defocus aberration is the effect of the pinhole on visual acuity testing.
defocus aberration is the effect of the pinhole on visual acuity testing.
what is the effect of the pinhole on visual acuity testing?
defocus aberration
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. because light passes only through the center of the eye's lens, defects in the shape of the lens (errors of refraction) have no effect while the occluder is used. 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. 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. the pinhole occluder can also be used in testing visual acuity in mydriatic patients. in this case the pinhole occluder compensates for the inability to contract the iris assisting the eye in obtaining a retinal projection similar to that of a non-cycloplegic eye.
pinhole occluder
bullet::::- sc: (latin "sine correctore") without correctors.









































bullet::::- pinhole occluder









































bullet::::- the abbreviation ph is followed by the visual acuity as measured with a pinhole occluder, which temporarily corrects for refractive errors such as myopia or astigmatism.









































so, distant visual acuity of 6/10 and 6/8 with pinhole in the right eye will be: dscod 6/20 ph 6/8. distant visual acuity of count fingers and 6/17 with pinhole in the left eye will be: dscos cf ph 16/17. near visual acuity of 6/8 with pinhole remaining at 6/8 in both eyes with spectacles will be: nccou 6/8 ph 6/8.
visual acuity