Aniridia

Description

  • congenital (ie present at birth) and hereditary (ie inherited)
  • aniridia means “the absence of the iris” (“an”-
    without, “iridia”- iris). In actual fact there is usually a
    thick collar of tissue around the outer edge of the iris but the muscles
    which open and close the normal pupil are entirely missing. This muscle
    normally controls the amount of light entering the eye, by opening and
    closing the pupil (the hole in the iris), as a reflex reaction to light
    levels. Without this muscle, the eye cannot control the amount of light
    entering it and hence will be photophobic (sensitive to light)
  • the student with aniridia will appear to have no iris or a very large
    black pupil. Some may have small stubs of iris visible
  • except in a few cases, aniridia affects both eyes
  • often associated with other eye defects including nystagmus, cataract,
    glaucoma, or under-development of the fovea
  • some students develop an induced ptosis (drooping of the eyelids) as
    a means of controlling the amount of light entering the eye.

Implications

  • the eye is extremely photophobic (sensitive to light)
  • the macula of the eye is often poorly formed therefore central vision
    is greatly impaired. With poor central vision, acuities can be low so
    that visual information may need to be enlarged
  • nystagmus (a rhythmic oscillation of the eyes which is almost always
    present in infants with aniridia) will cause a decrease in acuity
  • glaucoma (elevated pressure within the eye), if present, may cause
    peripheral field loss
  • contact lenses with an artificial iris may be prescribed. This will
    improve the appearance of the eye but will also reduce the amount of light
    entering the eye. The contact lens will not, however, make automatic changes
    to adjust to different lighting levels as occurs in the normal eye
  • some students are prone to headaches.

Suggested teaching strategies

  • ensure that all staff working with the student, including replacement
    teachers and volunteers, are aware of the vision impairment and its educational
    implications.

Outdoors:

  • teachers will need to be aware of the affects of various light conditions
  • the teacher should keep the sun behind the student when addressing
    him/her
  • the student should also be made aware of which lighting conditions
    are best for him/her. If the student is aware s/he can ask for variations
    which are favourable or control lighting and shading him/herself
  • to reduce photophobia, the student with aniridia may be prescribed
    tinted spectacles or contact lenses – student and/or teacher may need
    to be aware of methods of care and cleaning if appropriate
  • dark or tinted glasses may be necessary to shield eyes from the light
  • sun hats, preferably with a dark coloured brim, can be useful to shield
    the eyes from light and glare
  • students with aniridia may be more comfortable wearing darker colours,
    especially on their upper body. Light coloured clothing may cause glare
    and discomfort especially when outside
  • reading environmental signs eg street signs may cause difficulties.

In the Classroom:

  • seating position within the classroom is critical. The student should
    be seated taking into account her/his nystagmus (where present), and the
    light and glare during school hours
  • control of light, or more particularly glare, is important in the classroom.
    If too much light enters the room, blinds or artwork can be placed over
    windows
  • students often prefer artificial room lighting to be turned off
  • students with aniridia are extremely sensitive to reflected glare from
    chalkboards although chalkboards tend to be preferred to whiteboards
  • the use of shiny surfaces (eg white boards, shiny paper for flashcards
    or worksheets, shiny table tops) should be avoided as they can reflect
    light toward the student’s eyes
  • reading material may need to be modified eg tactual diagrams, audio
    format, enlargement. For young students it may be sufficient to bring
    reading material close to the eyes
  • utilise high contrast materials eg black texta for writing, textas
    for drawing, coloured paste, using clear bold illustrations to cut around
  • for writing sheets or exercise books, recycled paper (creamy or grey
    coloured) may be better than pure white paper, but remember that contrast
    is also important
  • for older students, a magnifier or CCTV may need to be prescribed for
    near work. If using a CCTV, students with aniridia will usually prefer
    to read white print on a black background
  • paper colour, print size and type of magnification (hand held or stand
    magnifier, photo-enlargement or CCTV) will need to be assessed on an individual
    basis
  • bold lined paper may assist
  • always use a clean chalk board with white or yellow chalk or white
    board with black marker. Use a consistent layout when presenting information
    on a board eg homework is always found on the far right hand side of the
    board
  • a reading/writing stand can often assist, especially in primary school
    or for prolonged visual tasks. The use of a reading/writing stand will
    also help to occlude light from the eyes
  • many students will benefit from a telescopic distance aid (eg a monocular)
    for chalkboard work
  • students will benefit from desktop demonstrations ensuring visual access
    eg correct handwriting formation of a new letter, science experiment etc
  • organisational skills may require development. Developing efficient
    organisational skills will assist a student with a vision impairment eg
    having a large pencil case to store pens, calculator and visual aids;
    setting aside extra time to collect any equipment required; allowing extra
    time to complete visual tasks etc
  • additional verbal description and verification may be required to ensure
    the student has access to his/her environment eg describe a new classroom
    or excursion venue, provide verbal praise etc. The student with a vision
    impairment may miss a smile of encouragement
  • the use of a personal computer (eg laptop) may be of great assistance
    to a student with a vision impairment as an alternative to handwriting
    and to reduce visual fatigue. Software is available for enlarging text
    and graphics, including icons, menus etc. Voice output is available for
    both IBM and Macintosh computers. Individual assessment of the needs of
    each student is essential. Keyboarding skills should be taught in primary
    school
  • strategies to reduce vision fatigue should be considered eg appropriate
    visual rests may include listening to audio tapes both for information
    and relaxation
  • students with a vision impairment often need to be taught social skills
    using a direct teaching approach. Modeling appropriate social behaviors
    can be difficult when you cannot see them accurately
  • students with a vision impairment may need additional orientation and
    mobility training
  • understanding and acceptance of the student’s vision impairment,
    individual learning modes and work production methods (eg braille, computer
    etc) may be facilitated through carefully planned simulation activities
    and class education programs.

These notes were made by the staff of the Statewide Vision Resource Centre.
They are general statements and may not apply to all students with this
condition.