Does the pinhole test's hole improve visual acuity in keratoconus?

The pinhole test uses a 1.0 mm hole in an opaque disk to determine how much of a visual problem is due to a "refractive error" rather than ocular pathology (like cataract or macular degeneration). It works by limiting the oncoming rays of light to the narrow, diffractive rather than refractive level (like nearsightedness and astigmatism). It definitely works in keratoconus as well where even the refractive error can be distorted and so cannot be fully corrected with glasses.

_Written by J. Trevor Woodhams, M.D. - Chief of Surgery, Woodhams Eye Clinic