Patient History, Visual Acuity, and Basic Testing
Core concepts
A structured history captures chief complaint, ocular and medical history, medications, allergies, family history, and social history, then the classic symptom descriptors: onset, duration, laterality, severity, and associated symptoms. For visual acuity, know Snellen notation, the 20/20 reference, the meaning of the numerator (test distance) and denominator (distance at which a normal eye sees that line), and when to use pinhole (to distinguish refractive from pathology-related loss). Understand near acuity cards, contrast sensitivity, color vision plates, Amsler grid, confrontation visual fields, and stereoacuity tests. Know how to record acuity with and without correction and how to test each eye separately.
Traps
Common traps include misreading the Snellen fraction-20/40 means the patient sees at 20 feet what a normal eye sees at 40 feet, so larger denominators mean worse acuity. Another trap is using pinhole to improve acuity when the cause is retinal or neural (it will not help). Watch for questions about which eye to test first and the importance of occluding rather than squinting. Also distinguish counting fingers, hand motion, light perception, and no light perception as ordered levels below the chart.
Worked example / rule of thumb
Rule of thumb: if acuity improves with a pinhole, the deficit is likely refractive; if it does not, suspect ocular disease and refer. Always record the method (e.g., "20/40 with pinhole").
Study focus
Practice documenting a complete history and acuity result accurately, since administrative and legal questions often hinge on thorough, legible records.