    U OF T PROFESSORS DEVISE BETTER WAY TO TEST SIGHT IN BABIES

           In  a  darkened  room  at  Toronto's  Hospital  for   Sick
    Children,  a baby,  its head dotted with electrodes,  sits in its
    mother's lap and watches flashing black and  white  checkerboards
    and stripes on a television screen.  Soon after the test, doctors
    will know if the child can see and how well it can see.

          The testing procedure,  which involves measuring brain wave
    activity prompted by visual stimuli (also  called  visual  evoked
    potentials or VEP's) has been perfected by Drs.  Barry  Skarf  of
    the Department of Ophthalmology and Moshe Eizenman of  U  of  T's
    Institute

          Their procedure is more accurate than tests used  elsewhere
    because Eizenman  has  developed  a  novel,   real-time  computer
    program to extract brain  wave  responses  from  extremely  small
    patterns (similar in size to the bottom line of  a  standard  eye
    test) which produce  much  more  reliable  results.   Until  now,
    doctors would have to  extrapolate  the  baby's  ability  to  see
    small stimuli from test results using large stimuli.  "In Effect,
    Dr.  Eizenman has developed a way of looking at brain waves  that
    is more sensitive  than  methods  previously  available,  "  says
    Skarf.

          At the HSC,   VEP's  are  used  in  a  number  of  clinical
    applications:   to  determine  whether  a   visual   problem   is
    cognitive;  to assess whether babies who don't appear to see well
    will see  better  in  the  future;   to  determine  a  course  of
    treatment for such problems in which  one  eye  turns  in  or  is
    weaker than the other eye.  The second aspect of the researchers'
    work involves the development of a stimulator for stereopsis,  or
    binocular vision,  which is the fusing of images from  both  eyes
    into one picture that  has  depth.   "The  problem  with  testing
    binocular vision,  "  explains  Skarf,   "is  that  most  stimuli
    presented to young children have other  cues  that  can  be  seen
    with one eye alone.  We wanted to devise stimuli that can only be
    seen by both eyes  together  and  would  produce  specific  brain
    waves to the stimuli."

          Based on a  binocular  stimulus  invented  by  an  American
    researcher,  Eizenman had developed a stimulus that  generates  a
    pattern on a tv  screen  which  looks  like  distortion  (a  snow
    storm) when viewed with only one eye,  but  when  viewed  through
    special  glasses  with  both  eyes  emits  a  distinctive  three-
    dimensional pattern.

          Skarf and Eizenman  are  now  testing  binocular  VEP's  on
    young children.  They are examining children  with  normal  sight
    and evaluating eye function in children  with  visual  disorders.
    This is the first test of binocular  vision  to  be  carried  out
    with large numbers.  "Using this binocular stimulus with the very
    sensitive detector system for analyzing responses,   we  hope  to
    have a system which will allow us to  test  binocular  vision  in
    young babies,  quickly and easily,  and to measure responses in a
    better way than before."

          In addition to this clinical research,  Skarf now wants  to
    direct his attention to some basic research questions  about  the
    development of vision.  "We are  interested  in  more  than  just
    developing tools.  We want to know how binocular vision  develops
    and which factors interfere with development.  We  want  to  find
    out what wheels turn in  the  brain  to  produce  lazy  eyes  and
    impaired binocular vision."

           Skarf  and  Eizenman  receive  funding  from  the  Medical
    Research Council of Canada. 

    CONTACT:

          Barry Skarf    (416)598-6133

          Moshe Eizenman (416)978-5523
