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ANAT 1111 > VISION - THE EYE > Flashcards

VISION - THE EYE Flashcards

1
Q

name the 3 layers of the eye?

A
  • outer = cornea and sclera
  • middle = uveal tract
  • inner = retina
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2
Q

explain the function of the eye?

A
  • transmits light to the sensitive tissue
  • metabolic functions mentioning the eye
  • direction and focus of gaze
  • protection of the delicate features
  • the conversion of light to a nerve impulse
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3
Q

state the requirements for vision?

A
  • transparency
  • refractive power
  • direction of gaze
  • metabolic functioning
  • brain capable of perceiving image
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4
Q

describe refractive power as a function of vision?

A

-the eye acts as a set of lenses focusing light onto the retina (macula).
—this is known as refraction
-this is mainly a function of the cornea and the length of the eyeball (e.g. position of the macula)
—the lens only makes adjustments for near vision

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5
Q

define myopia and how it is corrected?

A

too much refractive power (short sightedness)

-requires a minus spherical lens (concave) to reduce focusing power

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6
Q

define hypermetropia and how it is corrected?

A

not enough focussing power

-plus lenses (convex) are used to add focussing power to the eye

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7
Q

define presbyopia?

A

describes the changes which occur to the lens resulting in loss of accommodating power

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8
Q

define astigmatism?

A

a curvature in the eye that causes blurred distance and near vision
-measured along one axis as a cylinder

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9
Q

state which structures of the eye allow vision through transparency?

A
  • tear film
  • cornea
  • anterior chamber and aqueous
  • lens
  • vitreous
  • transparent layers of the retina
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10
Q

explain the functions of the transparent media (cornea and lens).

A
  • transmission of light to the sensitive tissues
  • focus of gaze
  • protection of delicate structures
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11
Q

what is the tear film and lacrimal gland?

A
  • produces by various glands in the eye lids

- the lacrimal gland produces excess tears seen in injury or times of emotion

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12
Q

state the role of the tear film?

A
  • protection

- transparency

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13
Q

what are the 3 layers to tear film?

A
  • oily outer layer
  • watery middle layer
  • inner mucin layer
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14
Q

what is the cornea, and what are its 2 main functions?

A
  • it covers the anterior one-fifth of the eye ball
  • it is a dome shaped oval consisting of 5 distinct layers
  • these are all transparent, allowing protection and refraction
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15
Q

describe the functions of the cornea and the lens?

A

-they are transparent and the main refractive media of the eye
-aqueous and vitreous have very low refractive power
-overall power of the eye is 58 dioptres
—lens contributes about 15 D (range of about 8D before presbyopia)
—cornea contributes to about 43D

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16
Q

describe the structure and function of the pupil?

A

-the pupil is a hole in the centre of the thin, contractile circular iris muscle
-regulates the amount of light entering the posterior segment of the eye
—avoiding bleaching of the retinal pigments
-pupil dilates in dark and constricts in bright light

17
Q

state the difference between the dilator and sphincter pupillae muscles of the iris?

A

*dilator pupillae
-when contracted = dilated pupil, sympathetic reflex follwoing 3rd nerve pathway (mydriasis)
*sphincter pupillae
-when contracted, moves pupil inwards
—e.g. constricts via parasympathetic reflex following blood vessel pathway (miosis)

18
Q

list the 9 positions of gaze?

A
  • forward gaze
  • elevation
  • depression
  • left and up
  • left gaze
  • left and down
  • right and up
  • right gaze
  • right and down
19
Q

describe binocular single vision (BSV)?

A

-each eye sees a slightly different image
-the brains ability to see this as one image is BSV
—simultaneous perception
—fusion
—stereopsis
-corneal light reflexes to assess alignment

20
Q

describe the 3 factors required for BSV development?

A
  • reasonable clear vision in both eyes
  • the ability of the visual areas in the brain to promote fusion of the two slightly dissimilar images
  • the precise coordination of the two eyes for all directions of gaze
21
Q

what is amblyopia?

A

-until the age of 8, the visual process has not matured
—if the eye is not used it may lose the ability to see
— this results in reduced visual acuity and is a condition called amblyopia (lazy eye)

22
Q

list the structures if the retina?

A

-ora serrata anterior
-optic disk posterior
-macula
-retinal artery arcades
-retina
—inner neurosensory
—outer pigmented

23
Q

what is the choroid and retinal blood supply?

A

-all branch from the ophthalmic artery: first branch off internal carotid
*central retinal artery supplies the inner 2/3 if retina and optic nerve = extraocular part
-anatomical idiosyncrasy = the posterior ciliary artery supplies optic nerve head including optic disk
= intraocular part
*the choroid supplies the other 1/3 (from ciliary artery too)

24
Q

name and describe the metabolic functions in the eye?

A 
*tear film production 
—goblet cells, meibomian glands, krausse + wolfring, lacrimal gland 
*cornea
—oxygen, deturgesence (Na pump)
*uveal tract 
—aqueous production 
*lens
—epithelial pump mechanism, glucose metabolism
*retina
—photoreceptor activity
25
Q

explain the uveal tract in the metabolic functioning of the eye and vision?

A 
*uveal tract form 
—iris, ciliary body, choroid
*uveal tract functions
—protection (iris)
—metabolic functioning (aqueous formation by ciliary body, blood supply to retina)
—absorption of excess light (choroid)
26
Q

describe intraocular pressure (IOP)?

A
  • the fluid pressure inside the eye

- achieved by glance between production and drainage of aqueous humour

27
Q

what are the 4 parts if the anterior lid structure?

A
  • skin
  • lashes
  • greyline
  • orbicularis muscle
28
Q

describe how eyelids open?

A

*levator muscle
—arises from lesser wing of sphenoid bone of the orbit
—follows superior rictus and shares its muscle sheath
—divides into:
aponeurosis which inserts into obicularis and skin
müllers muscle to tarsal plate
—enervated by CN 3

29
Q

list the 12 cranial nerves and their function?

A

1) olfactory = smell
2) optic = sight
3) oculomotor = moves eye, pupil
4) trochlear = moves eye
5) trigeminal = face sensation
6) abducens = moves eye
7) facial = moves face, salivate
8) vestibocochlear = hearing, balance
9) glossopharyngeal = taste, swallow
10) vagus = heart rate, digestion
11) accessory = moves head
12) hypoglossal = moves tongue

30
Q

how many cranial nerves are involved with the eye?

A

6

  • optic
  • oculomotor
  • trochear
  • trigeminal
  • abducens
  • facial
31
Q

explain the visual pathway (CN2)?

A
  • the retina and optic nerves
  • the chiasma
  • the optic tracts
  • the lateral geniculate bodies
  • the optic radiations
  • visual cortex and other areas if the brian
32
Q

describe the roles of cranial nerves 4 to 7 in the eye?

A

*4th = trochlear nerve
—supplies motor impulse to superior oblique muscle which moves the eye down and out
*5th = trigeminal nerve (has 3 divisions)
—1st sensory from conjunctiva, sclera, cornea, iris, eyelid, scalp, forehead, nose
*6th = abducent nerve
—supplies the lateral recuts muscle which moves the eye laterally
*7th = facial nerve
—has parasympathetic supply to lacrimal gland + motor supply to orbicularis muscle for lid closure

33
Q

describe visual perception in the brain as a function of vision?

A
  • visual pathway

- other contributing factors

34
Q

describe the 3 stages of perception?

A

1) the visual system analyses info from external world derived from a range of possible signals
—all of which are captured captured by the retina
—fixation/ attention, discrimination from surroundings

2) this info is integrated with input from other sensory systems and memory

3) the final stage is perception- involves brain editing to ensure normality and constancy, involves:
—form perception followed by
—object recognition, which depends on capacity to acquire + store info + accumulate experience

35
Q

what is vision?

A

the end profit if processing, by the cerebral cortex, of sensory responses made by the retina to light stimulation
-some degree of processing is thought to take place in the retina
—also includes appreciation of spatial perception or appreciation of size, distance and depth

36
Q

state the components of vision?

A
  • orientation perception (measuring by eye)
  • motion perception (BSV)
  • colour perception
  • shale detection (element of memory involved)
  • brightness discrimination (luminance/ contrast sensitivity)
  • image stabilisation

ANAT 1111 (9 decks)

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