The brain should have previously been removed from your cat (see Removal and Study of the Cat Brain). You should identify the upper and lower eyelids, and the nictitating membrane which comes up from below the eye. Note the conjunctival surfaces, and the inferior fornix.
Locate the optic nerves where they enter the cranium through the optic foramina.
Draw lines from each optic nerve to the medial and lateral limits of the orbits.
The accompanying image shows the location of the cut to make.
Cut on these lines with the end of a hack saw. Be certain to cut laterally enough to prevent part of the frontal from overhanging, and all the way to the optic foramina.
Lift off the triangular section of the roof of the orbit, cutting it free from any underlying tissue which may adhere to it, preserving features attached to the eye.
Mark the superior-most muscle with an indelible "X" to keep track of it later in the dissection.
(Can you find the superior oblique and its trochlea, on the medial superior border of the orbit? This is a challenge.)
Cut the anterior portion of the eye loose from the socket by cutting closely along the bone to free up the eye itself. Lift up the entire structure, cutting any peripheral tissues which may hold it down. After you have lifted it in the front, slide the scalpel under the rear-most portion to free it from the skull. Note that the nictitating membrane marks the inferior portion of the dissected portion.
Note the membrane which surrounds the entire orbit (periorbita). The lacrimal gland is under it on the lateral superior side. Work the periorbita open with a blunt probe, remove the adipose tissue which served as padding. The most superficial superior muscle will be the levator palpebrae superioris, which raises the eyelid. It does not insert into the bulb.