Orbit and Contents

Question 1

What is the function of lacrimal gland and nasolacrimal duct?

Answer 1

The lacrimal gland secretes tears, the eyelids sweep them across the eye medially where the nasolacrimal duct drains them into the nasal cavity.

Question 2

What is the function of the superior tarsal muscle?

Answer 2

It gives the upper eyelid “tone” keeping it elevated above the iris of the eye.

Question 3

What is the innervation of the superior tarsal muscle?

Answer 3

It is innervated by the sympathetic division of the ANS.

Question 4

What is the function of the tarsal gland?

Answer 4

It secretes a waxy material to keep eyelids from sticking together when closed.

Question 5

What is a sty?

Answer 5

It is a blocked ciliary gland.

Question 6

List the innervation of all the extraocular muscles?

Answer 6

Lateral rectus - CN VI (abducens);

Superior oblique - CN IV (trochlear);

All others - CN III (oculomotor).

Question 7

Describe the action of each extraocular m. on the direction of the iris.

Answer 7

Lateral rectus - aBduction;

Medial rectus - aDduction;

Superior rectus - medially and upward;

Inferior rectus - medially and downward;

Superior oblique - laterally and downward;

Inferior oblique - laterally and upward.

Question 8

How would you specifically test each muscle for integrity?

Answer 8

Ask the patient (while gazing in the visual axis) to look in the directions listed: Lateral rectus - aBduction; medial rectus - aDduction; superior rectus - medially and upward; inferior rectus - medially and downward; superior oblique - laterally and downward; inferior oblique - laterally and upward.

Question 9

How would a lesion of cranial n. VI appear?

Answer 9

In a lesion of the abducens nerve (VI) no aBduction is possible.

Question 10

How would a lesion of cranial n. IV appear?

Answer 10

In a lesion of the trochlear nerve (IV) no lateral depression is possible PLUS intortion is not possible resulting in double vision and patient tilting his head to minimize this.

Question 11

How would a lesion of cranial n. III appear?

Answer 11

In a lesion of the oculomotor nerve (III) no aDduction is possible among other movements - the pupil remains aBducted and depressed (“down and out”) due to the unoppsed actions of the lateral rectus (LR6) and superior oblique (SO4). In addition, the pupil will be fully dilated and unresponsive due to the unopposed action of the dilator pupillae (no parasympathetic innervation). The upper eyelid also droops (ptosis) as voluntary elevation through the levator palpebrae superiosis is gone.

Question 12

What is extorsion/intorsion?

Answer 12

These are movements involving the rotation of the eyeball around its visual axis (with eyeball NOT in its LOP).

Question 13

Which muscle(s) are responsible for extorsion? intorsion?

Answer 13

The superior oblique = intortion (rotation toward nose from above) and inferior oblique = extortion (rotation toward the nose from below).

Question 14

What is the function of these movements (extorsion/intorsion)?

Answer 14

To keep image viewed level regardless of the angle of tilt of the head.

Question 15

Which layer of the eye contains the photoreceptor cells?

Answer 15

The retina.

Question 16

What is the optic disc?

Answer 16

The site where the optic nerve attaches to the eye - no vision (photoreceptor cells) here.

Question 17

Why would you stay away from the fovea centralis when using a laser to reattach the retina?

Answer 17

It is the site of most acute vision on the retina.

Question 18

What is glaucoma?

Answer 18

An increased pressure of aqueous humor in the anterior chamber of the eye.

Question 19

What is the anatomical basis for development of this disorder?

Answer 19

Aqueous humor, constantly produced in the ciliary body, is not drained into the venous sinuses at the iridial angle due to compression of these thin-walled vessels as a result of the increased pressure exterted by the abnormal amount of aqueous humor present in the chamber.

Question 20

How does the mechanism of accommodation work?

Answer 20

The ciliary m. contracts circularly. For close vision (nearer than 20 ft. away) the lens must thicken to allow greater refraction of light required for viewing close objects. Parasympathetic innervation constricts the pupil for close vision. As the iris constricts the ciliary bodies come closer together allowing the suspensory ligaments of the lens to become lax. This allows the lens to bulge outward and thicken. The reverse is the way you focus on distant objects.