Part 1 - Features of the Superficial Orbit

• • Clean the entirety of the orbicularis oculi m.

    • • Distinguish the palpebral part from the orbital part of the muscle

  • Examine the palpebral fissure and lateral and medial angles of the eye

  • Reflect the four portions of the eyelids away from the eye

    • • investigate aspects of the conjunctiva and conjunctival fornices

  • Distinguish the sclera and cornea of the fibrous layer of the eyeball

  • Identify the iris and the pupil of the vascular layer of the eyeball

  • Locate the lacrimal gland in the superolateral portion of the orbit

    • • Visualize the route of lacrimal fluid to the medial portion of the eye, and identify the:

        • • lacrimal caruncle

          • lacrimal lake

          • lacrimal papilla and puncta

  • Remove the medial palpebral ligament from its attachment point on the maxilla

    • • Expose the lacrimal canaliculi (very small and difficult to identify) and lacrimal sac

      • Open the lacrimal sac to expose the nasolacrimal duct

  • On the opposite side of the face, remove the orbicularis oculi m.

    • • reveal the insertion of levator palpebrae superioris m. and the tarso-fascial layer of the eyelids

Part 2 - Cranial Nerves 

• • Carefully strip away the dura mater in the middle cranial fossa

  • Take care to only remove the meningeal layer of the dura covering the cavernous sinus, and do not interrupt cranial nerves: 

    • • Oculomotor nn. (CN III)

      • Trochlear nn. (CN IV)

      • Trigeminal nn. (V1, and V2)

  • Locate the abducens n. (CN VI) and the internal carotid a. 

  • Investigate the neurovasculature located in the lateral wall of the cavernous sinus:

    • • oculomotor n. (CN III)

      • trochlear n. (CN IV)

      • ophthalmic n. (V1)

      • maxillary n. (V2). 

      • The mandibular n. (V3) is located in the vicinity, exiting through the foramen ovale

Part 3 - Orbit (superior approach)

• • Remove the scalp from the frontal bone

  • Strip the dura mater from the anterior cranial fossa

  • Remove the roof of the orbit and reflect the associated frontal bone anteroinferiorly

  • Continue to remove bone to uncover the superior orbital fissure

    • Preserve the supra-orbital neurovasculature and the lacrimal gland as much as possible

  • Remove the orbital adipose connective tissue to uncover the most superior layer of neurovasculature and muscles

    • • frontal n. (with branches supratrochlear n. and supra-orbital n.)

      • trochlear n. (CN IV)

      • lacrimal n.

      • levator palpebrae superioris m.

      • superior oblique m.

  • Cut the levator palpebrae superioris m. approximately at its midpoint

  • Reflect the bulk of the body of the muscle anteriorly and posteriorly to better reveal the superior rectus m.

  • Cut the superior rectus m. near its insertion on the sclera

  • Locate the lateral rectus m. and the abducens n. (CN VI)

  • Move the superior oblique m. as medially as possible in order to better view the medial rectus m. 

  • Clean the neurovasculature deep to the superior oblique m. This includes:

    • • ophthalmic a. (and its branches - anterior and posterior ethmoidal aa.) 

      • vv (superior & inferior).

      • nasociliary n. and its branches (anterior and posterior ethmoidal nn., infratrochlear n., long ciliary nn.).

  • Locate

    • • optic n. (CN II)

      • ciliary ganglion

      • short ciliary nn

  • Distinguish between the superior and inferior divisions of the oculomotor n. (CN III)

  • Examine the optic n. in cross section to see the central artery of the retina

  • Move neurovasculature to locate and clean the inferior rectus m. 

    • • The inferior oblique m. is often difficult to see in the superior view

Part 4 - Orbit (anterior approach)

• • Remove the orbicularis oculi m. and the tarso-fascial layer of the eye

  • Cut the levator palpebrae superioris m. at its attachment to the superior tarsal plate

  • Cut both (medial and lateral) palpebral ligaments, and bluntly separate the orbital septum 

    • • Incise around the conjunctiva, and remove any palpebral conjunctiva 

  • Clean the extra-ocular eye mm.

  • Locate the insertions for the four rectus muscles and two oblique muscles on the eye

  • Cut each insertion as near to the eye as possible

  • Enucleate (remove) the eye

• • • Cut the optic n. (CN II) near the eye.

• • Remove orbital adipose to best visualize and appreciate the muscles and neurovasculature of the orbit

  • Locate the common anular tendon