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Optometry plays an important role in both diagnosing and managing binocular vision disorders. Binocular vision disorders have been associated with increased near-work symptoms1 and reduced academic achievement,2 while successful treatment of a binocular vision disorder has been associated with reduced adverse academic behaviours and reduced parental concern regarding academic achievement.3 A binocular vision assessment is therefore an important component of a routine optometric consultation.
Additionally, practitioners also need to know the effect a patients binocular vision status has on myopia-management. Deficiencies in various binocular vision functions have been associated with myopia progression. The various myopia-management strategies may also affect binocular vision, which may or may not be beneficial depending on the individuals binocular vision status. For example, centre-distance multifocal soft contact lenses increase near exophoria,4 and while this may be beneficial for eso-related or accommodative insufficiency-related disorders, it is less beneficial for exo-related or accommodative excess-related disorders. It is therefore incumbent on the practitioner performing myopia-management to be aware of a patients binocular vision status and manage a patients binocular vision disorder. Management of a binocular vision disorder may involve choosing myopia-management strategies that are beneficial to a patients binocular vision status, performing vision therapy or referring to another practitioner specialising in vision therapy.
The International Myopia Institute5 (IMI) recommends the following tests be performed at a baseline examination and at follow-up visits to monitor changes with myopia-management strategies:
- Accommodative accuracy / response (lag or lead)
- Amplitude of accommodation
- Distance and near accommodative facility
- Distance and near heterophorias
- Near fixation disparity
- Accommodative convergence / accommodation (AC/A) ratio
The IMI also lists various clinical methods that can be used to measure these outcomes.5
In addition to these tests, the practitioner may also consider tests at baseline that aid in differential diagnosis of a binocular vision disorder. These include monocular accommodative facility, near point of convergence, negative and positive fusional reserves at distance and near and negative and positive relative accommodation (B+ and B-, respectively) at near.6
Much of the interest in binocular vision and myopia-management stems from differences in myopes compared to non-myopes for various aspects of binocular function, particularly accommodative function. Myopes tend to have a higher lag of accommodation and a lower amplitude of accommodation. This need for the myope to increase accommodative effort at near is a a contributing factor to other differences in binocular vision function, such as tendency towards esophoria and increased gradient AC/A ratio.
References
- Borsting E, Rouse MW, Deland PN, et al. Association of symptoms and convergence and accommodative insufficiency in school-age children. Optometry 2003;74:25-34.
- Shin HS, Park SC, Park CM. Relationship between accommodative and vergence dysfunctions and academic achievement for primary school children. Ophthalmic Physiol Opt 2009;29:615-624.
- Borsting E, Mitchell GL, Kulp MT, et al. Improvement in academic behaviors following successful treatment of convergence insufficiency. Optom Vis Sci 2012;89:12.
- Gong CR, Troilo D, Richdale K. Accommodation and Phoria in Children Wearing Multifocal Contact Lenses. Optom Vis Sci 2017;94:353-360.
- Gifford KL, Richdale K, Kang P, et al. IMI – Clinical Management Guidelines Report. Invest Ophthalmol Vis Sci 2019;60:M184-m203.
- Scheiman M, Wick B. Clinical management of binocular vision: heterophoric, accommodative, and eye movement disorders: Lippincott Williams & Wilkins; 2008.
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