attenuation
Attenuation is a form of occlusion therapy for amblyopia in which a translucent occluder reduces the acuity of the dominant eye without blocking that eye completely.1,2 The usual device is the Bangerter foil, a frosted press-on film that adheres to a spectacle lens in the way a Fresnel lens does.1 The foils come in a series of increasing opacity and are graded by the decimal visual acuity typically obtained through each one.1
The foil is attached to the back of the spectacle lens before the dominant eye.2 Acuity in that eye is gradually reduced, and the child becomes accustomed to the occluder.2 Treatment can then be tapered off by reducing the density of the foil.2 Bangerter foils seem to work well in amblyopes with acuity of 6/18 (20/60) or better, and in anisometropic amblyopia they allow coarse stereopsis to be maintained.1
An inexpensive translucent occluder can also be made by sticking tape onto an ordinary spectacle lens.3 Bangerter foils are used for intractable diplopia as well, where the goal is to step down gradually until the patient is comfortable with no filter or an almost clear one.3
Sources (7)
- Pickwell's Binocular Vision Anomalies, ch. 13
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 24
- Pickwell's Binocular Vision Anomalies, ch. 14
- Beneish, R.G. et al. (2006) 'Occlusion Therapy for Amblyopia: Optimizing Compliance', Investigative Ophthalmology & Visual Science, 47(13), p. 2460.
- Laria, C., Piñero, D.P. and Alió, J.L. (2011) 'Characterization of Bangerter filter effect in mild and moderate anisometropic amblyopia: predictive factors for the visual outcome', Graefe's Archive for Clinical and Experimental Ophthalmology, 249(5), pp. 759–766.
- Pediatric Eye Disease Investigator Group (2019) 'A Randomized Trial of Levodopa as Treatment for Residual Amblyopia in Older Children', Ophthalmology, 126(3), pp. 456–464.
- Rutstein, R.P. et al. (2010) 'Comparison of Bangerter filters and patching for the treatment of moderate amblyopia', Optometry - Journal of the American Optometric Association, 81(10), pp. 527–533.
Reviewed October 2026