Binocular Function in Different Gaze Positions
Purpose: To evaluate varied aspects of binocular function in multiple gaze positions.
Methods: In 2018, this cross-sectional study was conducted on 21 participants (male = 11) with an age range of 19–25 years. Having emmetropia and 10/10 visual acuity in both eyes were conditions of the inclusion criteria for the crosssectional study. The following aspects of binocular function including amplitude of accommodation (AA), near point of convergence, near phoria, and monocular accommodative facility were evaluated in five gazes (primary, upward, downward, left, and right) for all subjects.
Results: Near point of convergence values showed significant differences in all gaze positions (P < 0.001). The lowest near point of convergence value was seen in the primary gaze (2.69 cm) and the downward gaze (3.47 cm) and the highest near point of convergence value was seen in the left gaze (7.5 cm). There was also a significant difference in the amplitude of accommodation among the upward, downward, and the primary gaze (P < 0.001) positions but no difference was observed among the temporal, nasal, and the primary gaze positions. There was a significant difference in near phoria between the upward gaze and the primary gaze (P = 0.008) while no significant differences were observed among the other gazes. There was no significant variance in the monocular accommodative facility among the different gaze positions (P = 0.175).
Conclusion: The results of this study indicated variations that exist in the convergence and accommodation reflex functions in multiple gaze positions, which proved to be more prominent in the convergence system. Although the accommodative sufficiency evaluation was inconsistent among the multiple gaze positions, the accommodative facility evaluation was consistent in all gazes.
Accommodation, Binocular Vision, Convergence, Facility, Gaze, Phoria
1. Schachar RA. The mechanism of accommodation and presbyopia. Int Ophthalmol Clin 2006;46:39–61.
2. McGregor ML. Convergence insufficiency and vision therapy. Pediatr Clin North Am 2014;61:621–630.
3. Murray C, Newsham D. The normal accommodative convergence/accommodation (AC/A) ratio. J Binocul Vis Ocul Motil 2018;68:140–147.
4. Demer JL, Clark RA. Functional anatomy of extraocular muscles during human vergence compensation of horizontal heterophoria. J Neurophysiol 2019;122:105–117.
5. Azonobi IR, Olatunji FO, Addo J. Prevalence and pattern of strabismus in Ilorin. West Afr J Med 2009;28:253–256.
6. Nizza A, Dufeck DR. The ’A’ and ’V’ pattern syndromes. J Am Optom Assoc 1985;56:133–140.
7. Taylor JN, Richardson B. The pattern of ”A” and ”V” syndromes. Aust J Ophthalmol 1974;2:24–26.
8. Ripple PH. Variation of accommodation in vertical directions of gaze. Am J Ophthalmol 1952;35:1630–1634.
9. Atchison DA, Claydon CA, Irwin SE. Amplitude of accommodation for different head positions and different directions of eye gaze. Optom Vis Sci 1994;71:339–345.
10. Atchison DA, Claydon CA, Irwin SE. Amplitude of accommodation for different head positions and different directions of eye gaze. Optom Vis Sci 1994;71:339–345.
11. Takeda T, Neveu C, Stark L. Accommodation on downward gaze. Optom Vis Sci 1992;69:556–561.
12. Nguyen D, Vedamurthy I, Schor C. Cross-coupling between accommodation and convergence is optimized for a broad range of directions and distances of gaze. Vision Res 2008;48:893–903.
13. Collins CC, Carlson MR, Scott AB, Jampolsky A. Extraocular muscle forces in normal human subjects. Invest Ophthalmol Vis Sci 1981;20:652–664.
14. Miller JM, Robins D. Extraocular muscle forces in alert monkey. Vision Res 1992;32:1099–1113.
15. Porter JD, Baker RS, Ragusa RJ, Brueckner JK. Extraocular muscles: basic and clinical aspects of structure and function. Surv Ophthalmol 1995;39:451–484.
16. Pavlov PI. Conditioned reflexes: an investigation of the physiological activity of the cerebral cortex. Ann Neurosci 2010;17:136–141.
17. Coakes RL, Clothier C, Wilson A. Binocular reflexes in the first 6 months of life: preliminary results of a study of normal infants. Child Care Health Dev 1979;5:405–408.
18. Pärssinen O, Kauppinen M. Associations of reading posture, gaze angle and reading distance with myopia and myopic progression. Acta Ophthalmol 2016;94:775–779.
19. Buehren T, Collins MJ, Carney LG. Near work induced wavefront aberrations in myopia. Vision Res 2005;45:1297–1312.
20. Mutti DO, Jones LA, Moeschberger ML, Zadnik K. AC/A ratio, age, and refractive error in children. Invest Ophthalmol Vis Sci 2000;41:2469–2478.