{"id":3567,"date":"2023-04-24T07:23:01","date_gmt":"2023-04-24T07:23:01","guid":{"rendered":"https:\/\/blog.internationalconsultancyservice.in\/?p=3567"},"modified":"2023-04-24T07:23:02","modified_gmt":"2023-04-24T07:23:02","slug":"the-eye-chart-explained","status":"publish","type":"post","link":"https:\/\/blog.internationalconsultancyservice.in\/?p=3567","title":{"rendered":"The Eye Chart, Explained"},"content":{"rendered":"\n

It’s a staple of every eye exam, but what do you really know about this humble\u00a0vision test?\u00a0<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Your optometrist\u2019s office runs on E. <\/p>\n\n\n\n

The decidedly low-tech eye chart with a massive E on the top line is found in nearly every eye doctor\u2019s office in the United States. <\/p>\n\n\n\n

And for good reason: More than 150 years after it was invented, it\u2019s still a quick and accurate way to measure a person\u2019s vision.<\/p>\n\n\n\n

There have been tweaks and variations over the past century and a half, but the eye chart itself hasn\u2019t really changed that much\u2014though it has been improved. (More on that later.) The version you\u2019re most familiar with was invented by Dutch ophthalmologist Herman Snellen in 1862, and the Snellen eye chart quickly became the standard.<\/p>\n\n\n\n

Before then, doctors tested vision by asking patients to read complete sentences\u2014each a different size\u2014but it was too easy to guess the next word. Plus, patients who didn\u2019t know how to read couldn\u2019t have their vision assessed.<\/p>\n\n\n\n

Along with a new chart, Snellen came up with concept of\u00a020\/20 vision. The top number is how far you stand from the chart (20 feet), and the bottom is the distance at which someone with normal eyesight can read the smallest line you can see clearly.<\/p>\n\n\n\n

In other words, if you\u2019re 20 feet from the chart, and the average person can read the smallest font you can see from 40 feet away, you have 20\/40 vision. Conversely, if you can read letters at 20 feet that the average person can only read at 15 feet, you have 20\/15 vision\u2014that is, better than normal. There\u2019s no such thing as \u201cperfect\u201d vision.<\/p>\n\n\n\n

5 Fascinating Facts About the Eye Chart <\/h2>\n\n\n\n
    \n
  1. The Snellen eye chart only uses nine letters: C, D, E, F, L, O, P, T, and Z.<\/li>\n\n\n\n
  2. The letters are known as optotypes. <\/li>\n\n\n\n
  3. The size of the letters is mathematically consistent. For example, optotypes designated 20\/40 are twice the height of the ones designated 20\/20.<\/li>\n\n\n\n
  4. The height and width of each letter are precisely five times thicker than the lines, and the thickness of the white spaces and lines is equal. <\/li>\n\n\n\n
  5. If you cannot read the big E on a Snellen chart, you have a visual acuity of less than 20\/200, which makes you legally blind.<\/li>\n<\/ol>\n\n\n\n
    \"Young<\/figure>\n\n\n\n

    Other Types of Eye Charts<\/h2>\n\n\n\n

    The Snellen chart isn\u2019t the only one used by eye care professionals. Several other types are common as well, notably: <\/p>\n\n\n\n

    J\u00e4ger:<\/strong> This chart, invented by Austrian ophthalmologist Eduard J\u00e4ger in 1854, tests near vision. Your eye doc hands you a card with 11 short paragraphs numbered 1 (smallest print) to 11 (largest print). You hold the card at a comfortable reading distance, which is roughly 14 inches from your nose.<\/p>\n\n\n\n

    Tumbling E:<\/strong> Also developed by Snellen, this chart is for kids and those who can\u2019t read. It shows a capital letter E facing different directions. The patient looks at each character and points in the direction the E is facing. This test is also often used for subjects who aren\u2019t familiar with the Roman alphabet.<\/p>\n\n\n\n

    Bailey\u2013Lovie:<\/strong> In 1976, Ian Bailey and Jan Lovie of the National Vision Research Institute of Australia redesigned the Snellen chart. Their chart has 14 rows of five letters. The font size gets smaller from the first row to the last. This chart is considered more accurate than the Snellen chart.<\/p>\n\n\n\n

    Landolt C:<\/strong> Similar with the Tumbling E, this chart features a C\u2014some say it looks more like a broken ring\u2014that points in different directions. It was developed by Swiss ophthalmologist Edward Landolt and is considered the laboratory standard by the International Council of Ophthalmology.<\/p>\n\n\n\n

    ETDRS<\/strong>: In 1982, researcher Rick Ferris modified the Bailey-Love chart based on recommendations from the National Academy of Science and National Research Council for his Early Treatment of Diabetic Retinopathy Study. The modified chart has a smaller testing difference (13 feet instead of 20 feet) and wider spacing between the letters within a row. A 2009 study found it to be significantly more accurate than the Snellen chart, particularly in patients with poor eyesight or conditions like age-related macular degeneration. It is now considered to be the gold standard.<\/p>\n","protected":false},"excerpt":{"rendered":"

    It’s a staple of every eye exam, but what do you really know about this humble\u00a0vision test?\u00a0 Your optometrist\u2019s office runs on E.  The decidedly low-tech eye chart with a massive E on the top line is found in nearly every eye doctor\u2019s office in the United States.  And for good reason: More than 150 years after it was invented, it\u2019s still a quick and accurate way to measure a person\u2019s vision. There have been tweaks and variations over the past century and a half, but the eye chart itself hasn\u2019t really changed that much\u2014though it has been improved. (More\u2026<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-3567","post","type-post","status-publish","format-standard","hentry","category-authorized"],"blocksy_meta":"","yoast_head":"\nThe Eye Chart, Explained - International Consultancy Service Blog<\/title>\n<meta name=\"description\" content=\"The decidedly low-tech eye chart with a massive E on the top line is found in nearly every eye doctor\u2019s office in the United States.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blog.internationalconsultancyservice.in\/?p=3567\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"The Eye Chart, Explained - 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