‘The Development of Myopia Among Children With Intermittent Exotropia.’ Am J Ophthalmol 2010;149:3:503-507
10. Fulk GW, Cyert A, Parker DE. ‘A Randomized Trail of the Effect of Single-Vision vs. Bifocal Lenses on Myopia Progression in Children with Esophoria.’ Optom Vis Sci 2000;77:8:395-401
11. Gwiazda J, Hyman L, Hussein M et al. ‘A randomized clinical trial of progressive addition lenses versus single vision lenses on the progression of myopia in children.’ Invest Ophthalmol Vis Sci 2003;44:4:1492-1500
12. Hunt OA, Wolffsohn JS, García-Resúa C. ‘Ocular motor triad with single vision contact lenses compared to spectacle lenses.’ Cont Lens Anterior Eye 2006;29:5:239-245