Incidence, risk factors and management of intractable diplopia

Opinions on Amblyopia Treatment in Microtropia - A Questionnaire Study of Orthoptists in Scandinavia

Background

Microtropia is a small angle strabismus of less than or equal to ten prism diopters. It often co-exists with anisometropia, and patients may require amblyopia treatment. Diplopia following amblyopia treatment is considered rare, but older literature can advise caution when treating amblyopia in microtropia. This study aimed to explore orthoptists' opinions on amblyopia treatment in microtropia.

Methods

Orthoptists working in Scandinavia were invited to complete an online questionnaire regarding their views on amblyopia treatment. They were presented with three different clinical scenarios: 1) patient with anisometropia; 2) patient with anisometropia and microtropia with identity; and 3) patient with anisometropia and microtropia without identity.

Results

The questionnaire received responses from 30 orthoptists, which were analysed. The results showed a significantly higher concern for diplopia in patients with microtropia undergoing amblyopia treatment than in patients with anisometropia. They responded that to prevent diplopia, it is more important to stop amblyopia treatment before equal visual acuity (VA) is reached in microtropia compared to anisometropia. Thus, amblyopia treatment was stopped more often in microtropia, even if VA was improving and diplopia was absent. Equal VA was perceived to be more difficult to achieve in microtropia, both with and without identity, compared to anisometropia.

Conclusion

Despite more recent evidence that diplopia following amblyopia treatment is extremely rare, orthoptists working in Scandinavia reported more concerns about diplopia when treating amblyopia in microtropia than in anisometropia. Stopping amblyopia treatment in microtropia before equal VA was achieved was considered somewhat important to prevent diplopia. Orthoptists also reported that equal VA was difficult to achieve in patients with microtropia, both with and without identity. Further research would help improve the evidence and inform clinical decisions about microtropia and amblyopia treatment in microtropia.

Feasibility of a new 'balanced binocular viewing' treatment for unilateral amblyopia in children aged 3-8 years (BALANCE): results of a phase 2a randomised controlled feasibility trial

OBJECTIVES

This study aimed to evaluate the safety of dichoptic balanced binocular viewing (BBV) for amblyopia in children, plus feasibility, adherence, acceptability, trial methodology and clinical measures of visual function.

DESIGN

We carried out an observer-masked parallel-group phase 2a feasibility randomised controlled trial.

SETTING

Two study sites, a secondary/tertiary and a community site.

PARTICIPANTS

We enrolled 32 children aged 3-8 years with unilateral amblyopia who had completed optical adaptation where indicated. 20 children attended the 16-week exit visit (retention 63%).

INTERVENTIONS

Children were randomised to BBV (movies customised to interocular acuity difference at baseline) for 1 hour a day (active intervention) or standard management as per parental choice (part-time occlusion or atropine blurring, control). All interventions were used at home, daily for 16 weeks.

PRIMARY OUTCOME MEASURE

'VacMan suppression test' of interocular balance at 16 weeks from randomisation.

SECONDARY OUTCOME MEASURES

feasibility outcomes (recruitment and retention ratios, adherence with the allocated intervention); safety outcomes at other time points (changes in prevalence of diplopia, manifest strabismus, suppression/interocular balance on a range of tests); efficacy outcomes (clinical measures of visual function, such as best-corrected visual acuity, BCVA). Outcome measures were identical to those planned in the protocol.

RESULTS

Primary outcome: At baseline, values for the interocular balance point were higher (indicating greater suppression of the amblyopic eye) in the occlusion group than in the BBV group. These values shifted downwards on average for the occlusion group, significantly decreasing from baseline to week 16 (t8=4.49, p=0.002). Balance values did not change between baseline and week 16 for the BBV group (t9=-0.82, p=0.435). At 16 weeks, there was no statistical difference in interocular balance/suppression change over time between the two arms. The difference at follow-up between the arms, adjusted for baseline, was -0.02 (95% CI -0.28 to 0.23, p=0.87).

FEASIBILITY

We prescreened 144 records of potentially eligible children. Between 28 October 2019 and 31 July 2021, including an interruption due to the COVID-19 pandemic, 32 children were screened and randomised (recruitment rate 22%), 16 to BBV and 16 to standard treatment. 20 children attended the 16-week exit visit (retention 63%). Mean adherence with BBV as proportion of viewing time prescribed was 56.1% (SD36) at 8 and 57.9% (SD 30.2) at 16 weeks. Mean adherence with prescribed occlusion time was 90.1% (SD 19.7) at 8 and 59.2% (SD 24.8) at 16 weeks.

SECONDARY SAFETY/EFFICACY OUTCOMES

One child in the BBV arm reported transient double vision, which resolved; two reported headaches, which led to withdrawal. BCVA improved from mean 0.47 (SD0.18) logMAR at randomisation to 0.26 (0.14) with standard treatment, and from 0.55 (0.28) to 0.32 (0.26) with BBV. Outcomes at 16 weeks did not differ between treatments.

PARTICIPANT EXPERIENCE

Families were generally positive about BBV, but families found both patching and BBV difficult to integrate into family routines.

CONCLUSIONS

Recruitment rates indicate that a future phase 3 trial will require multiple sites or a longer enrolment period. Retention and adherence rates were lower than anticipated, which will influence future study designs. Dichoptic treatment may be equal to occlusion treatment in safety and efficacy; headaches may lead to discontinuation. Integration into family routines may constitute a barrier to implementation.

TRIAL REGISTRATION NUMBER

NCT03754153.

Computer vision-based system for early diagnosis of stereoscopic vision alterations

Stereopsis is the three-dimensional perception capability, which is possible when binocular vision is present. Development of binocular vision system ends around 7-year-old, and after this time brain connections are already set, therefore, it will be difficult to recover stereopsis. Early diagnosis of Stereoscopic Visual Alterations (SVA) in the childhood is paramount to receive an appropriate treatment as soon as possible. Currently, to detect SVA, ophthalmologists commonly carry out tests based on cards. All these tests are based on the random-dot-stereogram principle, with different seconds of arc images, which allows doctors to graduate stereopsis. Some limits of this tests have been identified, such as monocular clues (e.g., the contours of the objects), or the non-standardized range levels depending on the test. This paper presents a novel concept of measuring stereopsis based on computer vision techniques. The system detects SVA in patients and calculates the degree of the perceived depth. As early diagnosis of SVA may suppose a therapeutic possibility, this platform is aimed at children by using stereoscopic models with varied and attractive designs. To validate the proposal, an early-stage prototype has been implemented and an objective evaluation of the measurement accuracy and reliability has been carried out with satisfactory results.

Phase 2a randomised controlled feasibility trial of a new 'balanced binocular viewing' treatment for unilateral amblyopia in children age 3-8 years: trial protocol

INTRODUCTION

Treatments for amblyopia, the most common vision deficit in children, often have suboptimal results. Occlusion/atropine blurring are fraught with poor adherence, regression and recurrence. These interventions target only the amblyopic eye, failing to address imbalances of cortical input from the two eyes ('suppression'). Dichoptic treatments manipulate binocular visual experience to rebalance input. Poor adherence in early trials of dichoptic therapies inspired our development of balanced binocular viewing (BBV), using movies as child-friendly viewable content. Small observational studies indicate good adherence and efficacy. A feasibility trial is needed to further test safety and gather information to design a full trial.

METHODS/ANALYSIS

We will carry out an observer-masked parallel-group phase 2a feasibility randomised controlled trial at two sites, randomising 44 children aged 3-8 years with unilateral amblyopia to either BBV or standard occlusion/atropine blurring, with 1:1 allocation ratio. We will assess visual function at baseline, 8 and 16 weeks. The primary outcome is intervention safety at 16 weeks, measured as change in interocular suppression, considered to precede the onset of potential diplopia. Secondary outcomes include safety at other time points, eligibility, recruitment/retention rates, adherence, clinical outcomes. We will summarise baseline characteristics for each group and assess the treatment effect using analysis of covariance. We will compare continuous clinical secondary endpoints between arms using linear mixed effect models, and report feasibility endpoints using descriptive statistics.

ETHICS/DISSEMINATION

This trial has been approved by the London-Brighton & Sussex Research Ethics Committee (18/LO/1204), National Health Service Health Research Authority and Medicines and Healthcare products Regulatory Agency. A lay advisory group will be involved with advising on and disseminating the results to non-professional audiences, including on websites of funder/participating institutions and inputting on healthcare professional audience children would like us to reach. Reporting to clinicians and scientists will be via internal and external meetings/conferences and peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03754153.

The effect of induced monocular blur by bangerter filters on measures of visual acuity and stereoacuity

To evaluate the effect of monocular blur induced by Bangerter filters (BF) on visual acuity (VA) and stereoacuity. Monocular blur was induced by a range of Trusetal BF strengths (0.1, 0.2, 0.4, 0.6) to 23 visually normal adult volunteers (aged 18-25, mean age 20.33 ± 1.79 years). The right monocular and binocular logMAR VA and distance stereoacuity using the FD2 were measured at 6 m with no filter (baseline) and with each filter strength. The order of testing the filters was randomized. Results were analyzed using one factor repeated measures ANOVAs, t-tests using Bonferroni correction and Pearson's product moment correlation. All filters degraded right monocular distance VA from baseline, but less significantly between the 0.4 and 0.6 filters than the other filters (p < .05 and p < .001, respectively). Degradation was in concordance with the labeled filter density, excluding filter strength 0.4. For all filter strengths, binocular VA was significantly but not clinically reduced from baseline (p < .05). Filters statistically and clinically significantly degraded distance stereoacuity from baseline (p < .001). A significant negative correlation existed between the mean degraded right monocular VA and stereoacuity (r = -0.998, p < .02). Trusetal BF significantly reduced monocular VA and stereoacuity but binocular VA remained within normal levels. The impact on VA and stereoacuity in a normal population can be of clinical relevance when applied to the use of BF for management of amblyopia and intractable diplopia. It is advised that clinicians ensure the desired level of degradation has been achieved in clinic before prescribing a particular filter strength.

Reverse exercises in a case of intractable diplopia

The aim of this presentation is to highlight how orthoptic exercises can be adapted from the standard implementation and gain results in an intractable diplopia case. A 16-year-old male presented with a 20 prism diopters residual right esotropia and intractable diplopia following Surgery and Botulinum Toxin. Having had further BT and surgery ruled out and no success with Fresnel prisms or occlusion, he commenced on standard orthoptic exercises without success. Additional orthoptic assessment discovered that the patient could achieve binocular single vision (BSV) on convergence at 10 cm. The patient then proceeded on a course of exercises to help extend this area of BSV. These exercises included a reverse dot card and a variation of the distance cat stereogram. Over the next couple of visits, the area of binocularity was extended to 30 cm and the esotropia measured 18 prism diopters. However, the patient felt that progress was slow, and they were keen to learn to drive and so opted for an occlusive contact lens instead. It is unfortunate that the patient did not continue with the exercise program as it showed potential to increase his area of BSV. However, this case does demonstrate how utilizing current knowledge concepts of both exercises and BSV, and adapting them to a specific patient could lead to improvement in the likes of intractable diplopia and be a potential management option.

Grey Filter Contact Lens as Therapeutic Option for Acquired Reduced Binocular Visual Performance

Disturbing binocular problems can be too complex to be treated in such a way that comfortable binocular single vision is restored. The grey filter contact lens could offer a safe and clinically useful way to help these patients.

A dichoptic feedback-based oculomotor training method to manipulate interocular alignment

Strabismus is a prevalent impairment of binocular alignment that is associated with a spectrum of perceptual deficits and social disadvantages. Current treatments for strabismus involve ocular alignment through surgical or optical methods and may include vision therapy exercises. In the present study, we explore the potential of real-time dichoptic visual feedback that may be used to quantify and manipulate interocular alignment. A gaze-contingent ring was presented independently to each eye of 11 normally-sighted observers as they fixated a target dot presented only to their dominant eye. Their task was to center the rings within 2° of the target for at least 1 s, with feedback provided by the sizes of the rings. By offsetting the ring in the non-dominant eye temporally or nasally, this task required convergence or divergence, respectively, of the non-dominant eye. Eight of 11 observers attained 5° asymmetric convergence and 3 of 11 attained 3° asymmetric divergence. The results suggest that real-time gaze-contingent feedback may be used to quantify and transiently simulate strabismus and holds promise as a method to augment existing therapies for oculomotor alignment disorders.

Near-infrared transmitting occlusive intraocular lens implantation for intractable diplopia: Report of two cases

OBJECTIVE

The objective of this article is to report two cases of black occlusive intraocular lens and implantation for treating intractable diplopia.

CASE DESCRIPTIONS

Two patients with intractable diplopia after orbitofacial, trauma, and surgical removal of pituitary adenoma failed to conservative management. After uneventful cataract, phacoemulsification, a black intraocular lens was implanted in every case. In both cases, a complete degree of satisfaction was achieved, with no symptoms of diplopia, and no complications have been observed in their follow-up. The use of optical coherence tomography has been possible in both cases to assess the macula and optic nerve, since a fundoscopy is not possible in such cases.

CONCLUSION

Implantation of a near-infrared transmitting occlusive intraocular lens for treating intractable diplopia provided a complete resolution of symptoms without eliminating the possibility of examining macula and optic nerve using optical coherence tomography.

'It's too late'. Is it really? Considerations for amblyopia treatment in older children

In recent years, media coverage has demonstrated instances in which families of children aged 7 and older, newly diagnosed with strabismic and/or anisometropic amblyopia through community eyecare services, were told it was 'too late' for their child to effectively respond to conventional amblyopia treatment (occlusion or atropine penalisation). Formal guidance pertaining to binocular vision anomalies from eyecare professional bodies does not specifically make reference to a child's age, beyond stating the importance of early diagnosis and treatment of strabismus/amblyopia. However, there have been many changes in the way we view the recovery period for amblyopia, and it is well demonstrated both within literature and clinical practice that conventional treatment can improve amblyopic eye visual acuity in children beyond the age of 7 years. The occurrence of these media described cases within the community eyecare sphere would suggest it is worthwhile revisiting the literature on the subject of amblyopia treatment in older children (aged 7+ years), to address misconceptions and place in the spotlight current considerations facing clinicians when treating newly diagnosed amblyopia within this age group. This perspective review provides an evidence-based update covering the various considerations associated with treatment of amblyopia in older children, along with recent amblyopia treatment advances that could have an impact on treatment prospects for this patient group. Considerations include the risks, benefits and efficacy of treating newly diagnosed amblyopia in older children, monitoring density of suppression to mitigate intractable diplopia risk, and recent findings regarding binocular treatments for amblyopia.

IOL-Induced Extreme Blur to Alleviate Intractable Diplopia Secondary to Dragged-Fovea Diplopia Syndrome

A 73-year-old male presented with one year of intractable binocular diplopia and metamorphopsia in the right eye. He was unable to maintain fusion with prismatic correction, refused cosmetically noticeable forms of occlusion, and was not an occlusive contact lens candidate due to chronic neuropathy affecting his hands. The patient underwent cataract surgery with placement of a high plus intraocular lens to induce extreme blur. The uncomplicated procedure was successful in eliminating his diplopia. Cataract extraction with a high minus refractive target is an option for treating intractable diplopia associated with dragged-fovea diplopia syndrome.

Stereopsis: are we assessing it in enough depth?

The assessment of stereoacuity is an integral part of the ophthalmic assessment, with the responses used to inform clinical management decisions. Stereoacuity impacts on many aspects of life, but there are discrepancies reported where people without measurable stereoacuity report appreciating 3-D vision. This could be due, in part, to the presentation of the stimuli. A literature review was undertaken to evaluate current assessment techniques, how they relate to patient outcomes, identify the limitations of current tests and discuss how they could be improved. Recent evidence has been collated on currently available tests, used commonly within vision clinics, with normative data provided allowing responses to the tests to be interpreted. The relevance of the results is evaluated in relation to a range of outcomes, where a reduced level of stereopsis has a negative impact on the ability of an individual to perform many tasks, and can lead to an increase in difficulty interacting in the world. Current tests are limited in the aspects of stereoacuity they assess and their ability to precisely measure stereopsis. The world is not static, yet clinical tests are limited to measuring static stereoacuity, even though higher grades of depth perception can be identified in the presence of changing depth. Presentation methods of stereoacuity tests have remained similar over time, with a limited number of disparity levels assessed. New assessment methods are becoming available that include automated staircase testing to present multiple levels of disparity using digital technology. Current clinical tests are limited in their presentation, and are poor at detecting/measuring stereoacuity in those with limited stereopsis. Given the relevance of the stereoacuity measurement to management choices and functional outcomes, new testing methods would be beneficial to fully assess stereoacuity, both static and dynamic.