Use of Bangerter filters with adults having intractable diplopia

Gaze behaviour during multiple object tracking is dependent on binocular vision integrity

INTRODUCTION

Despite the critical importance of binocular vision integrity in daily activities, there exists limited understanding of how alterations in binocular vision integrity impact gaze behaviour during dynamic, complex psychomotor skills. This study aimed to measure how alterations in binocular vision integrity, created by Bangerter filters (BF), affect gaze behaviour during multiple object tracking (MOT).

METHODS

During the experiment, 22 volunteers completed the MOT task under three different visual conditions. The first condition involved natural binocular viewing, while the second and third conditions used 0.4 and 0.2 neutral density BF, respectively, resulting in monocular blur in the sensorially dominant eye. During the MOT task, participants were instructed to track three of eight balls for 10 s, and the speed was adjusted using a staircase procedure. Throughout the task, the following gaze parameters were recorded: fixation duration, saccade duration, amplitude and frequency as well as blink rate.

RESULTS

During MOT execution, participants employed three gaze strategies regardless of viewing conditions: saccadic movements were predominant, followed by maintaining fixation on a central location throughout the trial and to a lesser extent, smooth pursuit eye movements. There was a significant effect of manipulating viewing conditions on the MOT scores (p = 0.046, η2  = 0.09). As the viewing conditions became more difficult, we observed a decrease in fixation duration (p = 0.004, η2  = 0.16) and blink rate (p < 0.001, η2  = 0.20) and an increase in saccadic amplitude (p < 0.001, η2  = 0.29).

CONCLUSIONS

The results support the notion that perceptual-cognitive skills depend on the integrity of binocular vision, underscoring the sensitivity of gaze behaviours to any impairment of binocular function.

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.

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.

'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.

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.

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

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.

Diplopia and driving: a problematic issue

The aim of this article was to review the literature regarding diplopia and driving license and to review the West European legislations about this topic, in order to obtain appropriate indications for hospitals specialists and patients. A systematic review of articles published about diplopia and driving was performed. In addition a review of West European national legislations about driving license regulations for medical illnesses was performed, in addition to the European Union Directive on driving licenses. In the literature, the presence of diplopia has not been considered a reliable predictor of the safety of driving behavior, or it has not appeared to be a contraindication for driving according to some authors who were unable to demonstrate significant differences on driving simulator performance between subjects with chronic stable diplopia and control subjects. Nevertheless, in all western European legislations, acute diplopia constitutes an important limitation for driving, thus making the knowledge of current regulations fundamental for specialists involved in managing patients with diplopia. Ophthalmologists and maxillofacial/head and neck surgeons, may advise patients before hospital discharge about current legislations in their respective countries.

Identifying potential themes for the Child Amblyopia Treatment Questionnaire

PURPOSE

Patient-reported outcome (PRO) instruments are increasingly common in both clinical practice and research. The data obtained from these instruments can be used to help inform decision making and policy-making decisions. The methodological approaches undertaken in developing PROs is not frequently reported. Literature on the development of the descriptive systems for PROs is sparse in comparison with that on the assessment of the psychometric properties of such instruments. The purpose of this study is to describe the results of qualitative interviews conducted to identify potential themes for the Child Amblyopia Treatment Questionnaire (CAT-QoL), a pediatric disease-specific health-related quality of life instrument for amblyopia designed for children aged 4 to 7 years.

METHODS

Semistructured interviews were undertaken with 59 children (aged 3 years 9 months to 9 years 11 months; average, 6 years 3 months) with amblyopia. The interviews were transcribed verbatim and imported into QSR NVivo 8. Interview transcripts were analyzed to identify potential items to be included in the descriptive system. Thematic content analysis was undertaken using Framework.

RESULTS

Eleven potential themes were identified for inclusion in the CAT-QoL instrument, namely, physical sensation of the treatment, pain, being able to play with other children, how other children have treated them, ability to undertake schoolwork, ability to undertake other tasks, sad or unhappy, cross, worried, frustrated, and feelings toward family members.

CONCLUSIONS

Children are able to identify their thoughts and opinions of their own health and to describe what impact their amblyopia treatment has had on their daily lives. Themes for the draft descriptive system for a pediatric self-reported amblyopia QoL instrument have been identified. A draft version of the CAT-QoL instrument has been developed. Further research is required to refine and assess the psychometric properties of the instrument.

Nonsurgical management of diplopia

Diplopia is a potential undesirable outcome of nearly any ocular surgery. In some cases, the unexpected strabismus and diplopia resolve quickly without intervention, especially if due to swelling or minor insult from the surgical procedure. When double vision persists, effective treatment may be more elusive in patients in which the strabismus is the result of a restrictive process. The sudden onset of strabismus makes treatment more challenging. Frequently these patients will require surgical intervention. Where possible, patients may be managed with nonsurgical treatments until the time of surgery or indefinitely if successful and acceptable to the patient. Diplopia has been documented as a result of restrictive strabismus following vitreoretinal surgery, glaucoma surgery, orbital decompression surgery, strabismus surgery, orbital surgery, conjunctival surgery, cataract surgery, blepharoplasty, and others. The treatment of diplopia after ocular surgery is complicated by the incomitance and torsion that may be associated with restrictive strabismus as well as the variability of the deviation during healing. Nonsurgical treatment options include prisms or occlusion. Fresnel prisms are used primarily, but occasionally the prism is ground into the spectacles. Occlusion of the involved eye may be partial or complete, using a "pirate" patch, adhesive patch, Bangerter foil, tape, or related method.

Visual acuity through Bangerter filters in nonamblyopic eyes

PURPOSE

To describe the amount of visual acuity degradation induced by Bangerter filters in the better seeing eye and to evaluate its stability over time in children with moderate amblyopia.

METHODS

Visual acuity with and without a Bangerter filter was measured in the nonamblyopic eye of 186 children with moderate amblyopia who were then treated with either patching or the Bangerter filters. A 0.2 filter was used for amblyopia of 20/80 and a 0.3 filter for amblyopia from 20/40 to 20/63. For the 89 children randomized to Bangerter filters, visual acuity was also measured in the nonamblyopic eye with and without the filters at both 6 weeks and 12 weeks after initiating treatment.

RESULTS

Mean degradation in visual acuity of the nonamblyopic eye at baseline was 5.1 logMAR lines with the 0.2 filter and 4.8 logMAR lines with the 0.3 filter. The degradation with each filter did not always agree with the manufacturer's specifications. Over time, the amount of degradation with the filters decreased.

CONCLUSIONS

The 0.2 and 0.3 Bangerter filters degrade nonamblyopic eye visual acuity sufficiently in amblyopic children. Because the amount of degradation decreases over time, it is recommended to periodically apply a new filter when using this type of amblyopia treatment.