VISUAL IMPAIRMENT/ DISABILITY

VISUAL IMPAIRMENT/ DISABILITY

The visually impaired are broadly classified in two groups based on the degree of visual impairment. They are 1. The Partially (Weak) sighted or persons with low vision and the 2. The Blind. The visual measurement made by Shnellen Chart Notations of Visual Acuity. This chart consists of symbols (numbers/letters) that decrease in size. It read at distance of 20 feet. Visual acuity is measured by reading letters, numbers, or other symbols from chart 20 feet away. It is otherwise called “20/20 Vision”. Symbol size corresponds to the standard distance at which persons with normal vision can recognize the symbol.
There are both legal and educational definitions of visual impairment (Vergason, 1990)
--The legal definition points out the measurement of visual acuity, which is the ability to clearly distinguish forms or discrimination of details at a t specific distance.--

LEGAL DEFENITION:
A: Partially Sighted/ Weak Sighted
It is a condition in which one’s vision is seriously impaired, defined usually as having between 20/200 and 20/70 central visual acuity in the better eye, with correction.
B: Blind (Blindness)
It is a descriptive term referring to a lack of sufficient vision for the daily activities of life. Legally, it is defined as having central visual acuity of 20/200 or less in the better eye with correction, or having the peripheral vision concentrated to an extent in which the widest diameter of the visual field covers an angular distance no greater than 20 degree (Vergason, 1990; Heward and Orlansky, 1988)

EDUCATIONAL DEFINITION:
A: Partially Sighted Pupils:
These are pupils who by reason of impaired vision can’t follow the normal regime of ordinary schools without determent to their sight or to their educational development, but can be educated by special methods involving the use of sight. Such pupils use print materials but may need modifications such as enlarged print or use of low vision aids (Magnification) (Yesetdyke and Algozine, 1995)
B: Blind Pupils: Those are pupils who are totally without sight or have little vision, and who must be educated thorugh channels other than sight (for eg., using Braille or audio-tapes) [Yesseldyke and Algozine, 1995]

WHO CLASSIFICATION:
Normal Vision: --None 0.8 (6/7.5); slight: <0.8 (Normal)
Low vision: -- Moderate <0.3 (6/18); Severe <0.12 (6/48)
Blindness: -- Profound <0.05 (3/60); Near Total <0.02 (1/60)

TYPES OF AND CAUSES OF VISUAL IMPAIRMENT
The following are the some types and causes of Visual Impairment.
1. Refractive Errors:- It is common eye problems. Eg., Myopia (Near sightedness); Hyperopia (farsightedness). The light rays that enter the ye do not fall exactly on the retina. When the eyeball is too long, the image falls in front of the retina and myopia results. They can see things at near to them and they can’t distinguish images at a distance. When the eyeball is too short, the images fall at the back of the retina and hyperopia occurs. They can see things clearly at various distance but requires the lens curvature. (eg. Concave & Convex)
2. Astigmatism: - refers to distorted or blurred vision caused by irregularities in the cornea or other surface of the eye; both distant and near objects may be out of focus.
3. Diabetic Retinopathy: Impaired vision due to hemorrhages and the growth of new blood vessels in the area of the retina.
4. Amblyopia/ lazy eye:- it is a dimness of vision in one eye, causing suppression of the weaker eye and use of stronger eye. This is due to eye muscle imbalance, refractive errors or other defects during infancy.
5. Cataract:- it is a condition of cloudiness in the lens of the eye that blocks the light necessary for seeing clearly. Vision loss depends on where the cataract located on the lens and how dense the clouding is. Treatment will be effective (surgery/ eye glass or contact lenses)
6. Glaucome:- it is a condition in which the normal fluid of the ye (aqueous humor) doesn’t drain properly. This results damage to the optic nerve and results in severe loss of slight or tunnel vision. This person can see only the center of the visual field. If detect early it can treat with controlling the pressure in the eye.
7. Retinitis Pigmentasa:- It is a hereditary condition caused by the progressive degeneration of the retina. Individual first loses peripheral vision, and gradually central vision decreases. Common symptoms indicated colour blindness and night blindness.
8. Retrolental Fibroplasa:- It is a loss of vision results in formation of sear tissue at the back of the lens of the eye. It is due to the concentration of oxygen administrated to the child at birth in incubator.
9. Trabismus:- It is condition in which the eye is turned inward or outward or squints because of weak or malfunctioning muscles. Treatment involves patching the stronger eye, corrective lenses and surgery.
10. Nystagmus: It is a condition results in involuntary, rapid, rhythmic eye movements, usually side to side continuously. It may cause severe visual problems, brain malfunctioning and inner ear problems.

Infectious Disease Trachoma:- It is a common among people of many countries who surroundings are unhygienic and who are crowded together in unhealthy environments wherein dirt abounds. It creates irritation and scaring of cornea which gradually leads to Visual Impairment.
 Syphilis
 Measles
 Typhoid
 Meningitis
 Hypertension
 Diabetes
 Malnutrition
 Vitamin A Deficiency
 Injury and poison

Identification, Assessment and InterventionIdentification:
 Frequently experiences red or inflamed eyes, infectious and rubs them.
 Eye movements are jumpy and blinks frequently
 Experiences difficulty – moving around, reading small print, and loosing place during reading; to identify small details in pictures.
 Lacks interests in lights and visual stimuli
 Rubs eyes frequently, has poor eye hand co-ordination.
 Complaints headaches and eye infection frequently
 Blurred or double vision
 Holding reading material at an inappropriate distance
 Eye discomfort – burning, itching or scratching.
 Unusual facial expression and behaviour.

Assessment:
1. Screen whether the child can see light or not.
2. Visual acuity measurement: -Distance Acuity measurement –Near Vision Acuity Measurement [Hyvarinen (1997) presented procedures]
3. Visual Field: The field of vision of the area which can be see without any movement of the eye or head.
4. Color Vision: - Pseudoisochromatic chart eg: Ishihara plates (These plates are made up of colored dots in which are embedded the shapes or numerals. They are confusion tests of colour blindness. –City University Color Vision Test
5. Contrast Sensitivity:- Luminance is a measure of the amount of light emitted by a surface, and contract sensitivity in the terms applied to the eye’s ability to register differences in the luminance of objects, whether 2/3 are dimensionally presented.
6. Reading Acuity:-
Myvarinen (1997) suggested four measurement methods in Reading Acuity
Threshold: Measure the smallest text size that the child can read at a comfortable distance and the smallest eye that the child can read at a closer distance.
Optimal Size:- Measure how much larger the text needs to be allow fluent reading for a longer period of time.
Reading Speed: Measure how many words per minute and how many errors makes.
Reading Comprehension: Given a story passage and answer the important parts of the story.

Intervention:
It should do at home and school.
Home: - Creating loving and acceptance from family environment. – Develop positive interaction with child and encourage to talk and discuss – giving orientation to senses, listening, touching, smelling and tests – allow child to move freely – maintain close contact with teachers of the child and seek advice from professionals, parents of visually impaired children.
The School:- Reduce distance between teacher and students – Use auditory cues when referring to objects in the class room – seat students near chalk board or overhead projections, or give them freedom to move close to areas of instructions – reduce unnecessary noise to help focus on contact of instructional presentation.