post midterm: keratoconus

Question 1

what is ectasia

Answer 1

Ectasia = Dilation or distention

of a tubular structure

Question 2

what is keratoconus

Answer 2

A non-inflammatory (?), self-limiting,
bilateral but asymmetric ectasia of the
axial cornea.

Question 3

is keratoconus genetic?

Answer 3

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

Question 4

eye rubbing is assoc with keratoconus and maybe is caused by what?

Answer 4

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

Question 5

what kind of changes are occurring at a biochemical level with keratoconus

Answer 5

• 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

Question 6

Besides atopy, what other kind of clinical assoc do you find with keratoconus?

Answer 6

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

Question 7

T/F: No clear gender or racial predilection w/ keratoconus

Answer 7

true

Question 8

when does keratoconus usually present?

how does onset usually affect progression?

Answer 8

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

Question 9

how is the bilateral and symmetry of keratoconus?

Answer 9

90% bilateral
Asymmetric
– BCVA, refraction, K-readings
5 year time lag between the eyes

Question 10

what are the average steep and amount of astigmatism for keratoconus?

Answer 10

• Steep K’s=
Mean flat-K: 49.49 + 6.01 D (CLEK)
Irregular astigmatism
Mean toricity: 3.53 + 2.87 D (CLEK)

Question 11

what is the nipple keratoconus pattern?

Answer 11

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

Question 12

what is the oval/sagging keratoconus pattern?

Answer 12

– 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

Question 13

what is the globus keratoconus pattern?

Answer 13

– 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

Question 14

what are vogts striae and where are they usually found?

Answer 14

– 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

Question 15

what kind of scarring might you see with keratoconus?

Answer 15

–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

Question 16

what is acute hydrops?

Answer 16

–rupture in Descemet's membrane
–influx of aqueous into cornea
–self-limiting
–scarring will result
–cornea usually flatter curvature after resolution

Question 17

what is Hurricane / Vortex / Whorl Staining?

Answer 17

• 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

Question 18

describe progression of keratoconus:

Answer 18

In general, rapid progression is followed by long periods of stability

Question 19

T/F: gas perms can retard keratoconus progression

Answer 19

false

Question 20

T/F: Irregular astigmatism cannot be fully corrected with spectacles

Answer 20

true