AIM: To investigate the differences between synoptophore and triple prism strabismometry and its possible cause.

METHODS: There were 347 patients with horizontal concomitant strabismus involved, in which 76 patients were esotropia, 37 patients were male while 39 were female, with average age of 13.27±7.77 years old. There were 271 patients with exotropia, 131 cases were male while 140 were female, with average age of 15.43±8.42 years old. All the patients were examined by synoptophore and prism plus shaded strabismometry in a long distance of 6m. Datas were analyzed by SPSS 17.0.

RESULTS: In the exotropia patients, the conversions of circular degree(°)and prism degree(^△)were: 1°=0.29^△～1.78^△, which was statistically significant with intermittent strabismus(P=0.001). While in the esotropia patients, the conversions were: 1°=2.01^△～2.15^△.

CONCLUSION: The diversity between the two methods is enlarged with the increase of squint angle for exotropia patients. While in esotropia patients, the diversity decreased with the increase of squint angle. Synoptophore equipped with +7.00D, defects of the triple prism itself and proximal convergence during exam may be the reasons for the diversity.