course covers the uses of two pieces of equipment, the keratometer and
the slit lamp, which are indispensable to the successful fitting and
evaluation of rigid and soft contact lenses. The keratometer (also known
as ophthalmometer) is used for measuring the curvature of the cornea.
It is capable of measuring two curves, the steepest and the flattest,
which are also referred to as the principal meridians. These measurements
provide the contact lens fitter with information about the cornea’s
curvature, focusing power, and whether or not astigmatism is present.
In addition to its uses for fitting contact lenses, keratometry is also
used for evaluating and following patients with keratoconus, and in
the determination of appropriate intraocular lens implant power for
patients undergoing cataract surgery.
slit lamp (or biomicroscope) is an instrument designed primarily to
observe the transparent structures of the human eye under a magnification
of from 10 to 50 times. Its two principal parts include a lamp equipped
with an optical system designed to project a slit of light upon the
eye, and a stereomicroscope which is mounted horizontally for direct
viewing of the patient’s eye. The slit lamp may be adjusted to project
a variety of light beams. By varying the light beam and the viewing
position, it is possible to improve the view of the various structures
of the eye. Since the biomicroscope is particularly useful for examining
the cornea it plays an especially important role in the fitting of contact
lenses. Symptoms of a poor fitting contact lens, for example, can usually
first be detected through the use of the slit lamp.