The Surgical Outcome and Stereopsis between Pseudodivergence Excess Type and Convergence Insufficiency Type

PURPOSE: To compare the surgical outcomes and stereopsis between pseudodivergence excess type and convergence insufficiency type in intermittent exotropia. METHODS: In a retrospective comparative analysis of 42 eyes, 18 eyes that were of the convergence insufficiency type (group 1) and 24 eyes that were or the pseudodivergence excess type (group 2) were analyzed. Recession-resection was performed in the same eye. Success was defined to be within ±8 PD after 12 months postoperatively; more than ±8 PD was defined as recurrence. Stereopsis was measured by the Titmus test. RESULTS: After the patch test, the mean preoperative near angle in group 1 was 35.56 ± 6.62 PD and the far angle was 23.06 ± 6.22 PD. In group 2, the mean preoperative near angle was 26.92 ± 6.30 PD and the far angle was 28.29 ± 7.41 PD. The group 1 postoperative (12 months) mean near angle was 6.89 ± 8.46 PD and the far angle was 6.11 ± 7.90 PD. In group 2, the mean postoperative near angle was 1.75 ± 2.85 PD and the far angle was 3.42 ± 3.98 PD. The success rate of group 1 was 50% and the success rate of group 2 was 83.3%. The success rate of both group were statistically significant differences (p = 0.021). The postoperative (12 months) mean of near stereopsis for group 1 was 588 ± 1,124 seconds, and group 2 was 101.25 ± 102 seconds. There were no statistically differences in postoperative (12 months) stereopsis. CONCLUSIONS: The success rate of the pseudodivergence excess type was significantly higher than in the convergence insufficiency type.

The Ratio of Accommodative-Convergence to Accommodation in Patients with Intermittent Exotropia

PURPOSE: To measure the ratio of accommodative-convergence to accommodation (AC/A ratio) in patients with pseudodivergence excess type and convergence insufficiency type of intermittent exotropia [X(T)], and to compare with a normal group. METHODS: A total of 55 subjects were divided into 3 groups: pseudodivergence excess type, convergence insufficiency type, and normal group. Age, gender, and refractive error of patients were examined. The deviation angle was measured at near and distance by using a prism cover test, followed by an interpupillary distance measurement. The AC/A ratio was calculated using a heterophoria and a gradient method. RESULTS: There was no statistically significant difference in age, gender, and the refractive errors among the 3 groups. The mean value of AC/A ratio using the heterophoria method was 9.50 in pseudodivergence excess type patients, 2.59 in convergence insufficiency type patients, and 5.47 in the normal group. Using the gradient method, the mean value of AC/A ratio was 1.47, 0.03, and 2.08 in each group, respectively. There was no statistically significant difference in mean values between patients with pseudodivergence excess type and the normal group, except when obtained using the gradient method (p = 0.43). CONCLUSIONS: A distinct difference in AC/A ratio existed when computed by the heterophoria method between patients with pseudodivergence excess type or convergence insufficiency type and the normal group. In the gradient method, however, the ratios of convergence insufficiency type patients were lower compared to the normal group, indicating the gradient method is more accurate than the heterophoria method.

The Ratio of Accommodative-Convergence to Accommodation in Patients with Intermittent Exotropia

PURPOSE: To measure the ratio of accommodative-convergence to accommodation (AC/A ratio) in patients with pseudodivergence excess type and convergence insufficiency type of intermittent exotropia [X(T)], and to compare with a normal group. METHODS: A total of 55 subjects were divided into 3 groups: pseudodivergence excess type, convergence insufficiency type, and normal group. Age, gender, and refractive error of patients were examined. The deviation angle was measured at near and distance by using a prism cover test, followed by an interpupillary distance measurement. The AC/A ratio was calculated using a heterophoria and a gradient method. RESULTS: There was no statistically significant difference in age, gender, and the refractive errors among the 3 groups. The mean value of AC/A ratio using the heterophoria method was 9.50 in pseudodivergence excess type patients, 2.59 in convergence insufficiency type patients, and 5.47 in the normal group. Using the gradient method, the mean value of AC/A ratio was 1.47, 0.03, and 2.08 in each group, respectively. There was no statistically significant difference in mean values between patients with pseudodivergence excess type and the normal group, except when obtained using the gradient method (p = 0.43). CONCLUSIONS: A distinct difference in AC/A ratio existed when computed by the heterophoria method between patients with pseudodivergence excess type or convergence insufficiency type and the normal group. In the gradient method, however, the ratios of convergence insufficiency type patients were lower compared to the normal group, indicating the gradient method is more accurate than the heterophoria method.