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GAS PERMEABLE PROBLEM SOLVING

GAS PERMEABLE PROBLEM SOLVING. GP PROBLEM SOLVING. Progress Evaluation Procedures Reduced Visual Acuity Decentration Reduced Surface Wettability Power Change Corneal Desiccation Refitting into GPs. GP PROBLEM-SOLVING. Progress Evaluation Procedures. PROGRESS EVALUATION PROCEDURES.

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GAS PERMEABLE PROBLEM SOLVING

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  1. GAS PERMEABLE PROBLEM SOLVING

  2. GP PROBLEM SOLVING • Progress Evaluation Procedures • Reduced Visual Acuity • Decentration • Reduced Surface Wettability • Power Change • Corneal Desiccation • Refitting into GPs

  3. GP PROBLEM-SOLVING • Progress Evaluation Procedures

  4. PROGRESS EVALUATION PROCEDURES • Lenses On: • Visual Acuity • Retinoscopy (OR) • Sphere-Cylinder • Biomicroscopy • Lag • Surface Quality • Edema

  5. PROGRESS EVALUATION PROCEDURES • Lenses Off • Biomicroscopy • Staining • Limbal Vasculature • Lids Keratometry Subjective Verification

  6. GP PROBLEM SOLVING • Progress Evaluation Procedures • Reduced Visual Acuity

  7. REDUCED VISUAL ACUITY • Flexure • Warpage • Decentration • Reduced Surface Wettability • Power Change

  8. REDUCED VISUAL ACUITY • Flexure: • Bending of a flexible GP lens on a toric cornea • Diagnosed via over-K’s; if toric & radiuscope is spherical = flexure • Managed via flatter BCR, smaller OZD &/or increased center thickness

  9. REDUCED VISUAL ACUITY • Flexure • Warpage: • Caused by excessive digital pressure, especially with high Dk material & digital cleaner

  10. REDUCED VISUAL ACUITY • Flexure • Warpage • Decentration: Causes include: • Lens Design • Lens Material • Corneal Topography • Lid Tension/Blink Quality

  11. REDUCED VISUAL ACUITY: DECENTRATION • Complications: • Reduced/Variable Vision & Flare • Limbal Irritation/ 3 & 9 staining • Lens Awareness • Lens Dislocation • Poor Corneal Alignment; excessive flattening & steepening with possibility of distortion

  12. REDUCED VISUAL ACUITY: INFERIOR DECENTRATION • Management: • Reduce Center Thickness • Proper Edge Design (- lent < -1.50D/+); +lent. > -5.00D • Bitoric > 2.50D corneal cyl • Lid Attachment Design

  13. REDUCED VISUAL ACUITY: LATERAL DECENTRATION • Causes: ATR Cyl./ displaced corneal apex • Management: Increase OAD or Steeper BCR; aspheric design

  14. REDUCED VISUAL ACUITY • Flexure • Warpage • Decentration • Reduced Surface Wettability • Power Change

  15. GP PROBLEM SOLVING • Progress Evaluation Procedures • Reduced Visual Acuity • Corneal Desiccation

  16. GP PROBLEM-SOLVING: CORNEAL DESICCATION • Definition: Dryness or peripheral desiccation staining occurring in 3 & 9 o’clock regions of the cornea. • Occurs in over 50% of rigid lens wearers (but decreasing) • Ranges from diffuse punctate staining (most common) to corneal opacification & neovascularization

  17. GP PROBLEM SOLVING: CORNEAL DESICCATION • Diameter: larger reduces area; smaller reduces mass • Lens Position: Inferior least desirable (Henry, Bennett & Forrest, AJO, 1086) • 3 & 9 o’clock staining-to-fit relationship • Position #Eyes 3 & 9 % Sup-Centr 125 48 38 Interpalp 193 111 57 Inf-Centr 46 34 73

  18. CORNEAL DESICCATION • Edge Lift: Too small versus too large • Center Thickness: Problems of large CT: Verify! • Edge Shape: well polished, thin & tapered

  19. GP PROBLEM SOLVING • Progress Evaluation Procedures • Reduced Visual Acuity • Corneal Desiccation • Refitting into GPs

  20. REFITTING INTO GPS • Complications • Edema (98%) • Corneal Warpage • Corneal Exhaustion

  21. REFITTING INTO GPS • Possible Applications (keratoconus, high astigmatism, presbyopia, soft failures, orthokeratology) • Liability • Explain GP benefits (effects of PMMA wear, O2 permeability, modern technology, vision in spectacles) • Audiovisuals: photographs/slides, videotapes

  22. REFITTING INTO GPS • Refitting Procedure • Immediate refit without loss in wearing time • If corneal warpage, reduce wear time to minimum they can wear and refit one week later • Same design or new design???

  23. REFITTING INTO GPS FROM SOFT LENSES • Most common reasons: • GPC • Poor Vision

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