Methods to Quantify Suppression in Amblyopia: A Scoping Review

PURPOSE: Suppression is the cortical inhibition of visual information from one eye. This scoping review identifies and collates the different methods, techniques, and tools used to measure and quantify suppression in the clinical management of amblyopia. METHODS: PRISMAScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses - Scoping Reviews) guidelines were followed to include peer-reviewed papers that describe methods to quantify suppression in patients with amblyopia. RESULTS: From 75 included papers, results show that suppression quantification is feasible in children as young as 3-years old. Only three randomized clinical trials have used suppression as a quantified outcome measure. Methodologies are broadly categorized by target size, electrophysiology, or contrast. Common clinical tools are primarily size-based (e.g. the worth four-dot test at varying distances) or contrast-based (e.g. neutral density filters). Conversely, most experimental assessments are software-driven contrast-based paradigms such as dichoptic motion coherence tests. CONCLUSION: Clinical implementation of suppression quantification remains limited. However, available clinical tools for quantifying suppression on a fine-graded continuous scale are minimal. Such finer tools for the quantification of suppression are used in lab-based research and are yet to be made commercially available. Future studies should focus on developing better clinical tools for quantifying suppression.