# Visual Acuity > Visual acuity testing for Optometry exams: Snellen 6/6 notation, logMAR charts, pinhole test, near vision and WHO visual impairment categories. - Canonical URL: https://prepelephant.com/topics/allied/optometry/visual-acuity-optometry-ss - Exam / course: Allied Health · Subject: Optometry - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Visual Acuity", PrepElephant, https://prepelephant.com/topics/allied/optometry/visual-acuity-optometry-ss ## Direct answer 6/6 means the patient reads at 6 metres a line a normal eye manages at 6 metres — the Snellen fraction, testing distance over the distance at which the letter subtends 5 minutes of arc with a limb width of 1 minute. Test each eye separately, unaided then with present correction, record the smallest line read (more than half its letters), and use the pinhole to separate refractive blur from organic disease: improvement through a 1–1.5 mm pinhole points to refraction; failure to improve points to amblyopia or pathology. Below the top line, vision is walked down the ladder of counting fingers, hand movements, perception of light and its projection. ## What you must remember - Snellen fraction V = d/D; 6/6 equals 20/20 in feet and 1.0 in decimal; a 6/60 letter subtends 5 minutes of arc at 60 metres. - The 6-metre test distance approximates optical infinity: rays are effectively parallel and accommodation demand falls to about 0.17 D. - Record the line read plus letters missed (6/9−2), unaided and aided, each eye separately with the fellow eye fully occluded. - Pinhole: acuity improves in uncorrected refractive error; fails to improve in amblyopia, macular disease and optic neuropathy — dense cataract may even worsen it. - logMAR charts (ETDRS/Bailey–Lovie): five letters per line in uniform 0.1 log steps — 6/6 = 0.00, 6/60 = 1.00; the standard for research and low-vision work. - If the top line is unreadable at 6 m, walk forward metre by metre (5/60, 4/60…), then counting fingers at a stated distance, hand movements, then perception of light with projection in four quadrants. - Near vision uses N-notation (N-6 approximates newsprint at 35–40 cm) or Jaeger types, always with the working distance stated. - WHO categories (presenting acuity, better eye): moderate below 6/18 to 6/60, severe below 6/60 to 3/60, blindness below 3/60 or field under 10 degrees — the classification behind India's National Programme for Control of Blindness reporting. ## Two patients, one pinhole, one decision A 52-year-old labourer reports blurred vision for a year. Uncorrected acuity is right 6/60, left 6/36. Through the pinhole he jumps to 6/9 in both eyes — refractive error, most likely uncorrected astigmatism or hypermetropia; the next step is refraction, not referral. Beside him, a 60-year-old diabetic reads 6/36 unaided and still 6/36 through the pinhole. The pinhole has just said the media are not the whole story: maculopathy, cataract or optic nerve — the pathway is slit-lamp and fundus examination. The recording discipline carries the clinical logic. For the labourer: "VA RE 6/60, improves to 6/9 with pinhole; LE 6/36, 6/9 with pinhole." For the diabetic: "VA RE 6/36, no improvement with pinhole." A reader — consultant, court or examiner — reconstructs both diagnoses from those two lines. Contrast the habit of writing "vision poor", or testing both eyes open so the better eye does all the work — a dense amblyope is found one occlusion at a time. ## Where students slip The traps are numerical and terminological. Converting between systems badly: 6/18 is logMAR 0.5, not 0.18 — it is the log of the reciprocal of the decimal fraction. Defining blindness as "cannot see" — in WHO and Indian programme terms it is presenting acuity below 3/60 in the better eye or a field under 10 degrees, and the shift from best-corrected to presenting acuity matters because uncorrected refractive error now counts. Recording "PL+" without projection: an eye with intact projection has a healthy retina behind the opacity and may retrieve vision after cataract surgery, while absent projection forecasts a poor outcome — the most prognostic piece of the entire low-vision exam. And the top-line rule: someone who cannot read 6/60 at 6 metres is walked closer and recorded 5/60 or 4/60, never "hand movements" straight from the chair. ## Frequently asked questions ### Why is visual acuity tested at 6 metres? Because 6 metres approximates optical infinity: entering light is effectively parallel, so accommodation is minimally engaged (about 0.17 D) and distance vision is tested without near effort. ### What does improvement with a pinhole indicate? Refractive error or early media opacity — a narrow pencil of rays bypasses blurred peripheral focus; no improvement suggests amblyopia or retinal and optic nerve disease. ### What is the logMAR value of 6/18? 0.5, since logMAR is the logarithm of the inverse of the decimal acuity (6/18 = 0.33 decimal; log 3 ≈ 0.5). ### How is vision recorded below the 6/60 line? By walking the patient forward (5/60, 4/60, 3/60…), then counting fingers at a stated distance, hand movements, and perception of light with its projection in four quadrants. ### What are the WHO categories of visual impairment? Based on presenting acuity in the better eye: moderate below 6/18 to 6/60, severe below 6/60 to 3/60, blindness below 3/60 or field under 10 degrees. ### How is acuity tested in pre-literate children? With matching or picture optotypes (Lea symbols, tumbling E, HOTV) and, in infants, behavioural methods — optokinetic nystagmus and preferential looking with Teller acuity cards.