What is the purpose of testing visual acuity with a pinhole?

Testing visual acuity with a pinhole primarily serves to differentiate refractive errors from eye diseases affecting vision. When a patient looks through a pinhole apparatus, the smaller aperture reduces the effects of refractive errors, such as myopia (nearsightedness) or hyperopia (farsightedness), allowing clearer vision by essentially letting only the central rays of light in through the pupil. If the patient's vision improves while using the pinhole, it suggests that a refractive error is present, and optical correction may be beneficial.

This method does not directly assess for eye diseases, color vision, or contrast sensitivity. Eye diseases may cause vision loss that is not improved with pinhole testing, indicating a more serious underlying problem unrelated to refractive errors. Assessing color vision and measuring contrast sensitivity require different testing methodologies altogether, focusing on other aspects of visual function rather than simply clarifying visual acuity in relation to refractive errors.