Cornea
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The cornea forms the fibrous layer inof the anterior portion of the eyeball. It functions to refract light entering the eye.
Summary
- location: anterior one-sixth of the eyeball
- blood supply: avascular
- innervation: long ciliary nerves
-
relations: continuous with the sclera posteriorly and covered by the conjunctiva anteriorly
.
Gross anatomy
Anteriorly, the cornea is a convex structure covered by bulbar conjunctiva. The curvature is greater than that of the rest of the eyeball covered by the sclera. Posteriorly, the cornea is concave and round.
It is made up of 5 layers.
Transparency
Transparency of the cornea is due to the regular arrangement of the collagen fibrils in lamellae, in the stroma.
Arterial supply
The cornea is largely avascular. The peripheral parts are related to capillaries from the anterior ciliary arteries. It is nourished by the aqueous humour and gaseous exchange occurs through the tear film.
Lymphatic drainage
The cornea is an alymphatic organ.
Innervation
Densely innervated by the long ciliary nerves, branch of the nasociliary branchnerve, which is derived from the ophthalmic division of the trigeminal nerve.
Histology
MicroscopicallyHistologically, the cornea is made up of 5 layers (from superficial to deep):
-
Epitheliumepithelium - Bowman's membrane
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Stromastroma (substantia propria) - Descemet's membrane
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Endotheliumendothelium
Radiographic features
Corneal Topography
Imaging of the cornea can be performed by a number of techniques, including:
-
characterizescorneal topography: characterises the shape of the cornea qualitatively and quantitatively
Anterior
- : produces a cross-section image of the cornea and other anterior segment structures
Ultrasound Biomicroscopy
High-
ultrasound biomicroscopy: high-frequency and high resolutions are required
.
CT and MRI are not performed for imaging of the cornea.
History and etymology
FromDerived from the Latin cornea tela (“horny tissue”), and from cornu (“horn”).
Related pathology
-
Astigmatism - refractiveastigmatism: refractive error due to aspheric or uneven cornea curvature -
Keratoconus -keratoconus: most common corneal ectasia, is a progressive corneal condition characterized by central thinning and steepening of the cornea. - Fuchs endothelial dystrophy
- non: non-inflammatory dystrophy of the cornea -
Keratitiskeratitis
-<p>The cornea forms the fibrous layer in the anterior portion of the eyeball. It functions to refract light entering the eye. </p><h4>Summary</h4><ul>- +<p>The <strong>cornea</strong> forms the fibrous layer of the anterior portion of the eyeball. It functions to refract light entering the eye. </p><h4>Summary</h4><ul>
-<strong>innervation</strong>: <a title="long ciliary nerves" href="/articles/long-ciliary-nerves">long ciliary nerves</a> </li>- +<strong>innervation</strong>: <a href="/articles/long-ciliary-nerves">long ciliary nerves</a> </li>
-<strong>relations</strong>: continuous with the sclera posteriorly and covered by the <a title="Conjunctiva" href="/articles/conjunctiva">conjunctiva</a> anteriorly.</li>-</ul><h4>Gross anatomy</h4><p>Anteriorly, the cornea is a convex structure covered by bulbar conjunctiva. The curvature is greater than that of the rest of the eyeball covered by the sclera. Posteriorly, the cornea is concave and round. </p><p>It is made up of 5 layers. </p><h5>Transparency </h5><p>Transparency of the cornea is due to the regular arrangement of the collagen fibrils in lamellae, in the stroma. </p><h4>Arterial supply </h4><p>The cornea is largely avascular. The peripheral parts are related to capillaries from the anterior ciliary arteries. It is nourished by the aqueous humour and gaseous exchange occurs through the tear film. </p><h4>Lymphatic drainage</h4><p>The cornea is an alymphatic organ. </p><h4>Innervation</h4><p>Densely innervated by the long ciliary nerves, branch of the nasociliary branch, which is derived from the ophthalmic division of the <a title="Trigeminal nerve" href="/articles/trigeminal-nerve">trigeminal nerve</a>. </p><h4>Histology</h4><p>Microscopically, the cornea is made up of 5 layers:</p><ol>-<li>Epithelium</li>- +<strong>relations</strong>: continuous with the <a title="Sclera" href="/articles/sclera">sclera</a> posteriorly and covered by the <a href="/articles/conjunctiva">conjunctiva</a> anteriorly</li>
- +</ul><h4>Gross anatomy</h4><p>Anteriorly, the cornea is a convex structure covered by bulbar <a title="Conjunctiva" href="/articles/conjunctiva">conjunctiva</a>. The curvature is greater than that of the rest of the eyeball covered by the sclera. Posteriorly, the cornea is concave and round. </p><p>It is made up of 5 layers. </p><h5>Transparency </h5><p>Transparency of the cornea is due to the regular arrangement of the collagen fibrils in lamellae in the stroma. </p><h4>Arterial supply </h4><p>The cornea is largely avascular. The peripheral parts are related to capillaries from the anterior ciliary arteries. It is nourished by the aqueous humour and gaseous exchange occurs through the tear film. </p><h4>Lymphatic drainage</h4><p>The cornea is an alymphatic organ. </p><h4>Innervation</h4><p>Densely innervated by the long ciliary nerves, branch of the <a title="Nasociliary nerve" href="/articles/nasociliary-nerve">nasociliary nerve</a>, which is derived from the ophthalmic division of the <a href="/articles/trigeminal-nerve">trigeminal nerve</a>.</p><h4>Histology</h4><p>Histologically, the cornea is made up of 5 layers (from superficial to deep):</p><ol>
- +<li>epithelium</li>
-<li>Stroma (substantia propria)</li>- +<li>stroma (substantia propria)</li>
-<li>Endothelium </li>-</ol><h4>Radiographic features</h4><h5>Corneal Topography </h5><ul><li>characterizes the shape of the cornea qualitatively and quantitatively</li></ul><h5>Anterior segment optical coherence tomography (AS-OCT) </h5><ul><li>produces a cross-section image of the cornea and other anterior segment structures</li></ul><h5>Ultrasound Biomicroscopy</h5><ul><li>High-frequency and high resolutions are required. </li></ul><p>CT and MRI are not performed for imaging of the cornea. </p><h4>History and etymology</h4><p>From Latin cornea tela (“horny tissue”), from cornu (“horn”)</p><h4>Related pathology</h4><ul>-<li>Astigmatism - refractive error due to aspheric or uneven cornea curvature </li>-<li>Keratoconus - most common corneal ectasia, is a progressive corneal condition characterized by central thinning and steepening of the cornea. </li>-<li>Fuchs endothelial dystrophy - non-inflammatory dystrophy of the cornea</li>-<li>Keratitis </li>- +<li>endothelium </li>
- +</ol><h4>Radiographic features</h4><p>Imaging of the cornea can be performed by a number of techniques, including:</p><ul>
- +<li>corneal topography: characterises the shape of the cornea qualitatively and quantitatively</li>
- +<li>anterior segment optical coherence tomography (AS-OCT): produces a cross-section image of the cornea and other anterior segment structures</li>
- +<li>ultrasound biomicroscopy: high-frequency and high resolutions are required</li>
- +</ul><p>CT and MRI are not performed for imaging of the cornea.</p><h4>History and etymology</h4><p>Derived from the Latin <em>cornea tela</em> (“horny tissue”) and from <em>cornu</em> (“horn”).</p><h4>Related pathology</h4><ul>
- +<li>astigmatism: refractive error due to aspheric or uneven cornea curvature</li>
- +<li>keratoconus: most common corneal ectasia, is a progressive corneal condition characterized by central thinning and steepening of the cornea</li>
- +<li>Fuchs endothelial dystrophy: non-inflammatory dystrophy of the cornea</li>
- +<li>keratitis </li>
References changed:
- 1. Richard S. Snell, Michael A. Lemp. Clinical Anatomy of the Eye. (2013) <a href="https://books.google.co.uk/books?vid=ISBN9781118691007">ISBN: 9781118691007</a><span class="ref_v4"></span>
- Snell, R., Lemp, M., & Grunther, I. (1998). Clinical anatomy of the eye. Oxford: Blackwell Science Ltd.
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