Sclera
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The sclera (plural: scleras or sclerae) is the fibrous, opaque white, coat of the eye. It functions to protect the intraocular contents.
Summary
- location: posterior fifth-sixths of the eyeball
- blood supply: ciliary arteries
- innervation: ciliary nerves
- relations: anteriorly continuous with the cornea
Gross anatomy
Outermost coat of the 3-layeredtrilaminar globe. Anteriorly continuous with the cornea. Posteriorly perforated by the optic nerve at the lamina cribrosa.
Arterial supply
Anteriorly
-
anteriorly, the anterior ciliary arteries form a dense episcleral plexus
. Posteriorly -
posteriorly, supplied by branches of the short and long posterior ciliary arteries
.
Lymphatic drainage
The sclera is an alymphatic organ.
Innervation
Anteriorly supplied by the long ciliary nerves. Posteriorly supplied by the short ciliary nerves.
Histology
The sclera may be divided into its three histological layers:
- episclera
- outermost, loose connective tissue layer, connected to the Tenon
'scapsule - rich vascular supply from anterior ciliary arteries
- outermost, loose connective tissue layer, connected to the Tenon
- scleral stroma
- dense fibrous tissue intermingled with fine elastic fibers
- irregular arrangement of type I and III collagen responsible for its opacity
- lamina fusca
- innermost layer with melanocytes
- weakly related to the choroid
Radiographic features
Ultrasound and CT are not useful modalities.
Anterior segment ocular coherence tomography (AS-OCT)
- readily used in clinical practice to measure
sclerascleral thickness, monitor therapeutic response in scleritis treatment - quantitative measurements obtained
MRI
- useful in the diagnosis of posterior scleritis and episcleritis
- T1-weighted sequences, sclera appears as the hypointense rim of the globe
History and etymology
The word derives from medical Latin, itself from the Greek sklera "the hard (membrane)," feminine form of skleros "hard".
Related pathology
- scleral plaques
- episcleritis/scleritis: inflammation of the sclera
-
staphyloma: full or partial thickness
sclerascleral defect lined by the uvea
-<strong>location</strong>: posterior fifth-sixths of the eyeball</li>- +<strong>location</strong>: posterior fifth-sixths of the <a title="Eyeball" href="/articles/ocular-globe-1">eyeball</a>
- +</li>
-<strong>blood supply</strong>: ciliary arteries</li>- +<strong>blood supply</strong>: <a title="ciliary artery" href="/articles/ciliary-artery">ciliary arteries</a>
- +</li>
-</ul><h4>Gross anatomy</h4><p>Outermost coat of the 3-layered <a href="/articles/ocular-globe-1">globe</a>. Anteriorly continuous with the cornea. Posteriorly perforated by the <a href="/articles/optic-nerve">optic nerve</a> at the <a href="/articles/lamina-cribrosa-sclerae">lamina cribrosa</a>. </p><h4>Arterial supply</h4><p>Anteriorly, the <a title="Anterior ciliary artery" href="/articles/anterior-ciliary-artery">anterior ciliary arteries</a> form a dense episcleral plexus. Posteriorly, supplied by branches of the short and long <a title="Posterior ciliary artery" href="/articles/posterior-ciliary-artery">posterior ciliary arteries</a>. </p><h4>Lymphatic drainage</h4><p>The sclera is an alymphatic organ.</p><h4>Innervation</h4><p>Anteriorly supplied by the <a href="/articles/long-ciliary-nerves">long ciliary nerves</a>. Posteriorly supplied by the <a href="/articles/short-ciliary-nerves">short ciliary nerves</a>. </p><h4>Histology</h4><p>The sclera may be divided into its three histological layers:</p><ol>-<li>episclera <ul>-<li>outermost, loose connective tissue layer, connected to the Tenon's capsule </li>-<li>rich vascular supply from anterior ciliary arteries </li>- +</ul><h4>Gross anatomy</h4><p>Outermost coat of the trilaminar <a href="/articles/ocular-globe-1">globe</a>. Anteriorly continuous with the cornea. Posteriorly perforated by the <a href="/articles/optic-nerve">optic nerve</a> at the <a href="/articles/lamina-cribrosa-sclerae">lamina cribrosa</a>. </p><h4>Arterial supply</h4><ul>
- +<li>anteriorly, the <a href="/articles/anterior-ciliary-artery">anterior ciliary arteries</a> form a dense episcleral plexus</li>
- +<li>posteriorly, supplied by branches of the short and long <a href="/articles/posterior-ciliary-artery">posterior ciliary arteries</a>
- +</li>
- +</ul><h4>Lymphatic drainage</h4><p>The sclera is an <a title="Lymph vascular system" href="/articles/lymphatic-system">alymphatic organ</a>.</p><h4>Innervation</h4><p>Anteriorly supplied by the <a href="/articles/long-ciliary-nerves">long ciliary nerves</a>. Posteriorly supplied by the <a href="/articles/short-ciliary-nerves">short ciliary nerves</a>. </p><h4>Histology</h4><p>The sclera may be divided into three histological layers:</p><ol>
- +<li>episclera<ul>
- +<li>outermost, loose connective tissue layer, connected to the <a title="Tenon's capsule" href="/articles/tenon-s-capsule">Tenon capsule</a>
- +</li>
- +<li>rich vascular supply from anterior ciliary arteries</li>
-<li>scleral stroma <ul>- +<li>scleral stroma<ul>
-<li>lamina fusca <ul>-<li>innermost layer with melanocytes </li>-<li>weakly related to the choroid </li>- +<li>lamina fusca<ul>
- +<li>innermost layer with melanocytes</li>
- +<li>weakly related to the choroid</li>
-<li>readily used in clinical practice to measure sclera thickness, monitor therapeutic response in scleritis treatment</li>- +<li>readily used in clinical practice to measure scleral thickness, monitor therapeutic response in scleritis treatment</li>
-<a href="/articles/staphyloma">staphyloma</a>: full or partial thickness sclera defect lined by uvea</li>- +<a href="/articles/staphyloma">staphyloma</a>: full or partial thickness scleral defect lined by the <a title="Uvea" href="/articles/uvea">uvea</a>
- +</li>
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