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Introduction to Healthcare Science > The eye > Flashcards

The eye Flashcards

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1
Q

What are the orbital components?

A
  • 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.
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2
Q

What are the extraocular muscles?

A
  • 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.
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3
Q

Name the extraocular muscles?

A
  • superior rectus.
  • medial rectus.
  • lateral rectus.
  • inferior rectus.
  • superior oblique.
  • inferior oblique.
  • optic nerve.
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4
Q

What is the levator palpebrae superioris muscle ?

A
  • It is the muscle in the orbit which elevates the superior (upper) eyelid.
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5
Q

What is the orbicularis oculi?

A
  • Muscle in the face that closes the eyelids.

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

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6
Q

What is the pupil?

A
  • 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.
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7
Q

What is the iris?

A
  • 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.
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8
Q

What is the lacrimal lake?

A
  • 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.
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9
Q

Where is the medial angle of the eye?

A
  • Tear duct.
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10
Q

Where is the lateral angle of the eye?

A
  • Towards the edge of the face.
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11
Q

What is the conjunctiva?

A
  • 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.
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12
Q

What is the sclera?

A
  • White part of the eye.

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

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13
Q

What is the lacrimal puncta?

A
  • 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.
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14
Q

What does lateral rotation or extorsion of the eye mean?

A
  • Looking away from face (also know as abduction).
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15
Q

What does medial rotation or intorsion of the eye mean?

A
  • Looking towards the nose (also know as adduction).
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16
Q

What is the transverse axis of the eye?

A
  • When cut straight through the middle (leaving a top and bottom half).
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17
Q

What is the vertical axis of the eye?

A
  • When cut straight up and down (leaving a left and right side of the eye).
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18
Q

What does the superior rectus muscle do?

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

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

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19
Q

What does the medial rectus muscle do?

A
  • 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.
20
Q

What does the inferior rectus muscle do?

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

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

21
Q

What does the lateral rectus muscle do?

A
  • Is the only muscle supplied by abductees nerve (cranial never 6).
  • Moves the pupil away from the midline (abducts eye).
22
Q

What is the orbit?

A
  • 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.
23
Q

What does the inferior oblique muscle do?

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

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

24
Q

What does the superior oblique muscle do?

A
  • It is the only muscle supplied by the trochlear nerve (cranial nerve 4).
  • Involved in Intorsion depression and abduction.
25
Q

What does the eyeball consist of?

A
  • 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).
26
Q

Where are photoreceptors cells found?

A
  • This is a specialised type of neurone found in the retina and is capable of phototransduction.
27
Q

What is phototransduction?

A
  • 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.
28
Q

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

A
  • Rods, cones and photosensitive retinal ganglion cells.
29
Q

What is the function of rods and cones?

A
  • Used by the visual system to form a representation of the visual world, sight.
30
Q

What is the function of photosensitive ganglion cells?

A
  • These do not contribute directly to sight but are thought to support circadian rhythms and pupillary reflex.
31
Q

What are rod cells?

A
  • 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.
32
Q

What are cone cells?

A
  • 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.
33
Q

What is right monocular blindness?

A
  • When you can’t see anything out of right eye at all.
34
Q

What is bitemporal hemianopsia?

A
  • When you can’t see the outer half from each eye.
35
Q

What is left homonymous hemianopsia ?

A
  • When you can’t see out of the left half of each eye.
36
Q

What are the symptoms of a detached retina?

A
  • Sudden appearance of ‘floaters’ - dark spots that float into your field of vision and sudden short flashes of light in one eye.
37
Q

What is a detached retina?

A
  • 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.
38
Q

What is ptosis?

A
  • Abnormal low lying upper eye lid margin with the eye in primary gaze.
39
Q

What is hyphema?

A
  • Haemorrhage within the anterior chamber of the eyeball.
40
Q

What is conjunctivitis?

A
  • Inflammation of the conjunctiva (infection or allergy).
41
Q

What are the causes of longsightedness? (Hyperopia)

A
  • eyeball too short.
  • cornea not curved enough.
  • lens is not thick enough.
42
Q

What are the causes of shortsightedness? (Myopia)

A
  • eye has grown too long.

- cornea more curved than normal.

43
Q

What is the aqueous humour?

A
  • 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.
44
Q

What is the choroid?

A
  • 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.
45
Q

What is the vitreous humour?

A
  • Clear gel that fills the space between the lens and the retina of the eye ball.
46
Q

What is the ciliary body?

A
  • 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.
47
Q

Which cranial nerves are involved with the eye?

A
  • 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.

Introduction to Healthcare Science (23 decks)

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