Dataset Information

Bilateral Occlusion Reduces the Ocular Deviation in Intermittent Exotropia.

ABSTRACT:

Purpose

The most common form of strabismus, intermittent exotropia, is thought to become manifest when the drive to fuse is overcome by excessive divergent muscle tone. This principle is tested by examining the alignment of the eyes in the absence of vision. We compare the ocular deviation in patients with intermittent exotropia under conditions of monocular versus binocular occlusion.

Methods

This prospective study of a patient cohort referred to our laboratory enrolled 18 patients with typical findings of well-controlled intermittent exotropia. Eye positions were recorded with video eye trackers while patients looked at a fixation spot at a distance of 57 cm. One eye was occluded, and the resulting ocular deviation was measured. Both eyes were then occluded, and the ocular deviation was re-measured.

Results

The majority of patients (11/18) had a smaller deviation when both eyes were covered. Occlusion of one eye resulted in a mean exotropia of 13.5° ± 4.7°. Occlusion of both eyes reduced the mean exotropia to 6.0° ± 6.5° (paired t-test, P < 0.001), corresponding to a 56% reduction in the ocular deviation. This reduction persisted during prolonged bilateral occlusion but reversed as soon as vision was restored.

Conclusions

Bilateral occlusion reveals a fixation-free state of alignment that is different from orthotropia and usually less than the exotropia that occurs spontaneously during binocular viewing. This finding demonstrates that the deviation angle in patients with intermittent exotropia is actively mediated by visual feedback, which the fixating eye is capable of providing alone.

SUBMITTER: Economides JR

PROVIDER: S-EPMC7794258 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Publications

Bilateral Occlusion Reduces the Ocular Deviation in Intermittent Exotropia.

Economides John R JR Adams Daniel L DL Horton Jonathan C JC

Investigative ophthalmology & visual science 20210101 1

<h4>Purpose</h4>The most common form of strabismus, intermittent exotropia, is thought to become manifest when the drive to fuse is overcome by excessive divergent muscle tone. This principle is tested by examining the alignment of the eyes in the absence of vision. We compare the ocular deviation in patients with intermittent exotropia under conditions of monocular versus binocular occlusion.<h4>Methods</h4>This prospective study of a patient cohort referred to our laboratory enrolled 18 patien ...[more]

PMID: 33393972

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Project description:BackgroundThe clinical management of intermittent exotropia has been discussed extensively in the literature, yet there remains a lack of clarity regarding indications for intervention, the most effective form of treatment and whether or not there is an optimal time in the evolution of the disease at which any treatment should be carried out.ObjectivesThe objective of this review was to analyse the effects of various surgical and non-surgical treatments in randomised trials of participants with intermittent exotropia, and to report intervention criteria and determine the significance of factors such as age with respect to outcome.Search methodsWe searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library, Issue 4, 2012), MEDLINE (January 1966 to May 2012), EMBASE (January 1980 to May 2012), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to May 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 4 May 2012. We are no longer searching the UK Clinical Trials Gateway (UKCTG) for this review. We manually searched the British Orthoptic Journal up to 2002, and the proceedings of the European Strabismological Association (ESA), International Strabismological Association (ISA) and American Academy of Paediatric Ophthalmology and Strabismus meeting (AAPOS) up to 2001. We contacted researchers who are active in the field for information about further published or unpublished studies.Selection criteriaWe included randomised controlled trials of any surgical or non-surgical treatment for intermittent exotropia.Data collection and analysisEach review author independently assessed study abstracts identified from the electronic and manual searches. Author analysis was then compared and full papers for appropriate studies were obtained.Main resultsWe found one randomised trial that was eligible for inclusion. This trial showed that unilateral surgery was more effective than bilateral surgery for correcting the basic type of intermittent exotropia.Authors' conclusionsThe available literature consists mainly of retrospective case reviews, which are difficult to reliably interpret and analyse. The one randomised trial included found unilateral surgery more effective than bilateral surgery for basic intermittent exotropia. However, across all identified studies, measures of severity and thus criteria for intervention are poorly validated, and there appear to be no reliable natural history data. There is therefore a pressing need for improved measures of severity, a better understanding of the natural history and carefully planned clinical trials of treatment to improve the evidence base for the management of this condition.

Project description:PurposeTo compare long-term outcomes after bilateral lateral rectus recession (BLRc) or unilateral lateral rectus recession combined with medial rectus resection in the same eye (R&R) for primary treatment of childhood intermittent exotropia (IXT).DesignMulticenter, randomized clinical trial.ParticipantsOne hundred ninety-seven children 3 to younger than 11 years of age with basic-type IXT, a largest deviation by prism and alternate cover test at any distance of 15 to 40 prism diopters (PD), and near stereoacuity of at least 400 seconds of arc.MethodsRandom assignment to BLRc or R&R and masked examinations conducted every 6 months after surgery for 3 years.Main outcome measuresProportion of participants meeting suboptimal surgical outcome by 3 years, defined as: (1) exotropia of 10 PD or more at distance or near using simultaneous prism and cover test (SPCT); or (2) constant esotropia of 6 PD or more at distance or near using SPCT; (3) loss of 2 octaves or more of stereoacuity from baseline, at any masked examination; or (4) reoperation without meeting any of these criteria.ResultsCumulative probability of suboptimal surgical outcome by 3 years was 46% (43/101) in the BLRc group versus 37% (33/96) in the R&R group (treatment group difference of BLRc minus R&R, 9%; 95% confidence interval [CI], -6% to 23%). Reoperation by 3 years occurred in 9 participants (10%) in the BLRc group (8 of 9 met suboptimal surgical outcome criteria) and in 4 participants (5%) in the R&R group (3 of 4 met suboptimal surgical outcome criteria; treatment group difference of BLRc minus R&R, 5%; 95% CI, -2% to 13%). Among participants completing the 3-year visit, 29% (25 of 86) in the BLRc group and 17% (13 of 77) in the R&R group underwent reoperation or met suboptimal surgical outcome criteria at 3 years (treatment group difference of BLRc minus R&R, 12%; 95% CI, -1% to 25%).ConclusionsWe did not find a statistically significant difference in suboptimal surgical outcome by 3 years between children with IXT treated with BLRc compared with those treated with R&R. Based on these findings, we are unable to recommend one surgical approach over the other for childhood IXT.

Dataset Information

Bilateral Occlusion Reduces the Ocular Deviation in Intermittent Exotropia.

Purpose

Methods

Results

Conclusions

Publications

Bilateral Occlusion Reduces the Ocular Deviation in Intermittent Exotropia.

Similar Datasets

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