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D. Newsham, A. R. O'Connor; Intractable Diplopia Resulting from the Treatment of Amblyopia and Use of the Sbisa Bar in the UK to Assess the Risk. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4347.
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© ARVO (1962-2015); The Authors (2016-present)
The Sbisa bar (Bagolini filter bar) is a method of assessing the density of suppression, thereby determining the risk of inducing intractable diplopia in patients without binocular functions who are receiving amblyopia treatment. Despite anecdotal evidence of its widespread use in the UK, other than a small retrospective study, no research has been undertaken to indicate how the results of the test should be interpreted to guide management. The aim of this study was to obtain an estimate of the frequency of intractable diplopia resulting from amblyopia treatment in the UK and determine current practice of the test among orthoptic practitioners.
A questionnaire was constructed to assess the occurrence of intractable diplopia, interpretation of the results for the management and communication/documentation of the risks to parents. The questionnaire was emailed to Head Orthoptists in every UK Eye Department, with the option of completing a copy by email/post or alternatively online via a web survey.
A satisfactory response rate of 51% was obtained. Intractable diplopia was a rare occurrence with (in the preceding 5 years) 91% reporting no cases, 6% 1 case, 2% 2 cases and 1% 3 cases. Assuming the same rate in responders and non-responders, it is estimated that there were 24 cases in the UK in the last 5 years. The youngest age at which the Sbisa bar would be used ranged from 2 to 8 years, with 6 years being the most common (45.6%). The minimum filter considered by most to be safe to continue with treatment was 7 (26.7%), though there was considerable variability (filter range 0-17; mean±sd:8.6±2.9). If patients reported diplopia on higher filters (>10); 38% continued to prescribe the same amount of occlusion, 5% increased the amount, 48% reduced the amount and 9% changed to atropine. Six percent of clinicians do not use the Sbisa bar at all. When patients are being monitored with the Sbisa bar the mean (weeks ±sd) interval between clinic visits (6.1±1.8) was reduced compared to that of routine amblyopia visits (7.1±1.5; p=0.001).The risk of intractable diplopia was not advised by 8% and not always documented by 30% of clinicians.
The prevalence of intractable diplopia though relatively small has substantial quality of life implications for the individuals affected. It is clear that a lack of research evidence to guide clinicians as to when it is still safe to occlude in amblyopes without binocularity has resulted in a large variation in practice. This could lead to preventable cases of intractable diplopia where the risk has not been established or interpreted accurately.
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