Scleral-Contact Lenses
Scleral-Contact Lenses Scleral-Contact Lenses
Landing Zone Angle Selection• The LZA is the only parameter that can produce properedge lift AND proper clearance at 10.5 mm chord (J2). Itdoes so simultaneously–Edge lift control with the LZA• Less angle is more lift and more angle is less lift• A greater LZA reduces edge lift and increases clearanceat 10.5 mm (J2)• A lesser LZA increases edge lift and reduces clearanceat 10.5 mm–The lens must have clearance at J2Lack limbal of clearance is seen as a black arcDual Axis Landing Zone• The modal eye has 300µ of elevation difference at the13 mmchord from highest to lowest.• The dual axis feature maintains:– more uniform sag circumferentially– minimizes flexureShallowDeep– provides orientational stability that enables front surfacetoric or HOA correction.• The Dual Axis feature allows the lens to have a varyingsagittal depth in one meridian compared to another whilemaintaining a spherical base curveEffect of LZA Differences• One degree of LZA change raises and lowers the edge lift andJ2 clearance about 50 microns• The point of maximum touch is at the 13.0 mm chord in a wellfit lens.• Increasing the LZA moves the edge down and J2 up• Decreasing the LZA moves the edge up and J2 down• The RZD must be adjusted when the LZA is changed to keepthe same optic zone clearance from the cornea• If the LZA is increased, the RZD must be decreased• If the LZA is decreased, the RZD must be increased• Consider a 50 µ RZD change for every 1°LZA change• Increase LZA then decrease RZD• Decrease LZA then increase RZDImpact of Each Degree of Change in LZABCR 8.0 Sag RZD8.0-10.5 ∆Sag LZA10.5-13.0∆ Sag6.60 1.350 0.650 0.650 48 0.7996.80 1.301 0.700 0.700 49 0.8317.00 1.256 0.750 0.750 50 0.8637.20 1.213 0.800 0.800 51 0.8967.40 1.174 0.850 0.850 52 0.9307.60 1.138 0.900 0.900 53 0.9657.80 1.104 0.950 0.950 54 1.0008.00 1.072 1.000 1.000 55 1.0378.20 1.042 1.050 1.050 56 1.0758.40 1.013 1.100 1.100 57 1.1138.60 0.987 1.150 1.150 58 1.1538.80 0.962 1.200 1.200 59 1.1949.00 0.938 1.250 1.250 60 1.2379.20 0.915 1.300 1.300 61 1.2809.40 0.894 1.350 1.350 62 1.3269.60 0.873 1.400 1.400 63 1.3731.450 1.450 64 1.42135 microns46 micronsLZA Too ShallowBlack ARC touch Inside limbusEvaluating LZALZA Adjusted HigherStill too shallow; See black arc bearing at 10.5 (A) ;and excessive edge lift (B)Excessive Edge LiftABB6
Evaluating LZAShallow LZA will immediately show excessive edge liftand dark ring at limbusEvaluating LZA• 54 / 58 LZA is too shallow post compressionNote Inadequate limbal clearance and apical clearanceInadequate ClearanceEvaluating LZA• Consider a1°increase inLZA• Will loweredge by 40µand raiselens at 10.5mm chordby 40µEdge Lift is good butcheck for limbal clearanceExcessiveEdge LiftBlack Arc Bearing at J2Conjunctival “Blanching” Indicates LZA isToo DeepIdeal LZAIdeal Fit After Conjunctival CompressionProper Clearance7
- Page 1 and 2: THE ROLE OF OCULARCONTOUR IN CONTAC
- Page 3 and 4: Contour Based Scleral Lens DesignPr
- Page 5: Fitting Scleral Lenses3. Select a b
- Page 9 and 10: RZD and LZA Too ShallowRZD Too Deep
- Page 11 and 12: Final Fit Success Criteria/post-Com
Landing Zone Angle Selection• The LZA is the only parameter that can produce properedge lift AND proper clearance at 10.5 mm chord (J2). Itdoes so simultaneously–Edge lift control with the LZA• Less angle is more lift and more angle is less lift• A greater LZA reduces edge lift and increases clearanceat 10.5 mm (J2)• A lesser LZA increases edge lift and reduces clearanceat 10.5 mm–The lens must have clearance at J2Lack limbal of clearance is seen as a black arcDual Axis Landing Zone• The modal eye has 300µ of elevation difference at the13 mmchord from highest to lowest.• The dual axis feature maintains:– more uniform sag circumferentially– minimizes flexureShallowDeep– provides orientational stability that enables front surfacetoric or HOA correction.• The Dual Axis feature allows the lens to have a varyingsagittal depth in one meridian compared to another whilemaintaining a spherical base curveEffect of LZA Differences• One degree of LZA change raises and lowers the edge lift andJ2 clearance about 50 microns• The point of maximum touch is at the 13.0 mm chord in a wellfit lens.• Increasing the LZA moves the edge down and J2 up• Decreasing the LZA moves the edge up and J2 down• The RZD must be adjusted when the LZA is changed to keepthe same optic zone clearance from the cornea• If the LZA is increased, the RZD must be decreased• If the LZA is decreased, the RZD must be increased• Consider a 50 µ RZD change for every 1°LZA change• Increase LZA then decrease RZD• Decrease LZA then increase RZDImpact of Each Degree of Change in LZABCR 8.0 Sag RZD8.0-10.5 ∆Sag LZA10.5-13.0∆ Sag6.60 1.350 0.650 0.650 48 0.7996.80 1.301 0.700 0.700 49 0.8317.00 1.256 0.750 0.750 50 0.8637.20 1.213 0.800 0.800 51 0.8967.40 1.174 0.850 0.850 52 0.9307.60 1.138 0.900 0.900 53 0.9657.80 1.104 0.950 0.950 54 1.0008.00 1.072 1.000 1.000 55 1.0378.20 1.042 1.050 1.050 56 1.0758.40 1.013 1.100 1.100 57 1.1138.60 0.987 1.150 1.150 58 1.1538.80 0.962 1.200 1.200 59 1.1949.00 0.938 1.250 1.250 60 1.2379.20 0.915 1.300 1.300 61 1.2809.40 0.894 1.350 1.350 62 1.3269.60 0.873 1.400 1.400 63 1.3731.450 1.450 64 1.42135 microns46 micronsLZA Too ShallowBlack ARC touch Inside limbusEvaluating LZALZA Adjusted HigherStill too shallow; See black arc bearing at 10.5 (A) ;and excessive edge lift (B)Excessive Edge LiftABB6
Change language