Pinhole occluder

A pinhole occluder is an opaque disk with small holes used to assess visual acuity in ophthalmology and optometry. It works by focusing light like a pinhole camera, temporarily eliminating the effects of refractive errors such as myopia. It helps estimate the potential visual improvement achievable with corrective lenses and distinguish refractive problems from other causes of vision loss. It can also be used in patients with dilated pupils. The effect is similar to squinting or looking through a small hole made with the fingers. This principle has also been applied to pinhole glasses as an alternative to conventional lenses.

This specific device is easy to print and assemble, and it folds for convenient portability.