{"id":1855,"date":"2026-10-20T08:53:09","date_gmt":"2026-10-20T08:53:09","guid":{"rendered":"https:\/\/laseristanbulclinic.com\/eye-glossary\/sclera\/"},"modified":"2026-10-20T12:57:19","modified_gmt":"2026-10-20T12:57:19","slug":"sclera","status":"publish","type":"page","link":"https:\/\/laseristanbulclinic.com\/en\/eye-glossary\/sclera\/","title":{"rendered":"Sclera: The White of the Eye, Its Function, Colour Changes and Problems"},"content":{"rendered":"\n
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  1. Home<\/a><\/li>
  2. Knowledge centre<\/a><\/li>
  3. Eye glossary A\u2013Z<\/a><\/li>
  4. Sclera: The White of the Eye, Its Function, Colour Changes and Problems<\/span><\/li><\/ol><\/div>\t\t\t

    Sclera: The White of the Eye, Its Function, Colour Changes and Problems<\/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

    Sclera<\/strong> (noun, plural sclerae or scleras)<\/em>: the sclera is the tough, white outer wall of the eye, the part everyone calls “the white of the eye”. It protects the eye’s delicate inner structures and holds the eyeball in shape, and it is where the eye muscles attach. At Laser Istanbul Clinic, inflammation and surface problems of the eye are assessed by our surgeons, including Do\u00e7. Dr. Muhammet Derda \u00d6zer (Do\u00e7. means Associate Professor), who leads cornea and uveitis care.<\/p>\n\t\t<\/div><\/div><\/div><\/div><\/section>\n\n\n\n\n

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    Sclera of the eye: 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 opaque, fibrous white outer layer of the eye, made mainly of type I collagen<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Where it is<\/span><\/dt>
    Covers most of the eyeball (about five-sixths of its outer wall); joins the clear cornea at a ring called the limbus; the optic nerve leaves through its back<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Thickness<\/span><\/dt>
    About 1 mm at the back of the eye and as thin as about 0.3 mm just behind the points where the eye muscles attach<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Layers<\/span><\/dt>
    Episclera (outer), stroma (the thick middle), and a thin inner suprachoroid lamina<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Blood supply<\/span><\/dt>
    Very little: the sclera itself is nearly avascular; most of the red vessels you see on the “white” are in the thin tissues covering it<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Covered by<\/span><\/dt>
    The conjunctiva, a clear membrane that lines the eyelids and covers the front of the sclera<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Main jobs<\/span><\/dt>
    Protection, shape, and an anchor for the eye muscles<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Specialist<\/span><\/dt>
    Ophthalmologist (eye doctor); inflammation is often managed together with a rheumatologist<\/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 sclera of the eye?<\/h2>\n\t\t\t\t

    The sclera of the eye is the outer coat that wraps the eyeball like a firm shell. Most of it is hidden behind the eyelids and the bony socket; the part you see in the mirror is only the front, on either side of the coloured iris. In front, it blends into the cornea, the clear dome over the iris and pupil. Behind, it forms a sleeve around the optic nerve.<\/p>\n

    Why is it white and opaque while the cornea is clear? Both are built from collagen, but in the sclera the fibres are interlaced and irregular, which scatters light, while in the cornea they are arranged in an exact, regular pattern that lets light through. That one difference in arrangement is the difference between a wall and a window.<\/p>\n

    The layers of the sclera<\/h3>
    Layer<\/th>What it is<\/th><\/tr><\/thead>
    Episclera<\/strong><\/th>A thin, loose layer of collagen tissue on the outside, just under the conjunctiva<\/td><\/tr>
    Stroma<\/strong><\/th>The thick main layer: dense type I collagen fibres interwoven with networks of elastic fibres; this is what makes the sclera strong<\/td><\/tr>
    Suprachoroid lamina<\/strong> (lamina fusca)<\/th>A thin inner layer containing fibroblasts and pigment cells, lying against the choroid<\/td><\/tr><\/tbody><\/table><\/div>

    The sclera is nearly avascular, meaning it has very few blood vessels of its own. This matters for diagnosis: a doctor judges a red eye partly by which layer the visible redness sits in.<\/p><\/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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    Sclera function: what does the sclera do?<\/h2>\n\t\t\t\t\t\t

    The sclera has three main functions.<\/p>\n\t\t\t\t\t\t

    1. Protection.<\/strong> It forms a strong barrier around the inner eye. Together with the eyelids, the bony socket and the tear reflex, it helps protect the delicate retina, choroid and other tissues from injury.<\/p>\n

    2. Keeping the eye’s shape.<\/strong> The eye works as an optical instrument only if its shape stays stable. The sclera gives the eyeball its architectural support, so that light from the cornea and lens reaches the retina in focus.<\/p>\n

    3. Anchoring the eye muscles.<\/strong> The muscles that move the eye attach to the sclera and pull on it to turn the eye. This is why the sclera matters in squint (strabismus) surgery, where the muscle attachments on the sclera are adjusted.<\/p>\n

    A fourth role is social: the visible white of the eye makes it easy to read where someone is looking, and changes in its colour are one of the first things others, and doctors, notice about health.<\/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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    Sclera vs conjunctiva: what is the difference?<\/h2>\n\t\t\t

    People often mix these up, because both are on the “white” of the eye.<\/p>\n\t\t\t

    <\/th>Sclera<\/th>Conjunctiva<\/th><\/tr><\/thead>
    What it is<\/th>The tough white wall of the eye<\/td>A thin, clear membrane<\/td><\/tr>
    Where<\/th>The eyeball’s outer coat<\/td>Covers the front of the sclera and lines the inside of the eyelids<\/td><\/tr>
    Blood vessels<\/th>Almost none<\/td>Many small, visible vessels, which is why a “red eye” usually looks red<\/td><\/tr>
    What goes wrong<\/th>Deep inflammation (scleritis), thinning, colour change<\/td>Conjunctivitis, subconjunctival bleeds, pinguecula, pterygium<\/td><\/tr><\/tbody><\/table><\/div>

    In short: the sclera is the wall, the conjunctiva is the thin clear covering over it. The conjunctiva and sclera sit so close together that doctors use the slit lamp to tell which one is affected. For example, a subconjunctival haemorrhage, the bright-red patch that appears after a cough or an eye rub, is blood leaking between the conjunctiva and the sclera. It looks alarming but usually heals by itself.<\/p>

    Glossary: Conjunctiva <\/svg><\/a><\/div><\/div>\t<\/div><\/div><\/div><\/section>\n\n\n\n\n
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    \"Close-up<\/div><\/div>\n\t\t
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    Why does my sclera look blue? Is blue sclera dangerous?<\/h2>\n\t\t\t\t\t\t

    Blue sclera is a bluish or grey tint to the white of the eye. It appears when the sclera is thin enough for the dark layers underneath (the uvea) to show through.<\/p>\n\t\t\t\t\t\t

    It is often harmless.<\/strong> A slightly blue sclera is normal in infants and young children, whose sclera is thinner. It usually fades as the sclera thickens with age.<\/p>\n

    It can be a clue to a connective-tissue condition.<\/strong> In older children and adults, a persistent blue tint can go with conditions in which collagen is faulty:<\/p>\n