Specific features of stereopsis in patients with exophoria depending on the form before and after surgery
Background Divergent strabismus occurs in 23% of patients with strabismus (K. Von Noorden, E. Campos, 2002). The causes of exophoria are congenital or acquired abnormalities in the structure of the orbits and eyeballs, anomalies in the attachment or location of the eye muscles. The presence of stereovision after correction of strabismus, according to a number of authors [17, 18], indicates the stability of the result and the restoration of binocular visionThe aim of this study was to study the state of stereovision before and after surgical treatment in patients with divergent strabismus, depending on the shape.Material and methods 59 patients with divergent strabismus were examined: 33 patients with permanent divergent strabismus (group 1) and 26 patients with intermittent (non-permanent) strabismus (group 2) at the age of 10-21 years with visual acuity with 0.83 ± (SD) 0.33 and 0.82 ± (SD) 0.35, respectively. Refraction in both groups ranged from -5.5 diopters to +7.5 diopters. In group 1, the angle of strabismus for distance was on average 21.42 ± (SD) 10.4 degrees, and for nearness on average 14.8 ± (SD) 12.7 degrees. In group 2, the angle of deviation for distance was. on average 14.5 ± (SD) 5.8 deg., and for near 8.75 ± (SD) 9.0 deg. Surgical treatment was carried out in accordance with the generally accepted tactics of interventions in one or both eyes. All patients undergone ophthalmologic examination, and also the binocular function were checked - the nature of the binocular vision for the color test, the state of fusion on the synoptophore before and after treatment. The stereovision thresholds were observed with tests: The Lang II test, Titmus-stereofly - "circles" and "animals" when illuminated at a 30 cm stand, with optimal correction as well as the presence or absence of stereo vision into the distance from 5 m on the HUVITZ CCP3100 projector. Results After treatment, the angle of exotropia decreased in all patients and averaged 3.9 ± 1.9 degrees for distance, and for nearness 3.5 ± 1.4 degrees, binocular vision recovered in 70%. In group 1 there was no stereovision according to the distance test before treatment, and in the second group it was only in 3 patients. After the elimination of strabismus in the group with permanent strabismus, stereovision appeared in 11 patients, and according to the tests "circles" and "animals" the threshold of 200-400arc sec became in 25% of patients, and in group 2 in 80% of patients stereovision was determined with a threshold of 1500arc sec, and in 75% it returned to normal and became 200arc sec according to the "circles" test, that is, the thresholds of stereovision significantly decreased after surgery, especially in the second group.Conclusions 1. Stereoscopic vision for distance in the group with a constant deviation angle is absent, in the group with periodic strabismus is determined in 14.28%, and for near in 25% of cases.2. Stereoscopic vision increases (thresholds decrease) in 70% - 80% of cases after surgical treatment, which indicates the effectiveness of surgical treatment and recovery of binocular functions.3.Preliminary data allow to suggest, that stereovision of 200 arc sec for a near distance is a favorable factor for the improvement of binocular functions and a parallel positioning of the eye after surgery.