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Visual Impairment :
Special Educational Needs

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Visually impaired students often have difficulty in reading work presented to them. This is related to the way in which we detect and process written work. It is the central area of the retina, the fovea in the macula, that contains the cone cells which are used for high resolution imaging and are necessary for sharp, clear vision, and which are used in reading. The rods in the peripheral region of the retina are unlikely to have any role in reading, though some speed reading experts dispute this. The width of the macula is small so the visual arc used in reading is narrow.

The arc of vision for each eye is about 120o. The arc for both eyes together is about 180-200o. The overlapping central part gives 3D vision. The visual arc for the central fovea is only 2o. This represents an area with a diameter of 2.4 cm at 70 cm from the eyes (an arm’s length), and 1.2 cm at 35 cm. The closer to the eye, the narrower the area. This affects the number of letters that can be read by the eye at any one time, and is normally 4 or 5 letters.

The diagram from shows the visual field when reading. The fixation point is the central part of the field and when we read we move the fixation point along the line of text.

Diagram showing fixation point


Recent research involving magnetic resonance imaging on volunteers has supported a theory of how we read that involves using a visual dictionary. This maintains that we don’t read individual letters but recognise the shape and pattern of words. Dr Maximilian Riesenhuber from the Laboratory for Computational Cognitive Neuroscience, Georgetown University Medical Centre said:

“We are not recognising words by quickly spelling them out or identifying parts of words, as some researchers have suggested. Instead, neurons in a small brain area remember how the whole word looks - using what could be called a visual dictionary.

The small area in the brain called the visual word form area is found in the left side of the visual cortex, opposite the fusiform face area on the right side, which remembers how faces look.”

Other research suggests that we do not read all of the words in a sentence, especially if reading quickly, and our brain fills in the missing words to make sense of the sentence.

The way in which we read has consequences for visually impaired people. When text is enlarged fewer letters fit in the central area of the visual field. At N36 it is probably only one or two letters. Consequently whole words or parts of letters can not be seen without extensive eye movement and the use of the visual dictionary is much more difficult or may not be available at all. A major mechanism used in reading in sighted people and which allows us to read quickly is not available or reduced so the process of reading is different to that used by fully sighted people and is more like the process of reading Braille.

Diagram of different text sizes

Reading occurs one letter at a time so the individual has to construct words from remembered letters and then memorise the sentence before understanding the meaning of the sentence. It is more difficult to reread parts of a sentence. The process is slower and more demanding and accounts for the literacy difficulties of severely visually impaired students.

In the case of those with nystagmus the eye has rapid, involuntary movements, a wobble, which makes it difficult to maintain the fixation point and consequently difficult to apply the visual dictionary when reading.

The visual dictionary theory can explain some types of dyslexia and visual agnosia, the inability to recognise objects visually, may therefore be a cause of dyslexia, as the individual is unable to access a visual dictionary, so it may be a type of cortical visual impairment, CVI.


The layout or organisation of the work becomes a barrier to the child’s understanding, learning and progress. Appropriate presentation of resources is essential in ensuring that the barriers to learning are removed. VI pupils can have difficulty reading ornate fonts, particularly those with serifs, such as Times New Roman, so plain fonts, enlarged to the recommended size, should be used.

Conditions such as loss of visual field, nystagmus and retinal dystrophy affect the width of text that the eye can scan. Enlargement of pages to A3, while increasing the font size, makes the work difficult for the child to access as he/she will be unable to read across the whole page.

Enlarging using a photocopier

All photocopiers will enlarge text and most will enlarge easily from A4 to A3. At first this can seem the best way to enlarge work for a visually impaired student.

Enlargement from A4 to A3 increases the page size by 141.4 %, producing a large, cumbersome page which is 42 cm long and 29.7 wide. The text enlargement for standard text is as follows :

N10 is enlarged to N15;    N12 is enlarged to N18

VI students will have a recommendation of a font size and style which is the most appropriate for them to read comfortably, often in the advice from a QTVI, for example :

N24 text comment

The advice given about font size results from assessments carried out by qualified, experienced professionals, and specifies the font size which will enable the visually impaired student to access the work on a par with his/her sighted peers. For students who need font sizes greater than N18 enlarging to A3 on a photocopier will not produce accessible work and therefore is totally inadequate.

In addition enlargement to A3 produces text which is 24 cm wide. This is difficult to read as it requires the reader to move his/her head from side to side so is tiring, and this especially the case for a visually impaired student. School furniture is designed for smaller pages and A3 pages often do not fit on a school desk and are unmanageable.

A visually impaired student should never be given work enlarged to A3.


Enlarging text inevitably increases the number pages that the text covers. One page of N12 text becomes 3 ½ pages when enlarged to N24, 8 pages at N36, 14 pages at N48 and 32 pages at N72. This means that at N48 a 100 page reading book would enlarge to 1,400 pages of text and 3,200 pages at N72, becoming totally unmanageable. For enlargements greater than N36 alternatives, such as use of Braille or ICT, must be used.

Note that the Copyright (Visual Impaired Persons) Act, 2002, and The Copyright and Rights in Performances (Disability) Regulations, 2014, allow enlarged copies of text to be made for visually impaired pupils. You can access these at these web addresses :


VI pupils can now be provided with a whole range of equipment and technology that was unavailable 20 years ago. Many, dependent of their specific needs, will use magnifiers, text readers, lap tops, CCTV, audio equipment, speech recognition and electronic Braille notes. The use of access and assistive equipment and technology has its own inherent problems. It is often bulky and heavy, and may need a competent technician to set it up. In a secondary school the child has to carry much of it around the school, and, in the case of electronic equipment, may also have problems of recharging batteries during the day.

Whenever work is planned or prepared for a pupil with visual impairment, staff should think about the child and ask the question :

Is this work appropriately modified ?

Will it be accessible and meaningful to the child ?

Does the child have access to the appropriate support and assistive technology ?

Will anything in the lesson present the child with a barrier to his/her learning, understanding or progress ?