OrthoK 100

1. OrthoK 100

2. How does the orthoK lens reduce myopia?

3. How does it work? Back in the day Jessen Factor The orthoK lens simply flattens the cornea

4. We have updated this theory based on experimental data.

5. What does the lens do? Rearranges the cellular structure of the cornea Flattens the corneal curvature Reduces the axial length of the eye Reduces the myopic correction

6. The Design of the OrthoK Lens

7. The mechanism of action is still not completely understood.

8. In what layers of the cornea do these effects take place?

9. What happens to the epithelium and stroma?

10. Tabb, then later Mountford and Noack Tear film uses hydraulic forces to resculpt The continuous action of the tear layer moves epithelial cells to periphery Hydraulic force theory

11. Swarbrick et al were the first to discuss central epithelial thinning and mid peripheral thickening Swarbrick HA, Wong G, O�Leary DJ. Corneal response to orthokeratology Optom Vis Sci 1998;75(11):791-799. Epithelium and Stroma

12. Alharbi and Swarbrick PURPOSE. To investigate corneal thickness changes during overnight orthokeratology with reverse-geometry rigid gas-permeable (RGP) contact lenses worn over a 3-month period.

13. Alharbi and Swarbrick Central epithelial corneal thinning from day 1 Mid peripheral stromal thickening by day 4 No change in peripheral thickness

14. Alharbi and Swarbrick corneal sag height change resulting from the thickness changes could account for the change in refraction. The Effects of Overnight Orthokeratology Lens Wear on Corneal Thickness Ahmed Alharbi and Helen A. Swarbrick Investigative Ophthalmology and Visual Science. 2003;44:2518-2523.)

15. Zhong et al Differences Between Overnight and Long-term Wear of Orthokeratology Contact Lenses in Corneal Contour, Thickness, and Cell Density Zhong, Xingwu MD, PhD*�; Chen, Xiaolian MB*�; Xie, Ruo Zhong MD, et al Cornea: April 2009 - Volume 28 - Issue 3 - pp 271-279

16. Zhong -Conclusions Short-term lens wear ?thickening of the midperipheral cornea. Long-term lens wear (>5yrs) ?midperipheral thickening cornea and thinning of the central corneal epithelium.

17. Epithelial Compression Cat model Central cornea - Primary epithelial response is cell compression Mid periphery-increased number of cell layers Jennifer Choo 2008

18. Stroma Central edema inhibited Normal edema response in the mid periphery Measured by OCT Alharbi A, La Hood D, Swarbrick HA. Overnight orthokeratology lens wear can inhibit the central stromal edema response. Invest Ophthalmol Vis Sci 2005; 46:2334-2340 Wang J, Fonn D, Simpson TL, Sorbara L, Kort R, Jones L. Topographical thickness of the epithelium and total cornea after overnight wear of reverse-geometry rigidcontact lenses for myopia reduction. Invest Ophthalmol Vis Sci 2003; 44: 4742�4746.

19. More Stromal Support Epi is only 50u 8u per 1D of change > 7.00D impossible to correct Change cannot be due simply to epithelial thinning

20. Stoma-continued Paracentral corneal thickens Produces flattening and a minus lens Stromal hypertrophy Study in progress Berke B. Corneal reshaping demystified. Vision by design 2009, Phoenix AZ, October 18, 2009.

21. Endothelium Endothelium cell density appears to be unaffected during orthoK Tx Lin JC (2004) The effect of orthokeratology on the morphology of the central and peripheral corneal endothelium, Paper presented at the Global Orthokeratology Symposium, Toronto, August

22. Conclusions Still not completely understood The epithelium and stromal mid periphery are changed The effects occur quickly

23. Adverse Responses

24. Adverse Responses Infection Lens binding SPK Abrasions Iron Rings Dimple Veiling

25. Infection

26. Is there an increased risk of infection with orthoK?

27. Infection China, Taiwan and Hong Kong 8 cases of severe microbial keratitis Lots of world-wide attention

28. Infection Linked to unregulated practice of orthoK Untrained lens fitters Patients were not trained on use and care Little to no follow up performed

29. Infection-continued orthoK does cause some central epi thinning The epithelium is the eye�s barrier to infection Does this thinning increase the risk?

30.

31. Jennifer Choo et al Cat studies Heavy doses of various pathogens placed in orthoK treated eyes.

32. Jennifer Choo �We found that despite the dramatic changes in the tissue with this procedure, the corneal defenses are still intact and these changes did not predispose the eye to infection� Vision Cooperative Research Centre in Sydney Jennifer Choo, BsC, O.D., Ph.D. et al

33. Infection and OrthoK Lenses New orthoK lenses �no higher colony of pseudomonas than controls Post wear - higher density compared to non orthoK RGP Adhesion of Pseudomonas aeruginosa to Orthokeratology and Alignment Lenses Choo, Jennifer D.*; Holden, Brien A. Optometry & Vision Science: February 2009 - Volume 86 - Issue 2 - pp 93-97

34. Infection and OrthoK Lenses Does the design of the orthoK lens make it more susceptible to lens binding by bacteria and a subsequently higher risk of infection?

35. Infection and OrthoK Lenses At this point studies indicate minimal effect Watt KG, Swarbrick HA. Trends in microbial keratitis associated with orthokeratology. Eye Contact Lens. 2007(33):373-377.

36. Infection and OrthoK Lenses �The risk of MK is similar to other overnight modalities� Bullimore MA, Jones L. The risk of microbial keratitis with overnight corneal reshaping lenses, American Academy of Optometry, Program Number 90583, Nov. 2009.

37. Pearls Educate your patients on lens care Educate them on hygiene Disinfect the orthoK lens daily Reinforce at every visit

38. Lens Binding

39. Lens Binding No movement at 2 hour or post overnight visit Ring impression seen at morning follow up Patient reports removal difficulty Patient reports stinging upon removal

40. Lens Binding Improper fit (eg., sag too great) Tight lids Dry eyes Lenses filthy A one-time occurrence

41. Lens is binding Picture of stuck lens with debris

42. Lens is binding Picture of stuck lens with debris

43. Lens is binding Picture of stuck lens with debris

44. Lens Binding Risks Abrasion upon removal -> infection Corneal edema Abrasion from trapped debris

45. Lens Binding Re-examine lens on eye Re-test for dry eyes Review care procedures Repeat closed eye visit

46. SuperficialPunctate Keratitis

47. SPK Can vary in severity from grade 1-4 Mild in occurrence (Grade 1) is often seen after first night of wear Grades 2-4 - TAKE SERIOUSLY

48. SPK Patient�s symptoms can vary Grade 3 SPK may generate no complaints

49. SPK - causes Too little sag Lens abrading centrally Solution reaction

50. SPK � grade 1 picture

51. SPK � grade 2

52. SPK � grade 3

53. SPK � grade 3+ picture

54. SPK � grade 4 picture

55. SPK Deal with SPK if: It persists beyond day 1 It is > grade 1

56. Abrasions

57. Abrasions-causes Foreign body under lens Improper removal Problem with fit

58. Abrasion-mild

59. Abrasion-dense Picture of abrasion

60. What to do? Discontinue lens wear until completely resolved When lens wear is resumed, follow closely If reoccurs, consider refit Take dense abrasion seriously Risk of infection Risk of recurrent erosion

61. Iron Rings

62. Iron Rings Sometimes seen with LASIK, PRK, keratoconus and other conditions Not unique to orthoK Usually located where the reverse curve hits the cornea

63. Iron Rings

64. Iron Rings Does not indicate a problem with fit or health No treatment needed No change in fit needed

65.

66. Dimple Veiling

67. Dimple Veiling Appear as �bubbles� between lens and cornea Leave impressions after lens is removed

68. Dimple Veiling-causes Solution Issues Educate patient Bubbles from squeezing the solution bottle Fill back surface with solution Verify correct solution being used

69. Dimple Veiling-causes Problem with lens design Too loose Too large a tear reservoir Tear frothing with movement Look at NAFL pattern and redesign

70. Dk/t and OrthoK Mid to high DK lenses VS low DK Reduced treatment effect with low Higher DK for better health and Tx Lum and Swarbrick

71. Pearls Properly fitted orthoK lenses are safe and effective Patient education is essential Prevent infection Recognize problems

72. NEVER IGNORE ADVERSE REACTIONS

73. Time to Stretch