Charts of 35 patients were available for analysis, and 6-month postoperative data were available in 29 patients (83%) and, in the remaining 6 patients, the 5-week postoperative data were used. Patient age ranged from 1 to 84 years.
Of the 35 patients with exotropia, 10 patients carried the diagnosis of intermittent exotropia, 2 of these 10 had convergence insufficiency type, 18 patients had consecutive exotropia, 4 patients had constant exotropia, 2 had congenital exotropia, and 1 had cerebral palsy and exotropia (e-Supplement 1
, available at jaapos.org
The preoperative and postoperative magnitude of the hypertropic deviation measured for distance and near is shown in . There was no difference in magnitude of preoperative hypertropia between the vertical offset group and the comparison group or the vertical muscle group at either distance or near. However, there was a statistically significant difference in the preoperative distance hypertropia between the comparison group and the vertical muscle group (p = 0.05) In the vertical offset group, the range of preoperative distance hypertropia was 6Δ-20Δ and preoperative near hypertropia was 0Δ-25Δ; this difference was not significant. In the vertical muscle group, the range of preoperative distance hypertropia was 5Δ-25Δ and preoperative near hypertropia was 0Δ-20Δ; the difference in the distance and near measurements was significant (p = 0.007).
Hypertropia correction (in prism diopters) by group
Success rate for correcting the hypertropia was 63% (7/11) in the vertical offset group, and 71% (12/17) in the vertical muscle group. A plot of the postoperative hypertropia is shown in (near deviation) and (distance deviation). The magnitude of change within each group was significant at both distance and near for the vertical offset and vertical muscle groups but not significant for the comparison group. The preoperative and postoperative magnitude of the exotropic deviation measured for distance and near was compared between groups. In the vertical offset group the distance exotropia measured 35Δ preoperatively and 9Δ postoperatively. In the vertical group it was 23Δ preoperatively and 3Δ postoperatively. There was no statistically significant difference between the 3 groups in postoperative horizontal alignment.
FIG 1 Box-and-whiskers plot showing residual postoperative hypertropia. Positive values along y-axis are residual hypertropia, and negative values are overcorrected hypertropia. Patients are listed by group and patient number in e-Supplement 1, available at (more ...)
FIG 2 Box-and-whiskers plot showing residual postoperative hypertropia. Positive values along y-axis are residual hypertropia, and negative values are overcorrected hypertropia. Patients are listed by group and patient number in e-Supplement 1, available at (more ...)
The vertical offset group consisted of 11 patents: 2 had X(T), 6 had CXT, 2 had XT, and 1 had cerebral palsy. In this group, 3 patients preoperatively had stereopsis. A comparison group was used to determine whether magnitude of the vertical correction in this vertical offset group was a true effect. Seven exotropic patients with hypertropia (6 with CXT and 1 with XT), and no preoperative stereopsis were identified. These patients had an average preoperative hypertropia of 7Δ distance and 4Δ near, and an average postoperative hypertropia of 5Δ distance and 4Δ near. The pre- and postoperative measurements for hypertropia were not statistically different.
Patients in this vertical offset group had a statistically greater correction for the distance vertical hypertropia than patients in the comparison group that did not undergo vertically corrective surgery (p = 0.0485). The magnitude of the hypertropia correction when vertically offsetting the horizontal muscles averaged 8Δ at distance and 5Δ at near. However, it should be noted that successful resolution of the hypertropia was highly correlated to successful and stable horizontal alignment. Of the 6 patients with hypertropia less than 5Δ at 6 months, 5 of these had horizontal deviations of less than 7Δ. Only one overcorrection of the hypertropia occurred in this group. Two patients in the vertical offset group had intermittent exotropia and hypertropia (12Δ and 14Δ), one patient had complete resolution of the exotropia and hypertropia for more than 2 years; however, the second had excellent alignment at 1 month but recurrence of the exotropia with reversal of the hypertropia at 6 months.
The vertical muscle group consisted of 17 patients, of whom 8 had X(T) (2 of these CI type), 7 had CXT, and 2 had congenital exotropia. Preoperatively, 6 patients had stereopsis. Of the 17, 11 patients underwent superior rectus muscle recession, and 6 underwent inferior rectus muscle recession (mean recession, 4.3 mm).
The magnitude of the vertical correction effect in the vertical muscle group averaged 10Δ for near and 11.5Δ for distance (3Δ per mm of recession). The difference was statistically different than the comparison group (p = 0.006 near; p = 0.007 distance), but not statistically different than the vertical offset group. There were 5 overcorrections of the vertical hypertropia in the vertical muscle group. Four of these patients had intermittent exotropia; this represented a 50% overcorrection rate for patients with basic intermittent exotropia. Taking all intermittent exotropia patients, there was a significant overcorrection of the hypertropia compared to nonintermittent exotropes (p = 0.01). However, there was no statistically significant difference in the magnitude of the exotropia or hypertropia in the intermittent exotropes that were overcorrected than in those that were not. Of the remaining 3 failures in the vertical muscle group, 2 were intermittent exotropes with preoperative stereoacuity, successful stable 6-month horizontal alignment, and no hypertropic deviation at near, but recurrent hypertropia at distance.
Of the 17 patients in the vertical muscle group, 9 had a distance near incomitant hypertropia, with the near vertical deviation measuring half the distance deviation or less, or 8Δ less near hypertropia than the distance hypertropia (if the distance hypertropia measured more than 15Δ). In general the amount of surgical recession on the vertical rectus muscle was calculated on the distance plus near measurement divided in half. This approach was successful in 7 of the 9 patients. Finally, 3 patients, despite initially having excellent resolution of the vertical tropia at one month, had partial recurrence of hypertropia at 6 months. No patient in either group developed stereopsis that was not present preoperatively, despite successful vertical and horizontal alignment.