The Relationship between Binocular Summation in Contrast Sensitivity and Stereopsis: Cross Sectional Study

Document Type : Original Articles


1 Instructor, Department of Optometry, School of Rehabilitation, Zahedan University of Medical Sciences, Zahedan, Iran

2 Assistant Professor, Health Promotion Research Center AND Department of Optometry, School of Rehabilitation, Zahedan University of Medical Sciences, Zahedan, Iran



Introduction: Binocular summation occurs in the presence of normal visual function of both eyes. Stereopsis is considered to be the finest function of binocular vision. Therefore, the aim of this study was to investigate the effect of binocular summation on contrast sensitivity and its relationship with stereopsis.
Materials and Methods: In this cross-sectional study, 60 students of Zahedan University of Medical Sciences, Zahedan, Iran (17 men and 43 women) with a mean age of 21.20 ± 1.45 years were selected by convenience sampling method. Monocular and binocular contrast sensitivity were measured with the best corrected vision in photopic conditions using the Metrovision test for spatial frequencies of 0.75, 1.75, 3, 6, 13, and 20 cycles per degree. Stereopsis was also measured by TNO and Titmus tests. Statistical analysis was performed using the repeated measures analysis of variance (ANOVA) and multiple linear regression.
Results: The results of repeated measures ANOVA showed that binocular vision compared to monocular vision significantly increased contrast sensitivity (P < 0.001). But there was no significant difference between the contrast sensitivity of right and left eyes (P = 0.266). Pearson corralation test did not show a significant relationship between stereopsis measured by crossed and uncrossed methods in Titmus and TNO tests with binocular contrast sensitivity at all spatial frequencies (P = 0.114).
Conclusion: Binocular summation in presence of normal binocular function can improve visual functions such as the increased binocular contrast sensitivity compared to monocular contrast sensitivity which confirms the importance of treating binocular anomalies such as amblyopia.


  1. Heravian Shandiz J, Ostadimoghaddam H, Akbarzadeh R, Danesh Z, Behroozfar Z, Mahjoob M, et al. Mechanism of illumination and color contrast sensitivity. Journal of Paramedical Sciences and Rehabilitation 2016; 5(3): 93-103. [In Persian].
  2. Hirji SH, Hood DC, Liebmann JM, Blumberg DM. Association of patterns of glaucomatous macular damage with contrast sensitivity and facial recognition in patients with glaucoma. JAMA Ophthalmol 2021; 139(1): 27-32.
  3. Mahjoob M, Heydarian S, Koochi S. Effect of yellow filter on visual acuity and contrast sensitivity under glare condition among different age groups. Int Ophthalmol 2016; 36(4): 509-14.
  4. Mahjoob M, Heydarian S. Effects of color filters and anti-reflective coating on contrast sensitivity under glare condition. J Res Clin Med 2020; 8(1): 28.
  5. Mahjoub M, Azimi A, Heravian J, Momeni Moghaddam H, Mahjoob F. The effect of various colors of sunglasses in visual function. Behbood J 2012; 16(1): 10-5. [In Persian].
  6. Alberti CF, Bex PJ. Binocular contrast summation and inhibition depends on spatial frequency, eccentricity and binocular disparity. Ophthalmic Physiol Opt 2018; 38(5): 525-37.
  7. Comas M, Castells X, Acosta ER, Tuni J. Impact of differences between eyes on binocular measures of vision in patients with cataracts. Eye (Lond) 2007; 21(6): 702-7.
  8. Valberg A, Fosse P. Binocular contrast inhibition in subjects with age-related macular degeneration. J Opt Soc Am A Opt Image Sci Vis 2002; 19(1): 223-8.
  9. Pardhan S, Gilchrist J. The importance of measuring binocular contrast sensitivity in unilateral cataract. Eye (Lond) 1991; 5 (Pt 1): 31-5.
  10. Cumings A. Spatio-temporal Variation of Binocular Contrast Summation [PhD Thesis]. Big Rapids, MI: Michigan College of Optometry; 2018.
  11. Pardhan S. A comparison of binocular summation in young and older patients. Curr Eye Res 1996; 15(3): 315-9.
  12. Schneck ME, Haegerstom-Portnoy G, Lott LA, Brabyn JA. Monocular vs. binocular measurement of spatial vision in elders. Optom Vis Sci 2010; 87(8): 526-31.
  13. Dorr M, Kwon M, Lesmes LA, Miller A, Kazlas M, Chan K, et al. Binocular Summation and Suppression of Contrast Sensitivity in Strabismus, Fusion and Amblyopia. Front Hum Neurosci 2019; 13: 234.
  14. Jia Y, Ye Q, Zhang S, Feng L, Liu J, Xu Z, et al. Contrast sensitivity and stereoacuity in successfully treated refractive amblyopia. Invest Ophthalmol Vis Sci 2022; 63(1): 6.
  15. Mahjoob M, Heravian J, Ansari H, Momeni-Moghadam H, Poudineh M, Mahjoob F. Effect of age on stereopsis. Bina J Ophthalmol 2011; 16 (4): 297-301. [In Persian].
  16. Frisby JP, Davis H. Clinical tests of distance stereopsis: State of the art. In: de Faber J, editor. Progress in strabismology. London, UK: CRC Press; 2003. p. 187-90.
  17. Vancleef K, Read JCA, Herbert W, Goodship N, Woodhouse M, Serrano-Pedraza I. Overestimation of stereo thresholds by the TNO stereotest is not due to global stereopsis. Ophthalmic Physiol Opt 2017; 37(4): 507-20.
  18. Momeni-Moghaddam H, Ehsani M, Asgarizadeh F, Mahjoob M, Hosseini S, Darban-Jafari S. The relation of binocular symptoms with stereopsis. Bina J Ophthalmol 2012; 17(3): 227-31. [In Persian].
  19. Kattan JM, Velez FG, Demer JL, Pineles SL. Relationship between binocular summation and stereoacuity after strabismus surgery. Am J Ophthalmol 2016; 165: 29-32.
  20. El-Gohary A, Siam G. Stereopsis and contrast sensitivity binocular summation in early glaucoma. Res J Med Med Sci 2009; 4: 85-8.
  21. Faul F, Erdfelder E, Buchner A, Lang AG. Statistical power analyses using G*Power 3.1: Tests for correlation and regression analyses. Behav Res Methods 2009; 41(4): 1149-60.
  22. Liou SW, Chiu CJ. Myopia and contrast sensitivity function. Curr Eye Res 2001; 22(2): 81-4.
  23. Garnham L, Sloper JJ. Effect of age on adult stereoacuity as measured by different types of stereotest. Br J Ophthalmol 2006; 90(1): 91-5.
  24. Azen SP, Varma R, Preston-Martin S, Ying-Lai M, Globe D, Hahn S. Binocular visual acuity summation and inhibition in an ocular epidemiological study: The Los Angeles Latino Eye Study. Invest Ophthalmol Vis Sci 2002; 43(6): 1742-8.
  25. Datta S, Foss AJ, Grainge MJ, Gregson RM, Zaman A, Masud T, et al. The importance of acuity, stereopsis, and contrast sensitivity for health-related quality of life in elderly women with cataracts. Invest Ophthalmol Vis Sci 2008; 49(1): 1-6.
  26. Pardhan S, Gilchrist J. Binocular contrast summation and inhibition in amblyopia. The influence of the interocular difference on binocular contrast sensitivity. Doc Ophthalmol 1992; 82(3): 239-48.
  27. Undrakonda V, Sahiti TK, Vennesh PS, Kamath YS. A comparative study of stereoacuity in patients with various grades of cataract and bilateral pseudophakia. Indian J Ophthalmol 2019; 67(11): 1834-7.