Diagnostic Procedures and Visual Acuity Testing
What the exam tests
Diagnostic Procedures and Visual Acuity Testing examines standardised measurement, accurate recording and interpretation of simple screening tests.
Visual acuity
Snellen acuity is tested at 6 m, each eye separately, with and without correction. A 6/12 result means the patient reads at 6 m what a normal eye reads at 12 m. LogMAR charts give finer grading. If acuity is below 6/9, repeat with a pinhole. Near vision is tested at 33–40 cm using Jaeger or N notation. If the chart cannot be read, record counting fingers, hand movements or light perception in that order.
Other tests
Ishihara plates screen red–green colour deficiency. The Amsler grid detects central metamorphopsia. Contrast sensitivity and perimetry assess function beyond acuity. Pupil examination records size, direct and consensual reaction, and a relative afferent pupillary defect on the swinging-flashlight test. Intraocular pressure and slit-lamp findings are recorded alongside acuity.
Worked example
A student reads 6/36 without correction and 6/9 with a pinhole. Reasoning: the improvement shows that the main limitation is uncorrected refractive error rather than media opacity or retinal disease. Record both values and refer for refraction.
Traps
Do not record a single acuity for both eyes, omit the pinhole when indicated, or write “6/6” without specifying the eye and correction. Pinhole improvement does not prove that the fundus is normal; it only makes refractive error likely. Avoid testing near vision at an arbitrary distance.