{"id":1826,"date":"2026-10-20T08:52:26","date_gmt":"2026-10-20T08:52:26","guid":{"rendered":"https:\/\/laseristanbulclinic.com\/eye-glossary\/eyeball\/"},"modified":"2026-10-20T12:56:48","modified_gmt":"2026-10-20T12:56:48","slug":"eyeball","status":"publish","type":"page","link":"https:\/\/laseristanbulclinic.com\/en\/eye-glossary\/eyeball\/","title":{"rendered":"Eyeball: Anatomy, Red in Eyeball, Pain and Blood Explained"},"content":{"rendered":"\n
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  1. Home<\/a><\/li>
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  4. Eyeball: Anatomy, Red in Eyeball, Pain and Blood Explained<\/span><\/li><\/ol><\/div>\t\t\t

    Eyeball: Anatomy, Red in Eyeball, Pain and Blood Explained<\/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

    Eyeball<\/strong> (noun, also called the globe)<\/em>: the eyeball is the nearly spherical organ of sight, about 24 mm from front to back in an adult, that sits in the bony eye socket (the orbit). It contains the cornea, iris, pupil, lens and retina, which together focus light and turn it into signals for the brain. Red in the eyeball is usually harmless (a burst surface vessel or mild irritation), but pain, light sensitivity or reduced vision with redness needs a doctor the same day.<\/p>\n\t\t\t

    Quick answer on red in eyeball:<\/strong> most red eyeballs come from infection, dry eye, conjunctivitis, blepharitis or a small burst blood vessel, according to the NHS. Our surgeons, Prof. Dr. Ahmet Sat\u0131c\u0131, Do\u00e7. Dr. Muhammet Derda \u00d6zer and Op. Dr. Aysan Bayram, treat the underlying eye conditions; a painful red eye is never something to wait out.<\/p><\/div>\n\t<\/div><\/div><\/div><\/div><\/section>\n\n\n\n\n

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    Eyeball: 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>
    The eye itself, without the eyelids, tear glands, muscles and socket around it<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Size<\/span><\/dt>
    About 24 mm front to back, 23.7 mm high and 24.2 mm wide; volume about 6.5 ml; full adult size is reached by about age 12<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Where it sits<\/span><\/dt>
    In the orbit, a bony socket made of seven bones with a volume of about 28 ml, so the eyeball fills only about a quarter of it<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Three coats (layers)<\/span><\/dt>
    Outer fibrous coat (clear cornea and white sclera), middle vascular coat or uvea (choroid, ciliary body, iris), inner coat (retina)<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Filling<\/span><\/dt>
    Watery aqueous humour at the front; jelly-like vitreous humour behind the lens<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Movement<\/span><\/dt>
    Six muscles outside the eyeball move it up, down, side to side and rotate it<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Specialist<\/span><\/dt>
    Ophthalmologist (eye doctor); at Laser Istanbul Clinic: Prof. Dr. Ahmet Sat\u0131c\u0131, Do\u00e7. Dr. Muhammet Derda \u00d6zer (Do\u00e7. = Associate Professor) and 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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    What is the eyeball made of? Structure and layers<\/h2>\n\t\t\t

    The eyeball is built in three coats, each with its own job, wrapped around two fluid-filled spaces.<\/p>\n\t\t\t

    Part<\/th>What it is<\/th>What it does<\/th><\/tr><\/thead>
    Sclera<\/strong><\/th>The tough white outer wall that covers nearly the whole surface of the eyeball<\/td>Protects the eye and gives it shape; the six eye muscles attach to it<\/td><\/tr>
    Conjunctiva<\/strong><\/th>A thin, clear membrane over the sclera and inside the eyelids<\/td>Protects and lubricates; this is where a “burst blood vessel” shows up<\/td><\/tr>
    Cornea<\/strong><\/th>The clear dome at the front<\/td>Does about 70% of the eye’s focusing (AAO)<\/td><\/tr>
    Iris and pupil<\/strong><\/th>The coloured ring and the opening in its centre<\/td>The iris muscles widen or narrow the pupil to control the light reaching the back of the eye<\/td><\/tr>
    Lens<\/strong><\/th>Clear flexible disc behind the pupil<\/td>Adds about 30% of focusing and changes shape for near vision<\/td><\/tr>
    Uvea (choroid, ciliary body, iris)<\/strong><\/th>The middle coat, rich in blood vessels<\/td>Feeds the eye and makes the aqueous humour<\/td><\/tr>
    Aqueous humour<\/strong><\/th>Watery fluid in the front of the eye<\/td>Nourishes the cornea and lens and keeps eye pressure steady through constant production and drainage<\/td><\/tr>
    Vitreous humour<\/strong><\/th>Clear, jelly-like gel between lens and retina<\/td>Keeps the eyeball round<\/td><\/tr>
    Retina<\/strong><\/th>Light-sensitive tissue lining the back<\/td>Rods and cones turn light into electrical signals<\/td><\/tr>
    Optic nerve<\/strong><\/th>The cable leaving the back of the eyeball<\/td>Carries those signals to the brain<\/td><\/tr><\/tbody><\/table><\/div>

    The surface is also protected by the tear film<\/strong>, three layers (mucous, watery and oily) that keep the front of the eye smooth and moist.<\/p>

    Glossary: Tear film and tear glands <\/svg><\/a><\/div>

    At the back, rod cells use a light-sensitive pigment to see in dim light.<\/p>

    Glossary: Rhodopsin <\/svg><\/a><\/div><\/div>\t<\/div><\/div><\/div><\/section>\n\n\n\n\n
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    \"Illustration<\/div><\/div>\n\t\t
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    How does the eyeball work?<\/h2>\n\t\t\t\t\t\t\t\t

    Light passes through the cornea, then the pupil, then the lens, which together focus it onto the retina. Photoreceptor cells in the retina convert it into electrical signals, and the optic nerve carries them to the brain, which turns them into the picture you see (National Eye Institute). Tears keep the front surface clear enough for this to work. Because the cornea and lens provide the focusing, small changes in their shape or clarity, or in the length of the eyeball, change how sharp vision is.<\/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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    Red in eyeball: what causes the eyeball to turn red?<\/h2>\n\t\t\t

    A red eyeball means the tiny blood vessels on the white of the eye are swollen, or one has bled.<\/strong> The NHS says a red eye is “often caused by an infection or dry eyes, but there are lots of possible causes.” The most common ones are:<\/p>\n\t\t\t

    Cause<\/th>What it usually looks and feels like<\/th>How serious<\/th><\/tr><\/thead>
    Conjunctivitis<\/strong> (pink eye)<\/th>Both eyes red, burning or gritty, watering, sticky discharge; viral, bacterial or allergic<\/td>Usually mild; most cases clear within two weeks (NHS)<\/td><\/tr>
    Dry eye<\/strong><\/th>Red, gritty, stinging eyes, often worse on screens or in wind or air-conditioning<\/td>Common and treatable<\/td><\/tr>
    Blepharitis<\/strong><\/th>Red, swollen lid edges with crusting; eyes look red and irritated<\/td>Chronic but manageable<\/td><\/tr>
    Burst blood vessel (subconjunctival haemorrhage)<\/strong><\/th>A bright red patch on the white of the eye, usually painless<\/td>Usually harmless<\/td><\/tr>
    Eyelid problems<\/strong><\/th>Styes, lid swelling and turned-in lashes irritating the surface<\/td>Varies<\/td><\/tr>
    Contact lens problems<\/strong><\/th>Red, sore eye in a lens wearer<\/td>Can be a corneal infection: urgent<\/td><\/tr>
    Keratitis or corneal ulcer<\/strong><\/th>Red, painful eye, light sensitivity, sometimes a white spot on the cornea<\/td>Urgent; can damage vision<\/td><\/tr>
    Uveitis or scleritis<\/strong><\/th>Deep, aching red eye, often with light sensitivity<\/td>Urgent; needs specialist treatment<\/td><\/tr>
    Acute angle-closure glaucoma<\/strong><\/th>Very red eye, intense pain, headache, haloes round lights, nausea<\/td>Emergency<\/td><\/tr><\/tbody><\/table><\/div>

    The pattern matters more than the colour. A red eye with no pain and normal vision often settles by itself; the NHS advises not touching the eye and stopping contact lens wear until it clears. A red eye with pain, light sensitivity or changes in vision is different.<\/p><\/div>\n\t\t\t

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    Why is there blood on my eyeball?<\/h3>

    A bright red patch on the white of the eye is most often a subconjunctival haemorrhage<\/strong>: a small blood vessel in the conjunctiva has broken and blood has collected between the conjunctiva and the sclera. According to the American Academy of Ophthalmology (AAO), it is usually harmless and often heals on its own, and the usual triggers are coughing, sneezing, straining or rubbing the eye. Less often it is linked to diabetes, high blood pressure or blood-thinning medicines such as aspirin, warfarin (Coumadin), clopidogrel (Plavix), apixaban (Eliquis) and rivaroxaban (Xarelto).<\/p>\n