Treatment with Bangerter filters

Abstract

A mblyopia is the most common cause of monocular visual dysfunction in children in Western countries. Patching is an effective treatment; however, it often fails because of inadequate compliance on the part of the patient. Therefore, more acceptable treatments are sought. Bangerter filters (Ryser Optik, St. Gallen, Switzerland) have been used in Europe since they were introduced approximately 50 years ago, particularly as secondary treatment after patching and to wean patients from occlusion therapy. The filters, which are attached to the back of the spectacle lens of the sound eye and worn full-time, have a selection of filter densities that are designed to reduce visual acuity to a range of 20/20 to\20/200. A filter that reduces the vision in the sound eye below the vision in the amblyopic eye usually is selected. The filter density can be selected by the use of a Bangerter foil bar to increase filter density until the patient switches fixation. Recent studies have shown that Bangerter filters are useful either as aprimary or alternative treatment in cases inwhich amblyopia therapywith patching no longer provides benefit. The filters can also be used to treat adults with diplopia. Two articles In this issue of the Journal of AAPOS evaluate different aspects of treatment with Bangerter filters. The authors of both studies are to be commended for their contributions toward improving patient care. Concerns regarding Bangerter filters are that visual degradation does not correspond to predicted levels, the filtersmay fade with wear, and the degradation in visual acuity does not remain stable over time.ThePediatricEyeDisease Investigator Group (PEDIG) investigated these questions in their study, which was part of a previously published randomized trial inwhich186 amblyopic children (average age, 6.3 years) were randomized to either Bangerter filters or patching. The authors found that the filtering effect degraded and the amount of degradationdecreasedwith 6weeks ofwear.However, because the first follow-up visit was at 6 weeks, it is unknown when the degeneration began. A future study with shorter follow-up intervals may provide an answer. With this study, it seems wise to evaluate visual acuity in the sound eye through the Bangerter filter at treatment onset and at each follow-up visit to determine the appropriate