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Keratoconus
Poor vision that cannot be
corrected fully with glasses may indicate a condition
known as conical cornea or keratoconus. A rare condition,
keratoconus primarily affects people in their early
20’s.
With keratoconus, the cornea,
the "clear window" at the front of the eye, may
become thin and bow outwards. It is this irregular
distortion of the cornea that makes vision correction
with glasses less than optimal.
Vision correction with rigid
gas permeable lenses.
Mild to moderate keratoconus is best corrected with rigid
gas permeable contact lenses, which provide a smooth
surface in front of the cornea, making clear vision
possible. Because the lens is rigid, the tears between
the lens and the cornea form a ‘liquid lens,’
which smooths out the irregularities of the cornea and
makes clear vision possible again. Specific forms of Gas
permeable contact lens, like the Rose K lens is
claimed to fit better than standard lenses and be more
comfortable. Soft lenses, which ‘wrap’ onto the
cornea and take up its shape much more closely than rigid
lenses, are less successful at correcting keratoconus.
Corneal replacement surgery
may be necessary.
As keratoconus progresses, some scarring of the cornea
can occur. The cornea can become deformed to such an
extent that it is physically very difficult to get an
adequate fit with a contact lens. As a result the level
of vision can be reduced. Eventually, contact lenses may
no longer be a successful treatment. Instead, the cornea
may need to be replaced surgically with a cornea of more
regular shape. The prognosis for corneal replacement
surgery is generally very good.
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