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19
OPERATION PROCEDURES
Turn the axis rotating handle and rotate the measuring head until the displacement in the
marks is eliminated. (This will result in fitting the measuring head to the axis of the corneal
astigmatism.)
Unify the "|" mark of the left mire image with the "¦" mark of the center mire image and the
" ---|---" m a r k o f th e t o p mi r e i m age with the "--|--" mark of the center mire image, at this angle,
with the horizontal and vertical knobs, which shows how simple and fast one-position mea-
surement is.
Read the measurement results. In the case of the above figure, the vertical scale indi-
cates the radius of curvature of the cornea, 7.50mm (refractive power of the cornea is 45.0
dptr) and the axis is 110° (read off the vertical index).
The horizontal scale shows that the radius of curvature of the cornea is 7.70mm (corneal
refractive power is 43.8 dptr) and the axis is 200° (the axis of the horizontal scale is read
off the horizontal index).
(b) When corneal astigmatism does not exist:
If corneal astigmatism does not exist, there will be no displacement in the marks, even
when the measuring head is rotated. Therefore, measurement will be the same as when
measuring the test ball. (See Step (3) of "PRACTICE MEASUREMENTS WITH THE TEST
BALL" on pg. 16.)
The measurement results are the value along the circumference of the corneal surface of
2.3mm to 4.9mm diameters (at 5.5mm to 12mm radius of curvature of the cornea).
V
H
38.5
3938
38.5
3938
8.5 8.6 8.7
8.5 8.6 8.7
V
H
45.5 44.5
45
44.5 43.5
44 43
7.6 7.5 7.4
7.6 7.5 7.4
0
10
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