Low Vision

Question 1

Low Vision

Answer 1

• Best corrected visual acuity less than 20/40 in the better-seeing eye.
• Can be Mild (up to 20/60); Moderate (up to 20/160); Severe (20/200+); Profound (20/500 to 20/1000); Near-total (<20/1000); or Total (no light perception).

Question 2

Blindness

Answer 2

Best-corrected visual acuity of 20/200 or worse in the better-seeing eye.

Question 3

Best-corrected Vision

Answer 3

The sharpest, clearest vision attainable by the client, under the best circumstances, using vision out of the best eye, with standard corrective lenses.

Question 4

Visual Perceptual Hierarchy

Answer 4

An organized hierarchy of processes that interact with and subserve each other. Each process is supported by the one that precedes it.
1. Visual acuity
2. Visual field
3. Oculomotor control
4. Visual attention
5. Pattern recognition
6. Visual memory
7. Visuocognition

Question 5

Visual Acuity

Answer 5

The ability to see small visual detail, ensuring that precise visual information is provided to the central nervous system.

Question 6

Snellen Fraction

Answer 6

• Results from use of the Snellen Eye Chart
• Most common visual acuity measurement.
• 20/20 means that when standing at a distance of 20 feet, the viewer can see the letter that a person with normal vision can see at 20 feet. Likewise, 20/200 visual acuity means that the viewer can see the letter at 20 feet that a person with normal vision can see at 200 feet.

Question 7

Presbyopia

Answer 7

• Difficulty focusing on near objects.
• Common age-related change in visual acuity occurring in adults over age 50 as the lens of the eye becomes less flexible, reducing the ability to read small print.

Question 8

Myopia

Answer 8

• Aka nearsightedness
• Normal deficiency in visual acuity in which near objects are seen more clearly than distant objects.
• Can be corrected with glasses

Question 9

Hyperopia

Answer 9

• Aka farsightedness
• A normal deficiency in visual acuity in which distant objects are seen more clearly than near objects.
• Can be corrected with glasses.

Question 10

Legal Blindness

Answer 10

Visual acuity of 20/200 or less in the better eye after correction.

Question 11

Contrast Sensitivity

Answer 11

The ability to perceive and detect objects in relationship to the background of their environment.
- The ability of the visual system to distinguish various shades of gray or color.
- Contrast sensitivity is essential to negotiating environments safely.

Question 12

Visual Field

Answer 12

Contains two components:
1. Peripheral visual field (aka “ambient visual system”) = Provides background information about one’s position in relation to the environment and is quick to detect motion. Consists of scope of vision in each eye.
2. Central visual field encompasses the central 20 degrees of vision.

Question 13

Ocuolomotor Control

Answer 13

The ability of the eyes to move smoothly and in a coordinated manner through full range of motion. Provides binocular vision.

Question 14

Accomodation

Answer 14

• The ability to adjust focus of vision at different distances.
• Can be affected by the normal aging process that causes presbyopia.
• Component of oculomotor control.

Question 15

Convergence

Answer 15

• The muscle action of the eyes that moves them inward (in adduction) to allow focusing on nearby objects.
• Component of oculomotor control.

Question 16

Diplopia

Answer 16

• Causes the perception of two images of a single object.
• In order to eliminate the double image, the client may assume a head position or tilt that eliminates the need to use the paretic eye muscle, resulting in stabilized vision.

Question 17

Exophoria vs. Esophoria

Answer 17

• “-phoria” is the suffix used when a client has a deviation of the eye that is held in check by fusion and is not noticeable when the client focuses on an object.
• Exophoria = the eye turns OUT when the client is not focusing on an object.
• Esophoria = the eye turns IN when the client is not focusing on an object.

Question 18

Visual Attention

Answer 18

• The ability to identify specific features of an object and ignore other irrelevant sensory information.

Question 19

Hemi-inattention

Answer 19

• Issue with visual attention which occurs when visual search patterns are confined to one side of the visual array, creating an asymmetric search pattern in which the client misses information on the other side.

Question 20

Pattern Recognition

Answer 20

The ability to identify the configuration and holistic aspects of an object as well as specific features of the object.

Question 21

Visual Memory

Answer 21

The mental manipulation of visual stimuli, requiring the ability to create and retain a picture of the object of which visual analysis is being completed.

Question 22

Visuocognition

Answer 22

The ability to manipulate and integrate visual input with other sensory information.

Question 23

Age-Related Macular Degeneration

Answer 23

• Affects the macula, the central portion of the eye that is responsible for providing the fine detail required for near-distance activities (e.g., reading).
• Functional implications include:
  1. Reading-dependent activities become difficult because objects appear distorted in shape (e.g., straight lines appear wavy or crooked).
  2. Difficulty develops with aspects of functional mobility, such as identifying low-contrast surfaces (e.g., curbs, steps, drop-offs).

Question 24

Glaucoma

Answer 24

• Occurs when the intraocular fluid becomes blocked, resulting in increased intraocular pressure. This pressure reduces blood flow to the optic nerve, causing loss of PERIPHERAL vision.
• Functional implications include:
  1. Difficulty with functional mobility because the client may not see objects in pathways.
  2. Objects and people outside of the client’s residual peripheral vision suddenly appearing and startling the client.
  3. Difficulty with reading and writing if the client can only see a small portion of the page.

Question 25

Diabetic Retinopathy

Answer 25

• Syndrome causing fluctuating vision, blurred vision, central vision loss, decreased contrast sensitivity, and difficulty with night driving and color discrimination.
• Caused by changes in the blood vessels of the retina. Blood vessels may swell and leak fluid, or abnormal blood vessels may grow on the surface of the retina.
• Functional implications include:
  1. Fluctuating vision, including blurred vision, spots or “floaters”, and central vision loss.
  2. Decreased contrast sensitivity and difficulty identifying low-contrast items in the environment, including steps, curbs, and water on the floor.
  3. Difficulty with night driving and color discrimination, which can be necessary for identifying traffic signals or locating and identifying clothing.

Question 26

Cataracts

Answer 26

• Occur when the lens of the eye becomes more opaque or clouded, reducing the light going into the retina and altering vision.
• Most often related to aging and very common in older adults. Can occur in one or both eyes, however cannot spread from one eye to the other.
• Can be corrected with surgery.
• Functional implications include:
  1. Cloudy or blurry vision (leading to difficulty with near-distance tasks especially, e.g., reading).
  2. Faded colors (leading to difficulty distinguishing/identifying clothing, food and other items).
  3. Glare (leading to lights appearing too bright and/or a halo appearing around lights).
  4. Poor night vision (leading to difficulty driving and identifying curbs/steps etc. after dark).

Question 27

Homonymous Hemianopsia

Answer 27

• A type of vision loss following brain injury in which half of the visual field in each eye is lost.
• Functional implications include:
  1. Difficulty with reading as the client does not see the full line of text.
  2. Difficulty with functional mobility secondary to reduced visual field and reduced visual search and scanning patterns.

Question 28

Visual Neglect

Answer 28

• A combination of hemi-inattention and visual field deficit resulting in exaggerated inattention toward the left (or right) half of the visual space surrounding the body. The client often does not move the eyes past midline.
• Impacts all daily tasks, although specific functional implications depend on the visual attention required for the tasks to be completed.
• Reading and driving are two tasks often altered by visual neglect.

Question 29

Eccentric Viewing

Answer 29

Intervention technique whereby a person with central vision loss rotates the head or turns the trunk to view on object using an area of the peripheral vision called the preferred retinal locus.

Question 30

Macula

Answer 30

Central portion of the eye that is responsible for providing the fine detail required for near-distance activities, including reading.

Question 31

Perceptual Completion

Answer 31

• A process whereby the central nervous system of a person with a visual field deficit samples a visual array and internally completes a visual scene on the basis of visual information expected to be found in the array.
• Allows a client with visual field deficit to be unaware of the absences of vision caused by the deficit.
• Clients may report difficulty with functional mobility (e.g., running into obstacles on one particular side) and/or objects seeming to appear and then disappear (also on that same particular side).

Question 32

Accommodative Facility

Answer 32

• The speed of focus adjustment and ability to maintain focus over time.
• Clients who have accommodative INfacility will have difficulty driving a car because looking at the speedometer (near distance) and then at the road (far distance) requires adjusting focus at different distances.