Page 57 - DEDU506_SPECIAL_EDUCATION_ENGLISH

Unit 7: Visually Impaired: Definition, Types and Characteristics

(i) Partially Sighted: A visual impairment that adversely affects a student's educational Notes
performance even when corrected to the extent possible.
(ii) Low Vision: If someone's vision is between 20/70-20/160 and cannot be corrected, the student
has moderate to low vision.
(iii) Legally Blind: From 20/200-20/400 is legally blind with severe low vision. From 20/400-20/
1000 is profound visual impairment, and is very close to total blindness.
(iv) Totally Blind: The lack of light perception is known as total blindness or total visual
impairment.

7.3 Refractive Errors
The most common types of visual impairments are simple refractive errors. These include
nearsightedness, farsightedness, and astigmatism. In nearsightedness images are focused in front of
the retina, making far away images appear blurry. Farsightedness results from an image being focused
behind the retina, which means the child will have trouble focusing on objects that are close up.
Astigmatism results from curvature of the cornea, which keeps light rays from focusing properly in
one area of the retina. This condition results in the inability to focus on objects far or near. Fortunately,
refractive errors are correctable.

Many children use glasses and enjoy clear vision. These students will have no need for
special services unless the refractive error is not correctable for some reason.

Self Assessment
2. Fill in the blanks:
(i) ........................ is a visual impairment that adversely affects a student's educational performance
even when corrected to the extent possible.
(ii) From 20/200-20/400 is legally blind with severe low vision from ............................. is profound
visual impairment, and is very close to total blindness.
(iii) The lack of light perception is known as .................................. .
(iv) The most common types of visual impairments are ............................. .
(v) ........................ results from curvature of the cornea, which keeps light rays from focusing
properly in one area of the retina.

7.4 Common Eye Conditions

(i) Amblyopia: Amblyopia is also known as lazy eye. Children with a lazy eye may or may not
be perceptible. Sometimes a lazy eye visibly turns in or out, but sometimes there is no outward
sign. Amblyopia causes the eye to have reduced acuity due to the poor positioning of the eye
and weak muscles. The treatment is commonly a patch over the normal eye that makes the
lazy eye work harder. Surgical corrections are also common.
(ii) Retinitis Pigmentosa: This is a degenerative condition that is inherited. Retinitis pigmentosa
results in a loss of peripheral vision, and eventually the student is left with a severe visual
impairment.
(iii) Retinopathy of Prematurity: This condition is common in children who were premature
babies that required high concentrations of oxygen at birth. Scarring and detachment of the
retina can result from this condition.
(iv) Strabismus: In this condition, both eyes are unable to gaze at an object at the same time.
Strabismus is caused by a muscle imbalance.

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