Orbit and Eye Ball

What is the shape of the orbit?

Pyramidal shape with base anterior and apex posterior.

What lines the bones of the orbit?

The bones are lined with periorbita (periosteum).

What forms the fascial sheath of the eyeball?

Periorbita forms a fascial sheath of the eyeball.

Which bones contribute to the superior wall of the orbit?

The superior orbital part of the frontal bone and the lesser wing of the sphenoid.

What bones are found in the medial wall of the orbit?

Ethmoid, lacrimal, maxilla, and sphenoid.

Which two bones make up the inferior wall of the orbit?

Maxilla and zygomatic bone.

What is the least protected part of the orbit?

The lateral orbital margin, but it provides the greatest view.

What communicates with the middle cranial fossa?

Superior orbital fissure.

Which cranial nerves pass through the superior orbital fissure?

Oculomotor nerve, trochlear nerve, lacrimal nerve (V1), frontal nerve (V1), nasociliary nerve (V1), and abducent nerve.

What is the function of the optic canal?

It allows passage for the optic nerve and ophthalmic artery.

What is Tenon's capsule?

A fascial sheath extending from the optic nerve to the corneoscleral junction.

What provides free movement of the eyeball?

Tenon's capsule, which separates the eyeball from orbital fat.

What are the three layers of the eye?

1. Outer fibrous layer (sclera, cornea); 2. Middle vascular layer (uveal tract: iris, ciliary body, choroid); 3. Inner nervous layer (retina).

What is the sclera?

Opaque, white, strong part covering the posterior 5/6 of the eyeball.

What is the cornea?

Transparent part covering the anterior 1/6 of the eyeball and the first refractive surface contributing to image formation.

What nourishes the cornea?

Aqueous humor, tears, and oxygen from air.

What forms the iris?

A circular disc that lies on the anterior surface of the lens with a central aperture called the pupil.

What are the two smooth muscles of the iris?

Sphincter pupillae (closes pupil, parasympathetic) and dilator pupillae (opens pupil, sympathetic).

What does the ciliary body connect?

It connects the choroid with the iris.

What is the function of the ciliary processes?

They secrete aqueous humor, which fills the anterior and posterior chambers.

What is the purpose of the retina?

It serves as the receptor organ for vision.

What is located at the ora serrata?

The anterior edge of the neural layer of the retina.

What is the physiological cup of the optic disc?

A central depression in the optic disc where there are no rods or cones (blind spot).

What fills the posterior part of the eye?

Vitreous humor, a transparent gel.

What is the role of the vitreous humor?

It supports the lens and holds the two layers of the retina in place.

How does the eye accommodate for near objects?

Ciliary muscle contracts, suspensory ligament relaxes, lens becomes globular.

How does the eye accommodate for far objects?

Ciliary muscle relaxes, suspensory ligament contracts, lens becomes thin.

What is the common tendinous ring?

A fibrous cuff from which the recti muscles arise.

What movements do the superior rectus and inferior oblique muscles perform?

Elevation and abduction.

What nerves innervate the extraocular muscles?

Oculomotor (III), Trochlear (IV), and Abducent (VI).

What happens during an oculomotor nerve lesion?

Drooping of the eyelid (ptosis), diplopia, dilatation of pupil, and loss of accommodation.

What is diplopia?

Double vision caused by paralysis of one or more extraocular muscles.

What is the function of the lacrimal gland?

Produces tears to keep the eye moist.

What is the pathway of tears?

Tears flow from lateral to medial corners, into the lacrimal sac, and then through the nasolacrimal duct.

What is conjunctivitis?

Inflammation of the conjunctiva.

What are the two parts of the conjunctiva?

Palpebral conjunctiva (covers eyelid) and bulbar conjunctiva (covers sclera of eye).

What is myopia?

Near sightedness.

What is hyperopia?

Far sightedness.

What is presbyopia?

Decreased lens elasticity and accommodation with age.

What is astigmatism?

Irregular curvature of lens or cornea.

What causes papilloedema?

Swelling of the optic disc due to increased CSF pressure.

What are the two layers of the inner nervous layer of the retina?

Outer: Retinal pigmented epithelium (RPE); Inner: Neural layer.

What is the ciliary zonule?

Also known as the suspensory ligament of the lens.

What supplies the retina?

The central retinal artery.

Where does the optic nerve leave the retina?

At the optic disc.

What is the key feature of the fovea centralis?

It is the central depression in the macula lutea responsible for most distinct vision.

What are some common lesions of cranial nerves in the orbit?

Squint or medial and lateral strabismus.

How is glaucoma characterized?

Elevated pressure of aqueous humor in the anterior chamber.

What happens during cataract surgery?

Phacoemulsification breaks up and removes the clouded lens.

What causes dilated pupils during an oculomotor nerve lesion?

Loss of parasympathetic function.

Which muscles are responsible for intorsion and extorsion of the eye?

Intorsion: Superior oblique and superior rectus; Extorsion: Inferior oblique and inferior rectus.

What is the purpose of the lacrimal apparatus?

To produce and drain tears.