Keratoconus is a non-inflammatory, usually bilateral ectatic disorder of the cornea where there is paraxial stromal thinning and weakening leading to corneal distortion. It presents in puberty or early adulthood and causes irregular astigmatism and myopia. While the cause is generally unknown, there are suspected risk factors like family history, eye rubbing, and connective tissue disorders. Diagnosis involves examining the cornea using a slit lamp, retinoscopy, keratometry, and corneal topography which can detect signs like Vogt's striae and an asymmetric bowtie pattern. Treatment ranges from eyeglasses or contact lenses in mild cases to intrastromal corneal ring segments, keratoplast

1. By: Marika Mohammed

2.  Progressive, non-imflammatory ectatic disorder of the
cornea
 Usually bilateral but asymmetric
 Paraxial stromal thinning and weakening leading to
corneal surface distortion

4.  Primary- irregular astigmatism
- myopia
 Secondary- corneal scarring

5.  Presents at puberty or early adulthood
 50-230 per 100,000
 Equal prevalence in both sexes and all races

6.  Generally unknown, likely multifactorial
 Suspected:
 Family history in 6-8% of cases
 x15-67 higher incidence if first degree relative
 Eye rubbing
 Contact lens use
 Systemic disorders eg. Downs Syndrome, Ehlers-Danlos,
Osteogenesis Imperfecta

7.  All layers of the cornea believed to be affected
 Epithelial cells may be enlarged and elongated
 Early degeneration of basal epithelial cells
 Disruption of basement membrane

8.  Growth of epithelium posterior to Bowman’s layer
forming z-shaped interruptions or breaks
 Scarring of Bowman’s layer and anterior stroma
 Stromal thinning due to normal-sized fibres but low
numbers of llamelae

9. Symptoms:
 Progression until 4th decade
 Asymmetric visual complaints
 Blur and distortions
 Glare/flare
 Monocular diplopia
 Photophobia
 Initial correction by spectacles then soft contact lenses

10. Signs:
 Slit lamp:
 Fleisher ring: Iron deposits in epithelial layer at cone base
 Vogt striae: Vertical stress lines at thinnest part of cornea
 Central and inferior paracentral corneal thinning
 Corneal scarring

11.  Scissor reflex on retinoscopy due to irregular astigmatism
 Rizzutti’s sign: conical reflection on the nasal cornea
when light is shone temporally
 Munson’s sign: corneal protrusion may cause angulation
of the lower lid on downgaze (advanced)
 Corneal Hydrops: stromal edema due to leakage of
aqueous through a tear in descemet membrane

12. Vogt Striae
Corneal HydropsMunson’s Sign

13.  Complete history and clinical examination
 Visual acuity testing
 Slit lamp examination
 Retinoscopy- for scissoring reflex
 Keratometry- may demonstrate irregular mires and
progressive corneal steepening
 Diagnostic rigid contact lenses
 Corneal Topography

14.  Maps the corneal curvature
 Indicates any distortions or scarring
 Common characteristics:
 Asymmetrical bowtie
 Inferior corneal steepening
 Skewed radia axes

15.  K value – Measures central steepening of the cornea; ≥
47.20 D suggests keratoconus
 I-S value – Measures inferior-versus-superior corneal
dioptric asymmetry; ≥ 1.4 D suggests keratoconus
 KISA% - Incorporates K and I-S values quantifying
regular and irregular astigmatism into a single index;
60-100% suggests keratoconus, ≥ 100% strongly
suggests frank keratoconus

18. Non-Surgical:
 Spectacle correction- early, as long as visual acuity
allows
 Contact lens-
 With progressive astigmatism
 Soft-tonic initially
 Rigid gas-permeable lenses most common
 Until corneal irregularity becomes too advanced
 Collagen cross-linking

19. Surgical:
 Intrastromal corneal ring segments:
 thin, semi-circular plastic inserts implanted into the
mid-corneal layers to flatten the cornea
 Keratoplasty – 10-15% patients
 penetrating keratoplasty (full thickness corneal
transplant) : most common
 Deep anterior lamellar keratoplasty (partial thickness
corneal transplant)

20. Thank you!
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21.  References
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