9
DEUTSCH
ENGLISH
FRANÇAIS
ITALIANO
ESPAÑOL
NEDERLANDS
PORTUGUÊS
SVENSKA
DEUTSCH
ENGLISH
FRANÇAIS
ITALIANO
ESPAÑOL
NEDERLANDS
PORTUGUÊS
SVENSKA
© HAAG‑STREIT AG, 3098 Koeniz, Switzerland
–
HS‑Doc. no. 1500.7006000.04220 – 22. Edition / 2016 – 06
is being measured, around the spots where the measuring prism contacts the
cornea.
•
On the other eye, irregular, 'map-like', fluorescein-containing dry patches are
formed that prevent the taking of usable measurements.
•
Extensive dryness disappears quickly without treatment. Visual acuity is affected
by these slight epithelial defects.
WARNING!
Reusable measuring prisms must be cleaned and disinfected after ev‑
ery examination.
5.2. Astigmatism
•
If the cornea is spherical, measurements can be taken on any meridian, but it is
most convenient to measure on the 0° meridian.
•
The choice of meridian is of significance, however, when measuring eyes with
corneal astigmatism greater than 3 dioptres, since the flattened area is not circu
‑
lar but elliptical.
•
It has been calculated that, in cases of greater corneal astigmatism, a surface of
7.354 mm
2
(ø 3.06 mm) is applanated if the measuring prism is at an angle of 43°
(mark (A)) to the meridian of the greatest radius.
Example: If the corneal astigmatism measures
6.5 mm / 30°
8.5 mm / 120°
=
=
52.0 dpt / 30° and
40.0 dpt / 120°
(A) 43°
the 120° graduation mark on the prism is set on the mark (A)
of the prism holder.
If, on the contrary, the measurements are
6.5 mm / 120°
8.5 mm / 30°
=
=
40.0 dpt / 120° and
52.0 dpt / 30°
then the 30° graduation mark is set on the mark (A), meaning that simply the axis
position of the largest radius is placed on the mark (A).
5.3 How pressure is measured
The applanation tonometer functions according to the 'Goldmann method': measure‑
ment of the pressure required to maintain a uniform applanation of the surface of the
cornea.
•
The readings obtained are based on the assumption that a cornea with a 'nor‑
mal' thickness is being measured; a different corneal thickness leads to changes
in the measured IOP. A 'normal' corneal thickness is considered to fall within the
range of 530 to 560 Mikrometer.
•
If inaccurate measuring results are suspected, please conduct a functional verifi
‑
cation in accordance with Section 'Maintenance'.
5.4 Preparing the patient
NOTE!
A smooth operation can only be guaranteed with the use of original
HAAG‑STREIT measuring prisms and Tonosafe. Should the measur‑
ing prism come into contact with the cornea without the correct pressure
having been previously set, vibrations may occur in the sensor arm that
could be unpleasant for the patient.
1. Anaesthetise each eye by applying e.g. 2‑3 drops of an anaesthetic within half
a minute. Always anaesthetise both eyes as blinking will be unavoidable other‑
wise.
2. The correct eye height of the patient can be set via the chin rest.
5.5 Patient instructions
1.
Press the head firmly against the chin and forehead rests and use a headband,
if necessary, to fix the head’s position.
2.
The patient must look straight forward. If necessary, the small fixing light can be
used to steady the eyes.
3. It is recommended that the patient be repeatedly reminded to keep his eyes
open wide during the examination. It might be necessary for the examiner to
keep the eye open by splaying the eyelids with thumb and index finger.
4. This must be done without applying any pressure to the eye. In this case, the
angle between the microscope and the illumination apparatus is reduced to ap‑
proximately 10° for the model AT 900 model T, whereby the light beam is guided
through the prism body.
5.
A non-reflecting image is to be strived for.
5.6 Preparation of the tonometer
For all HAAG-STREIT slit lamps and tonometers
1. The eyepiece adjustment is to be checked before the examination.
2.
Set the magnification to 10x.
3. Set the power supply / the illumination potentiometer to the lowest setting.
4.
Position the blue filter in the beam path of the slit lamp's illumination apparatus
and open the slit diaphragm fully.
5. Insert the disinfected measuring prism into the (0° position) holder on the sensor
arm. For Tonosafe, see the separate instructions for use.
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