{"id":1802,"date":"2026-10-20T08:52:08","date_gmt":"2026-10-20T08:52:08","guid":{"rendered":"https:\/\/laseristanbulclinic.com\/eye-glossary\/anisometropia\/"},"modified":"2026-10-20T12:56:23","modified_gmt":"2026-10-20T12:56:23","slug":"anisometropia","status":"publish","type":"page","link":"https:\/\/laseristanbulclinic.com\/en\/eye-glossary\/anisometropia\/","title":{"rendered":"Anisometropia: What It Is, Symptoms, Causes and Treatment"},"content":{"rendered":"\n
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  1. Home<\/a><\/li>
  2. Knowledge centre<\/a><\/li>
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  4. Anisometropia: What It Is, Symptoms, Causes and Treatment<\/span><\/li><\/ol><\/div>\t\t\t

    Anisometropia: What It Is, Symptoms, Causes and Treatment<\/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

    Anisometropia<\/strong> (noun, pronounced an-eye-so-me-TROH-pee-a)<\/em>: anisometropia means the two eyes need different glasses prescriptions, so one eye focuses less well than the other. In studies it is most often defined as a difference of 1.00 dioptre (D) or more between the eyes. It can be caused by short-sightedness, long-sightedness or astigmatism that is stronger in one eye, and in children it can lead to a lazy eye (amblyopia) if it is not corrected early.<\/p>\n\t\t<\/div><\/div><\/div><\/div><\/section>\n\n\n\n\n

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    Anisometropia: key facts<\/h2><\/div>\n\t\t\t\t\t<\/div>\n\t\t\t
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    <\/svg>What it is<\/span><\/dt>
    A difference in refractive error (focusing power) between the right and left eye<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Common threshold<\/span><\/dt>
    A spherical-equivalent difference of 1.00 D or more is the most widely used definition<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>How common<\/span><\/dt>
    A small difference is very common: about 20% of people have 0.5 D or more, falling to about 2\u20133% at 3 D or more<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Main risk in children<\/span><\/dt>
    Amblyopia (lazy eye): anisometropia was the most common cause of it in a 2018 worldwide meta-analysis<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Main problem in adults<\/span><\/dt>
    Eyestrain, headache and poorer 3D vision; with glasses, the two eyes can see images of different sizes (aniseikonia)<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>First-line treatment<\/span><\/dt>
    Glasses or, often better when the difference is large, contact lenses<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Other treatment<\/span><\/dt>
    Patching or blurring drops for amblyopia in children; laser or lens surgery for suitable adults<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Specialist<\/span><\/dt>
    Ophthalmologist or paediatric ophthalmologist; at Laser Istanbul Clinic, Prof. Dr. Ahmet Sat\u0131c\u0131 and Op. Dr. Aysan Bayram for adult correction<\/dd><\/dl><\/div>\n\t\t\t<\/div>\n\t\t<\/div><\/div><\/div><\/section>\n\n\n\n\n

    Anisometropia: what is it and how is it measured?<\/h2><\/div>

    Every eye has a refractive error, even if it is tiny: the amount by which it fails to focus light exactly on the retina. Refractive error is measured in dioptres (D)<\/strong> and written on your prescription as sphere (short- or long-sightedness) and cylinder (astigmatism). In anisometropia, the right eye and the left eye have clearly different values.<\/p>\n

    To compare two eyes, eye care professionals usually look at the spherical equivalent<\/strong>, which is the sphere plus half of the cylinder, and also at the cylinder on its own. A scoping review published in 2026 notes that the most commonly used cut-off for anisometropia is a spherical-equivalent difference of 1.00 D or more between the eyes. Studies of preschool children also use a cylinder difference of 1.0 D or more.<\/p>\n

    A worked example.<\/strong> If your right eye is \u20131.00 and your left eye is \u20133.50, the difference is 2.50 D: you have anisometropia. Our guide to reading a prescription shows where each number sits.<\/p>

    Eye prescription reader (sphere, cylinder, axis, dioptres) <\/svg><\/a><\/div>

    How common is anisometropia?<\/h3>\n

    It depends on where you draw the line. A 2013 review found that about 20% of people have an inter-eye difference of 0.5 D or more, but only about 2\u20133% have 3 D or more. A study of 134,603 adults who were considered for refractive surgery in 2010\u20132020 found a median difference of 0.38 D and a prevalence of 17.9% (using the study’s own definition). In preschool children the figure is lower: a population study of 2,090 Australian children aged 6 months to 6 years found 2.7% with a spherical-equivalent difference of 1.0 D or more, and 3.0% with a cylinder difference of 1.0 D or more.<\/p><\/div><\/div><\/div><\/div><\/div><\/section>\n\n\n\n\n

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    Types of anisometropia<\/h2>\n\t\t\t

    Eye specialists group anisometropia by which eye has which error. The examples below are only illustrations, written as right eye \/ left eye.<\/p>\n\t\t\t

    Type<\/th>What it means<\/th>Example (right \/ left)<\/th><\/tr><\/thead>
    Simple myopic<\/strong><\/th>One eye is short-sighted, the other has no significant error<\/td>\u20133.00 \/ plano (0.00)<\/td><\/tr>
    Simple hyperopic<\/strong><\/th>One eye is long-sighted, the other has no significant error<\/td>+2.50 \/ plano<\/td><\/tr>
    Compound myopic<\/strong><\/th>Both eyes are short-sighted, one more than the other<\/td>\u20131.50 \/ \u20134.00<\/td><\/tr>
    Compound hyperopic<\/strong><\/th>Both eyes are long-sighted, one more than the other<\/td>+1.00 \/ +3.50<\/td><\/tr>
    Antimetropia (mixed)<\/strong><\/th>One eye is short-sighted and the other long-sighted<\/td>\u20132.00 \/ +1.50<\/td><\/tr>
    Astigmatic<\/strong><\/th>The astigmatism (cylinder) differs between the eyes<\/td>\u20131.00 \u20130.50 \/ \u20131.00 \u20132.50<\/td><\/tr><\/tbody><\/table><\/div>

    The type matters for treatment: in children, the amount and kind of difference decides how likely a lazy eye is, and in adults it decides whether glasses will be comfortable.<\/p><\/div>\t<\/div><\/div><\/div><\/section>\n\n\n\n\n

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    Anisometropia causes: why do the eyes differ?<\/h2><\/div>

    The eye’s focusing depends on the curve of the cornea, the power of the natural lens and the length of the eyeball. If any of these differs between the two eyes, you get anisometropia. The American Association for Pediatric Ophthalmology and Strabismus (AAPOS) puts it simply: one eye is shaped differently, so it is more long-sighted, more short-sighted or more astigmatic than the other.<\/p><\/div><\/div>\t\t\t

    Common causes of anisometropia:<\/strong><\/p>\n\t\t\t