The cornea, alongside the aqueous humour, lens, and vitreous body, makes up the refractive media of the eye. In this section, we will describe the detailed anatomy of the cornea.
The cornea and the sclera make up the outer covering of the eyeball, meeting at at the limbus. Unlike the sclera however, the cornea is a transparent and avascular tissue.
This coating is a structural barrier which works to protect the eye against infections, in addition to providing the anterior refractive surface of the eye together with the tear film.
<aside> đź’ˇ The cornea contributes 2/3 of the refractive power of the eye, contributing to about 40-44 D of refractive power.
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The cornea has an oval shape, with a horizontal diameter measuring 11-12mm and vertical diameter measuring 9-11mm. It is convex, with the anterior curvature measuring 7.8mm and posterior curvature measuring 6.5mm. Its thickness increases from the central cornea to the periphery, attributed to increased collagen in the peripheral stroma (the stroma is one of the corneal layers - we talk about it later on in the article!).
The cornea is composed of both cellular and acellular components. The cellular components include epithelial cells, keratocytes and endothelial cells. The acellular part consists of collagen and glycosaminoglycans. From an embryological point of view, the epithelial cells are derived from epidermal ectoderm, whilst the keratocytes and endothelial cells are derived from the neural crest.
The layers of the cornea are as follows:
<aside> 💡 Pro tip: a nice way to remember the layers of the cornea is ABCDE: Apithelium, Bowman’s layer, Citroma, Descemet’s membrane, Endothelium.
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