APPASAMY ASSOCIATES KMS 6, Руководство пользователя

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very blurred. These will be cleared with the focusing knob. By swiveling the instrument
slightly and by making fine adjustments of the elevation knob, the black cross is placed
near the centre of the doubled circle, (This doubled circle is called the focusing circle). This
accomplished, lock the instrument with “Instrument position locking knob,” and the corneal
surfaces are read for measure.
It is important that the cross in the eyepiece be near the centre of the focusing circle. At this
point, the optic axis of the instrument will coincide with the visual axis of the patient’s eye.
These conditions constitute the “triple alignment.” In the Appasamy keratometer’ the
focusing does not depend alone upon the apparent sharpness of the target image, but is
accomplished more precisely by coincidence of overlapped focusing circle appearing
single. When the instrument is out of focus, the central focusing circle and the plus and
minus signs are doubled. But when the exact focus is located, the focusing circle will
appear single and sharp.
It should he noted that with an astigmatic eye all of the central focusing circle will not
appear exactly in focus of the same time. Therefore for greater accuracy, direct attention to
the doubled plus sign and focus it sharply. The focus of the minus sign is disregarded until
later.
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Locating the Cylindrical Axis