occluder

An occluder is any device or object that blocks all or part of a light beam or line of sight between a source and a detector or observer. The term is used across disciplines to describe objects that serve to obscure, shield, or regulate visibility.

In vision science and ophthalmology, occluders are used both experimentally and clinically. In psychophysics experiments, opaque or translucent shields block parts of a visual scene to control stimulus location and luminance. Clinically, occluders such as eye patches are used for occlusion therapy to treat amblyopia by depriving the dominant eye of input. Occluders also appear in diagnostic testing to cover one eye during binocular assessments.

In computer graphics and real-time rendering, occluders are geometric primitives used in occlusion culling and shadow computations. An occluder geometry is used to determine which scene elements are hidden from the camera, allowing the renderer to avoid drawing them, improving performance.

In astronomy, an occluder is any body that blocks light from a distant source, such as a Moon occulting a star during an occultation, or a planet occluding a star during a transit. The term highlights the role of the secondary body in diminishing the observed light.

In interventional medicine, occluders are devices that temporarily block a blood vessel to stop bleeding or to isolate a lesion during procedures. Examples include vascular occlusion balloons and occluder plugs used in endovascular or surgical contexts.