{"id":1863,"date":"2026-10-20T08:52:21","date_gmt":"2026-10-20T08:52:21","guid":{"rendered":"https:\/\/laseristanbulclinic.com\/eye-glossary\/visual-acuity\/"},"modified":"2026-10-20T12:57:28","modified_gmt":"2026-10-20T12:57:28","slug":"visual-acuity","status":"publish","type":"page","link":"https:\/\/laseristanbulclinic.com\/en\/eye-glossary\/visual-acuity\/","title":{"rendered":"Visual Acuity: What It Is, How It Is Measured and What 20\/20 Means"},"content":{"rendered":"\n
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  1. Home<\/a><\/li>
  2. Knowledge centre<\/a><\/li>
  3. Eye glossary A\u2013Z<\/a><\/li>
  4. Visual Acuity: What It Is, How It Is Measured and What 20\/20 Means<\/span><\/li><\/ol><\/div>\t\t\t

    Visual Acuity: What It Is, How It Is Measured and What 20\/20 Means<\/h1>\n\t\t\t\t\t\t

    Medically reviewed by {{surgeon}}<\/span><\/strong>, {{surgeon’s title and specialty}}<\/span>, on {{review date}}<\/span>. Last updated {{date}}<\/span>.<\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

    \"Illustration<\/figure><\/div>\n\t\t\t<\/div><\/div>\n<\/section>\n\n\n\n\n
    \n\t\t<\/svg>Definition<\/span>\n\t\t\t

    Visual acuity<\/strong> (noun)<\/em>: visual acuity is the sharpness of your vision, meaning how small a detail you can pick out at a set distance. It is measured with an eye chart and written as a fraction such as 20\/20 (feet) or 6\/6 (metres), or as a decimal or logMAR number. Clinicians record it for each eye separately, with and without glasses or contact lenses.<\/p>\n\t\t\t

    In short:<\/strong> visual acuity of 20\/20, also written 6\/6 or 1.0, is the standard for normal distance sharpness: you see at 20 feet (6 metres) what an average person sees at that distance. It is not “perfect vision”. A reduced result can come from a focusing error, cataract, a corneal or retinal problem, or lazy eye, and an eye surgeon such as Prof. Dr. Ahmet Sat\u0131c\u0131, Do\u00e7. Dr. Muhammet Derda \u00d6zer or Op. Dr. Aysan Bayram can find the cause and treat it.<\/p><\/div>\n\t<\/div><\/div><\/div><\/div><\/section>\n\n\n\n\n

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    Visual acuity: key facts<\/h2><\/div>\n\t\t\t\t\t<\/div>\n\t\t\t
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    <\/svg>What it measures<\/span><\/dt>
    Clarity of detail vision, usually at distance; near acuity is tested separately<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Normal result<\/span><\/dt>
    20\/20 in feet, 6\/6 in metres, 1.0 as a decimal, 0.00 in logMAR<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>How to read the fraction<\/span><\/dt>
    The bottom number is the distance at which an average person reads the same line, so 20\/40 is poorer than 20\/20<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Better than 20\/20<\/span><\/dt>
    Possible: 20\/15 means you read at 20 feet what an average person needs to be 15 feet from<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Typical chart<\/span><\/dt>
    Snellen chart (letters), ETDRS\/logMAR chart (clinics and research), tumbling E or picture charts (children and non-readers)<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>What it does not measure<\/span><\/dt>
    Side vision, colour, depth perception, contrast, or eye disease such as glaucoma<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Who treats low acuity<\/span><\/dt>
    An ophthalmologist; at Laser Istanbul Clinic, Prof. Dr. Ahmet Sat\u0131c\u0131, Do\u00e7. Dr. Muhammet Derda \u00d6zer or Op. Dr. Aysan Bayram<\/dd><\/dl><\/div>\n\t\t\t<\/div>\n\t\t<\/div><\/div><\/div><\/section>\n\n\n\n\n
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    \"Illustration<\/div><\/div>\n\t\t
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    What does 20\/20 vision mean?<\/h2>\n\t\t\t\t\t\t\t\t

    20\/20 vision means you can see what an average person can see on an eye chart when standing 20 feet away, according to the American Academy of Ophthalmology (AAO). The top number is your testing distance. The bottom number is the distance at which a person with typical sight could read the same line. So 20\/40 means you need to be at 20 feet to read what most people can read from 40 feet, and 20\/15 means your sharpness is better than average.<\/p>\n

    Outside the United States the same idea is written in metres: 6\/6 is the equivalent of 20\/20<\/strong>. In the UK, Ireland, Australia and much of Europe you will see 6\/6, 6\/9 or 6\/12 on a prescription or eye test report, while the US uses 20\/20, 20\/30 or 20\/40.<\/p>\n

    Is 20\/20 perfect vision?<\/strong> No. The AAO states that 20\/20 is normal clarity and sharpness, not perfect vision. Vision sharper than 20\/20 is possible, and healthy young eyes often read better than 6\/6. The AAO also reports that only about 35% of adults see 20\/20 without any correction, while about 75% reach it with glasses, contact lenses or surgery. A 20\/20 result also says nothing about side vision, colour vision, depth perception or eye health.<\/p><\/div>\n\t\t\t\t\t\t\t\t\t\t\t<\/div>\n<\/div><\/div><\/div><\/div><\/div><\/section>\n\n\n\n\n

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    Visual acuity chart: Snellen, decimal and logMAR notations<\/h2>\n\t\t\t

    The same acuity can be written in several ways. The table below converts common values. The 20\/200, 20\/100, 20\/40, 6\/6, 6\/12 and 6\/60 rows follow the standard conversion table; the other rows are calculated with the same formula (decimal = the first number divided by the second; logMAR = the logarithm of the minimum angle of resolution, which is 1 divided by the decimal).<\/p>\n\t\t\t

    Snellen (feet)<\/th>Snellen (metres)<\/th>Decimal<\/th>logMAR<\/th>In plain words<\/th><\/tr><\/thead>
    20\/10<\/th>6\/3<\/td>2.00<\/td>\u22120.30<\/td>Exceptionally sharp<\/td><\/tr>
    20\/15<\/th>6\/4.5<\/td>1.33<\/td>\u22120.12<\/td>Better than average<\/td><\/tr>
    20\/20<\/strong><\/th>6\/6<\/strong><\/td>1.00<\/strong><\/td>0.00<\/strong><\/td>Normal acuity<\/strong><\/td><\/tr>
    20\/25<\/th>6\/7.5<\/td>0.80<\/td>0.10<\/td>Just below normal<\/td><\/tr>
    20\/30<\/th>6\/9<\/td>0.67<\/td>0.18<\/td>Mildly reduced<\/td><\/tr>
    20\/40<\/th>6\/12<\/td>0.50<\/td>0.30<\/td>Reduced: you need to be at 20 feet for what others read at 40<\/td><\/tr>
    20\/50<\/th>6\/15<\/td>0.40<\/td>0.40<\/td>Noticeably reduced<\/td><\/tr>
    20\/60<\/th>6\/18<\/td>0.33<\/td>0.48<\/td>Clearly reduced<\/td><\/tr>
    20\/100<\/th>6\/30<\/td>0.20<\/td>0.70<\/td>Markedly reduced<\/td><\/tr>
    20\/200<\/th>6\/60<\/td>0.10<\/td>1.00<\/td>Severely reduced<\/td><\/tr><\/tbody><\/table><\/div>

    For an instant conversion between 20\/20, 6\/6, decimal and percentage-style values, use our free tool.<\/p>

    Visual acuity converter (20\/20, 6\/6, decimal, %) <\/svg><\/a><\/div>

    Why “percent vision” is misleading.<\/strong> Acuity is a ratio of distances, not a percentage of sight. Someone with 20\/40 does not have “50% vision” in the everyday sense, and a decimal such as 0.5 is only a convenient way of writing the same ratio.<\/p>\n

    What do 6\/9, 6\/12 and 6\/60 mean?<\/h3>\n