Haag-Streit Perkins MK3 Manual De Instrucciones página 21

5.71 Sources of Error
Flourescein ring / Distance to the patient
Result
The fluorescein ring
is too wide
The fluorescein ring
is too narrow
No semi circular
rings appear, only
the centre line
Both of the too large
semi circular rings
appear partly
Image in ocular Cause
The measuring prism
was not dried after
cleaning, or the
eyelids came into
contact with the
measuring prism
whilst measuring.
The lacrimal fluid
has dried.
The measuring prism
is not touching the
cornea. Should the
patient withdraw their
head slightly, the
irregular pulsations
will occur and the
prism will only contact
the eye intermittently.
Should the patient
withdraw the head
further, then the
fluorescein rings will
disappear together.
Should the tonometer
be moved forward
towards the patient,
or should the patient
move towards the
tonometer whilst
the measurement is
being taken, then the
feeler arm will come
into contact with a
sprung stop piece. The
applanation surface is
then too large.
en
Correction
The tonometer should
be withdrawn and the
measuring prism dried
with a cotton wool swab
Let the patient close the
eyes once or twice. Then
repeat the measuring
procedure.
Steady patient's head
The image will not
change when turning
the milled thumb wheel.
Withdraw the tonometer
until the regular
pulsations of a
corresponding smaller
applanation surface
indicate the correct
measuring position and
pressure changes lead
to immediate applanation
surface changes.
21