Haag-Streit CLEMENT CLARKE OPHTHALMIC Perkins Mk3 Manuel D'instructions page 24

9. Measurement
1. Immediately before taking the measurements,
the patient should be made to close the eyes
briefly so that the cornea becomes sufficiently
moistened with the lacrimal fluid and fluorescein.
2. By moving the tonometer forward, the
measuring prism is brought into contact with the
centre of the cornea over the area above the
pupils. The limbus of the cornea will be illumin-
ated with a bluish hue. This illumination is best
observed by direct sight from the opposite side of
the illumination unit by the examiner.
As soon as the limbus of the cornea illuminates,
cease any further forward movement of the ton-
ometer immediately.
3. After obtaining contact, commence observing
the cornea. A regular pulsation of the two semi
circular fluorescein rings, which can be of varying
size dependent on the ocular pressure, when the
measuring drum is at setting 1, will show that the
tonometer is in the correct measuring position.
4. The pressure on the eye is increased by turning
the milled thumb wheel on the tonometer, until the
edges of both fluorescein rings just meet (Fig. 9).
The edges cross over each other with the
pulsation of the eye.
The width of the fluorescein ring around the
contact position of the measuring prism should be
1/10 approx. of the diameter of the applanation
surface (0.3 mm).
5. Reading the scale:
• The reading
• multiplied by 10
• gives the ocular pressure in mm Hg
- continued
Note
The following are schematically simplified
illustrations!
Fig. 8
Semi circular images in the centre of the field
of sight
Fig. 9
Correct final position
en
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