A pinhole occluder is an opaque disk with one or more small holes through it, used by ophthalmologists, orthoptists and optometrists to test visual acuity.

The occluder is a simple way to focus light, as in a pinhole camera, temporarily removing the effects of refractive errors such as myopia.

In this way, the ophthalmologist, orthoptist or optometrist can estimate the maximum improvement in a patient's vision that can be attained by lenses to correct errors of refraction.

[2] This can be used to distinguish visual defects caused by refractive error, which improve when the occluder is used, from other problems, which do not.

Squinting and looking through a tiny hole made with a finger works similarly to a pinhole occluder, by blocking light through the outer parts of the eye's lens.