Binocularity following surgery for secondary esotropia in childhood

An external pilot study to test the feasibility of a randomised controlled trial comparing eye muscle surgery against active monitoring for childhood intermittent exotropia [X(T)]

INTRODUCTION

The evidence base for the treatment of strabismus (squint) is poor. Our main aim is to improve this evidence base for the treatment of a common type of childhood squint {intermittent exotropia, [X(T)]}. We conducted an external pilot study in order to inform the design and conduct of a future full randomised controlled trial (RCT).

METHODS

Children of between 6 months and 16 years with a recent diagnosis of X(T) were eligible for recruitment. Participants were recruited from secondary care at the ophthalmology departments at four UK NHS foundation trusts. Participants were randomised to either active monitoring or surgery. This report describes the findings of the Pilot Rehearsal Trial and Qualitative Study, and assesses the success against the objectives proposed.

RECRUITMENT AND RETENTION

The experience gained during the Pilot Rehearsal Trial demonstrates the ability to recruit and retain sites that are willing to randomise children to both trial arms, and for parents to agree to randomisation of their children to such a study. One child declined the group allocation. A total of 231 children were screened (expected 240), of whom 138 (60%) were eligible (expected 228: 95%) and 49 (35% of eligible) children were recruited (expected 144: 63% of eligible). Strategies that improved recruitment over the course of the trial are discussed, together with the reasons why fewer children were eligible for recruitment than initially anticipated. Attrition was low. Outcome data were obtained for 47 of 49 randomised children.

TRIAL PROCESSES AND DATA COLLECTION

The Trial Management processes proved effective. There were high levels of completion on all of the data collection forms. However, the feedback from the treatment orthoptists revealed that some modifications should be made to the length and frequency of the health service assessment and travel assessment questionnaires, thus reducing the burden on participants in the main trial. Modifications to the wording of the questions also need to be made.

MONITORING OF BIAS

Children who recruited to the trial were older and had more severe strabismus than those children eligible but declining participation. Strategies to account for this in a full trial are proposed.

REASONS FOR PARTICIPATION OR DECLINING STUDY

These were identified using qualitative interviews. The principal reasons for declining entry into the study were strong preferences for and against surgical treatment.

HARMS

There were no serious unexpected adverse events. Two children had overcorrection of their X(T) with reduction in binocular vision following surgery, which is in line with previous studies. No children in the active monitoring arm developed a constant strabismus although two showed some reduction in control.

CONCLUSIONS

The SamExo study has demonstrated that it is possible to recruit and retain participants to a randomised trial of surgery compared with active monitoring for X(T). For longer-term full RCTs, in order to maximise the generalisability of future studies, consideration needs to be given to planning more time and clinic appointments to assess eligibility and to allow consideration of participation; the greater use of research nurses for recruitment; and accommodating the strong preferences of some parents both for and against surgical intervention.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN44114892.

FUNDING

This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 19, No. 39. See the NIHR Journals Library website for further project information.

Binocular vision outcomes following surgery for long-standing large angle exodeviation

INTRODUCTION

One goal of pre-operative sensorimotor testing is to determine fusion potential. Potential for recovery of binocularity following surgical repair of strabismus is inversely correlated to duration of misalignment. The purpose of this study was to determine binocular vision outcomes in long-standing, large-angle, constant exotropia, when the pre-operative sensorimotor exam predicts poor sensory outcome.

METHODS

Patients with constant exotropia >35Δ, present for ≥20 years, and scheduled to undergo strabismus surgery were recruited. Subjects were sorted into 3 groups based on pre-operative sensorimotor results. Group A had evidence of fusion pre-operatively, Group B demonstrated suppression on all tests, and Group C demonstrated paradoxical diplopia on at least one test.

RESULTS

Twenty patients were included: 11 in Group A, 5 in Group B, and 4 in Group C. Binocular vision was regained following surgery by 100% in Group A, 80% in Group B, and 50% in group C.

CONCLUSION

Surgical realignment leads to improvements in binocular vision in most patients, even in the case of very long-standing, large, constant deviations. The presence of paradoxical diplopia or dense suppression pre-operatively does not preclude a good sensory outcome.

[Surgical results in childhood primary comitant large-angle exotropia]

INTRODUCTION

The purpose of this study was to evaluate the surgical results in childhood primary comitant large-angle exotropia (>30Delta) after a single operation and to analyze the factors that could influence these results.

PATIENTS AND METHODS

We carried out a retrospective study in all children presenting with comitant primitive exotropia at an angle greater than 30Delta, who were operated on in our department from January 1996 to December 2000 by various surgeons. One hundred thirty-eight (138) cases were reviewed. The children with a substantial A or V phenomenon, retraction syndromes, nystagmus, those presenting with a neurological disease and those who had had previous eye surgery were excluded. The postoperative results were classified in three categories: residual exotropia over 10Delta, good postoperative result (esotropia<10Delta, orthotropia or exotropia<10Delta), and consecutive esotropia over 10Delta.

RESULTS

Ninety-seven children fulfilled the study criteria. Forty (41.2%) were boys and 57 (58.8%) girls. The average age at the time of surgery was 6.5 years (SD 3.1). Sixty-eight of 97 (70.1%) had intermittent exotropia. Twenty-six children (26.8%) underwent a bilateral recession of the lateral rectus, 67 (69.1%) a unilateral operation, recession of a lateral rectus/resection of a medial rectus, and four (4.1%) an operation on three horizontal muscles. Sixty-nine percent of the children operated on had a good postoperative result, according to criteria defined in our study, 1 year after surgery.

DISCUSSION/CONCLUSION

Childhood primary comitant large-angle exotropia can be corrected with a single surgical procedure, unilateral or bilateral, with a success rate which, in our study, reached 69%.

Binocular status after surgery for constant and intermittent exotropia

PURPOSE

To investigate whether constant exotropia patients with a previous history of intermittent exotropia X(T), like X(T) patients, can achieve postoperative bifixation, and whether they have a better postoperative sensory outcome than those without previous history of X(T).

DESIGN

Prospective comparative clinical study.

METHODS

Sixty-three consecutive patients with intermittent or constant exotropia were divided into three groups: X(T) (group 1), constant exotropia with a previous history of X(T) (group 2), and constant exotropia without previous history of X(T) (group 3). The surgical outcomes were assessed and compared in motor and sensory terms separately between the three groups. Successful motor alignment was defined as within 8 prism diopters (PD) (exo or eso). A stereoacuity < or =60 seconds of arc was considered as bifixation, and a stereoacuity < or =800 seconds of arc was considered as gross stereopsis.

RESULTS

The successful motor alignment rates of group 1, group 2, and group 3 were 79%, 71%, and 67%, respectively (group 1 vs group 2, P = .826; group 1 vs group 3, P = .551; group 2 vs group 3, P = 1.000). Twenty-five (74%) patients in group 1 achieved bifixation and none achieved in group 2 or group 3 (group 1 vs group 2, P = .001; group 1 vs group 3, P = .001). Meanwhile, 34 patients (100%) in group 1, 11 (79%) in group 2, and 5 (33%) in group 3 achieved gross stereopsis (group 1 vs group 2, P = .021; group 2 vs group 3, P = .025; group 1 vs group 3, P = .001). Compared with patients in the two constant exotropia groups, patients in X(T) group had a significantly better sensory outcome in both bifixation and gross stereopsis. Patients in group 2 had a better sensory outcome than those in group 3 in gross stereopsis.

CONCLUSIONS

Constant exotropia patients with a previous history of X(T) have a better postoperative sensory outcome in gross stereopsis than those without previous history of X(T), but a worse surgical sensory outcome when compared with X(T) patients in both bifixation and gross stereopsis. Constant exotropia patients decompensated from X(T) may have missed the best time for treatment.

Timely surgery in intermittent and constant exotropia for superior sensory outcome

PURPOSE

To determine whether time of strabismus surgery for patients with acquired intermittent exotropia and constant exotropia influences postoperative sensory outcome.

METHODS

In a retrospective, cross-sectional study, 76 patients with acquired intermittent or constant exotropia and motor realignment were evaluated for postoperative sensory status. Age at surgery, duration of exotropia, and presence of intermittent or constant exotropia were correlated with postoperative sensory status. The 23 male and 53 female patients had an average age of 9.3 years at the time of surgery and a mean follow-up of 5.9 years.

RESULTS

Patients had a significantly greater chance of having postoperative stereoacuity better than 60 seconds of arc (bifixation) if they were surgically aligned before 7 years of age (P <.01) or before 5 years of strabismus duration (P <.05), or with intermittent as compared with constant exotropia (P <.001). Patients with postoperative bifixation had earlier surgical intervention (P <.025) and shorter duration of exotropia (P <.025) than those with postoperative monofixation.

CONCLUSIONS

Patients with intermittent or constant exotropia may achieve superior sensory outcome with motor realignment before age 7, before 5 years of strabismus duration, or while the deviation is intermittent.

The outcome of strabismus surgery in childhood exotropia

The results of squint surgery in 42 children with primary, non-paralytic, childhood exotropia are analysed. A 'favourable outcome', defined as a final alignment for near and distance within +/- 10 dioptres of straight, or within +/- 20 dioptres of straight with evidence of binocular single vision, was achieved in 39 (93%) children. The factors affecting the final outcome are discussed, including age of onset, age at the time of surgery, preoperative and post-operative amblyopia, refractive error, anisometropia, the surgical procedures used, and postoperative ocular alignment.

Bilateral lateral rectus recession for exotropia: a survival analysis

Exotropia may progress during the childhood years, and the ideal time for surgical intervention remains uncertain. We reviewed our results following bilateral lateral rectus recession in 57 consecutive patients. In order to identify possible predictive covariates, we performed survival analysis using survival time as the time from surgery to failure. The patients' age at the time of surgery ranged from 11 months to 50 years (mean, 68 months). Follow up after surgery ranged from 1 to 105 months (mean, 47 months). Outcomes were considered failures if there was (1) a distance exodeviation greater than 10 prism diopters at any time after surgery, (2) a distance esodeviation greater than 10 delta more than 6 months postoperatively, or (3) further surgery for exotropia or esotropia. By these criteria, surgery was successful in 58% of cases. Results of the survival analysis indicated an estimated mean time to failure of 68 months. Patients with intermittent exotropia were more likely to remain aligned postoperatively than were those with constant deviations. The age at onset of exotropia, age at surgery, angle of deviation at different fixation distances, early postoperative alignment, and presence of symptoms, amblyopia, anisometropia, or incomitance before surgery were not predictive of success. We conclude that exotropia surgery may be performed with the same likelihood of success at any age, but patients with intermittent deviations do better.