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GAS PERMEABLE PROBLEM SOLVING

Learn about procedures for progress evaluation, reduction of visual acuity, corneal desiccation, and refitting into GP lenses. Understand causes, complications, and management techniques. Explore potential solutions and complications when refitting from soft lenses.

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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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