Khanna Vision Institute Keratoconus
:: Causes of Keratoconus
Cause or aeitology as we physicians like to impress
with our knowledge of Latin, of keratoconus is under
heavy research right now.History of Keratoconus spans two centuries.
It appears so far that there
may be more than one cause or that it is multifactorial.
Either one or many factors acting in concert can lead
tokeartoconus.
1.Genetic: is keratoconus hereditary. This is what
research on keratoconus has produced so far
There is positive family history in 6-8 percent of the
patients. The various different research studies have
shown that the prevelance in first degree relatives is
15-67 times higher then in general population. Even
unaffected first degree relatives have higher incidence
of abnormal corneal topography. Linkage mapping
and mutation analysis haveindicated the location for
autsomal dominant inherited Keratocones.
2. Inflammatory:though keratoconus has traditionally
been defined as non inflammatory disease recent
insight into the causes of keratoconus have shown that
inflammation may be involved. The levels of
immunoglobin Ig G , Ig M and Ig E are elevated.
Other mediators of inflammation like cIL-6, TNF-α,
and MMP-9 are higher in keratoconus patients as
compared to patients without keratoconus. MMP-9
may be involved in corneal inflammation.The cornea is
made of collagen fibers, intact collagen compromises
70% by weight. In keratoconus , there is damage to
the extracellular matrix associated with a decreas in
type 1 and 4 collagen. Collagen degradation products
called telopeptides are 3.5 times higher in keratoconus
patients. A“cascade hypothesis of keratoconus” has
been proposed. Enzymes cause a change in corneal
proteins predisposing to oxidative damage, leading to
cell death, altered signaling pathways, increased
enzyme activities and fibrosis. There is evidence that
the inhibitors of destructive enzymes - alpha one (α1
proteinase inhibitor, alpha two (α2) macroglobulin, and
tissue inhibitor metalloproteinase one (TIMP-1 are
decreased in keratoconus corneas; the latter can
prevent cell death.
3. Eye rubbing it may cause micro trauma , also
rubbing may be a response to the inflammatory factors.
4: contact lenses causing microtrauma
5: atopy or allergies
Knowledge about the pathology of keratoconus is instrumental in devising treatment of keratoconus.
Suspect keratoconus . When there are no obvious signs displayed for keratoconus, but there is high suspicion of subclinical keratoconus, the eye is labeled as suspect keratoconus. Some examples are the supposedly normal fellow eye of a patient with keratoconus. If both parents’ and/or siblings have keratoconus and the person has thin corneas or steep corneas he may be suspected to develop keratoconus later in life.
