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Anatomy of the Cornea

Anatomy

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CLINICAL ANALOGY

Think of the cornea as a five-layered bulletproof glass panel in a high-security building. The outer glass (epithelium) repels water and bacteria; the laminated polycarbonate core (stroma) provides tensile strength; the inner coating (endothelium) actively pumps out fluid to keep the glass crystal-clear. Between each layer sit specialised membranes - Bowman's and Descemet's - acting as adhesive laminas and selective barriers. Unlike most 'glass', this panel is self-healing (epithelium), partially self-renewing at its margins (limbal stem cells), but with very limited repair capacity in its pump layer (endothelium). Understanding each layer's biology explains every corneal disease you will encounter.

The cornea is the anterior transparent avascular tissue of the eye contributing approximately 43–44 D of the
total ~60 D refractive power of the eye. It is the primary refractive surface and a critical immune barrier.

Parameter	Value / Detail
Horizontal diameter	• 11.7 millimetres (slightly > vertical: 10.6 millimetres)
Central thickness (central corneal thickness)	• 520–540 micrometres (mean ~540 micrometres)
Peripheral thickness	• ~670 micrometres close to the corneoscleral junction (thicker peripherally)
Radius of curvature (anterior)	• ~7.8 millimetres (anterior surface power ~48 dioptres)
Radius of curvature (posterior)	• ~6.5 millimetres
Refractive index	• 1.376 (stroma); total 1.336 effective
Refractive power	• ~43 dioptres (about 70% of total eye power)
Oxygen supply	• Primarily from atmosphere via tears (awake) • Limbal vessels (periphery)
Innervation	• Ophthalmic division of the trigeminal nerve (cranial nerve V1) via long ciliary nerves (nasociliary branch)

Parameter	Value / Detail
Horizontal diameter	• 11.7 millimetres (slightly > vertical: 10.6 millimetres)
Central thickness (central corneal thickness)	• 520–540 micrometres (mean ~540 micrometres)
Peripheral thickness	• ~670 micrometres close to the corneoscleral junction (thicker peripherally)
Radius of curvature (anterior)	• ~7.8 millimetres (anterior surface power ~48 dioptres)
Radius of curvature (posterior)	• ~6.5 millimetres
Refractive index	• 1.376 (stroma); total 1.336 effective
Refractive power	• ~43 dioptres (about 70% of total eye power)
Oxygen supply	• Primarily from atmosphere via tears (awake) • Limbal vessels (periphery)
Innervation	• Ophthalmic division of the trigeminal nerve (cranial nerve V1) via long ciliary nerves (nasociliary branch)

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