3. Dr. Mohammad Amiri , OD
Department of Optometry ,Faculty of
Rehabilitation
Shahid Beheshti Medical Sceince University
Vision Care of Menicon
Keratoconus
And specialty contact lens fitting of irregular
corneas

4. Keratoconus
• Is a progressive disorder in which the cornea has irregular
shape
• Onset: around puberty
• Autosomal dominant
• Usually bilateral; but assymetrical
• Systemic association: e.g. Down syndrome; Turner syndrome;
Marfan syndrome
• Ocular association: e.g. retinitis pigmentosa; vernal
keratoconjunctivitis;

5. • According to
morphology can be
classified into
• Nipple cones: small size
5mm; steep curvature;
the apex of the cone is
central or infero-nasally

6. • Oval cones: 5-6mm size;
ellipsoid (oval) &
displaced
inferotemporally

7. • Globus cones: the
largest >6mm

8. • Presentation: visual impairment due to progressive myopia & astigmatism
(usually reported for one eye); changes in spectacle Rx; decrease tolerance
to contact lens wear;
• Signs: central or paracentral stromal thinning; apical protrusion; irregular
astigmatism; steepening of the cornea graded according to keratometry
readings (mild <48D, moderate 48-54D, severe >54D)
Early in the disease: oil droplet reflex on ophthalmoscopy; irregular scissor
reflex on retinoscopy; Vogt lines (i.e. deep vertical stromal striae) on slit-
lamp exam; irregular astigmatism on keratometry; abnormal corneal
topography

9. Vogt striae (i.e. line) in keratoconus

10. Munson sign in keratoconus
Late in the disease:
Munson sign (i.e.
bulging of the lower lid
on downgaze); visual
acuity worsens;
watering; oedema;
stromal scarring after
beaks healing;

11. Keratoconus
• What have the years taught us?

12. Keratoconus Characteristics
Non-inflammatory.
Central or para-central corneal thinning.
Corneal steepening or protrusion.
Increased astigmatism and possibly myopia.
Loss of best spectacle corrected visual acuity.
Corneal striae and scarring.
Corneal hydrops (inflammatory).

13. Keratoconus
• Non-Inflammatory Ectasia
• Stromal Thinning
• Disruption of Bowman’s
Membrane
• Corneal Ectasia
• Myopia
• Irregular Astigmatism
• Optical Correction
• Spectacles– early
• Contact Lenses– later

14. Keratoconus
• Demographics
• Estimates vary from 50 to 170
per 100,000
• Obscure Etiology
• Heredity
• Allergies, Eye Rubbing

15. Why Does the Cornea Bulge in
Keratoconus?
• Corneal tissue is
abnormal
• Too elastic?
• Abnormal cross-linking of
collagen?
• Loss of structural
integrity of Bowman’s
Layer?
• Keratocyte apoptosis
• Trauma (eye rubbing)
• Corneal tissue bulges
because it is too thin?

16. Pathology of Keratoconus
 Loss of Bowman’s Layer.
 Stromal Thinning.
 Apoptosis.
 Increased Enzyme Activity.
 Enlarged Prominent Corneal Nerves.

17. Causes of Keratoconus
• Heredity vs. Mechanical
• Cellular
• Tissue
• Genetic

18. Cellular Changes
• Keratoconus cells are hypersensative.
• Increased enzyme activity, lack of enzyme
inhibitors.
• Matrix substrate instability in response to
environmental stress factors.
• mtDNA damage and exaggerated oxidative
response causing cellular damage.

19. Tissue Changes
 Loss of Bowman’s layer.
 Lamellar slippage.
 Lack “anchoring” lamellar fibrils.
 Apoptosis of the stroma causing anterior
thinning.

20. Heredity vs. Mechanical
• Does eye rubbing cause Keratoconus?
• 2 out of 250 doctors feel that rubbing is a
cause.
• KC patients do rub their eyes more often than
those without KC.
• What is it that makes KC patients rub their
eyes?

21. Genetics
• Autosomal dominant w/variable penetrance.
• SOD1, an antioxidant enzyme, is abnormal in
some KC corneas.
• No single gene responsible.
• 10 different chromosomes have been
associated with KC.
• Most likely multiple genes involved.

22. Additional Information
Male to Female Ratio = 3:1
Approximately 20% result in PKP.
90% are diagnosed by optometrists.
Mean age of diagnosis is 22.88 years.
Visual outcome with RGP is better than PKP.
More prevalent in certain ethnic groups (4x
higher in Asians from Indian sub-continent
regions than White Europeans).

23. Progression and Prognosis
Age is a big factor.
The younger the diagnosis, the poorer the
prognosis.
Less likely to progress to the point of a
transplant if diagnosed in the 30’s.
20% of Keratoconus patients result in corneal
transplants.
35 to 45% of all transplants are due to
Keratoconus.

24. Possible Aggravating Factors
• UV exposure.
• Allergies.
• Vigorous eye rubbing.
• Poorly fitting contact lenses.
• Inflammation.

25. Types of Keratoconus
• Nipple/Oval cone - central or mildly para-
central localized thinning and steepening.
• Keratoglobus - Large generalized thinning and
steepening.
• PMD (pellucid marginal degeneration) –
peripheral thinning and steepening.
• Keratoconus Fruste – Less progressive and less
manipulative.

26. Nipple/Oval Cone
• Central Steepening
• Steepest form

27. Keratoglobus
• Wider – 75 to 90% of cornea.
• Not as steep.

28. Pellucid Marginal Degeneration
• Peripheral Thinning

29. Orbscan Analysis

33. How to Treat Keratoconus
 Spectacles
 Contacts
 Soft Standard
 Soft Custom
 RGP Standard
 RGP Custom
 Hybrid
 Surgery
 Intacs
 Penetrating Keratoplasty
 Riboflavin/UV treatment

34. When to Intervene?
• Best Spectacle/Soft CL Acuity 20/30 or better?
– Good tolerance of acuity.
– Corneal health is not compromised.
– “If it aint broke, don’t fix it.”
• Best Spectacle/Soft CL Acuity worse than
20/30?
– Specialized contact lenses.
– My opinion, use RGP lenses.

35. Which RGP Design?
• Early Keratoconus
– Standard RGP
– KC RGP
• Mid-stage Keratoconus
– KC RGP
– Custom KC RGP
• Advanced Keratoconus
– Custom KC RGP
– Intra-limbal or Scleral RGP

36. My “GO TO” Lens – Rose K
• Developed by Dr. Paul Rose.
• Designed to fit the irregular cornea.
• “Very forgiving lens”
• Multiple designs to fit all shapes of corneas
and corneal conditions.
• Blanchard is very good to work with and has
staff to assist with very difficult cases.

37. Nipple/Oval Cone Fitting
• Most common form of KC.
• Early stages - simple RGP or KC RGP
• Later stages – KC RGP usually small and steep.
• The steeper the cone, the smaller the lens
diameter.

38. Rose K2
• Rose K vs. Rose K2
• 72% of patients notice an increase in acuity
with aspheric, aberration control.
• Lens to be centered on the cone.
• Reduce excessive movement (1 to 2mm).

39. Fitting the Rose K2
• Too high – tighten edge lift
reduce OAD
steepen base curve
• Too low – increase edge lift
increase OAD
flatten base curve

40. Fitting the Rose K2
• Centrally fitting the
lens on a nipple
cone better insures
optimal acuity and
comfort.

41. Rose K2IC
• IC stands for irregular cornea
• Larger diameter
• Larger optic zone
• Aspheric for aberration control
• Reverse geometry design

42. • PMD
• Keratoglobus
• LASIK induced ectasia
• Corneal transplants

43. Corneal Dystrophies
Traumatic Corneas with Scars
Post RK
Irregular Astigmatism or Corneal Warpage

44. What is That?

46. Asymmetric Corneal Technology
• ACT.

47. ACT – Continued…

48. Fitting with ACT
Using ACT ( Asymmetric Corneal Technology)
• 3 standard grades available
• Option also to specify degree of tuck in 0.1 steps from 0.4 to 1.5mm
Grade 1 ( 0.7mm steeper) Grade 3 (1.3mm steeper)
Grade 2 (1.0mm steeper)

49. Fitting with ACT
ACT - Improved comfort , lens stability and vision
NO ACT WITH ACT

50. Toric Peripheral Curves

51. Fitting Pearls
 Tendency to tighten after initial fitting.
 Light central touch will increase acuity.
 Avoid central staining.
 Movement is necessary but slight movement is
usually sufficient.
 Pay attention to tear flow beneath lens.
 The steeper the lens, the smaller OAD and less
movement.
 Don’t change too many parameters at once.

52. Penetrating Keratoplasty
When to refer?
 Acuity is 20/50 or worse.
 Patient intolerance to visual decrease.
 Scars within the visual axis.
 Multiple episodes of Hydrops.
 Contact lens intolerance.
 Unable to get adequate/healthy CL fit.
 Consider OD to OD referral.
 Give reasonable expectations.

53. Post PKP Management
• How soon can you fit with lens?
• Why are the curvatures so strange?
• Do you have to wait for all sutures to be
removed?
• Corrective options.
– Spectacles
– RGP contact lenses.
– LASIK

54. Rose K2 Post Graft

55. PKP Topography

56. Rose K2 Post Graft
 Much more difficult to fit than KC.
 Patients are less tolerable to CL.
 Eyes are more dry.
 Ill-fitting contact lenses can lead to graft
rejection.
 Lens design is crucial to success.

57. K2PG Fitting Pearls
• Don’t be intimidated!
• Watch tear flow!
• Also good lens for ectasia patients.
• Stay with your fitting basics
– Fit base curves.
– Adjust diameter.
– Adjust peripheral curves.
– Use ACT or Toric PC if needed.

58. Post Graft – Too Steep

59. Post Graft – Too Flat

60. Post Graft – Good Fit

61. Watch Vasculature

62. The Difficult Ones
• Nothing is comfortable.
• Acuity isn’t improving..
• Eyes are too dry. (Sjogren’s Syndrome)
• Cornea is too irregular for any lens to fit
properly or in a healthy manner.

63. What Do You Do?