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Contact Lens Options
The normal cornea (the front clear lens of the eye)
supplies about 75% of the eye's focusing power. In keratoconus, the
cornea becomes thinner and loses its structural integrity. As a
result, it loses its uniform, domelike configuration and develops
irregular astigmatism. It, thus, is unable to produce a clear image
inside the eye.
Because the optical surface of the cornea is irregular in
keratoconus, glasses cannot give crisp focused vision. Contact
lenses, in particular rigid gas permeable contacts (RGP), can cover
these irregularities and better focus incoming light. Applying a
rigid lens allows tears to fill the space between the contact lens
and the cornea. This layer of fluid optically neutralizes the
irregularities of the cornea such that, for all practical purposes,
the cornea itself ceases to have any optical effect. The front
surface of the contact lens now effectively becomes a new corneal
surface... but a surface that we can control, being perfectly
smooth, clear, and regular, and also containing the patient's
prescription. The contact lens produces a clear image in the
eye, often with a dramatic visual improvement for the keratoconus
patient.
Adapting lenses of this type is challenging and rewarding for
both doctor and patient. These highly specialized lenses feature a
complex series of curves to enable us to fit the lens such that
patients may enjoy vast improvements in vision and be able to
utilize the lenses throughout their active day. These lenses range
from the very tiny (6 mm) to quite large (14 mm). Some lenses
(scleral lenses) extend beyond the iris onto the white of the eye.
Softperm lenses are sometimes used for proper centration and for
very sensitive eyes. These lenses have a rigid gas permeable center
with a soft skirt around the lens edge. Recently, we introduced the new
Synereyes lens to our practice, a rigid gas permeable center with a soft lens
periphery. This lens has the advantage of excellent oxygen permeability combined with comfort and availability in a number of configurations for unusual corneal shapes. Some special cases require a
"piggy-back" fitting, an RGP lens fitted over a soft contact lens.
A
variety of keratoconus lenses is necessary to fit all the varied shapes and requirements of the keratoconic cornea. Because of this, the CLEI Center for Keratoconus has available every modern technology for the diagnosis and treatment of this disease and a vast specialized
KC contact lens inventory (including our own Hersh Palpebral Traction
Lens). This gives us the tools to meet the challenge of the keratoconic cornea and restore the patient to useful vision.
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