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The New Children’s Gratings Test (alternative to Teller Cards)

Product Ref: NEW CHILDRENS GRATINGS

Web Price

£400.00 EX VAT

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INTRODUCTION
These acuity cards provide a rapid method of determining the visual acuity of infants and young
children within a variety of clinical settings. The apparatus forms part of the “acuity card procedure”, a
technique pioneered in the United States and subsequently used in clinical practice in Europe. The
standard procedure is based on infants’ known “preference” for patterned stimuli as indicated by their
looking behaviour.
This test is also being used to test stroke victims.
THE APPARATUS
The Infant Assessment Set consists of eight acuity cards. Each card contains two circular apertures. In
seven of the cards one of the apertures contains a grating patch of known spatial frequency (i.e. the
number of black and white stripes per degree of visual angle). The eighth card does not contain a
grating in either aperture- this is marked the “blank”. A small round peep-hole is located at the centre
of each card through which the patient is observed during the test.
A further set of 10 cards can be purchased separately and are called The Children’s Additional Set.
This set includes 4 cards in the nominal acuity range 14.5 to 35.4 c/deg, and six cards within the range
of 0.29 to 9.6 c/deg (see table). The additional cards extend the use of the Infant Assessment Set
beyond about the first year of life and provide greater sensitivity when testing acuities below 12.5
c/deg.
Most users prefer the combined version of 18 card
PROCEDURE
A ONE MONTH OLD BABY
The infant is held by the seated parent (or if possible by an assistant) at a distance of 38cm from the
centre of the card. The tester presents the acuity cards whilst observing the infant’s looking behaviour
through the peep-hole. The test is begun with a coarse grating (less than the infant’s expected acuity) in
order to establish their looking pattern. Further cards of increasing spatial frequency are presented and
the looking responses are observed. In this manner the finest grating that elicits a looking response is
determined and recorded as the visual acuity in cycles per degree (c/deg), or Snellen equivalent if
preferred.
It is advisable that the examiner be unaware of the location of the grating patch: the left-right position
of the grating should be randomised before carrying out the test. N.B. no indication of the grating’s position is given on the reverse of the card. Each card can be presented once, then rotated through 180 degrees and the observed responses compared with the position of the grating patch. Intermittent use of the “blank” can be used to confirm responses,as can small movements of the cards at the acuity limit. Three presentations are recommended.

The term “looking response” refers to any consistent behaviour observed upon presentation of the cards. For example, eye movements, fixation, head turning or pointing. The nature of the response varies according to the age of the patient and the proximity to the acuity limit. For guidance, the following responses are associated with particular age groups.

NEONATES: often slow to respond and the grating patch may be positioned more centrally and then
moved sideways to confirm fixation.
AROUND 6 MONTHS OLD: the easiest age to test at, looking responses are pronounced and therefore
readily interpreted.
AROUND 9 MONTHS AND OVER: the older the infant, the quicker the response. The grating may
not hold attention and the infant may only glance at the grating and then look quickly to the other side
of the card. The tester should be aware that after a few trials, the infant may anticipate which side the
grating will appear (usually where it was last shown).
Several techniques can be used to assist in the smooth running of the procedure and these will already
be appreciated by those with previous experience in measuring vision in infants and children. For
example, toys can be presented within the examination area to gain the infants attention, and for
monocular testing, co-operation can be achieved by playing “pirate”.
The standard procedure can be adapted for use with a variety of patient populations.
In all cases, distracting influences should be minimised. For toddlers, additional behaviours can be
elicited, for example, the cards may be presented with the child lying on the floor.
Age norms have yet to be established for these acuity cards, although as a rule of thumb, visual acuity
expressed in cycles per degree is approximately equal to the age in months up to about 1 year.
However, it should be remembered that the range of acuities obtained using preferential looking tests of
acuity in normal infants may span 2 octaves, an octave being a doubling of spatial frequency. For age
norms obtained with similarly designed acuity cards, see the references.

Accessories and other items can also be purchased by phone if you prefer. To make a telephone order, or to discuss any item purchase please call 01438 740823.