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鄭永豐

角膜塑形術理論與實際 Orthokeratology Principles & Practice John Muuntford,David Ruston,Trusit Dave Frank Spors Dr. Tung Hsiao-Ching Invest Ophthalmol Vis Sci Eye Contact Lens 2005;31(5). 鄭永豐. General Principle. What is Orthokeratology?.

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鄭永豐

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  1. 角膜塑形術理論與實際OrthokeratologyPrinciples & Practice John Muuntford,David Ruston,Trusit DaveFrank Spors Dr. Tung Hsiao-Ching Invest Ophthalmol Vis SciEye Contact Lens 2005;31(5) 鄭永豐

  2. General Principle

  3. What is Orthokeratology? Orthokeratology is the elimination and/or the reduction of an refractive error with an active changing of corneal shape through the fitting of RGP lenses with an special backsurface design. The procedure is non-invasive and completely reversible. The term Orthokeratology means: • Ortho  correct • Kerato  Cornea • Logie  Science (lat. Logos)

  4. „Evolution“ of Orthokeratology - Part 1 • Begin in the 1960 years • American Optometrist Jessen invents „Orthofocus“ • Normal three curved RGP lenses • 1/10 bis 2/10 mm flatter than Flat K • Flattening of Cornea in small steps • Large number of lenses until „Zero“ refraction • High pathological risks for the cornea • Mechanical pressure and deficiency of Oxygen • Direct contact between CL und Cornea • Wearing only by Day allowed (couple hours)

  5. Reverse Geometry Lens Design • Jesson (1962): It would be necessary to grind a concave surface with a flatter portion in its center and steep portion peripherally. The center portion would act to flatten the central apex. The intermediate portion would act to center the lens. • Advantages: improved lens centration, rapid corneal flattening effects, relatively large optic zone created, good maintenance of effect.

  6. „Evolution“ of Orthokeratology - Part 2 • Single Reverse CL in den 1990 years (SRG) • Americans Richard Wlodyga and Nick Stoyan • Three curved CL (BC  RC  PC) • BC flatter than CK • RC steeper than BC • PC equal to normal RGP lenses • Two or three CL changings until „Zero“ refraction • Often decentered fit  decentered Opticzone • Myopiareduction ~ 2,00 D • No FDA Approval for Overnight wearing

  7. „Evolution“ of Orthokeratology - Part 3 • Today: Double Reverse CL (DRG) • Five curved aspheric CL (BC  RC  AC1+AC2  PC) • BC flatter than CK • RC steeper than BC • AC parallel to peripheral Cornea („Landing Zone“) • PC flatter than standard PC at normal RGP CL • Normally no changings neccessary • Good Fit and Centering, fast refractive Changing • Myopia reduction up to 4,50 D ~ 6,00 D • FDA Approval for Overnight wearing (Boston-XO / HDS-100)

  8. Structure of an Double Reverse CL • Treatment Zone / Target Power • Myopia + Regressionreserve • Treatment Zone / Base Curve • Kapillar Pressure to Tear Layer • Reverse Curve / Fitting Curve • Kapillar Suction / negative Pressure to Tear Layer • Alignment Curve (AC1+AC2) • Stabilisation / CL Fit • Peripher Curve (Bevel) • Tear Layer Exchange / Oxygen

  9. Structure of an Double Reverse CL

  10. How OK lens works? • Not only Push, but also Pull the central superficial cornea to the mid-periphery! • Tear film under lens is thinner in the center and thicker in the periphery. Thus, a pressure is created as the fluid tries to find equilibrium. • The central corneal epithelium thins and a midperipheral thickening of the stroma follows.

  11. How does the Lens works on the Eye? • The Variation of the Tear Layers Thickness creates differentKapillar Forces • Important: Lid Pressure and Lens Centering • Thin Layer  High Adhesive Force „Pressure“ • Thick Layer Low Adhesive Force „Suction“

  12. How does the Cornea changes? • Combination of „Pressure“ and „Suction“ on the Tear Layer induces an definate Movement of the free movable epithelal corneal Cells • Changing of corneal Shape  Myopia Reduction (Corneal Moulding, Shaping, Bending) • Corneal Epithelium is thinning central and cornea stroma thickening paracentral • Corneal Eccentricity will reduced  ε = Zero or negative • Result is Emmetropia or slight Hyperopia (+0,50 D) as Regression Reserve

  13. Law No. 1 • Law of Conservation of Corneal Power • „In Orthokeratology corneal power can never be created or destroyed, but can only be redistributed.” • Caroline and Campbell, 1991 am. Optometrists, Pacific University

  14. Law No. 2 • Blooms Law: • An correctly fitted OrthoK Lens does not touch the Cornea at any Time during the Fitting Procedure or in normal Wear.There is no Contact pressure between Contactlens and Cornea.The traditional Idea, that OrthoK Lenses are pushing down on the Cornea and flatten it to cause the Change is not true. • Basil H. Bloom, BSc(Hons) british Optometrist, Pioneer of modern Orthokeratology

  15. Fitting and Training of the Patient • Anamnesis and Conversation (What does he/she want?) • Carefully Patient selection (Hygiene, Cognition) • Refraction with CVD- and VA- Measurement (sc / cc) • Slitlamp (Biomikroskopy / Ophthalmoskope) • Cornea Topography • Calculation of CL- Surface Dates and Trial Fit from the Set • CL Fitting and Fluo Pattern Interpretation • Order the Final Lenses at FCL • Patient should train Handling and Cleaning Routines • Go on for the first Wearing • Tip: Let the CL wear only by Day at the first week

  16. Wearing and Control Schemes of Daytime Wearing • 1Day  3 h, 2Day  4h, 3Day  6h from 4Day  7h • Control after the first week with inserted CL • Ocular Examination (VA cc/sc, Fluo Pattern, Refraction, Cornea Topography) • Low Astigmatism Rectus (-0,5 D bis -0,75 D) possible (Lens Movement and superior higher Lid Pressure) • Low Residual Myopia possible (Movement at the Blink, Lid Pressure) • CL should move 0,5 - 1 mm vertical at the blink • Important: Cleaning and Wetting (Lipid and Protein Deposits, bad Wetting, CL Binding, irritated Cornea) • Go on to first Night Wearing

  17. Control Scheme at the Overnight Wearing • at the Morning after the first Night (with inserted CL) • at the Morning after one Week (with inserted CL) • at the Afternoon after one week (without CL) • at the Morning after one Month (with inserted CL) Attention: Key Control for Lens Binding Lens Tightening Syndrome • at the late afternoon after one Month (without CL) Goal: Determine the Myopia Regression within the Day Lens Wearing every second Night possible? • at the Morning after three Monthes (with inserted CL) • Follow Up Three monthly Controls

  18. The special view • Lenses must center • First time 1,0 mm, later 0,5 mm vertical Lens Movement at the Blink • Eyes should not be irritated • Check the Fluo Pattern (Changings good or bad?) • Within the wearing Time the Surface of the Cornea is going more equal to the Back Surface of the Lens • Check Visual Aquity with inserted Lenses • Check Visual Aquity and Refraction without Lenses • Corneal Topography • Slitlamp, if necessary with Fluorescein • Are the Lenses really clean?

  19. Who is an good Candidate? • interested, friendly, motivated People • Myopes up to -4,50 D and Astigmatism Rectus up to 1,50 D • In Case of professional Requirements • Police, Army, Fire Fighter • People in Sports, Pilotes, Diver, Parachutes Jumper • Problems with the Comfort of conventionel Lenses • Eyes must be good in Health

  20. Who is not an good Canidate? • Inner Astigmatism and Astigmatism Inversus > 1,00 D • Candidates, which want to „pin“ the Fitter • Dirty People • Eye Diseases, Infections, Allergies • Diabetic Diseases, Immunology Diseases, Metabolic Problems • Hypochondric and psychologic instable People • People with endocrinologic Conditions

  21. Before Ortho-k After Ortho-k

  22. Changes in Central Cornea Invest Ophthalmol Vis Sci 2003;44(6):2518-23.

  23. Changes in Midperipheral Cornea Invest Ophthalmol Vis Sci 2003;44(6):2518-23.

  24. Practice

  25. Orthokeratology • Planned Corneal Molding • Serial hard CL applied • Hydraulic Massage • Epithelium Redistribution

  26. Accelerated OK • Reverse Geometric Lenses • B.C. Flatter than K for about 2D • R.C. Steeper than B.C. for 3 ~ 4 D • 270o Crescent Touch • Effective up to 2.5~3.0 D • 3 ~ 4 Pairs of lenses needed

  27. Advanced OK • Double Reverse Geometric Lenses • B.C. Flatter than K. for 3~5 D • Fitting Curve : 8 ~ 12 D steeper • Alignment Curve 3 ~ 5 D steeper • Bulls eye F.S. pattern • 1~2 Pairs

  28. Proper Lens Design • Pressure balance Central pressure (optical zone) Peripheral pressure (alignment zone) • Sufficient tear circulation Tear ring (fitting zone) Tear pumping (PC & edge lift) • Well centration

  29. 4-Curve Advanced OK Lens • Base Curve (B.C.) Central Touch Hydraulic Massage • Fitting Curve (F.C.) Connecting 1st & 3rd curve Tear circulation Space for Tissue Remolding

  30. 4-Curve Advanced OK Lens • Alignment Curve (A.C.) Peripheral compression Central positioning • Peripheral Curve (P.C.) Form edge lift Tear pumping

  31. 4-Curve Lens Drawing

  32. Fluorescent Pattern (non-touch) (touch) EDGE LIFT Perpheral P. TEAR RING Central P.

  33. Parameters of 4-Curve Lens • Zone Widths O.Z.: 5.6~6.0 mm F.Z. : 0.4~0.8 mm A.Z.: 1.0~1.4mm • Curvatures B.C. : 2 ~ 5 D Flatter Than K. F.C. : 8 ~ 12 D Steeper Than B.C. A.C. : 3 ~ 5 D Steeper Than B.C.

  34. Proper Lens Design • Pressure Balance Central pressure (Optical zone) Peripheral pressure (Alignment zone) • Sufficient Tear circulation Tear ring (Fitting zone) Tear Pumping (PC & Edge lift) • Well Centralization

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