The eye

Question 1

What are the orbital components?

Answer 1

• the eye.
• the orbital and retrobulbar fascia.
• extraocular muscles.
• cranial nerves 2,3,4,5,6.
• blood vessels.
• fat.
• lacrimal gland with its sac and nasolacrimal duct.
• eyelids.
• medial and lateral.
• palpebral ligaments.
• septum.
• ciliary ganglion.
• short ciliary nerves.

Question 2

What are the extraocular muscles?

Answer 2

• 6 muscles that control movement of the eye and one muscle that controls eyelid elevation.
• The actions of the 6 muscles for eye movement depend on the position of the eye at the time of muscle contraction.
• Four control movement of the eye in four cardinal directions (up, down, left, right).
• The remaining two control the adjustments involved in counteracting head movement.

Question 3

Name the extraocular muscles?

Answer 3

• superior rectus.
• medial rectus.
• lateral rectus.
• inferior rectus.
• superior oblique.
• inferior oblique.
• optic nerve.

Question 4

What is the levator palpebrae superioris muscle ?

Answer 4

• It is the muscle in the orbit which elevates the superior (upper) eyelid.

Question 5

What is the orbicularis oculi?

Answer 5

• Muscle in the face that closes the eyelids.

- Surrounds the circumference of the eye and moves downward on the cheek.

Question 6

What is the pupil?

Answer 6

• Opening in the centre of the eye.
• Light enters through the pupil and goes through the lens, which focuses the image on the retina.
• The size of the pupil is controlled by muscles.
• When more light needed pupil made larger.
• Surrounded by the iris which is the coloured part of the eye.

Question 7

What is the iris?

Answer 7

• It’s the structure in the eye which controls the diameter and size of the pupil and therefore the amount of light reaching the retina.
• Coloured part of eye.
• The iris consists of two layers: the front pigmented fibrovascular known as the stroma and beneath this pigmented epithelial cells.

Question 8

What is the lacrimal lake?

Answer 8

• The pool of tears in the lower conjunctival cul-de-sac, which drains into the opening of the tear drainage system.
• The volume has been estimated to be between 7-10ul of tears.
• Maximum it can hold is 25-30ul before tearing occurs.

Question 9

Where is the medial angle of the eye?

Answer 9

• Tear duct.

Question 10

Where is the lateral angle of the eye?

Answer 10

• Towards the edge of the face.

Question 11

What is the conjunctiva?

Answer 11

• Lines the inside of the eyelids and covers the sclera (white part of the eye).
• Composed of non-keritinized, stratified columnar epithelium with goblet cells.
• It helps lubricate the eye by producing mucus and tears (although a smaller volume of tears than the lacrimal gland).
• Contributes to immune surveillance.

Question 12

What is the sclera?

Answer 12

• White part of the eye.

- Fibrous, protective outer layer containing collagen and elastic fibre.

Question 13

What is the lacrimal puncta?

Answer 13

• There are two in the inside portion of each eye.
• One at top and one at bottom.
• Hole that collects tears produced by the lacrimal glands.

Question 14

What does lateral rotation or extorsion of the eye mean?

Answer 14

• Looking away from face (also know as abduction).

Question 15

What does medial rotation or intorsion of the eye mean?

Answer 15

• Looking towards the nose (also know as adduction).

Question 16

What is the transverse axis of the eye?

Answer 16

• When cut straight through the middle (leaving a top and bottom half).

Question 17

What is the vertical axis of the eye?

Answer 17

• When cut straight up and down (leaving a left and right side of the eye).

Question 18

What does the superior rectus muscle do?

Answer 18

• Supplied by the occulomotor nerve (cranial nerve 3).

- Looking straight ahead its primary function is elevation however it also contributes to intorsion and adduction.

Question 19

What does the medial rectus muscle do?

Answer 19

• Supplied by the occulomotor nerve (cranial nerve 3).
• Largest muscle in the orbit and only action is adduction.
• Function is to bring the eyeball closer to the midline of the body.

Question 20

What does the inferior rectus muscle do?

Answer 20

• Supplied by occulomotor nerve (cranial nerve 3).

- Involved in depression, adduction and extorsion (rotate laterally) of the eye.

Question 21

What does the lateral rectus muscle do?

Answer 21

• Is the only muscle supplied by abductees nerve (cranial never 6).
• Moves the pupil away from the midline (abducts eye).

Question 22

What is the orbit?

Answer 22

• Cavity or socket of the skull in which the eye and its appendages are situated.
• The volume of the orbit is 30mL of which the eye occupies 6.5mL.

Question 23

What does the inferior oblique muscle do?

Answer 23

• Supplied by occulomotor nerve (cranial nerve 3).

- It’s involved it extorsion, elevation and abduction.

Question 24

What does the superior oblique muscle do?

Answer 24

• It is the only muscle supplied by the trochlear nerve (cranial nerve 4).
• Involved in Intorsion depression and abduction.

Question 25

What does the eyeball consist of?

Answer 25

- connective tissue layer (anterior: bulbar conjunctiva and posterior: fascial sheath of eyeball). - fibrous layer (sclera and cornea). - vascular layer (choroid, ciliary body and iris). - inner layer (retina - optic and non-visual parts).

Question 26

Where are photoreceptors cells found?

Answer 26

- This is a specialised type of neurone found in the retina and is capable of phototransduction.

Question 27

What is phototransduction?

Answer 27

- Process by which light is converted into electrical signals in the rod cells, cone cells and photosensitive ganglion cells of the retina of the eye which can then stimulate biological processes.

Question 28

What are the three types of photoreceptor cells in mammalian eyes?

Answer 28

- Rods, cones and photosensitive retinal ganglion cells.

Question 29

What is the function of rods and cones?

Answer 29

- Used by the visual system to form a representation of the visual world, sight.

Question 30

What is the function of photosensitive ganglion cells?

Answer 30

- These do not contribute directly to sight but are thought to support circadian rhythms and pupillary reflex.

Question 31

What are rod cells?

Answer 31

- Photoreceptor cells in the retina, can function in less intense light than cones. - Concentrated at the outer edges of the retina and used in peripheral vision. - Approx 90 million in eye. More sensitive than cone cells rods are almost entirely responsible for night vision. - Have only one type of light sensitive pigment.

Question 32

What are cone cells?

Answer 32

- Responsible for colour vision and respond best in relatively bright light. Approx 6-7 million cones. - Less sensitive to light than rod cells. Cones are normally one of three types each with a different pigment - S, M or L. - Each cone is therefore sensitive to visible wavelengths of light that correspond to short, medium and long wavelengths of light.

Question 33

What is right monocular blindness?

Answer 33

- When you can't see anything out of right eye at all.

Question 34

What is bitemporal hemianopsia?

Answer 34

- When you can't see the outer half from each eye.

Question 35

What is left homonymous hemianopsia ?

Answer 35

- When you can't see out of the left half of each eye.

Question 36

What are the symptoms of a detached retina?

Answer 36

- Sudden appearance of 'floaters' - dark spots that float into your field of vision and sudden short flashes of light in one eye.

Question 37

What is a detached retina?

Answer 37

- Occurs when the thin lining at the back of your eye called the retina begins to pull away from the blood vessels that supply it with oxygen and nutrients. - Without prompt treatment will lead to blindness.

Question 38

What is ptosis?

Answer 38

- Abnormal low lying upper eye lid margin with the eye in primary gaze.

Question 39

What is hyphema?

Answer 39

- Haemorrhage within the anterior chamber of the eyeball.

Question 40

What is conjunctivitis?

Answer 40

- Inflammation of the conjunctiva (infection or allergy).

Question 41

What are the causes of longsightedness? (Hyperopia)

Answer 41

- eyeball too short. - cornea not curved enough. - lens is not thick enough.

Question 42

What are the causes of shortsightedness? (Myopia)

Answer 42

- eye has grown too long. | - cornea more curved than normal.

Question 43

What is the aqueous humour?

Answer 43

- Transparent gelatinous fluid similar to plasma but containing low protein concentrations. - Secreted from the ciliary epithelium, a structure supporting the lens. - Located in the anterior and posterior chambers of the eye, the space between the lens and the cornea.

Question 44

What is the choroid?

Answer 44

- Vascular layer of the eye. - Eyes blood supply. - Fills space between white of eye and retina. - Produces melanin. - Stops light reflecting within the eye. - Structure divided in 4 layers.

Question 45

What is the vitreous humour?

Answer 45

- Clear gel that fills the space between the lens and the retina of the eye ball.

Question 46

What is the ciliary body?

Answer 46

- Releases a transparent liquid within the eye called aqueous humour and contains the ciliary muscle which changes the shape of the lens when your eyes focus on something.

Question 47

Which cranial nerves are involved with the eye?

Answer 47

- 2, 3, 4 and 6. - the optic nerve (cranial nerve 2) transmits visual information. - the oculomotor nerve (cranial nerve 3), the trochlear nerve (cranial nerve 4) and the abducens nerve (cranial nerve 6) all coordinate eye movement.