Abstract
Aim: The density of suppression is often assessed in children undergoing amblyopia treatment. The pur- pose of this study was to assess the repeatability of the Sbisa bar to measure density of suppression by the same and different observers. Methods: A prospective repeated measures study was performed on participants aged 5–16 years. Partici- pants with constant suppression due to strabismus had the Sbisa bar test performed twice by one observer and once by a second observer with a period of 15 minutes between each test. Results: Thirty participants were recruited with a mean age 7.3 years (range 5.1–15.1 years). Median filter value for the first test was 15 (interquartile range (IQR) 14–17), for the second test was 15 (IQR 13–17) and for the third test was 14 (IQR 13–17). Interclass correlation coefficient was 0.70 (95% CI 0.46 to 0.85) for the same observer and 0.73 (95% CI 0.44 to 0.87) for different observers. Inter-rater repeatability coefficient, k , was 0.32, SE 0.11 (95% CI 0.10 to 0.54). There was no correlation between the median filter value from the first observer’s tests with age ( R = 0.08), visual acuity in the amblyopic eye ( R = 0.01) or visual acuity difference ( R = 0.01). Conclusions: The results show that in patients with suppression > filter 10 the Sbisa bar is repeatable within one to three filters when assessed by the same or different observers. There is no correlation between density of suppression and visual acuity or age.
Highlights
The Bagolini filter bar or Sbisa bar was developed by Bagolini in 1957 as a series of red filters in a ladder arrangement.[1]
There is no correlation between density of suppression and visual acuity or age
In a retrospective audit[5] of the use of the Sbisa bar in children results indicated that the reliability of the Sbisa bar in predicting diplopia following amblyopia treatment is questionable
Summary
The Bagolini filter bar or Sbisa bar was developed by Bagolini in 1957 as a series of red filters in a ladder arrangement.[1]. It is used to investigate the density of suppression in Correspondence and offprint requests to: Laura Crawford, Orthoptic. Sbisa bar in front of the patient’s fixing (non-strabismic) eye and the filters are gradually increased; this reduces illumination to the fixing eye to induce diplopia or a fixation swap to the previously suppressing eye.[3]. A comparison between patients who demonstrated diplopia during Sbisa bar testing and those who did not, showed that the age of onset of occlusion, duration of occlusion and starting visual acuity were not significantly different.[5] There have been no reports of correlation between age and density of suppression; it has been found that those reporting diplopia had a better initial visual acuity.[5,6]
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