Sense organs (eye and ear)
Zonular fibres
Fibrae zonulares (Zonula ciliaris)
- Origin
- Fine fibres running from the ciliary body to the lens equator (zonule of Zinn)
- Insertion
- Attach to the anterior and posterior lens capsule around the equator
- Function
- Keep the lens centred and transmit the pull of the ciliary muscle, which makes accommodation possible
- Innervation
- Not innervated themselves; driven through the ciliary muscle (oculomotor nerve)
- Movement & chain
- Relax when the ciliary muscle contracts, allowing the lens to become more convex
- Palpation
- Only visible on slit-lamp after dilation; a wobbling lens (phacodonesis) points to weak zonules
- Clinical
- Zonular weakness in Marfan syndrome (superotemporal lens dislocation) and homocystinuria (inferior), pseudoexfoliation syndrome
- Segmental innervation
- No segment of its own
- In clinical practice
- Known zonular weakness changes the surgical plan in cataract surgery; record it in the handover
- Region in the model
- Sense organs (eye and ear)