Role of fusional convergence amplitude in postoperative phoria maintenance in children with intermittent exotropia

Purpose

To examine the role of fusional convergence amplitude in postoperative phoria maintenance in childhood intermittent exotropia [X(T)].

Methods

The medical records of 29 children aged 15 years or younger (mean age, 10.8 ± 2.4 years) and treated with monocular recession-resection for X(T) were reviewed retrospectively. The patients’ fusional convergence amplitude (break point/total amplitudes), physiologic diplopia, and phoria maintenance (presence/absence of phoria maintenance and ability to maintain phoria) were assessed. The presence of phoria maintenance was confirmed by a cover test, and the ability to maintain phoria was quantified using the Bagolini red filter bar. Correlations of the amplitude size with the presence and ability of phoria maintenance were investigated.

Results

A significant correlation was seen between fusional amplitude (break point/total) and ability to maintain phoria at near and at far (break point: P < .05 at near/P < .01 at far; total: P < .05 at near/far). Neither the break point amplitude nor the total amplitude significantly differed between the patients with phoria maintenance and those without it (break point: P = .71 at near, P = .29 at far; total: P = .98 at near, P = .85 at far). Phoria maintenance correlated with the suppression of physiologic diplopia during phoria (P < .01). The deviation angle did not significantly correlate with fusional amplitude either at near (P = .58) or at far (P = .27).

Conclusions

In childhood X(T), fusional amplitude plays a role in enforcing the patient’s ability to maintain phoria. However, sufficient fusional amplitude does not guarantee fully functioning fusion if suppression is present during phoria.

     

Age-related changes of phoria myopia in patients with intermittent exotropia

Purpose  To investigate the age-related changes in a myopic shift under binocular conditions (phoria myopia) in patients with intermittent exotropia (IXT). Methods  Forty-five patients with IXT were studied: 21 were ≤9 years old (children), 11 were between 10 and 19 years (adolescents), and 13 were between 20 and 43 years (adults). The angle of strabismus was determined by the alternating prism cover test. The spherical refractive error was measured at 1 m using infrared video retinoscopy under monocular and binocular viewing conditions. Results  The change in the spherical refractive error (ΔR) between binocular and monocular conditions was significantly larger in adults (ΔR = −1.11 ± 1.01 diopters (D), average ± standard deviation) than in children (ΔR = −0.34 ± 0.34 D; P < 0.05, analysis of variance). ΔR was significantly correlated with the angle of exotropia only in adults (r = 0.55, P = 0.04). After strabismus surgery, ΔR decreased in adults (n = 3). Conclusions  Because a significant myopic shift under binocular conditions was detected in IXT patients older than 20 years, phoria myopia can occur after age 20 even if functional disturbances are not observed in children or adolescent IXT patients, a fact that specialists need to bear in mind when treating younger patients.     

Female predominance in intermittent exotropia

PURPOSE: To evaluate gender differences among children diagnosed with intermittent exotropia. DESIGN: Retrospective, population-based cohort study. METHODS: The medical records of all Olmsted County, Minnesota residents younger than 19 years diagnosed with intermittent exotropia from January 1, 1975, through December 31, 1994, were reviewed. RESULTS: One hundred eighteen (64.1%) of the 184 study patients were girls with an age-adjusted incidence rate of 38.3 (95% CI: 31.4-45.2) per 100,000 compared to 20.8 (95% CI: 15.7-25.8) per 100,000 for boys (P < .0001). There were no significant differences between girls and boys in their family history of strabismus, birth weight, prevalence of prematurity, age at diagnosis and surgery, refractive error, and initial angle of deviation. CONCLUSIONS: Intermittent exotropia was nearly twice as common in girls compared with boys in this defined population. There were, however, no significant historical or clinical differences between the genders.     

Distance stereoacuity in intermittent exotropia

BACKGROUND: Studies of distance stereoacuity in intermittent exotropia suggest that normal stereoacuity corresponds to good control of the deviation and that reduced or negative stereoacuity signifies poorer control. AIM: : To evaluate distance stereoacuity in intermittent exotropia using the Frisby Davis Distance stereo test (FD2). METHODS: Children with intermittent exotropia where the near angle was less than or equal to distance were eligible for recruitment. Standardised prospective data collection included FD2 distance stereoacuity. This was a longitudinal study in which outcomes are reported for baseline, last follow-up (> or =6 months before any surgery) or preoperative and last postoperative visits for those undergoing surgery. RESULTS: 110 children with intermittent exotropia had FD2 stereoacuity tested at baseline: 70 comprehended the test. Mean (standard deviation (SD)) age was 4.6 (1.7) years (range 2-10 years). 41/70 (59%) showed positive responses: mean (SD) stereoacuity 30 (12) s of arc. The mean follow-up period before any surgery was 13 months (range 6-27 months). At follow-up, mean (SD) stereoacuity was 24 (11) s of arc. Preoperative and postoperative stereoacuity were not significantly different from those not undergoing surgery. CONCLUSION: This study was the first to report distance stereoacuity in intermittent exotropia using the FD2 stereo test: patients with intermittent exotropia can achieve normal levels of distance stereoacuity, but a considerable proportion, despite comprehending, showed a negative response. This suggests that using the FD2, distance stereoacuity in intermittent exotropia is either absent or normal rather than reduced. Possible reasons for this and its implications are discussed.     

Variability of stereoacuity in intermittent exotropia

PURPOSE: Distance stereoacuity is used to monitor deterioration of intermittent exotropia (IXT), but variability of stereoacuity has not been studied rigorously. The purpose of this study was to assess the variability of stereoacuity over one day in children with IXT. DESIGN: Prospective cohort study. METHODS: Twelve children with IXT were recruited. Stereoacuity was assessed using the Frisby Davis Distance test and the Distance Randot test at distance, and the Frisby and Preschool Randot tests at near. Tests were repeated three or four times over the day, with at least two hours between assessments. The main outcome measure was variable stereoacuity defined as a change by two or more log levels between any two time points over the day. RESULTS: Variable stereoacuity at distance was found in five (42%) of 12 patients. Four (33%) of 12 patients demonstrated variable results using the Distance Randot test, three of whom also showed variable results using the Frisby Davis Distance test. One patient had variable results using the Frisby Davis Distance test only. Nine (75%) of 12 patients completed near stereoacuity testing; two (22%) of nine showed variable near stereoacuity. Two (22%) of nine showed variable results using the Preschool Randot test, one (11%) of whom also had variable results using the Frisby test. In some cases, stereoacuity changed from measurable stereoacuity on one assessment to nil on another. CONCLUSIONS: Nearly half of children with IXT show marked changes in stereoacuity over the course of a single day. When based on isolated measures, an apparent change in distance stereoacuity between visits should be interpreted with caution.     

间歇性外斜视的手术治疗

间歇性外斜视是介于外隐斜与恒定性外斜视之间的一种斜视,是儿童最常见的外斜视。起病较早,发病年龄通常为6月龄～ 4岁。与其他类型的斜视不同,间歇性外斜视的儿童在很长一段时期内仍可维持正常眼位和双眼视功能,因此如何选择合适的干预时机及治疗方式对临床医师是个挑战,同时手术方式的选择及术后效果也存在不同的观点。本文旨在对间歇性外斜视的发病机制和临床特征、手术时机和手术方式的选择进行简要介绍,为间歇性外斜视的治疗提供参考。     

不同年龄段儿童间歇性外斜视手术疗效分析

目的：探讨不同年龄段儿童间歇性外斜视手术的疗效。

方法：选择2015-03/2017-04于我院行间歇性外斜视手术的患儿300例作为研究对象,根据患儿年龄分为A组110例,年龄3～5岁; B组100例,年龄6～8岁; C组90例,年龄9～12岁。三组患儿均行间歇性外斜视手术。比较三组患儿的临床疗效、手术前后斜视度数、融合功能及立体视锐度。

结果：术后6wk,A组临床疗效总有效率为92.7%,明显高于B组(67.0%)和C组(68.9%),三组患儿临床疗效总有效率差异有统计学意义(P<0.05)。术前,三组患儿斜视度数、融合功能、立体视锐度水平差异均无统计学意义(P>0.05); 术后6wk,三组患儿斜视度数下降,立体视锐度与融合功能均明显改善,且A组患儿斜视度数和立体视锐度弧秒值均明显低于B组和C组,融合功能明显高于B组和C组,差异均有统计学意义(P<0.05)。

结论：间歇性外斜视患儿的年龄与术后双眼视觉恢复、重建有密切关系,年龄越小术后视觉恢复越好。     

间歇性外斜视的研究进展

间歇性外斜视是介于外隐斜与恒定性外斜视之间的一种斜视.起病较早,发病年龄通常为1岁到4岁.与其他类型的斜视不同,间歇性外斜视的儿童在很长一段时期内仍可维持正常眼位及双眼视功能,因此如何选择合适的干预时机及治疗方式对临床医师是个挑战.本文旨在回顾近年来间歇性外斜视的最新研究进展,重点对间歇性外斜视的严重度分级、非手术治疗方式、手术时机及手术方式、过矫及欠矫处理等方面的研究进展进行简要介绍,为间歇性外斜视的治疗提出改善化建议.     

间歇性外斜视发病与近视的关系

间接性外斜视(intermittent exotropia,IXT)患者为维持双眼视轴的平行而做出过度的辐辏时,可导致视力、屈光度的一过性改变,出现调节性近视.研究表明,IXT可能促进近视发展,在眼球正位时出现屈光状态改变,此时双眼调节力加强,表现为调节超前,而调节超前与近视有一定联系.因此临床工作中对IXT患者选择适当的干预时机及治疗方式尤为必要.