VISUAL IMPAIRMENT

VISUAL IMPAIRMENT Blindness It refers to a condition where a person suffers from any of the following conditions Total absence of sight Visual acuity not exceeding 6/60 or 20/200 (Snellen) in the better eye even with correction lenses; or Limitation of the field of vision subtending an angle of 20 degree or worse

Low Vision A person with low vision is one who has impairment of visual functioning even after treatment, and/or standard refractive correction, and has a visual acuity of less than 6/18 to light perception or a visual field of less than 10 degrees from the point of fixation, but who uses, or is potentially able to use, vision for the planning and /or execution of a task.

How do the different visual conditions affect what we see? Clarity (That image is unclear or blurred) Completeness (Completeness) Comprehension ( Although a clear image is sent to the brain, the capacity to attach meaning to it is impaired)

Clarity Any condition that interferes with the transparency of the cornea, the lens, the aqueous and vitreous interferes with the refraction of light, resulting in an unclear or fuzzy image The shape of the eye and the capacity of the lens to accommodate can cause the image to be focused behind or in front of the retina gain resulting in the loss of clarity Conditions that affect the optic nerve and the retina

Common areas of difficulty in Clarity Trouble seeing detail Trouble seeing if light is low Trouble seeing when contrast is poor Likely to have trouble seeing if plain surfaces reflect light or when there is glare

Some behavioral clues Brings objects close to see them Mistakes people or objects that have the same general shape Does not respond to facial expression Shy, hesitant or reserved when light is poor (Example in the evenings) Squints, blinks, hesitates, cries when going outdoors into the light

Strategies Increase the size of the object Outline shapes, work areas and increase contrast Use non-glare surfaces and objects Adjust the direction and intensity of light

Completeness The field of vision is affected Due to the damage to the retina, optic nerve or visual pathway and the are of loss depends on the location of the damage Peripheral field loss Tunnel Vision Central field loss

Common areas of Difficulty Trouble adapting to changes in lighting Trouble seeing in low lighting Miss people or objects to the sides, above and below eye level

Some behavioral Clues Turns head to one side of the object being viewed (Effectively using one eye to see it) Often bumps into things, misses things that are close by Holds objects at arms length or moves back to see Has trouble following quickly moving objects, does not like outdoor games

Strategies Find the best viewing distance for presenting objects of a particular size Increase light on object (Tunnel vision), avoid glare (Central vision loss) Mark work, play and living areas clearly

Comprehension The optic nerve carries the image to the visual cortex as electrical impulses where it is processed and recognized as images. When there is damage to the visual cortex, the brain does not consistently understand or interpret what that eyes see. Visual processing problems

Common areas of difficulty Able to recognize familiar objects, trouble with new ones Easily overwhelmed when several senses need to be used together Trouble distinguishing object from background

Some behavioral clues Prefers tactile and auditory to visual exploration May use peripheral vision exploration May be visually unresponsive or inattentive May not make eye contact, or have very brief eye contact

Strategies Use multi-sensory approach Reduce visual distractions - the number of objects in the environment Use single colored , clearly outlined objects

Cause of Visual Impairment Cataract Glaucoma Coloboma of diff. Eye parts Refractive errors Strabismus (squint) Nystagmus Retinopathy of Prematurity (ROP) Infants born prematurely (It is caused by damage to Retina)

Albinism Optic nerve atrophy Myopia(Nearsightedness) Astigmatism (Cornea is not proper in shape) Cortical Visual impairment

Functional Vision Assessment How children use their vision to explore, learn, plan and execute their plans in the context of their daily activities? Use of vision is typically observed in the areas of movement, communication and interaction with people & Object Identifying the circumstances and strategies that facilitate the use of vision and determining how best to support the child’s learning and development are major objectives of a functional vision assessment.

What does the child see ? What does the child vision for ? What affects the use of vision ? What will help the child use vision better?

How do I know if the child has actually seen something ? Common responses are listed below : Visual Responses Searching movements of the eyes Turning eyes toward the stimulus Closing eyes Increase in nystagmus

Also see whether the child can follow a moving object in various directions - vertical, horizontal, circular find an object easily among other scattered toys (remember to use objects she likes) reach directly for an object judge distance well

During play or interaction using distance vision observe if she sees: objects of different sizes at different distances follows moving objects in different directions (eg. A person walking by, a rolling ball, a floating balloon) locates a person or an object among others recognizes, imitates people at a distance notices objects or people that in her field of vision if she is mobile can she avoid obstacles above, below and to the sides

When a child displays no visual responses: darken the room and introduce a bright light to see if you get awareness, orientation or localization check for the presence of reflexive visual responses such as blink response to visual threat.

Things to watch out for while doing your assessment: Learn to read the child’s signs Let the child set the pace Children may get easily bored or quickly over-stimulated Traditional mear testing is usually done at 40 cms, while testing for distance is done at 6 metres. But, many children find maintaining this distance difficult. So for testing establish the distance at which the child is able to maintain

Visual attention with ease and note the size and type of object used Understand the child’s developmental level With children with severe impairments and those with severe motor involvement, you may have to wait a long time before the child can organize his system adequately to give you a response

Important things to remember: Write down questions regarding the child’s vision you want to address during the assessment Organize the environment in terms of lighting and space Set up your materials and activities in separate boxes so that it is accessible to you and at the same time not distracting to the child Mark basic distances in the working area - 6,4,2 and 1 meters, 40 and 20 cm - so you do not have to measure when interacting with the child Get someone to observe you

What kind of information should a functional vision report include? Implications of diagnosis Learning style Response to visual stimuli Good materials to use Pacing Preferred gaze Best positions for the child Optimal environmental conditions Visual fatigue Recommendations

How do I determine what modifications are appropriate for the child? Pacing Space Illumination Color and contrast Position

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