what is ectasia
Ectasia = Dilation or distention
of a tubular structure
what is keratoconus
A non-inflammatory (?), self-limiting,
bilateral but asymmetric ectasia of the
axial cornea.
is keratoconus genetic?
possibly/probably but not definite
- -Higher prevalence in homogenous populations
(e. g. islands, valleys) - *It is thought that there is a genetic component to the condition but an environmental trigger that results in some patients having the condition and others with the same genotype not getting the condition
eye rubbing is assoc with keratoconus and maybe is caused by what?
atopic conditions
It has also been noted that a lot of these patients have atopic conditions such as allergies and the association with eye rubbing may be secondary to these conditions
-Both tend to manifest at puberty and both are seldom found to
-Managing allergies could decrease the eye rubbing have an onset after the age of 30
what kind of changes are occurring at a biochemical level with keratoconus
• Increased protease levels-breakdown collagen
• Decreased levels of protease inhibitors
• Loss of keratocytes due to increased
interleukin-1 receptors
– IL-1 causes apoptosis of keratocytes
Besides atopy, what other kind of clinical assoc do you find with keratoconus?
Connective tissue disorders:
- Mitral valve prolapse
- Specifically collagen disorders
Down’s syndrome:
-maybe genetic or due to mechanical damage from the characteristic behaviors that these patients commonly have
T/F: No clear gender or racial predilection w/ keratoconus
true
when does keratoconus usually present?
how does onset usually affect progression?
Onset in 2nd or 3rd decade of life: – Average age 16 – almost all are 12-39 y/o • Early onset (childhood) =faster progression and more severe disease • Late onset (adulthood) =slower progression and milder disease
how is the bilateral and symmetry of keratoconus?
90% bilateral
Asymmetric
– BCVA, refraction, K-readings
5 year time lag between the eyes
what are the average steep and amount of astigmatism for keratoconus?
• Steep K’s=
Mean flat-K: 49.49 + 6.01 D (CLEK)
Irregular astigmatism
Mean toricity: 3.53 + 2.87 D (CLEK)
what is the nipple keratoconus pattern?
Tends to be closer to center than oval
-easiest type of cone to fit a lens to because lens will center and stabilize on the central steep cornea
what is the oval/sagging keratoconus pattern?
– larger area of involvement: up to 50% of cornea – more inferior in location – most common type of cone – more difficult to fit due to inferior positioning
what is the globus keratoconus pattern?
– up to 90% of cornea involved – generalized bulging of entire cornea – may be different sub-class of degeneration – rigid lens difficult to fit – soft lens may be the best option
what are vogts striae and where are they usually found?
– Stress lines in Descemet's membrane – Central cornea, near apex – Usually vertical in orientation – More pronounced as keratoconus progresses **Can be induced by RGP wear
what kind of scarring might you see with keratoconus?
–Anterior: breaks in Bowman’s or
mechanical from CL
–Posterior: hydrops-
-Rupture of epithelium and descemets causing the aqueous to flood into the stroma
causes edema and haze
-temporarily have a significant decrease in VA
Self-limiting—will recover after several months
-left with a deep scar though
–Linear: natural
–Hazy/nebular: CL-induced
what is acute hydrops?
–rupture in Descemet's membrane –influx of aqueous into cornea –self-limiting –scarring will result –cornea usually flatter curvature after resolution
what is Hurricane / Vortex / Whorl Staining?
- Circular staining at the apex due to breaks in the basal cell layer of the epithelium
- from the cellular or tear flow as the cornea heals
- Most commonly over the apex of the cornea
- Can be seen with or without contact lens wear
- More severe in patients with more severe keratoconus and can be seen with flat fitting lenses
describe progression of keratoconus:
In general, rapid progression is followed by long periods of stability
T/F: gas perms can retard keratoconus progression
false
T/F: Irregular astigmatism cannot be fully corrected with spectacles
true
