Sense organs (eye and ear)
Cornea
Cornea
- Origin
- Transparent, avascular anterior sixth of the fibrous tunic; continues into the sclera at the limbus
- Insertion
- Anchored at the corneal limbus, where the epithelium continues into the bulbar conjunctiva
- Function
- Provides about 40 dioptres, two thirds of the total refractive power of the eye, and protects the anterior chamber
- Innervation
- Ophthalmic nerve (V1) via the long ciliary nerves; the most densely innervated tissue in the body
- Movement & chain
- Follows the globe during every eye movement; does not bend itself, but changes curvature with pressure or scarring
- Palpation
- Slit-lamp examination with fluorescein; the corneal reflex (cotton wisp) tests V1 afferent and the facial nerve efferent
- Clinical
- Keratitis (bacterial or herpes simplex with a dendritic ulcer), contact-lens erosion, keratoconus, endothelial decompensation after cataract surgery
- Segmental innervation
- Sensory V1 (trigeminal nerve, pons); blink reflex efferent via the facial nerve (VII)
- In clinical practice
- Never patch an eye with suspected infection; stain with fluorescein and refer urgently when pain is combined with reduced vision
- Region in the model
- Sense organs (eye and ear)