Session 4 Reading

Vision

by Cece Quintana

The term "Blindness" means . . .?
There are actually very few people in the world who are totally blind. Most people who are considered blind have some amount of vision. This may range from being able to discern only light and dark to having quite useful vision.

What you need to look for in an eye report.

*Diagnosis (Name of the eye condition)
*Acuity (How clearly the student sees)
*Field Loss (Parts of visual picture missing)
*Prognosis (Is it progressive?)
*Recommendations for treatment

How to interpret the acuity

Acuity - How clearly the person sees: On the report form, the acuity usually follows the symbol:

OD Numbers in a fraction format

V

OS

sc = without correction (glasses), cc = with correction
OD (oculus dexter) stands for the right eye. Think of dexterity - most people are right-handed and therefore have greater dexterity in their right hands.
OS (oculus sinister) stands for the left eye. In the Middle Ages, it was considered evil, or sinister, to be left-handed.
OU (oculus uterque) stands for both eyes together.

Numbers in a fraction format, such as 20/40

· The first number is the testing distance, so in the example above, the student was tested from a distance of 20 feet.

· The second number is the distance from which a normal eye would see the same symbols being viewed. The bigger the second number is, the worse the visual acuity.

· So in the example above, this child sees from 20 feet, the same thing that a normal eye would see from 40 feet.

· A person with an acuity of 20/200 or less (which means the second number would be bigger) is considered "legally blind."

Initials and a number

· CF at 5' = Count Fingers at five feet - small object perception, but no fine detail
· HM at 5' = Hand Motion at five feet - gross object perception

Initials

· LP - Light Perception - Student can tell whether it is light or dark where they are
· NLP - No Light Perception - Totally blind
· CSM – Central, Steady, Maintained (This is a good thing)

Other terms associated with Vision.

Other Possibilities

· Light Projection - can determine the source of light, and probably see, as a shadow, objects that are as large as, or larger than a person.

· Numbers followed by a degree sign, indicates how much area the student can still see to the right and left, while still keeping their eyes forward. An average field of vision, in a person with normal vision is 170 - 190 degrees. A visual field of 20 degrees or less is considered "legally blind."

Effects of Vision Loss on Learning

First, let’s remember that 80% or more of all information received is visual!

When that channel is missing or impaired, we see the following results:

· Concept development difficult
· Social skills must be taught
· Lack of incidental learning
· Learned helplessness

Effects of Blindness on Communication

· Lack of initial bonding and attachment
· Absence of eye contact in communication
· Lack of body language

Effects of Blindness on Mobility

· Decreased motivation to move
· Mental imagery difficult
· Sense of self and body image often delayed
· Perception of Safety

Environmental Modifications (Some possibilities to consider)

· Multi-sensory approach to learning
· Increased/decreased lighting
· Larger/smaller print sizes
· Use of real objects
· Reduced visual clutter
· High contrast materials

Common Eye Conditions

(These conditions are commonly found in students who experience deaf-blindness)

Cortical Visual Impairment (CVI)

Cortical Visual Impairment (CVI) - The term "cortical blindness" or "cortical visual impairment" indicates that there is some type of damage in the visual cortex (also called the occipital lobe) of the brain, and/or the primary visual pathways. The result varies from a slight reduction in visual functioning to total blindness. This condition often occurs in conjunction with neurological disorders, and the rest of the eye may or may not be intact and healthy. This condition is also referred to as “Cerebral Visual Impairment” or “Neurological Visual Impairment.”

Common Causes

The most common causes of cortical visual impairment include: anoxia at birth, traumatic head injury, differences in brain development, and infections to the central nervous system (such as meningitis and encephalitis).

Visual functioning

The student with cortical visual impairment experiences quite a bit of fluctuation in visual functioning, may often ignore visual stimuli, frequently cannot recognize faces (agnosia), has difficulty seeing when visual clutter is present, and may prefer to explore tactually, rather than visually. Recent research indicates that these students often make use of a "secondary visual pathway," which allows them to interpret some of the visual information they are receiving from the peripheral retinal area. This part of the eye is most sensitive to light and movement. Research also indicates that improvement in visual functioning (or increased attention to visual functioning) most often occurs over a period of time, usually up until age 8 or 10. Color discrimination is usually intact in these students.

CVI is usually diagnosed by behavior, rather than physical evidence. Typical behaviors include:

· Normal or near normal eye exam
· Visual attention in near space only
· Looking away while reaching behavior
· Inability to deal with visual clutter
· Easier to see moving objects or while they are moving
· Drastic variability in ability to see

Common recommendations for environmental modifications:

High illumination, bright color contrast in materials, presentation of visual targets in isolation, reduction of visual clutter, use of familiar toys/objects, consistency among visual cues in the environment, color coding of some materials, strategies for recognizing people that do not include facial recognition.

More information about CVI at http://www.aph.org/cvi/define.html

Optic Nerve Hypoplasia (ONH)

The optic nerve is responsible for carrying visual images to the brain. The optic nerve in a person with optic nerve hypoplasia failed to fully develop. This essentially results in the brain receiving only partial visual information, or part of the "picture" sent by the eye. Students with this eye condition often experience fluctuating visual performance, blurred vision, nystagmus (involuntary, jerky eye movements) and field deficits. This condition is often seen in children with additional neurological issues.

Common Recommendations for environmental modifications

High illumination (unless they have light sensitivity), enlarged print or Braille, high contrast, avoidance of visual clutter, visual stimulation for younger children may be appropriate.

More information at http://www.blindbabies.org/factsheet_onh.htm

Optic Nerve Atrophy

Optic nerve atrophy (also optic atrophy) refers to a degeneration of the optic nerve which carries images to the brain. This essentially results in the brain receiving only partial visual information, or part of the "picture" sent by the eye. Students with this eye condition often experience fluctuating visual performance, and blurred vision.

Common recommendations for environmental modifications

High illumination, enlarged print, magnification, high contrast materials.

More information at http://www.tsbvi.edu/Eudcation/anomalies/optic_atrophy.htm

Retinopathy of Prematurity (ROP)

Retinopathy of prematurity (formerly known as retrolental fibroplasia) is a retinal disease (usually bilateral) of premature infants. It is caused by initial curtailment and then excessive proliferation of blood vessels in the retina, which may lead to bleeding, scarring and retinal detachment. This condition most typically results in reduced acuity, strabismus (an inward or outward turning of one eye), blind spots and/or field loss. In some cases, total blindness may occur.

Common recommendations for environmental modifications

High illumination, magnification or enlarged print materials, telescopes for distance viewing.

More information at http://www.nei.nih.gov/health/rop/index.asp

Retinitis Pigmentosa (RP)

Retinitis pigmentosa is a hereditary condition that is characterized by progressive degeneration and atrophy of the retina. The most typical pattern of deterioration is as follows: the first area to deteriorate is the peripheral vision (which usually results in "night blindness"), and the visual fields than steadily decrease inwardly toward the macula (responsible for central vision and color discrimination). The condition may or may not result in a total loss of vision. Photophobia (extreme sensitivity to or discomfort cased by light) and a sensitivity to glare is often present. May not be diagnosed until puberty if there is no previous family history.

Common recommendations for environmental modifications

Good illumination with no glare, preferential seating away from windows and toward the back of the room (to increase their visual field), prism glasses, regular sized print.

More information at http://www.genome.gov/13514348

Strabismus/Amblyopia

Strabismus is an inward or outward turning of one eye, usually due to a muscle imbalance. When the eyes are misaligned, it results in double vision. In most cases, the brain does not like to receive double images, so it will begin to suppress the images received from one eye, resulting in a partial or total loss of vision in that eye. This loss of vision is called amblyopia. There is a loss of depth perception, and often field losses. Visual fatigue is often a factor.

Common recommendations for environmental modifications

High contrast materials, glare control/reductionprism glasses, eye doctor interventions (patching, surgery).