Evaluation of distance and near stereoacuity and fusional vergence in intermittent exotropia

Abstract

Aim:To evaluate the role of distance and near stereoacuity and fusional vergence in patients with intermittent exotropia [X(T)] and their change after surgery.Materials and Methods:This prospective interventional institution-based clinical study included 31 cases of X(T) requiring surgery and 33 age, sex-matched controls. All subjects underwent complete orthoptic assessment including near stereopsis (Randot stereogram) and distance stereopsis by polaroid stereo- projector apparatus using special paired slides and fusional vergence assessment at distance and near prism bar at baseline and one week, one month, three months and six months after surgery in X(T).Results:The successful surgical alignment rate was 74.2%. Preoperatively, cases demonstrated significantly poor distance and near stereoacuity, compared to controls (P < 0.001). Mean distance stereoacuity (sec of arc) in normals, (X)T preoperatively and postoperatively was 344.8 ± 139.5, 1149.2 ± 789.4 and 450.1 ± 259 while mean near stereoacuity was 34.7 ± 9.5, 68.7 ± 31.1 and 47.4 ± 22.6 respectively. Postoperatively at six months, significant improvement in stereoacuity was observed both at near and distance (P < 0.05). Mean distance fusional convergence (in prism diopter) in normals, X(T) preoperatively and postoperatively was 20.7 ± 4.7, 18.0 ± 3.3 and 21.4 ± 3.6 respectively, mean near fusional convergence was 27.8 ± 6.3, 24.1 ± 5.5 and 29.1 ± 5.5 respectively. There was good correlation between fusional vergence amplitudes for distance and near indicating any one would suffice.Conclusion:Early detection of abnormal stereoacuity (near and if possible distance) and near fusional vergence amplitudes may help to decide proper timing of surgery in X(T).

Fusional Vergence Detected by Prism Bar and Synoptophore in Chinese Childhood Intermittent Exotropia

“…Various studies have found variability in reporting divergence break points. Sharma et al reported reduced divergence amplitudes in IXT subjects that differed from the results of our present study [ 11 ]. Liebermann et al have reported that most children with IXT have normal near fusional divergence, but that nearly half had reduced distance fusional divergence [ 10 ].…”

“…Hatt et al have recently reported that the mean convergence break points (defined as convergence reserve) were significantly lower at distance fixation for children with IXT compared with orthophoric children [ 9 ]. Nevertheless, they found that near convergence break points were comparable to visually normal children, but we observed reduced convergence break points at both distance and near, in accordance with the study by Sharma et al [ 11 ]. The mean near convergence break point values in subjects with IXT were similar in the present study compared with these two studies.…”

Fusional Vergence Detected by Prism Bar and Synoptophore in Chinese Childhood Intermittent Exotropia

“…Various studies have found variability in reporting divergence break points. Sharma et al reported reduced divergence amplitudes in IXT subjects that differed from the results of our present study [ 11 ]. Liebermann et al have reported that most children with IXT have normal near fusional divergence, but that nearly half had reduced distance fusional divergence [ 10 ].…”

“…Hatt et al have recently reported that the mean convergence break points (defined as convergence reserve) were significantly lower at distance fixation for children with IXT compared with orthophoric children [ 9 ]. Nevertheless, they found that near convergence break points were comparable to visually normal children, but we observed reduced convergence break points at both distance and near, in accordance with the study by Sharma et al [ 11 ]. The mean near convergence break point values in subjects with IXT were similar in the present study compared with these two studies.…”

Evaluation of FD2 (Frisby Davis distance) stereotest in surgical management of intermittent exotropia

“…Previous studies evaluating the FD2 stereotest have demonstrated significant reduction in X(T) which has shown improvement after surgery 7–11. Previous studies by the authors have shown improvement in distance (FD2) and near (TNO and Randot) stereoacuity after surgery for X(T), though they did not reach normal levels even 6 months postoperatively 7 8. Contrary to our study, Adams et al did not find a significant improvement in near stereoacuity (near FD2 and preschool Randot) after surgery for X(T) despite an improvement in distance stereoacuity 9.…”

Sensory Outcome After Surgery for Intermittent Exotropia

“…Of a total number of 25 X(T) patients, 13 were females (52%) & 12 were males (48%). This agrees with most studies of female predominance (51.6%, 53.8% and 60.3%) [6][7][8]. But 20 only continued the study as the rest were lost for follow-up.…”

Fusional Vergence Detected by Prism Bar and Synoptophore in Chinese Childhood Intermittent Exotropia

“…Various studies have found variability in reporting divergence break points. Sharma et al reported reduced divergence amplitudes in IXT subjects that differed from the results of our present study [ 11 ]. Liebermann et al have reported that most children with IXT have normal near fusional divergence, but that nearly half had reduced distance fusional divergence [ 10 ].…”

“…Hatt et al have recently reported that the mean convergence break points (defined as convergence reserve) were significantly lower at distance fixation for children with IXT compared with orthophoric children [ 9 ]. Nevertheless, they found that near convergence break points were comparable to visually normal children, but we observed reduced convergence break points at both distance and near, in accordance with the study by Sharma et al [ 11 ]. The mean near convergence break point values in subjects with IXT were similar in the present study compared with these two studies.…”

Evaluation of FD2 (Frisby Davis distance) stereotest in surgical management of intermittent exotropia

“…Previous studies evaluating the FD2 stereotest have demonstrated significant reduction in X(T) which has shown improvement after surgery 7–11. Previous studies by the authors have shown improvement in distance (FD2) and near (TNO and Randot) stereoacuity after surgery for X(T), though they did not reach normal levels even 6 months postoperatively 7 8. Contrary to our study, Adams et al did not find a significant improvement in near stereoacuity (near FD2 and preschool Randot) after surgery for X(T) despite an improvement in distance stereoacuity 9.…”

Sensory Outcome After Surgery for Intermittent Exotropia

“…Of a total number of 25 X(T) patients, 13 were females (52%) & 12 were males (48%). This agrees with most studies of female predominance (51.6%, 53.8% and 60.3%) [6][7][8]. But 20 only continued the study as the rest were lost for follow-up.…”

Fusional Vergence Detected by Prism Bar and Synoptophore in Chinese Childhood Intermittent Exotropia

“…Various studies have found variability in reporting divergence break points. Sharma et al reported reduced divergence amplitudes in IXT subjects that differed from the results of our present study [ 11 ]. Liebermann et al have reported that most children with IXT have normal near fusional divergence, but that nearly half had reduced distance fusional divergence [ 10 ].…”

“…Hatt et al have recently reported that the mean convergence break points (defined as convergence reserve) were significantly lower at distance fixation for children with IXT compared with orthophoric children [ 9 ]. Nevertheless, they found that near convergence break points were comparable to visually normal children, but we observed reduced convergence break points at both distance and near, in accordance with the study by Sharma et al [ 11 ]. The mean near convergence break point values in subjects with IXT were similar in the present study compared with these two studies.…”

Evaluation of FD2 (Frisby Davis distance) stereotest in surgical management of intermittent exotropia

“…Previous studies evaluating the FD2 stereotest have demonstrated significant reduction in X(T) which has shown improvement after surgery 7–11. Previous studies by the authors have shown improvement in distance (FD2) and near (TNO and Randot) stereoacuity after surgery for X(T), though they did not reach normal levels even 6 months postoperatively 7 8. Contrary to our study, Adams et al did not find a significant improvement in near stereoacuity (near FD2 and preschool Randot) after surgery for X(T) despite an improvement in distance stereoacuity 9.…”

Sensory Outcome After Surgery for Intermittent Exotropia

“…Of a total number of 25 X(T) patients, 13 were females (52%) & 12 were males (48%). This agrees with most studies of female predominance (51.6%, 53.8% and 60.3%) [6][7][8]. But 20 only continued the study as the rest were lost for follow-up.…”