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COMPASS Operating Manual
Pag. 12 di 53
6.
PREPARING THE SUBJECT
This paragraph explains how to prepare a subject for the COMPASS test.
There are no restrictions as to the selection of the subjects undergoing testing, but since the test
requires the subject to maintain concentration and to follow the below instructions for several
minutes, very young subjects (before primary school), as well as mentally diseased persons may
not be able to co-operate appropriately.
COMPASS compensates for
a subject’s spherical refractive error in the range -12 to +15 diopters:
testing a subject presenting a spherical error out of the above range may result in inaccurate
measurements.
COMPASS
does not compensate for a subject’s astigmatism. Subjects with astigmatism within ± 4
diopters can be tested normally. Testing a subject with astigmatism outside of the above range
may result in inaccurate measurements.
The subject can wear contact lenses or spectacles while being examined, although in the latter
case artifacts may appear in the retinal image.
Patient contacting parts are indicated in Fig. 1 and Fig. 3.
COMPASS is a non-mydriatic device: there is no need to dilate the subject unless if the pupil is
smaller than 3 mm. The eye which is not examined should be patched.
Before starting the test, please check the following:
subject should sit in a comfortable position, with the fore head and chin in firm
contact with the rests;
height of the table and chair should be adjusted so that the subject can
comfortably place her/his chin on the corresponding rest;
the subject’s head should be vertical (not tilted forward / backward);
chin rest should be positioned so that the subject’s eye is aligned to the eye
mark found on the sides of the metal frame. If this is not the case the chin rest
height needs to be adjusted.
Before the test inform the subject about the following:
COMPASS will test your ability to perceive light while looking at a steady target.
the test is non-invasive, in particular you will only perceive some light.
find a comfortable position and keep the chin and forehead firmly pressed against
the rests;
at the beginning of each test, the unit will move around to find your pupil: this is
absolutely normal;
always keep your eyes wide open, so that eyelids do not interfere;
when the test starts, look straight in front of you and when a small green, circular
spot appears anywhere, look at it;
do not move, nor speak during the test;
you can blink whenever you feel necessary, unless instructed not to do so;
you will be given this push-button: press it when you see, or believe to see, a whitish
small spot appearing anywhere;
it is absolutely normal that you do not see many of the spots.
