General Information And Suggestions Concerning Measurement; Astigmatism - Keeler D-Kat R Gebrauchsanweisung

D-KAT Tonometer by KEELER
9. GENERAL INFORMATION AND SUGGESTIONS CONCERNING
MEASUREMENT
IMPORTANT NOTE
Measurement must be performed as quickly as possible on each eye. Should epithelial drying
be observed, we recommend the patient's acuity and visual fields should be examined.
The pressure measurement procedure may be repeated several times. Nervous or anxious
patients often have higher intraocular pressure during the first measurement procedure.
It has been found that pressure decreases during the first few minutes of the procedure,
when the patient realises that the tonometric examination is not unpleasant. When correctly
anaesthetised and with their eyes fully open, the patient will feel absolutely nothing. Therefore,
we recommend running a preliminary measurement procedure on each eye, the results of
which need not be taken into consideration. After completing the preliminary procedure, run
three measurement procedures on each eye. These readings will be correct if the pressure
has stabilised. When the measurement procedures are performed correctly, the results of the
subsequent measurements will vary by only about 0,5 mmHg.
When the measurement procedure for one eye is prolonged excessively, a drying phenomena
will occur on the corneal epithelium of both eyes.
A ring of fluorescent deposits will form around the cornea contact surface and around the
measuring prism on the eye being examined. The other eye will show fluorescent dry areas,
resembling a map, which will hinder and make measurement unreliable.
The eye will rapidly recover from any corneal dryness without the need for any treatment, visual
acuity may be temporarily affected by fine epithelial defects.

10. ASTIGMATISM

If the cornea is spherical, measurements may be made along any meridian, but it is usual to
measure along the horizontal 0° meridian. This is not the case when measurements are made
on eyes affected by corneal astigmatism of greater than 3 dioptres, since the flattened areas
will not be circular but elliptical.
It has been calculated that in cases of more severe corneal astigmatism a surface area of
7,354 mm (ø 3,06 mm) must be applanated; in this case the measuring prism forms an angle
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of 43° to the meridian of the maximum
43° marker
radius.
For example:
For corneal astigmatism of 6.5mm /
30º= 52.0 diopters / 30º and 8.5mm /
120º = 40.0 diopters / 120º, the 120°
prism value will be aligned with the 43°
0° marker
"A" mark on the prism support.
For corneal astigmatism of 8.5mm /
EN
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