Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Neuro > Structure and function of the eye > Flashcards

Structure and function of the eye Flashcards

1
Q

Which bones form the medial wall of the bony orbit?

A

orbital plate of Ethmoid bone
Lacrimal bone
orbital surface of the maxilla
lesser wing of the spenoid bone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Which bones make up the roof and floor of the bony orbit?

A

Roof – orbital plate of frontal bone

Floor – orbital plate of maxillary bone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Which bones make up the lateral wall of the bony orbit?

A

greater wing of the sphenoid bone + zygomatic bone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Where does the eye sit?

A

Within the orbit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the palpebral fissure?

A

Just the opening between eyelids

Epileptic space between medial and lateral canthi of two open eye lids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the limbus?

A

Border between the sclera and cornea
Also where the corneal stem cells sit in, 36-48hr stem cell turnover of epithelial corneal cells, move to centre of the eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the sclera?

A

The white bit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe eye from most central to outward

A

Pupil
Iris
Limbus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is caruncle?

A

Made of skin covering sabaceous and sweat glands

Medial aspect of the eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the average anterior-posterior diameter of the orbit?

A

24 mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the three layers of the eye? Describe their properties and function.

A 
Sclera
•	Hard and opaque
•	Maintains the shape of the eye 
Choroid 
•	Pigmented and vascular 
•	Provides circulation to the eye 
•	Shields out unwanted scattered light 
Retina 
•	Neurosensory
•	Converts light into neurological impulses
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the anterior and posterior segment of the eye separated by?

A

The lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the two anatomical spaces within the anterior segment?

A 
Anterior chamber (cornea to iris)
Posterior chamber (iris to lens)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What types of humour does each segment produce?

A

Ant. segment - aqueous humour

Post. segment - vitreous humour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Which part of the eye is visible at the back of the eye?

A

Optic disc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the zonules?

A

fibrous strands that hold the lens in place in line with the pupil, connected to the ciliary muscles, also called SUSPENSORY LIGAMENTS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Summarise the anterior segment?

A

Aq fluid produced by ciliary body and it passes into ant. chamber and then through angle via trabecular meshwork
The drainage important in maintenance of intraocular pressure
Aq supplies nutrients to cornea and other tissue in ant. chamber
No blood vessels in middle of eye, need a clear window for passage of light
THUS needs tissue needs to be bathed in fluid to receive nutrients and remove waste

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Summarise the posterior segment?

A

Between lens and retina
vitreous humour is 99% water, trapped inside jelly matrix providing mechanical support to eye
collagen and GAGs in the vit. humour
Regular structure allows it to be transparent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What happens to vit. humour as we get older?

A 
Loses its jelly consistency 
liquefies
detaches from the retina
SEEING FLOATERS
normally harmless, small tear in peripheral retina sometimes if this does happen then vit. can get into subretinal space and cause detachment of retina which can lead to BLINDNESS so needs prompt attention
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Where is the lacrimal gland located and what are the 3 types of tears it produces?

A

latero-superior to the globe

Basal tears - constant level even in absence of stimulation or irritation
Reflex tears - increased tear production in response to irritation - Afferent to cornea to CN v1, efferent is parasympathetic and ACh
Emotional tears = crying

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe the passage of tears

A

Tear produced by lacrimal gland
Tear drains through two puncta, opening on medial lip margin
tear flows through the superior and the inferior canaliculi
tear gathers in the tear sac
Tear exits the tear sac via tear duct in nasal cavity (nasolacrimal duct into inferior meatus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is it and what is the purpose of tear film?

A

Thin layer of fluid that covers the cornea
Maintains smooth cornea air surface
Maintains clear vision and removes surface debris during blinking
Source of oxygen and nutrient supply to anterior segment
It is a bactericide ( kills bacteria)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the three layers of the tear film?

A

Superficial oily layer : 0.1uM, reduces tear film evaporation, produced by a row of Melbomian Glands along the lid margins

Aqueous tear film: main bulk of tear film, 9uM, delivers oxygen and nutrients and includes the bactericide

Mucinous layer: 0.3uM, maintains surface wetting, ensure tear film sticks to they eye surface, mucin binds water molecules to hydrophobic corneal epithelial cell surface
Conjunctiva is a transparent layer on top of the cornea that is very vascular - it has goblet cells that produce mucin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What does conjunctiva cover?

A

Outer surface of the eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Describe the sclera

A

The white of the eye
tough opaque tissue that is protective
high water content

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is a blowout fracture?

A

Fracture of the floor of the orbit and so eyeball can fall into the cheek a bit, maxilla fracture

27
Q

Describe the cornea

A 
Front most anterior part of ant. seg.
continuous with sclera
transparent
2/3 of refractive power
convex curvature and higher refractive index than air
physical barrier from opportunistic inf.
28
Q

What are the 5 layers of the cornea?

A

Epithelium
Bowman’s membrane
Stroma - regularity contributes to transparency (corneal nerve endings, no blood vessels)
Descemet’s membrane
Endothelium - pumps fluid out of the corneal and prevent corneal oedema ( only 1 cell layer, no regeneration power, density down with age, dysfunction = oedema/cloudy)

IF YOU HYDRATE CORNEA GOES WHITE BECAUSE CORNEA H20 IS DOWN AND SCLERA H20 UP

29
Q

What is the uvea?

A

Composed of iris, ciliary body and choroid

Disease of one part of uvea can affect other parts

30
Q

Where does vascular coat of eyeball lie?

A

Between the sclera and retina

31
Q

What is the choroid?

A

Between retina and sclera
Layers of blood vessels
Nourish the back of the eye

Retina requires 2 ways of feeding some vessels for outer and inner retina

32
Q

What is the iris?

A

The coloured part of the eye
Controls light levels inside the eye
Round opening = pupil
Iris is embedded with tiny muscles that dilate and constrict the pupil size SPHINCTER PUPILLAE

Anterior – stromal layer containing muscle fibres
Posterior – epithelium

33
Q

What is the structure and function of the lens?

A 
Structure
– Outer Acellular Capsule
– Regular inner elongated cell
fibres – transparency
– May loose transparency with
age – Cataract
Function
– Transparency
• Regular structure
– Refractive Power
• 1/3 power
• Higher refractive index than
aqueous fluid and vitreous
– Accommodation
• Elasticity
Increases refractive power by CN3, can vary thickness and shape working as biconvex lens controlled by ciliary body
34
Q

How is the lens suspended?

A

Lens is suspended by lens zonules consisting of passive connective tissue
These fibres don’t stretch at all, they merely transmit force from the contraction of the ciliary muscles

35
Q

Summarise focusing light

A

Ciliary muscle contraction is pushing towards themselves making lens thicker

When ciliary relaxed the choroid acts like a spring pulling on lens and zonulae fibres causing the lens to flatten

THICKER LENS = increased refractive and closer viewing
THINNER LENS = decreased refractive power and further viewing

36
Q

What is the retina?

A

Thin layer of tissue that lines the inner part of the eye
Capturing light rays that enter the eye
These light impulses then sent to brain via the optic nerve

37
Q

Where is the highest concentration of photoreceptors?

A

Macula ( red circle)

Optic nerve head (yellow circle)

38
Q

Describe the blood supply of retina

A

Retinal arteries and veins provide circulation to inner 2/3 and outer 1/3 is by choroid vasculature

4 branches of vessel arcades:
sup and inf temporal
sup and inf nasal

39
Q

Where is macula located?

A

Roughly in centre of the retina
temporal to the optic nerve
Small highly sensitive part of retina reported for detailed central vision
Fovea is the very centre of the macula, allows us to appreciate detail and perform tasks that require central vision - reading

40
Q

What can macula degeneration cause?

A

1st cause of irreversible blinding disease, silent and asymptomatic
Cataract = highest cause of reversible blindness
glaucoma linked to degeneration of retina and optic nerve

41
Q

What is the ciliary body?

A

Ring shaped tissue surrounding the lens

Between anterior and posterior segments and is located behind the iris

42
Q

What does retina and choroid give rise to?

A

Retina gives rise anteriorly to ciliary body epithelium and posterior layer of iris (epithelial)

Choroid gives rise to ciliary body stroma and the stromal Ant. layer of iris

43
Q

Function of ciliary body?

A

Ciliary body secretes aq. fluid
Aq. fluid then travels anteriorly into ant. chamber
Trabecular network drains the fluid out of the eye into canals of schlemm

10-20% = uveal scleral outflow not a distinctive pathway

44
Q

What is normal intraocular pressure?

A

12-21 mmHg

45
Q

What are the two types of glaucoma?

A

Primary open angle glaucoma

Closed angle glaucoma

46
Q

What is primary open angle glaucoma?

A

Commonest

Functional blockage of trabecular meshwork

47
Q

What is Closed angle glaucoma ?

A

relatively common
acute or chronic
forward displacement of iris/lens complex narrowing trabecular meshwork
occurs in patients with small eyes (hypermetropic)
Sudden painful red eye with acute drop in vision
Treatment - peripheral laser iridotomy

48
Q

How can you differentiate venule and arteriole?

A

Veins are thicker and darker

49
Q

What is glaucoma?

A

Sustained raised increased intraocular pressure
gradual and accumulative damage to optic nerve
Retinal ganglion cell death and ENLARGED optic disc cupping
Untreated = loss of peripheral vision GRADUAL, eventual blindness

50
Q

Where is the blind spot?

A

Where the optic nerve meets the retina there are no light sensitive cells

51
Q

Describe the cone and rod cell concentration of fovea

A

Fovea has highest concentration of cones but low conc. of rods (more sensitive to light hence everything in periphery brighter)
Fovea is most central macula and most sensitive part of the retina

52
Q

What are the responsibilities of central and peripheral vision>

A

Central:
detail day vision (fovea has highest cone)
Reading, facial recognition
Assessed by visual acuity assessment
loss of foveal vision = poor visual acuity

Peripheral:
shape, movement, night vision
navigation vision
assessed by visual field assessment
With loss become unable to navigate in environment, patient may need white stick even with perfect visual acuity.
53
Q

Describe retinal structure?

A

Outer layer: photoreceptors first order (detect light, point away from pupil and light bounces pack of pigmented epithelium of retina and is then detected)
Light hitting different parts of retina gives spatial awareness

Middle layer: bipolar cells = 2nd order = local signal processing to improve contrast sensitivity, regulates sensitivity

Inner layer: retinal ganglion cells - signal from eye to brain

54
Q

What is the foveal pit?

A

Fovea forms pit at centre of macula due to absence of overlying ganglion cell layer, can be assessed with OCT

55
Q

Describe the visual processing photoreceptors

A

Rod - longer outer segment with photosensitive pigment 100 times more sensitive than cones to light
Slow response to light
Night vision, 120 mill rods

Cone - less sensitive to light, faster response, fine vision during day, 6 mill

Photopigments are synthesised in inner photoreceptor segments and are transported to outer segment discs
Distal discs with de-activated pigment are shredded from tips by phagacotytic retinal pigment epithelial cells and regenerated inner and bulk transfer

56
Q

What is light dark adaption?

A

Dark - Increase in light sensitivity on dark. cone adaption in 7 mins and rod in 30 mins after regeneration of rhodopsin

Light: dark to light, 5 mins, bleaching of photopigments, inhibition of rod/cone functoin

pupil adaption - constriction of pupil with light

57
Q

What is emmetropia?

A

Perfect focusing
Parallel rays converge exactly on fovea forming a clear image on the retina
No accommodation needed

Cornea - 2/3
lens - 1/3

58
Q

What is ametropia?

A

Mismatch between axial length and refractive power

Dont fall on retina - myopia(near sight), hyperopia(far), presbyopia, astigmatism

59
Q

What is myopia?

SHORT SIGHTED

A

Parallel rays converge at focal point ant. to the retina, etiology is not clear maybe genetic
Cause: excessive long globe more common and excessive refractive power
symptoms: blurred distance vision, headache, squinting
CONCAVE LENSE

60
Q

What is hyperopia?

LONG SIGHTED

A

Parallel rays focus behind the retina
blurred vision
Not enough focusing power or short globe
CONVEX LENS
symptoms: visual acuity at near tends to be blurry, eyepain, headache in frontal region, burning sensation, blepharoconjunctivitis

61
Q

What is astigmatism?

A

cornea is OVAL rather than spherical so you get different refraction along one meridian
parallel rays come to focus in 2 focal lines rather than a single focal point
hereditary
symptoms: astenopic symptoms (headache and eye pain)
blurred vision
distorted vision
head tilting and turning
treatment: cylindrical lenses, if irregular you need surgery

62
Q

Summarise accommodation

A 
-Contraction of the Circular
Ciliary Muscle inside the
Ciliary Body
– This relaxes the zonules that
are normally stretched
between the ciliary body
attachment and the lens
capsule attachment
– Note that zonules are passive
elastic bands with no active
contractile muscle
– In the absence of zonular
tension, the lens returns to
its natural convex shape due
to its innate elasticity
– This increases the refractive
power of the lens
• Mediated by the efferent
Third Cranial Nerve
63
Q

What is near response triad?

A 
Adaptation for Near
Vision
• Near Response Triad
– Pupillary Miosis (Sphincter
Pupillae) to increase depth
of field, maintain clear focus across range of distances without accommodation
If shallow lose focus easily with movement of an object. 
– Convergence (medial recti
from both eyes) to align
both eyes towards a near
object
– Accommodation (Circular
Ciliary Muscle) to increase
the refractive power of
lens for near vision, lens becomes thicker
64
Q

What is presbyopia?

A

Naturally occurring loss of accommodation
onset from 40
distant vision intact
corrected by reading glasses to increase refractive power of the eye

Neuro (17 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions