Understanding Vision Impairment

Think laterally, on an individual basis.

(Student with vision impairment)

An example

On entering an unfamiliar classroom, a sighted student is able to take in something of the whole at a glance. They can perhaps work out the overall position of the room in relation to other, more familiar places, such as the library, computer room, hall, or the secretary's office. Paying closer attention to details, the same student will be able to focus selectively on a wall chart, signs that identify work areas such as a listening centre or the writing corner, or a display of students' work.

For the student with vision impairment, constructing an inner map of this new classroom presents a problem of synthesising information from small, local details to achieve a sense of the whole. This must then be largely memorised.

A vision impairment may be:

• Congenital (present from birth);
• Hereditary (genetic, congenital or later onset);
• Acquired (through accident, illness or disease).

Reduced visual acuity: Distance vision

Visual acuity is a measurement used internationally by eye specialists to describe the ability of the eye to perceive the size and shape of objects in a direct line of vision. Reduced visual acuity results in reduced clarity of images and fine detail.

Normal visual acuity is expressed as 6/6, ie, a person with normal vision can see a letter approximately one centimetre high from six metres away. A student with a visual acuity of 6/24 needs to be at six metres to see what a person with normal vision can see from 24 metres away. Distance visual acuity measurements are used to establish eligibility for driving licences (6/12 with normal visual fields is required for driving a car) and some occupations.

Reduced visual acuity: Near vision

Students with moderate vision impairment can still use print as their main medium for learning. Visual acuity measurement is used to describe the ability of the eye to perceive the size and shape of an object involved in near tasks, eg, reading, and for this measurement print sizes are used. The ability to read N5 size print at 33cms (as used in small newspaper advertisements) is considered normal near visual acuity.

It is important to be aware of each student's near visual acuity measurement to establish the most suitable print size for learning materials. This need for adaptation will apply to the full range of near tasks across all areas of the curriculum (eg, Technology, the Arts, Social Sciences). Some students with vision impairment can see small print. They can also achieve magnification by holding materials at much closer distances than those with normal vision.

Depending on the eye condition, some students wear glasses or use magnifying aids. For others, visual aids are of no assistance.

Resource Teachers Vision provide assistance to the class teacher in interpreting information on students' vision and in choosing the most appropriate print size for each student's educational needs.

The following are examples of print size:

The effect of a vision impairment

Students with vision impairment have a visual condition in which distance vision, central vision or peripheral vision is affected and thereby reduces visual functioning. Some students experience both reduced acuity and visual fields.

Further information on specific eye conditions may be found through the Resource Teacher Vision, through the resource materials section of this booklet, or on the following websites:

http://home.swipnet.se/macula-lutea

www.tsbvi.edu

www.rnzfb.org.nz

www.pvi.org.nz

www.afb.org

Functional vision

Functional vision refers to the way in which vision is used in everyday life. Visual acuity is a reasonably good predictor, however individual students will vary in their use of vision and two students with the same visual acuity or eye condition may function quite differently.

Teachers need to be familiar with medical details and, in particular, need to observe how each student functions in educational settings.

Factors that can influence functional vision include:

• Eye condition;
• Visual acuity (distance and near);
• Other medical conditions;
• Medication;
• Attitude of the student;
• Strategies students adopt;
• Attitude of others (eg, parents, teachers, peers);
• Physical environment (eg, building and room layout, play and sports areas);
• Access to and use of low vision aids;
• Access to and use of specialised equipment and resources;
• Access to specialised support.

Undiagnosed visual problems

Teachers are good observers and while in many instances, vision impairment is identified early, there are signs or behaviours that may indicate a student could have a vision problem. If a student experiences any of the signs or behaviours listed, parents should be advised to have their child's vision formally tested - either by an optometrist (a professional with a science degree who examines the eyes, identifies indicators of diseases and prescribes lenses); or by an ophthalmologist (a medical eye specialist).

Possible indicators of visual problems: Teacher's checklist

Appearance of eyes

• One eye turned in or out;
• Frequent blinking;
• Squints or screws up eyes;
• Red eyes or lids, crusting on lids;
• Frequent styes or infections;
• Excessive eye movements;
• Excessive watering of eyes or light sensitivity.

Behaviour

• Holds book very close;
• Avoids close work;
• Loses place when reading, skips lines;
• Omits words or makes errors when reading or copying;
• Closes or covers one eye when reading or doing near work;
• Confuses similar words, fails to recognise same word in different context;
• Has a short attention span when reading or writing;
• Has a poor or unusual sitting posture when reading;
• Tilts head excessively to one side, up or down;
• Makes excessive head movement when reading;
• Squints or frowns to see blackboard clearly;
• Rubs eyes frequently;
• Thrusts head forward to see distant objects;
• Has an obvious tendency to favour one eye;
• Is nervous, irritable, tense or restless after maintaining visual concentration;
• Makes errors in copying close work or from distance to near.

Complaints

• Headaches;
• Difficulty seeing clearly at a distance;
• Blurring of vision while reading or writing;
• Seeing double;
• Eye burning or itching during or after close work.