Progressive increase in the angle of deviation in acquired nonaccommodative esotropia of childhood

Classifying stability of misalignment in children with esotropia using simulations

OBJECTIVE

To determine the sensitivity and specificity of several classification rules for stability and instability of angle in childhood esotropia.

METHODS

We conducted 10 000 Monte Carlo simulations of participants with no actual change in angle of esotropia during follow-up, where "observed" changes in ocular alignment were sampled from a distribution of measurement errors for the prism and alternate cover test. Additional simulations were conducted for a range of "true" changes (1.0, 2.5, 4.2, 5.0, 7.5, and 10.0 prism diopters [PD] per visit) with up to 10 follow-up visits. We then estimated sensitivities and specificities for specific rules for retrospectively classifying stability (all measurements within 0, 5, 10, or 15 PD) and instability (≥2 measurements differing by ≥10 PD, etc) across a fixed number of visits. Results were extended to classifying ocular alignment stability and instability prospectively based on a varying number of measurements.

RESULTS

For a series of 4 measurements, the rules that optimized sensitivity and specificity were "all measurements within 5 PD" for stability and "at least 2 measurements differing by 15 PD or more" for instability. For a series of 3 measurements, all 3 measurements needed to be identical to confirm stability.

CONCLUSIONS

We derived definitions of stability and instability in childhood esotropia using estimates of actual measurement error that may be useful for clinical practice and for future clinical studies of esotropia.

The relationship between preoperative alignment stability and postoperative motor outcomes in children with esotropia

PURPOSE

To examine the effect of preoperative alignment stability on postoperative motor outcomes in children who underwent surgery for esotropia.

METHODS

One hundred sixty-seven subjects (68 with infantile esotropia and 99 with acquired esotropia) aged less than 6 years had surgery after completing 18 weeks of follow-up as part of an observational study. Preoperative alignment was classified as stable, uncertain, or unstable, based on measurements taken at baseline and every 6 weeks for 18 weeks. Distance alignment measured by prism and alternate cover test was compared among stability classification groups at 6 weeks and 6 months after surgery.

RESULTS

Among subjects with infantile esotropia, median 6-week postoperative deviation was 2(Delta), 6(Delta), and 2(Delta) for subjects with stable, uncertain, and unstable preoperative alignment, respectively (p = 0.73 for stable vs unstable). Median 6-month postoperative deviation was 1(Delta), 9(Delta), and 1(Delta) for stable, uncertain, and unstable, respectively (p = 1.00 for stable vs unstable). Among subjects with acquired esotropia, median 6-week postoperative deviation was 6(Delta), 4(Delta), and 4(Delta) for subjects with stable, uncertain, and unstable preoperative alignment, respectively (p = 0.69 for stable vs unstable). Median 6-month postoperative deviation was 8(Delta), 4(Delta), and 6(Delta) for stable, uncertain, and unstable, respectively (p = 0.22 for stable vs unstable).

CONCLUSIONS

Postoperative alignment at 6 weeks and 6 months appears similar in children with stable versus unstable preoperative esotropia. Nevertheless, our finding should be interpreted with caution due to small sample size.

Short-Term Motor and Sensory Outcomes in Acquired Nonaccommodative Esotropia of Childhood

Information on the management of acquired nonaccommodative esotropia (ANAET) of childhood is incomplete. Most prior reports combine the results of patients with both accommodative and nonaccommodative esodeviations. The primary objective of this study was to describe the early postoperative motor and sensory results of children with acquired nonaccommodative esotropia. The medical records of 72 consecutive children with ANAET who underwent surgical correction at East Tennessee State University College of Medicine from August 1, 1995 through October 1, 2001 were retrospectively reviewed. The median age at surgery for the 72 study patients was 43.8 months with a median angle of deviation of 30 prism diopters (PD) at both distance and near. Ten patients (13.9%) required a second surgical procedure while one patient (1.4%) required a third. The cumulative probability of a second surgery within two years of the first procedure was 24% (95% CI 4-43%). During a median postoperative follow-up period of 7.1 months, 64 (88.9%) patients were within 8 PD of orthotropia on the last postoperative examination. Normal postoperative stereoacuity was achieved in several children whose deviation began after 30 months of age, as well as in one child who was misaligned for at least two years prior to surgery. Although the postoperative follow-up on these patients with acquired nonaccommodative esotropia managed without prism adaptation is short, the motor results are similar to other studies on patients with acquired esotropia, with sensory outcomes superior to those obtained in children with congenital esotropia.

Instability of ocular alignment in childhood esotropia

OBJECTIVE

Instability of ocular alignment may cause surgeons to delay surgical correction of childhood esotropia. The authors investigated the stability of ocular alignment over 18 weeks in children with infantile esotropia (IET), acquired nonaccommodative esotropia (ANAET), or acquired partially accommodative esotropia (APAET).

DESIGN

Prospective, observational study.

PARTICIPANTS

Two hundred thirty-three children aged 2 months to less than 5 years with IET, ANAET, or APAET of less than 6 months' duration.

METHODS

Ocular alignment was measured at baseline and at 6-week intervals for 18 weeks.

MAIN OUTCOME MEASURES

Using definitions derived from a nested test-retest study and computer simulation modeling, ocular alignment was classified as unstable if there was a change of 15 prism diopters (PD) or more between any 2 of the 4 measurements, as stable if all 4 measurements were within 5 PD or less of one another, or as uncertain if neither criteria was met.

RESULTS

Of those who completed all 3 follow-up visits within time windows for analysis, 27 (46%) of 59 subjects with IET had ocular alignment classified as unstable (95% confidence interval [CI], 33%-59%), 20% as stable (95% CI, 11%-33%), and 34% as uncertain (95% CI, 22%-47%). Thirteen (22%) of 60 subjects with ANAET had ocular alignment classified as unstable (95% CI, 12%-34%), 37% as stable (95% CI, 25%-50%), and 42% as uncertain (95% CI, 29%-55%). Six (15%) of 41 subjects with APAET had ocular alignment classified as unstable (95% CI, 6%-29%), 39% as stable (95% CI, 24%-56%), and 46% as uncertain (95% CI, 31%-63%). For IET, subjects who were older at presentation were less likely to have unstable angles than subjects who were younger at presentation (risk ratio for unstable vs stable per additional month of age, 0.85; 99% CI, 0.74-0.99).

CONCLUSIONS

Ocular alignment instability is common in children with IET, ANAET, and APAET. The impact of this finding on the optimal timing for strabismus surgery in childhood esotropia awaits further study.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.