Scleral-Contact Lenses
Scleral-Contact Lenses Scleral-Contact Lenses
Selection of RZDEVALUATING THE RZDSELECTION• Select the RZD to provide total corneal clearance• RZD lifts the optic zone of the lens to causeoptic zone junction and lens apex to clear thecorneal surface by at least 50 microns postcompression• OZ touching = RZD too shallow• Bubbles under OZ = RZD too deepFitting Scleral Lenses with TopographyTopography Chord Value – 10.5 mm (J2)• Close determinationof initial BC fromElevation Map (BestFit Sphere).• Close determinationof initial RZD fromsagittal depthanalysis at the givenjunctionsSag at the 10.5 mm chord is 1950 micronsTopography Chord Values – 8 mm (J1)Calculating the RZD from TopographySag DataA=10.5mm(J2) B= 8.0mm(J1)J 1B : Sag at 8.0 mmSag at the 8 mm chord is 1090 micronsA : Sag at 10.5 mmRZD = A - BEstimated RZD 1950 – 1090 = 860 micronsJ 28
RZD and LZA Too ShallowRZD Too Deep and LZA GoodPost lens tear film too deepNot enough central clearanceExcessive centralclearanceInsufficient Limbal ClearanceEdge lift is goodIdeal Corneal ClearanceGoal is 80 to 100µm AFTER conjunctivalcompression or 200 to 240 µm before compression.Use Parallel Pipette for RZDEvaluationCornea is about 550 µmLens is about 240 µmThis post lens tear filmabout equal to lensthicknessBest evaluated with parallel pipette or OCTBase Curve CalculationBASE CURVECALCULATIONSelected using• Flat meridian keratometry• Flatter than flat K from lens selection chart• Reference sphere from corneal topography• For irregular corneas• If too steep:• Lens will be closer at J1 than at the apex and may facilitate centralbubble• If too flat:• Lens will be closer at apex than J1 and may facilitate central touch orarccuate bubble at J1Base Curve is not very critical if RZD and LZA are correct9
- Page 1 and 2: THE ROLE OF OCULARCONTOUR IN CONTAC
- Page 3 and 4: Contour Based Scleral Lens DesignPr
- Page 5 and 6: Fitting Scleral Lenses3. Select a b
- Page 7: Evaluating LZAShallow LZA will imme
- Page 11 and 12: Final Fit Success Criteria/post-Com
Selection of RZDEVALUATING THE RZDSELECTION• Select the RZD to provide total corneal clearance• RZD lifts the optic zone of the lens to causeoptic zone junction and lens apex to clear thecorneal surface by at least 50 microns postcompression• OZ touching = RZD too shallow• Bubbles under OZ = RZD too deepFitting <strong>Scleral</strong> <strong>Lenses</strong> with TopographyTopography Chord Value – 10.5 mm (J2)• Close determinationof initial BC fromElevation Map (BestFit Sphere).• Close determinationof initial RZD fromsagittal depthanalysis at the givenjunctionsSag at the 10.5 mm chord is 1950 micronsTopography Chord Values – 8 mm (J1)Calculating the RZD from TopographySag DataA=10.5mm(J2) B= 8.0mm(J1)J 1B : Sag at 8.0 mmSag at the 8 mm chord is 1090 micronsA : Sag at 10.5 mmRZD = A - BEstimated RZD 1950 – 1090 = 860 micronsJ 28
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