Anna R. O’connor

Conservative management of intermittent distance exotropia: a review

Background and Purpose Intermittent distance exotropia is difficult to conservatively manage, with techniques varying widely between institutions. This review aims to examine current literature on conservative management for intermittent distance exotropia, investigate its impact upon current clinical practice, and identify areas for further research. Method A literature search was performed using PubMed, Web of Knowledge, LILACS, and the University of Liverpool Orthoptic Journals and Conference Transactions Database. All English-language papers published between 1950 and the present day were considered. Results Intermittent distance exotropia is a difficult condition to manage because of its variability/uncertain natural history, although control scores can facilitate management decisions. Research is required to establish recommended dosages for antisuppression occlusion and determine whether other treatments such as minus lenses are more effective. Use of orthoptic exercises has declined, but recently certain exercises have been shown to improve surgical outcomes if applied preoperatively. Prisms are mainly used postoperatively. Minus lens therapy is recommended as a first line treatment, but may not always be successful. Conclusion Conservative management techniques for intermittent distance exotropia have their place as both an alternative and an adjunct to surgery. However, further research needs to be conducted to determine which techniques are appropriate for which patients.

Assessment of the Density of Suppression to Identify Risk of Intractable Diplopia in the United Kingdom

ABSTRACT Background/Aims: Occlusion used to treat amblyopia towards the end of the developmental component of the critical period gives a risk of inducing intractable diplopia. In the United Kingdom, the density of suppression is assessed via the Sbisa/Bagolini filter bar, but there is very little research evidence to guide clinical practice or interpretation of the tests used. The aims of this study were to determine current practice and estimate the incidence of intractable diplopia following amblyopia treatment. Methods: Current practice and incidence of intractable diplopia following amblyopia were determined via a questionnaire distributed to head orthoptists in every eye department in the United Kingdom. The questionnaire explored testing and test conditions, interpretation of the test results, and cases of intractable diplopia over the last 5 years. Results: There was considerable variation in clinical practice of the measurement of the density of suppression and interpretation of the results to guide the treatment of amblyopia. The minimum age of patients taking the test ranged from 2 to 8 years and the minimum filter considered still safe to continue treatment ranged from 4 to 17. It is estimated there were 24 cases of intractable diplopia over the last 5 years. Conclusion: The issue of intractable diplopia and amblyopia treatment is likely to become increasingly important as there appears to be greater plasticity and scope to treat amblyopia in teenagers and adults than was previously thought. Lack of knowledge of how to evaluate the risk may lead to more cases of intractable diplopia or alternatively treatment being withheld unnecessarily.

Clinical Assessment of Stereoacuity and 3-D Stereoscopic Entertainment.

Abstract Background/Aims: The perception of compelling depth is often reported in individuals where no clinically measurable stereoacuity is apparent. We aim to investigate the potential cause of this finding by varying the amount of stereopsis available to the subject, and assessing their perception of depth viewing 3-D video clips and a Nintendo 3DS. Methods: Monocular blur was used to vary interocular VA difference, consequently creating 4 levels of measurable binocular deficit from normal stereoacuity to suppression. Stereoacuity was assessed at each level using the TNO, Preschool Randot®, Frisby, the FD2, and Distance Randot®. Subjects also completed an object depth identification task using the Nintendo 3DS, a static 3DTV stereoacuity test, and a 3-D perception rating task of 6 video clips. Results: As intraocular VA differences increased, stereoacuity of the 57 subjects (aged 16–62 years) decreased (eg, 110”, 280”, 340”, and suppression). The ability to correctly identify depth on the Nintendo 3DS remained at 100% until suppression of one eye occurred. The perception of a compelling 3-D effect when viewing the video clips was rated high until suppression of one eye occurred, where the 3-D effect was still reported as fairly evident. Conclusion: If an individual has any level of measurable stereoacuity, the perception of 3-D when viewing stereoscopic entertainment is present. The presence of motion in stereoscopic video appears to provide cues to depth, where static cues are not sufficient. This suggests there is a need for a dynamic test of stereoacuity to be developed, to allow fully informed patient management decisions to be made.

Normative Values for Near and Distance Clinical Tests of Stereoacuity

ABSTRACT Purpose: Extensive literature exists on normative stereoacuity values for younger children, but there is less information about normative stereoacuity in older children/adults. Individual stereotests cannot be used interchangeably—knowing the upper limit of normality for each test is important. This report details normative stereoacuity values for 5 near/distance stereotests drawn from a large sample of participants aged 16-40 years, across 3 studies. Methods: Participants (n=206, mean age 22.18±5.31 years) were administered the following stereotests: TNO, Preschool Randot, Frisby, Distance Randot, and Frisby-Davis 2. Medians and upper limits were calculated for each test. Results: Upper limits for each stereotest were as follows: TNO (n=127, upper limit=120” arc), Preschool Randot (PSR, n=206, upper limit=70” arc), Frisby (n=206, upper limit=40” arc), Distance Randot (n=127, upper limit=160” arc), and Frisby-Davis 2 (n=109, upper limit=25” arc). Conclusions: Normative values for each stereotest are identified and discussed with respect to other studies. Potential sources of variation between tests, within testing distances, are also discussed.

Incidence, risk factors and management of intractable diplopia

Aims There is a paucity of literature concerning intractable diplopia. The aims of this study were to determine the incidence of intractable diplopia in the UK, identify the causes and any associated risk factors, establish how cases are managed and if the treatment is successful and tolerated. Methods A 1-year prospective observational study was undertaken via the British Ophthalmological Surveillance Unit (BOSU). This involved implementation of a reporting mechanism, which then triggered distribution of an incident questionnaire to explore clinical details concerning each case and a follow-up questionnaire 6 months later to explore how the case had been managed. Results The incidence of intractable diplopia was 53 cases per year. The most common preceding events were strabismus surgery (32%), no known preceding event, that is,spontaneous (25%), severe head trauma (8%), cataract surgery (6%) and vitrectomy (6%). In the at-risk age group of 7 years and above, the incidence of intractable diplopia following strabismus surgery is 1 in 494 (95% CI; 1 in 296 to 790) cases. A total of nine different treatments were used in the management, with many patients receiving between two and four different methods. The overall success rate was poor, but most effective were opaque intraocular lenses (IOLs) (86%) and opaque contact lenses (50%). Conclusion Intractable diplopia is a relatively rare but important condition. The main risk factor is a pre-existing strabismus, and careful counselling is needed when planning surgical correction in patients with no demonstrable binocular function. Treatment success of intractable diplopia is high when using opaque IOLs, although with additional risk, but is often disappointing via other methods where it can be difficult to eradicate the diplopia successfully.

Stereopsis Outcomes in Children Treated for Congenital Cataracts

Visual deprivation due to congenital cataracts significantly disrupts binocular cortical development during a critical period, typically resulting in reduced or nil stereoacuity. Recent laboratory and clinical research highlights the need to tailor treatment protocols to ensure adequate binocular visual experience during infancy. Additional factors that may affect stereoacuity outcomes include the timing of surgery, treatment modality, post-surgical complications, and the methods for assessing stereoacuity. While there is a range of stereoacuity outcomes, high-grade stereoacuity is rare. Nonetheless, the acquisition of any degree of binocularity has measurable functional benefits. These benefits encompass fine and gross motor skills, improved eye alignment resulting in improved health related quality of life, and reduced risk for strabismus.