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Keratoconus And specialty contact lens fitting of irregular corneas

Marc L. Braithwaite, OD Vision Care of Maine. Keratoconus And specialty contact lens fitting of irregular corneas. Keratoconus. What have the years taught us?. Keratoconus Characteristics. Non-inflammatory. Central or para -central corneal thinning. Corneal steepening or protrusion.

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Keratoconus And specialty contact lens fitting of irregular corneas

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  1. Marc L. Braithwaite, OD Vision Care of Maine KeratoconusAndspecialty contact lens fitting of irregular corneas

  2. Keratoconus • What have the years taught us?

  3. 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).

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

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

  6. 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?

  7. 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.

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

  9. 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.

  10. 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).

  11. 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.

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

  13. 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.

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

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

  16. Pellucid Marginal Degeneration • Peripheral Thinning

  17. Orbscan Analysis

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

  19. 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.

  20. 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

  21. 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.

  22. 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.

  23. 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).

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

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

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

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

  28. Corneal Dystrophies • Traumatic Corneas with Scars • Post RK • Irregular Astigmatism or Corneal Warpage

  29. What is That?

  30. Asymmetric Corneal Technology • ACT.

  31. ACT – Continued…

  32. 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 3 (1.3mm steeper) Grade 1 ( 0.7mm steeper) Grade 2 (1.0mm steeper)

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

  34. Toric Peripheral Curves

  35. 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.

  36. Penetrating KeratoplastyWhen 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.

  37. 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

  38. Rose K2 Post Graft

  39. PKP Topography

  40. 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.

  41. 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.

  42. Post Graft – Too Steep

  43. Post Graft – Too Flat

  44. Post Graft – Good Fit

  45. Watch Vasculature

  46. 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.

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