The Effect of Unilateral Induced Astigmatism on Stereopsis

Document Type : Research Paper


1 Associate professor of Mashhad University of Medical Sciences

2 MSc in Optometry

3 Epidemiolojist, Assistant professor of Mashhad University of Medical Sciences.


Blur vision due to astigmatism and spherical refractive errors reduce stereopsis and develop amblyopia in children. The aim of this study was to determine the effect of different type and amount of induced unilateral myopic and hypropic astigmatic anisometropia on stereopsis.
Materials and Methods
This interventional study was performed on 60 normal patients after primary examination and refraction, the primary stereopsis was determined by TNO and Titmus stereotests. Myopic and hypropic astigmatic anisometropia were induced using trial lenses of 1 to 4 D, minus and plus in horizontal, vertical and oblique axis. The stereopsis was then determined by TNO and Titmus stereotests. Data were analyzed, using SPSS version 11.50.Patients with previous amblyopia, manifest deviations, ocular pathology and more than 4 prism heterophoria and abnormal fusion response with Bagolini test were excluded from the study.
Mean stereopsis was 40.83±2.78 and 31.50±6.59 seconds of arc with Titmus and TNO stereotests respectivley before intervention in all patients. Stereopsis levels were reduced significantly with respect to the degree and types of meridional anisometropia (p< 0.001). Maximum reduction of stereopsis occurred with 4 D myopic and hypropic astigmatic anisometropia in oblique axis. It was 1930±271/5 and 1780±518/6 second of arc for TNO test and 773.33±101/4 and 693.33±/179.9 second of arc for Titmus stereotest. Comparison between mean stereopsis in myopic or hypropic astigmatic anisometropia was statistically significant in all three axes; horizontal, vertical and oblique (p< 0.000).
According to the findings of this study, uncorrected meridional anisometropia(myopic and hypropic anisometropia) like spherical anisometropia has advers effect on binocular vision development and stereopsis. It can also develop amblyopia in critical age of children. 4 D meridional anisometropia reduced stereopsis to below 1% which indicated liner relation between them. These findings show that the low oblique and vertical astigmatic anisometropia reduce stereopsis more than the horizontal axis.


1- Eskridge JB, Amos JF, Bartlett JD. Clinical procedure in optometry. 3thed. Philadelphia: J.B. Lippincatt Company;
2- Dandona R, Dandona L, Naduvilath TJ, Srinivas M, McCarty CA, Rao GN. Refractive errors in an urban
population in Southern India the Andhra Pradesh Eye Disease Study. Invest Ophthalmol Vis Sci 1999; 40:2810–2818.
3- Satterfield DS. Prevalence and variation of astigmatism in a military population. J Am Optom Assoc 1989; 60:14–18.
4- Mohindra I, Held R, Gwiazda J, Brill J. Astigmatism in infants. Science 1978; 202:329–331
5- Gwiazda J, Scheiman M, Mohindra I, Held R. Astigmatism in children: changes in axis and amount from birth to six
years. Invest Ophthalmol Vis Sci 1984; 25:88–92.
6- Montes-Mico R. Astigmatism in infancy and childhood. J Pediatr Ophthalmol Strabismus 2000; 37:349–53.
7- Dobson V, Fulton AB, Sebris SL. Cycloplegic refractions of infants and young children: the axis of astigmatism.
Invest Ophthalmol Vis Sci 1984; 25:83–87.
8- Attebo K, Ivers RQ, Mitchell P. Refractive errors in an older population: the Blue Mountains Eye Study.
Ophthalmology 1999; 106:1066–1072.
9- Bear JC, Richler A. Cylindrical refractive error: a population study in Western Newfoundland. Am J Optom Physiol
Opt 1983; 60:39–45.
10- Abrahamsson M, Sjostrand J. Astigmatic axis and amblyopia in childhood. Acta Ophthalmol Scand 2003; 81:33–37.
11- Brown SA, Weih LM, Fu CL, Dimitrov P, Taylor HR, McCarty CA. Prevalence of amblyopia and associated
refractive errors in an adult population in Victoria, Australia. Ophthalmic Epidemiol 2000; 7:l249–58.
12- Dobson V, Tyszko RM, Miller JM, Harvey EM. Astigmatism, amblyopia, and visual disability among a Native
American population .In: Vision Science and Its Applications. OSA Technical Digest Series1996. Washington DC:
Optical Society of America; 1996.p.139–142.
13- Dobson V, Miller JM, Harvey EM, Mohan KM. Amblyopia in astigmatic preschool children. Vision Res 2003;
14- Mitchell DE, Freeman RD, Millodot M, Haegerstrom G. Meridional amblyopia: evidence for modification of the
human visual system by early visual experience. Vision Res 1973; 13:535–358.
15- Freeman RD, Mitchell DE, Millodot M. A neural effect of partial visual deprivation in humans. Science 1972;
16- Brooks SE, Johnson D, Fischer N. Anisometropia and binocularity. Ophthalmology 1996; 103:1139–1143.
17- Oguz H, Oguz V. The effects of experimentally induced anisometropia on stereopsis. J Pediatr Ophthalmol
Strabismus 2000; 37:214–218.
18- Romano PE, Goodwin RT, Romano PE. Stereoacuity degradation by experimen tal and real monocular and
binocular amblyopia. Invest Ophthalmol Vis Sci 1985; 26:917–923.
19- Lovasik JV, Szymkiw M. Effects of aniseikonia, anisometropia, accommodation, retinal illuminance and pupil size,
on stereopsis. Invest Ophthalmol Vis Sci 1985; 26:741–750.
20- Simpson T. The suppression effect of simulated anisometropia. Ophthalmic Physiol Opt 1991; 11:350–358.
21- Appelle S. Perception and discrimination as a function of stimulus orientation: the “oblique effect” in man and
animals. Psychol Bull 1972; 78:266–278.
22- Morgan MJ, Castet E. The aperture problem in stereopsis. Vision Res 1997; 37:2737–2744.
23- Shimojo S. Development of interocular vision in infants. In: K. Simons, eitord. Early Visual Development, Normal
and Abnormal. New York: Oxford University Press; 1993.p.201–23.
24- Birch EE. Binocular Vision Introduction. In: K. Simons, editor. Early Visual Development, Normal and Abnormal.
New York: Oxford University Press; 1993.p.197–199.
25- Kaye SB, Siddiqui A, Ward A, Noonan C, Fisher AC, Green JR, et al. Monocular and binocular depth
discrimination thresholds. Optom Vis Sci 1999; 76:770–782.
26- Dadeya S, Kamlesh Shibal F. The effect of anisometropia on binocular visual function Guru Nanak Eye Centre.
Maulana Azad Medical College, New Delhi, India:
27- Larson WL, Blocud M. Effect of induced blur on visual acuity and stereoacuity. Optom Vis Sic 1991; 68:294-298.
28- Gawecki M, Adamski J. Anisometropia and stereopsis. Klin Oczna 2004; 106:561-653.
29- Levy NS, Glick EB. Stereoscopic perception and Snellen visual acuity. Am Ophthalmol 1974; 78:722-724.
30- Peters HB. The influence of anisometropia on stereo sensitivity. Am J Optom Arch Am Acad Optom 1969; 46:120-23
31- Simons K, Elhatton K, Novak A. Small target random dot stereogram and binocular supperssion testing for
preschool vision screening. J Pediatr Ophthalmol Strabismus 1996; 33:104-113.
32- Cooper J, Feldman J. Random dot stereogram performmance by strabismic, amblyopic and ocular pathology in an
aparent discrimination task. Am J Optom Physiol opt 1978; ss:
33- Cooper J, Feldman J. Comparing stereopic performance of children using the Titmus, TNO. Am J Opthal 1974;
34- Repka M, Beck RW, Kraker RT, Cole SR. The clinical profaile of moderate amblyopia in children younger than 7
years. Arch Ophthalmol 2002; 126:281–288.