{"id":20378,"date":"2022-01-03T12:47:30","date_gmt":"2022-01-03T12:47:30","guid":{"rendered":"https:\/\/www.optometrists.org\/?page_id=20378"},"modified":"2022-01-03T12:47:30","modified_gmt":"2022-01-03T12:47:30","slug":"the-4-main-refractive-errors-clearly-explained","status":"publish","type":"page","link":"https:\/\/www.optometrists.org\/general-practice-optometry\/guide-to-eye-exams\/eye-exams\/the-4-main-refractive-errors-clearly-explained\/","title":{"rendered":"The 4 Main Refractive Errors: Clearly Explained"},"content":{"rendered":"

According to the <\/b>Oxford Handbook of Ophthalmology<\/i><\/b> over 2 billion people are affected by refractive errors worldwide – that\u2019s as much as 25% of the world\u2019s population.<\/b><\/h2>\n

Refractive errors occur when light entering the eye is not clearly focused on the retina, at the back of the eye. This happens as a result of the shape of the cornea and lens inside the eye and the length of the eye overall.<\/p>\n

A refractive error in the eye causes blurry or double vision, headaches and eye strain.<\/b><\/p>\n

The cornea provides approximately 70% of the focusing power of the eye, the other 30% is from the lens inside the eye.<\/p>\n

The lens is flexible and changes shape to allow the focus to change depending on the distance of the objects we are looking at.<\/p>\n

Clear vision is achieved when the cornea and lens, in combination, focus light directly onto the retina, the nerve layer at the back of the eye<\/b>.<\/p>\n

The four most common refractive errors are:<\/p>\n

    \n
  1. Myopia<\/a> (nearsightedness)<\/li>\n
  2. Hyperopia<\/a> (farsightedness)<\/li>\n
  3. Presbyopia<\/a><\/li>\n
  4. Astigmatism<\/a><\/li>\n<\/ol>\n

    These are outlined in more detail below:<\/p>\n

    1. Myopia (Nearsightedness)<\/b><\/h2>\n

    An article published in the February 2014 edition of Eye: The Scientific Journal of The Royal College of Ophthalmology <\/i>estimates that as many as 1.5 billion people, or 22% of the world population, are affected by myopia – this makes it by far the most common refractive error.<\/p>\n

    Over 1 in 5 of the global population has myopia.<\/b><\/p>\n

    Also known as nearsightedness, myopia happens as a result of the eye being too long, or the focusing power of the cornea being too strong.<\/p>\n

    In myopia, the light entering the eye is focused before reaching the retina<\/b>, rather than directly on the retina itself.<\/p>\n

    People with myopia will have a hard time seeing objects clearly at a distance, while objects close up will be in focus. They might also experience eye strain and headache.<\/p>\n

    A number of factors seem to contribute to the development of myopia<\/a>.<\/p>\n

    One of the leading factors is genetics. Children with two parents that have myopia are significantly more likely to also develop it than children with only one parent or neither parent with myopia.<\/p>\n

    Other factors that may contribute to the development of myopia include too much time spent indoors<\/a> and extended periods of time doing close work, such as staring at a computer screen.<\/p>\n

    SEE RELATED: When to See My Eye Doctor? 8 Q&As<\/a><\/strong><\/p>\n

    If you feel that your vision isn\u2019t clear, see your local eye doctor for an eye exam<\/a>.<\/strong><\/p>\n\n\t

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