[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Ophthalmology](https://durgical.com/en/ophthalmology/) › [The eye exam](https://durgical.com/en/ophthalmology/areas/exam/) › Visual acuity: Snellen, logMAR and pinhole # Visual acuity: Snellen, logMAR and pinhole - Examination Visual acuity is the vital sign of the eye: each eye is measured separately, with glasses, and repeated through a pinhole if it is low. Updated Nov 5, 2026 **See it in 3D:** [Macula](https://durgical.com/en/anatomy/macula/) · [Cornea](https://durgical.com/en/anatomy/cornea/) · [Lens](https://durgical.com/en/anatomy/lens/) ## Key points - 6/6 = 20/20 = logMAR 0.0. - Better with pinhole = refractive error. - Blindness (WHO): worse than 3/60 in the better eye. - Each eye separately, with glasses. ## What it is Visual acuity measures the smallest detail each eye can resolve at a set distance. It is the first measurement in any eye complaint and the basis for referral, follow-up and medico-legal records. The Snellen chart gives a fraction (6/6 or 20/20 is normal); logMAR charts (ETDRS) are more precise and used in research and low vision. The pinhole separates refractive blur from disease. ## Normal values and scales - Normal adult acuity: 6/6 (20/20) or better; the Snellen numerator is the test distance and the denominator the distance at which a normal eye reads that line. - logMAR 0.0 equals 6/6; each line is 0.1 logMAR, and higher numbers mean worse vision. - Below the chart: counting fingers, hand movements, light perception, no light perception. - WHO grades of distance visual impairment: mild worse than 6/12, moderate worse than 6/18, severe worse than 6/60, blindness worse than 3/60. - A two-line difference between the eyes of a child suggests amblyopia. ## How it is done - Seat the patient at the chart's distance (usually 6 metres, or 3 metres with a mirror or a reduced chart), wearing their distance glasses. - Cover one eye fully with an occluder or the palm, without pressing, and test the other eye; then swap. - Record the smallest line read with no more than one or two mistakes, as a fraction (for example 6/9 or 20/30). - If the top letter cannot be read, walk the patient closer and record the distance, then try counting fingers, hand movements and light perception. - If acuity is below 6/6, repeat looking through a pinhole occluder. - Test near vision with a reading card at the patient's usual reading distance. - In young children, use picture or matching charts (Lea, HOTV), or fixing and following in infants. ## How to interpret it - Improvement with the pinhole means a refractive error; no improvement means disease of the media, retina or optic nerve. - Acuity tests central (foveal) vision only: a patient with advanced glaucoma can read 6/6. - Always record which eye, with or without glasses, and with pinhole: the record is used to compare over time and in medico-legal reports. ## Next step / Initial management - Acuity worse than 6/12 that improves fully with the pinhole: refraction by optometry. - Acuity worse than 6/12 that does not improve with the pinhole: ophthalmology, with priority set by the history (same day if sudden). - Child with reduced acuity in one eye or a two-line difference: paediatric ophthalmology for amblyopia. - Sudden loss of acuity, or loss with pain: same-day ophthalmology. ## Test yourself Think of the answer, then tap the question to see it. ## What does a Snellen acuity of 6/18 mean? The patient reads at 6 metres the line that a normal eye reads at 18 metres. ## Acuity improves from 6/24 to 6/9 with a pinhole. What is the cause? A refractive error, which glasses would correct. ## How does WHO define blindness by visual acuity? Presenting acuity worse than 3/60 in the better eye. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/ophthalmology/visual-acuity-snellen-logmar-and-pinhole/) ## Elsewhere in DurgiPedia - [Eye exam: visual acuity, visual fields and eye movements](https://durgical.com/en/clinical-exam/eye-exam-visual-acuity-visual-fields-and-eye-movements/) - [Optics of the eye, accommodation and refractive errors](https://durgical.com/en/physiology/optics-of-the-eye-accommodation-and-refractive-errors/) ## Connections ## See it in 3D 3 The structures of Durgical's 3D anatomy where it is found. - [Macula](https://durgical.com/en/anatomy/macula/) - [Cornea](https://durgical.com/en/anatomy/cornea/) - [Lens](https://durgical.com/en/anatomy/lens/) ## Related 4 - [Gradual visual loss in adults](https://durgical.com/en/ophthalmology/gradual-visual-loss-in-adults/) - [Refraction: dioptres and reading a prescription](https://durgical.com/en/ophthalmology/refraction-dioptres-and-reading-a-prescription/) - [Visual impairment and blindness: how they are graded](https://durgical.com/en/ophthalmology/visual-impairment-and-blindness-how-they-are-graded/) - [Childhood vision screening by age](https://durgical.com/en/ophthalmology/childhood-vision-screening-by-age/) ## Related conditions 3 - [Refractive errors and presbyopia](https://durgical.com/en/conditions/refractive-errors-and-presbyopia/) - [Cataract](https://durgical.com/en/conditions/cataract/) - [Strabismus and amblyopia](https://durgical.com/en/conditions/strabismus-and-amblyopia/) [← All of ophthalmology](https://durgical.com/en/ophthalmology/) Educational content; not a clinical guideline and no substitute for assessment by a health professional. For sudden visual loss, severe eye pain, a chemical burn or an eye injury, go to an emergency department at once. Sources: [Evaluation of Visual Acuity](https://www.ncbi.nlm.nih.gov/books/NBK564307/) (StatPearls Publishing (NCBI Bookshelf), 2024); [World report on vision](https://www.who.int/publications/i/item/9789241516570) (World Health Organization, 2019). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/ophthalmology/visual-acuity-snellen-logmar-and-pinhole/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/ophthalmology/visual-acuity-snellen-logmar-and-pinhole/