Investigation On Pre-and Post-operative Stereopsis And Effect Factors And The Optimal Timing Of Surgery In Intermittent Exotropia

Objective:To investigate the damage of the stereopsis in intermittent exotropia pre-operation, the reconstruction of stereopsis post-operation and effect factors.To opproach the optimal timing of surgery.Methods:Case control study, non-match type.To collect the patients with intermittent exotropia in Tianjin Eye Hospital from Oct.2009 to Jan.2010.All the cases (female 35 cases and male 55 cases) were classified 3 groups, in which had 30 cases in each group, age between 4 to 8 years old in group 1, age between 8 to 18 years old in group 2 and age beyond 18 years old in group 3.There were 66 cases with basic type and 24 cases with convergence insufficient type. Pseudo-divergence excess was combined with basic intermittent exotropia. Pre- and Post- operation examinations to each patient include the tests of ocular alignment, assessment of eye movements, Worth four-dot test at 6 meters for central fusion, synoptophore with the picture of cat and butterfly for peripheral fusion, Titmus, Frisby, Digital Stereoscopic Test Charts (DSTC) composed by Yan Shaoming, synoptophore with the Picture of RDS triburated by Tianjin Eye Hospital. To compare the damage of stereopsis, the reconstruction of stereopsis and its influencing factors among three groups.Results:(1).There was no statistically significant difference between the stereoacuity tested by Frisby arid Titmus before surgery (P>0.05). The average stereoacuity tested by DSTC, OPTEC6500 and synoptophore with RDS in group 2 was respectively less than that in other groups, however, there was no statistically significant difference between the group 1 and group 3. Stereoacuity tested by FD2 increased gradually in turn of group2, group 1 and group 3. Onsetting age in group 1 was the mimimus, and there was no statistically significant difference between the other groups.The course of disease became longer gradually with increasing average age of every group, and the deviation became larger gradually at the same time. (2). There was no statistically significant difference among the Post-operation stereoacuity of three goups tested by Frisby, Titmus, OPTEC6500, and FD2 respectively (P>0.05). Stereoacuity tested by DSTC in group 1 was more than the other groups. However, there was no statistically significant difference between the other groups. Stereoacuity tested by synoptophore with RDS in grouP 2 was less than the other groups. However, there was no statistically significant difference between the other groups. (3). There is no chang Post-operation in Titmus, but there were significantly differeces in Frisby, DSTC, OPTEC6500, synoptophore with RDS and FD2 between pre- and post -operation. (4).Both surgical overcorrection and undercorrection hindered stereopsis reconstruction. Overcorrection did the more, while undercorrection did the less. Postoperative distant stereoacuity tested by synoptophore with RDS was positive correlative to course of disease and distant stereoacuity tested by OPTEC6500 and FD2 was negative correlative to onset age. All tests were not correlative to ocular movement mild disorder and amplitude of diviation. Stereoacuity tested by synoptophore with RDS and FD2 was negative correlative to pre-operative peripheral fusion range, and stereoacuity tested by OPTEC6500 was negative correlative to preoperative central fusion.Conclusion:(1).Distant stereopsis is damaged severely, while near stereopsis is damaged lightly. Stereopsis is damaged more severely with earlier age of onset and longer course of disease. (2).Both near and distant stereopsis improve after surgery, especially distant stereopsis. (3).Reduction of distance stereopsis can labell the progression of intermittent exotropia, so stereopsis is important to estimate prognosis and treatment effect of surgery. (4).Different stereoscopic tests have particular emphasis on different aspects of binocular vision. Therefore we should assess synthetically binocular vision by different tests. (5). Postoperative stereopsis is better when age of onset is older, and course of disease is shorter. (6). A successful surgery can improve significantly stereopsis, but overcorrection hinders the postoperative stereopsis reconstruction.