Chapter 56 - Surgery of the Globe and orbit Flashcards
Figure 56-1. A normal skull, demonstrating the complete anterior bony
orbital rim of the horse. The pertinent bones that form the orbit of the
horse are labeled. LAC, Lacrimal bone; OF, orbital foramina including
ethmoid, optic, orbital fissure, and rostral alar; S, sphenoid bone; SF,
supraorbital foramen; T, temporal bone; Z, zygomatic bone; ZPF, zygomatic
process of the frontal bone; ZPT, zygomatic process of the temporal bone.
Note that part of the coronoid process of the mandible is missing.
What is the primary function of the orbits?
To protect the eye and its associated structures.
What are the average dimensions of the equine orbit?
62 mm in width, 59 mm in height, and 98 mm in depth.
Which bones compose the orbital rim in horses?
The frontal, lacrimal, and zygomatic bones.
At what angle are the axes of the eyes and orbits directed?
Laterally at 80 degrees off the midline.
How wide is the average equine eye globe?
48 mm in widt and 47 mm height
What forms the lateral border of the equine orbit?
The descending zygomatic process of the frontal bone, the ascending frontal process of the zygomatic bone, and the zygomatic process of the temporal bone.
What does the lacrimal sac contain?
The lacrimal fossa, which is an indentation in the lacrimal bone.
Where is the supraorbital foramen located?
Dorsolaterally within the zygomatic process of the frontal bone.
What structure disrupts normal tear flow when affected?
The lacrimal bone.
Which bones form the medial wall of the orbit?
The lacrimal, sphenoid, and palatine bones.
What is the risk during surgical manipulation of the orbital floor?
Potential for extensive hemorrhage and nerve damage.
What foramina are found at the orbital apex?
Ethmoidal foramen, optic foramen, orbital fissure, and rostral alar foramen.
Which nerve passes through the optic foramen?
the optic nerve (CN II).
Which muscle does the trochlear nerve (CN IV) innervate?
The dorsal oblique muscle.
What does the oculomotor nerve innervate?
Several extraocular muscles, including the levator palpebrae superioris and the iris sphincter.
What does the ophthalmic branch of the trigeminal nerve (CN V) provide?
Sensation to the cornea, conjunctiva, and dorsal eyelid.
What muscles are responsible for globe movement?
The extraocular muscles: dorsal, ventral, medial, and lateral rectus, as well as the oblique muscles.
What is the role of orbital fascia?
It supports the globe and maintains anatomic relationships.
How is the periorbita related to the orbital bones?
It is a periosteal layer that lines the orbital bones and is continuous with the dural sheath of the optic nerve.
What connects the periorbita with the eyelids?
The orbital septum.
Where is the lacrimal gland located?
Dorsolateral to the globe within the periorbita.