{"id":1808,"date":"2026-10-20T08:52:38","date_gmt":"2026-10-20T08:52:38","guid":{"rendered":"https:\/\/laseristanbulclinic.com\/eye-glossary\/coloboma\/"},"modified":"2026-10-20T12:56:29","modified_gmt":"2026-10-20T12:56:29","slug":"coloboma","status":"publish","type":"page","link":"https:\/\/laseristanbulclinic.com\/en\/eye-glossary\/coloboma\/","title":{"rendered":"Coloboma: What It Is, Types, Causes, Symptoms and Treatment"},"content":{"rendered":"\n
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  1. Home<\/a><\/li>
  2. Knowledge centre<\/a><\/li>
  3. Eye glossary A\u2013Z<\/a><\/li>
  4. Coloboma: What It Is, Types, Causes, Symptoms and Treatment<\/span><\/li><\/ol><\/div>\t\t\t

    Coloboma: What It Is, Types, Causes, Symptoms 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

    Coloboma<\/strong> (noun, plural colobomas or colobomata)<\/em>: a coloboma is a gap in the eye, present from birth, where part of the normal tissue is missing. It happens when a seam in the developing eye fails to close in early pregnancy, and it can affect the iris (giving a “keyhole” pupil), the retina and choroid, the optic nerve, the lens or the eyelid. Vision can be normal or reduced, depending on where the gap is and how large it is; the gap itself cannot be repaired, but many complications can be treated.<\/p>\n\t\t<\/div><\/div><\/div><\/div><\/section>\n\n\n\n\n

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    Coloboma: 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 congenital (from birth) gap in eye tissue; the word comes from the Greek for “mutilated” or “with a defect”<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Cause<\/span><\/dt>
    Incomplete closure of the optic (embryonic) fissure in early pregnancy, usually in the first two months<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Where<\/span><\/dt>
    Typically the lower, inner (inferonasal) part of the eye; one or both eyes<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>How rare<\/span><\/dt>
    About 1 in 10,000 people (MedlinePlus); published estimates of 0.5\u20132.2 per 10,000 live births for ocular coloboma<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Types<\/span><\/dt>
    Iris, lens, chorioretinal (retina and choroid), optic nerve, eyelid<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Inheritance<\/span><\/dt>
    Often no family history; can be inherited (dominant, recessive or X-linked), and can be part of a syndrome such as CHARGE<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Main risk<\/span><\/dt>
    Retinal detachment when the retina or choroid is involved; amblyopia (“lazy eye”) in children<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Cure<\/span><\/dt>
    No. The gap stays, but glasses, lenses, laser, surgery and low-vision support manage its effects<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Specialist<\/span><\/dt>
    Ophthalmologist, ideally with retina experience; at Laser Istanbul Clinic, Do\u00e7. Dr. Muhammet Derda \u00d6zer (retina, cornea, cataract) and Op. Dr. Aysan Bayram (retinal disease)<\/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 is a coloboma of the eye?<\/h2>\n\t\t\t\t\t\t\t\t

    A coloboma of the eye is a congenital defect in which a piece of the eye’s structure is missing. The American Academy of Ophthalmology describes it as normal tissue in or around the eye that is missing at birth. It can involve the eyelid, iris, lens, ciliary body, the zonules that hold the lens, the choroid, the retina or the optic nerve, and EyeWiki notes it most often sits in the lower, inner (inferonasal) quadrant and is often linked with an unusually small eye (microphthalmia).<\/p>\n

    Many people first meet the word because an iris coloboma is visible: the pupil is not round but pear- or keyhole-shaped, a bit like a cat’s eye. Others have a coloboma at the back of the eye that nobody sees from the outside, and it is found at an eye test. The same term, “coloboma”, is used for all of these, which is why the effect on vision ranges from none at all to severe.<\/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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    Types of coloboma<\/h2>\n\t\t\t

    The type depends on which part of the eye is affected, and one person can have more than one.<\/p>\n\t\t\t

    Type<\/th>What is missing or affected<\/th>What it looks like or does<\/th><\/tr><\/thead>
    Iris coloboma<\/strong><\/th>A segment of the iris, usually at the bottom<\/td>A keyhole or cat-eye pupil; glare and light sensitivity are common<\/td><\/tr>
    Chorioretinal coloboma<\/strong><\/th>Part of the choroid and retina at the back of the eye<\/td>Often unseen from outside; a blind patch (field defect) in the vision; risk of retinal detachment<\/td><\/tr>
    Optic nerve coloboma<\/strong><\/th>A gap or hollow in the optic nerve head<\/td>Reduced vision, depending on how much of the nerve is involved<\/td><\/tr>
    Lens coloboma<\/strong><\/th>A notch or flattening at the edge of the lens<\/td>The lens tissue is not truly missing; the problem is in the supporting fibres (zonules). It can blur vision<\/td><\/tr>
    Eyelid coloboma<\/strong><\/th>A notch in the lid, most often at the inner third of the upper lid<\/td>The lid does not cover the eye fully, so the cornea can dry out and be damaged<\/td><\/tr><\/tbody><\/table><\/div>

    The iris is the most commonly affected site, and these gaps are often found together: an iris coloboma can go with a coloboma of the ciliary body, choroid, retina or optic nerve. Because of that, a child or adult with an iris coloboma should always have the back of the eye examined as well.<\/p><\/div>\t<\/div><\/div><\/div><\/section>\n\n\n\n\n

    What causes coloboma?<\/h2><\/div>

    Colobomas happen when the optic fissure does not close properly during early eye development.<\/strong> In the womb, the eye forms as a cup with a seam along its underside. That seam normally closes during roughly the fifth to seventh week of pregnancy; if it stays partly open, a gap remains. If the gap is at the front, it affects the iris; if at the back, the choroid, retina or optic nerve.<\/p>\n

    What makes the seam fail to close is not always clear. The known causes are:<\/p>\n