Keratoconus

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!


21.  References
 1. Espandar L, Meyer J. Keratoconus: Overview and Update on Treatment.
Middle East Afr J Ophthalmol [Internet]. 2010 [cited 9 January 2015];. Available
from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880369/
 2. Wayman L, Trobe J, Park L. Keratoconus. [Internet]. 2014 [cited 9 January
2015];. Available from:
http://www.uptodate.com.ezproxy.sastudents.uwi.tt:2048/contents/keratocon
us?source=search_result&search=keratoconus&selectedTitle=1~13
 3. Weissman B, Roy H. Keratoconus [Internet]. Medscape. 2014 [cited 9 January
2015]. Available from: http://emedicine.medscape.com/article/1194693-
overview#showall
 4. Romero-Jiménez M M, Santodomingo-Rubido J, Wolffsohn J. Keratoconus: a
review. Elsevier [Internet]. 2010 [cited 9 January 2015];. Available from:
http://www.ncbi.nlm.nih.gov/pubmed/20537579
 5. OphthaClass. Amsler-Krumeich Classification for Grading Keratoconus -
OphthaClass [Internet]. 2015 [cited 9 January 2015]. Available from:
http://ophthaclassification.altervista.org/krumeichclass/
 6. Sinjab M. Quick Guide to the Management of Keratoconus A Systematic
Step-by-Step Approach. New York: Springer; 2012.