Visual Function

Question 1

Warren Model of Visual Functioning

Answer 1

A visual hierarchy theorizing that higher level visual skills are built on the skills of visual acuity, visual fields, and oculomotor skills.
Visual fields, visual acuity and oculomotor skills → attention → scanning → pattern recognition → visual memory → visuocognition → adaption through vision

Question 2

Oculomotor skills

Answer 2

the ability to purposefully contract the eye muscles to produce coordinated movement, which is necessary for clear vision. INCLUDES:
– Binocular vision
– Saccades
– Tracking/pursuits
– Fixation
– Convergence/divergence
– Pupillary function
CN II carries visual sensory information that comes through the retina, while CNs III, IV, V and VI are responsible for the movements of the eye.

Question 3

Saccades

Answer 3

the oculomotor ability of the eye to make quick movements from one target to another, and display an image accurately.

Question 4

Tracking/pursuits

Answer 4

the oculomotor ability to smoothly follow a slow moving target and keep it in the central vision.

Question 5

Fixation

Answer 5

the oculomotor ability to maintain focus on an object in central vision

Question 6

CN II

Answer 6

cranial nerve II carries visual sensory information through the retina of the eye to the brain.

Question 7

Which cranial nerves support oculomotor function?

Answer 7

CNs III, IV, V, VI

Question 8

Visual Acuity

Answer 8

The sharpness and clarity of an image at a certain distance. Refractive errors of visual acuity include myopia, hyperopia, astigmatism, presbyopia.

Question 9

Refractive errors of visual acuity

Answer 9

Occur when the eye’s shape prevents light from focusing correctly on the retina, causing blurry vision.
– Myopia
– Hyperopia
– Astigmatism
– Presbyopia

Question 10

Myopia

Answer 10

nearsightedness → the eye is too long or the cornea/lens has too much focusing power → objects from far away appear blurry

Question 11

Hyperopia

Answer 11

farsightedness → the image overshoots the retina → causing objects close by to appear blurry
presbyopia is a form of hyperopia

Question 12

Presbyopia

Answer 12

an error of visual acuity that occurs from the loss of aqueous fluid in the eye with aging, which causes a shortening of the eye that results in hyperopia.

Question 13

Astigmatism

Answer 13

asymmetrical or distorted vision at any distance → caused by a curvature of the eye or the lens.
(the curvature bends the light as it passes through, which distorts the image on the retina.)

Question 14

Oculomotor deficits

Answer 14

1. Strabismus
2. Nystagmus
3. Reduced ability to move the eye through ranges of motion
4. Convergence/divergence insufficiencies
5. Inability to smoothly or accurate track or pursue a target

Question 15

Nystagmus

Answer 15

small, involuntary, and repetitive movements of the eye (can cause blurry vision and dizziness)

Question 16

Strabismus

Answer 16

a misalignment of the eyes. could look like hypertropia (one eye turned up), esotropia (eyes turned in) exotropia (eyes turned out)

Question 17

Hypertropia

Answer 17

(type of Strabismus) Misalignment of the eyes in which one eye turns up

Question 18

Esotropia

Answer 18

(type of Strabismus) Misalignment of the eyes in which one’s eyes turned in

Question 19

Exotropia

Answer 19

(type of Strabismus) Misalignment of the eyes in which one’s eyes turn out

Question 20

Visual Fields

Answer 20

each visual field is perceived by 1/2 of each eye. (the optic nerve (CN II) is divided into 1/2 and wraps around each eye.)
includes
– scanning
– line bisection
– drawings
– confrontations

Question 21

Convergence

Answer 21

movement of the eyes in towards each other; occurs when focusing on near objects. (allows the eye to keep a clear, single image)

Question 22

Divergence

Answer 22

movement of the eyes away from each other, to adjust for the increased distance between the eyes and the object.

Question 23

Contrast Sensitivity

Answer 23

the ability to see differences between light and dark, important for distinguishing an object from its surroundings and perceiving in low-light conditions.

Question 24

Visual Screening

Answer 24

Should be done with every client you work with, especially before testing cognition and ADLs
– Visual acuity: Snell Chart
– Fixation: focus on a single object for a few seconds
–Convergence: follow an object towards their nose, and confirm the eyes move inward slightly
– Oculomotor ROM: keep your eyes still but move your eyes up/down/left/right/diagonals to four corners
– Tracking: smoothly follow the slow object from one side to another with just your eyes
– Saccades: look quickly from one object to another, watch for nystagmus
– Visual fields: stand behind client and check peripheral vision at top, bottom, and both sides (ask when the object enters their vision)

Question 25

Levels of Visual Impairment

Answer 25

can be congenital or acquired, and are diagnosed by Moderate, Severe, Profound, Near-total, and Total levels of impairment. MODERATE: less than 20/60 SEVERE: less than 20/160 or visual field is 20° or less. PROFOUND: less than 20/400 or visual field is 10° or less. NEAR-TOTAL: less than 20/1000, or visual field is 5° or less. TOTAL: no light perception.

Question 26

Moderate Visual Impairment

Answer 26

best corrected visual acuity is less than 20/60.

Question 27

Severe Visual Impairment

Answer 27

best corrected visual acuity is less than 20/160, or visual field is 20° or less. -- legal blindness

Question 28

Profound Visual Impairment

Answer 28

best corrected visual acuity is less than 20/400, or visual field is 10° or less.

Question 29

Near-total Visual Impairment

Answer 29

best corrected visual acuity is less than 20/1000 or visual field is 5° or less.

Question 30

Total Visual impairment

Answer 30

no light perception, total blindness.

Question 31

Binocular Vision

Answer 31

the ability to coordinate and integrate images from both eyes for volume and depth. (oculomotor ability)