Orbit

Atlas References

• Netter: 94–104

• McMinn: 54–57

• Gray's Atlas: 508–519

Before You Begin

Remove all soft tissues with a scalpel and expose the frontal and temporal bones. Reflect the temporalis muscle as laterally as possible.

Osteotomy of Orbital Roof

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  With an electric saw or a mallet and chisel, make a second vertical cut through the frontal bone, lateral to the supraorbital notch ( Fig. 24.1 ).

  

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  Extend this cut posteriorly through the roof of the orbit between the optic nerve and ethmoidal sinuses ( Fig. 24.2 ).

  

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  With an electric saw or a mallet and chisel, make a second vertical cut through the squamous part of the temporal bone.

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  Continue the cut horizontally toward the orbital process of the zygomatic bone at the infraorbital margin (see Fig. 24.2 ).

Dissection Tip

Once all bones are cut, the orbital roof and the orbital process of the zygomatic bone can be reflected en bloc, while the periorbita (periosteal covering of orbital bones) is left intact ( Fig. 24.3 ). This is referred to as an orbitozygomatic approach.

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  Complete the reflection of the orbital roof anteriorly but do not detach it from the orbit ( Fig. 24.4 ).

  

Orbit

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  With sharp scissors, make a small cut in the periorbital fascia ( Fig. 24.5 ).

  

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  Identify the frontal nerve and its two branches, the supraorbital and supratrochlear nerves ( Fig. 24.6 ).

  

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  Clean and expose the frontal nerve and note the levator palpebrae superioris muscle lying underneath it ( Fig. 24.7 ).

  

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  Lateral and inferior to the levator palpebrae superioris, expose the superior rectus muscle ( Fig. 24.8 ).

  

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  Medial to the levator palpebrae superioris muscle, remove a small portion of the periorbital fat and identify the nasociliary nerve ( Fig. 24.9 and Plate 24.1 ).

  
  

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  Trace the terminal branches of the nasociliary nerve—the posterior ethmoidal, anterior ethmoidal, and infratrochlear nerves.

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  The superior oblique muscle is usually hidden medially under the orbital roof. Break away portions of the orbital roof to identify and clean the superior oblique muscle.

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  Clean the periorbital fat around the superior oblique muscle, and note the trochlear nerve entering the superior surface of the muscle proximally (see Fig. 24.9 ).

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  Distal to the interval between the superior oblique and levator palpebrae superioris muscles, look for a flat vessel, the superior ophthalmic vein.

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  Remove all small tributaries of the ophthalmic veins (see Fig. 24.9 ).

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  On the lateral surface of the superior rectus muscle, trace and expose the lacrimal nerve and lacrimal gland (see Fig. 24.9 ).

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  Deep to the lacrimal nerve, expose the lateral rectus muscle ( Fig. 24.10 ).

  

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  Pull the lateral rectus muscle laterally, and expose the abducens nerve on its medial side ( Fig. 24.11 ).

  

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  Look for the superior ophthalmic vein in the space between the superior rectus and lateral rectus muscles ( Fig. 24.12 ).

  

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  After identifying the superior ophthalmic vein, remove the periorbital fat between the superior and lateral rectus muscles ( Fig. 24.13 ).

  

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  Observe the optic nerve, surrounded by short and long ciliary nerves ( Fig. 24.14 ).

  

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  Identify the ciliary ganglion on the lateral surface of the optic nerve and medial to the lateral rectus muscle (see Fig. 24.14 ).

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  At the interval between the optic nerve and the lateral rectus muscle, identify the ophthalmic artery ( Fig. 24.15 ).

  

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  Inferior to the optic nerve, remove the periorbital fat and identify the inferior division of the oculomotor nerve, which runs parallel to the inferior rectus muscle (see Fig. 24.15 ).

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  Clean the periorbital fat inferior to the superior oblique muscle.

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  Trace the anterior and posterior ethmoidal nerves to their entrance into the anterior and posterior ethmoidal foramina, respectively ( Fig. 24.16 and Plate 24.2 ).

  
  

Anatomy Note

The four recti muscles arise from a fibrous ring that encircles the optic foramen and a portion of the superior orbital fissure. The superior oblique and levator palpebrae muscles arise from points superior and medial to this anulus (anulus of Zinn) ( Fig. 24.17 ).

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  Reflect the nasociliary nerve and ophthalmic artery posteriorly and expose the medial rectus muscle ( Fig. 24.18 ).

  

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  Pull the lateral rectus muscle laterally and the optic nerve medially, and expose the inferior rectus muscle ( Fig. 24.19 and Plate 24.3 ).