8
Points for Attention in Operation
An observer who has relatively high refractive error should wear the appropriate spectacle or
contact lens correction while using the lensometer.
Among the green dividing lines, the two lines are spherical marking lines and the three lines are
cylindrical marking lines.
To achieve the most accurate measurement, rotate the diopter measuring handwheel from minus
powers to plus powers.
Placement of Lens
The lens should be placed on the objective lens bearing seat with the front of the lens facing
upward.
Lightly release the lens pressing unit so that the pressing feet press the lens lightly.
Observe the lens through the eyepiece and rotate the diopter measuring handwheel to make the
green dividing line of the (3) marker reticule clearest. At the same time, move the lens so that the
green dividing line of the (3) marker reticule and the center of the black cross dividing line of (8)
eyepiece reticule coincide.
Measurement of Spherical Lens
Rotate the diopter measuring handwheel so that the green dividing line of (3) marker reticule becomes
clearest. Then the scale interval on the reading window is the spherical diopter of the said lens.
Measurement of Sphero-Cylindrical Lens
Sphero-cylindrical lens means astigmatic lens. Normally its outer surface is spherical and the inner
surface is cylindrical. Each section of the internal surface has different refractive powers, in which
two mutually vertical sections have weakest refractive power and strongest refractive power.
When this instrument is used to measure such kind of lens, two green lines and three green lines of
(3) marker reticule will not get clear simultaneously. The measurement of this lens takes two steps.
First step: Rotate diopter measuring handwheel so that the torus (composed of 12 small green dots) is
imaged into clear looped short cylindrical lines. Then rotate the astigmatic axis measuring handwheel
again so that the spherical marking line (two green lines) and torus short lines are in the same
direction. At the same time, conduct fine tuning of the diopter measuring handwheel to make the two
lines the clearest. Now write down the reading value of the diopter.
Second step: Rotate the diopter measuring handwheel again so that the cylindrical marking lines
(three long lines) are focused the most clearly and in the same direction of the torus short lines. Next
write down the reading value of the diopter and note the reading value of the lens angle astigmatism
axis on the astigmatism axis measuring handwheel. This can also be read off of (8) eyepiece reticule.
Third step: To calculate the degree of astigmatism, subtract the reading values of the two above
measurements.
The diopter value of a sphero-cylindrical lens may be written in plus cylinder form or minus cylinder
form. This example is written in minus cylinder form.
Example: Calculation of +1.00 –3.50 x 030º
Rotate the diopter measuring handwheel and at the same time rotate the astigmatism axis
measuring handwheel to focus spherical marking lines clearly. Now the measured data are +1.00D
and 30º. Then rotate the astigmatism axis measuring handwheel by 90º to focus the spherical
marking lines clearly. Now the measured data are –2.50 and 120º. Note +1.00 as the spherical
diopter value.
