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About Keratoconus and its effects on the Cornea

Keratoconus is an eye disease which leads to a conical distortion and/or a progressive thinning of the central Cornea.

At the beginning it often only effects one eye, however over the medium term the second eye follows. Most frequently it effects only the central region of the cornea, a linear ethiopathology can’t be proved. Males suffer Keratoconus more than females (ratio 2:1)

Often, a person who has keratoconus is Myopic, and in addition to the Myopia the cone-shaped distortions also creates irregular astigmatism. With glasses this ametropia is often not possible to correct 10/10.

Indications of keratoconus

Objective observation

  • Frequent refractive changes
  • Increase of astigmatism
  • Advanced Keratoconus can be determined with a horizontal observation of the eye

Subjective observation

  • Diplopia
  • Blur
  • Halo-effects
Possible causes for keratoconus:
  • Genetic imprinting
  • Metabolic reasons
  • Weak collagen corneal connective tissue
  • Frequent eye-grating can increase the chances of keratoconus
  • Fissure in the cornea, Corneal thinning
  • Thinning of cornea after Lasik
  • Stress

Although the condition of Keratoconus has been recognised for over 200 years, an unequivocal cause has not yet been defined
Keratoconus progression and relative corrective progression
Relatively smooth divergence between the central and peripheral corneal topography:
Corrective glasses with contact lenses
Steeper divergence between central and peripheral corneal topography:
Specialised keratoconus contact lenses
High divergence between central and peripheral corneal topography Specialised keratoconus contact lenses, corneal transplantation

Alternatives to stabilise the corneal surface:

Crosslinking: A modern alternative to stabilise the cone
Intacs: 2 plastic parts are implanted into the cornea to decrease the irregularity.

Grading (Table Grades 1-4) Amsler-Krumeich keratoconus classification
Krumeich criteria:
 Grade      Clinical criteria
1
  • eccentric corneal steepening
  • induced myopia and/or astigmatism ≤5D
  • corneal curves ≤ 48D
  • no corneal imprint
2
  • induced myopia and/or astigmatism > 5D and ≤8D
  • corneal curves ≤ 53D
  • no central corneal imprint
  • corneal thickness ≥ 400 µm2
3
  • induced myopia and/or astigmatism > 8D and ≤10D
  • corneal curves > 53D
  • no central corneal imprint
  • corneal thickness 200-400 µm
4
  • eye examination (refraction) impossible
  • corneal curves > 55D
  • central corneal imprint
  • corneal thickness ≤ 200 µm

 

After affects with Keratoconus
  • Enduring red eye
  • Diplopia
  • Ghosting
  • Distortions
  • Photo-sensitivity
  • Dazzling and glare
  • Depleted facial muscles
  • Halos
  • Streaking effects
  • Decreased vision at twilight and at night
  • Dry eye and hypersensitivity
  • Decreasing comfort/tolerance of contact lens wear especially over longer periods of wear (e.g. they slip or even drop off the eye)
  • Decreased tear-quality