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Pinhole Visual Acuity
PURPOS To determine if a decrease in vision is correctable by lenses．Viewing the acuity chart through a pinhole will increase the patient’s depth of focus and decrease the retinal blur．If the retina and visual pathway are free of abnormalities the patient’s acuity will improve．
INDICATIONS
Pinhole acuities are taken when the VA is worse than 20/30 at distance and near through the habitual or induced correction．
EQUIPMENT
·Projector with visual acuity slide or wall mounted acuity chart．
·Pinhole disc(PH)．
·Occluder．
SET-UP
·The patient wears his distance correction while looking at the distance VA chart．
·Pinhole acuities are taken only at distance．
STEP-BY-STEP PROCEDURE
1．The patient is asked to occlude the eye not being tested．If both eyes are to be tested，test the right eye first．
2．Instruct the patient to position the PH disc until the chart is as clear as it will get and then read the smallest line of letters he can．
3. Encourage the patient to read the next smallest line, even if he has to guess. Continue until the patient has missed more than half the letters on a line.
RECORDING
·Write “PH” followed by the visual acuity．This notation is usually recorded next to the distance VA through correction．
·PHNI may be used to indicate no improvement in VA with the pinhole．
EXAMPLES
·VAcc OD： 20/50+2 PH：20/30+2
OS： 20/40 PH：20/25
·Vsc OD： 20/40+1 PHNI
OS： 20/100 PH：20/50
EXPECTED FINDINGS
·If the cause of the patient’s decreased acuity is due to an uncorrected refractive error，the visual acuity is expected to improve through the pinhole．
· If the cause of decreased acuity is not optically based，no improvement, and possibly a decrease，will occur through the pinhole．
·A refraction should improve the acuity level of the patient at least to the level obtained through the pinhole． |
