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Soft Toric Contact Lenses

Soft Toric Contact Lenses

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Soft Toric Contact Lenses

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  1. Soft Toric Contact Lenses Courtesy Pat Caroline Vinita Allee Henry, OD, FAAO UMSL College of Optometry

  2. Astigmatism Education • Cross on the front of the eye • Football • Have the patient take their spectacles off, so that they can rotate the specs in front of their eye • Spectacle correction versus CL (Stable versus rotation) • Spherical CL versus Toric CL (Fees, rotation, expense due to manufacturing & fit time)

  3. Who Needs Soft Toric CL’s? How much astigmatism?

  4. How much Astigmatism? • Spherical GP’s for? • <2D corneal astigmatism • Toric GP’s for? • >2D corneal astigmatism • Front toric for lenticular astigmatism • Spherical Soft for ? • <1D of astigmatism • Aspheric Soft for? • 0.50-0.75D astigmatism • Toric Soft for? • >0.75D astigmatism

  5. If the patient does not need much correction for astigmatism, should it be corrected?

  6. DISTRIBUTION OF ASTIGMATISM > 0.25D = 76.5% > 1.50D = 19.2% > 0.50D = 61.5% > 1.75D = 15.8% > 0.75D = 45.5% > 2.25D = 10.0% > 1.00D = 34.8% > 2.50D = 6.0% > 1.25D = 24.8% > 3.00D = 3.4% Courtesy of D. Becherer

  7. How does the patient’s refraction affect correction? • Demonstrate with phoropter-may give an idea if toric lens will help • As cylinder goes up, rotational stability is more critical

  8. Patient Selection • Low amounts of astigmatism • More astigmatism error than spherical error • More spherical error than astigmatism error • Presbyopes • Need to be good soft lens candidate

  9. Becherer Twist • Subjective refraction in phoropter • Twist cylinder knob until patient notices blur • 20 degrees or > = 90% success first lens • 10 degrees = 70% success with 3 lenses • 5 degrees = <5% chance of success

  10. Remba Rule of Thumb • Sphere > 2(minus cylinder) • Becherer Rule of Thumb • Sphere > 3(minus cylinder if oblique)

  11. Aspheric Lenses • Do not optically correct astigmatism • May improve spherical aberration of CL & eye • Enhance focus by minimizing aberration, improve contrast sensitivity, enhance optics • May report better vision even if not measurably so

  12. Spherical Aberration Becherer and CLS Snyder

  13. Spherical Aberration Becherer & CLS Snyder

  14. Aspheric Lenses • Frequency Aspherics, Biomedics XC, Biomedics 55 Premier • PureVision • Focus N&D, O2 Optix, Air Optix • Biofinity, Avaira

  15. Lens Design • Prism Ballast • Double Slab Off/Thin Zones • Eccentric Lenticulation • Accelerated Stabilization Design • Back Surface Toric • Front Surface Toric

  16. Watermelon Seed Principle • Upper lid tends to push away the thickest portion, like squeezing a watermelon seed between your fingers, the thickest portion will be forced out. • Works with prism ballast and double thin zones-more so double thin zones

  17. Prism Ballast(1-1.5PD) • Vertex Toric, Proclear Toric & Frequency Toric – Back surface • Focus Toric – Back surface • Extreme H2O Toric – Back surface • Optima Toric – Front surface • SF 66 & PureVision Toric – Back surface • Air Optix for Astig. – Thin at 6, thick at 4&8

  18. Eccentric Lenticulation • Hydrasoft Toric –Back surface

  19. Binocular problems Use non-prism lens

  20. Double Slab-Off/Thin Zones • Freshlook Toric – Back surface • AV Toric – Back surface • Torisoft – Front surface • Focus Dailies Toric – Back Surface • Accelerated Stabilization Design • AV Advance for Astigmatism (4 active zones, mid-periphery)

  21. Initial Lens Selection • Realistic expectations • Use up-to-date Refraction, not previous Toric CL Rx • Cyl and axis match Rx (Less is better) • Figure nasal rotation?

  22. Initial Lens Selection • Vertex both meridians >+ 4D • Check Parameter Availability • Can insert with laser markings in correct location

  23. Initial Lens Selection • If the Rx you need is not available, then order correct lens • Go lower than expected cyl, works well (e.g. Focus Dailies Toric)

  24. Vertex Rx -4.00-1.75 X 180 Converts to -4.00 @ 180 to -3.75 -5.75 @090 to -5.25 -3.75 -1.50 X180, try on -3.75-1.25 X 180

  25. Fitting • Allow 15-20 minutes to settle • Lag up & down, rotate little • Large & Steep to stabilize • Be familiar with markings and separation • Poor fit, ditch the lens prior to VA and OR

  26. Fitting • Oblique and ATR astigmatism harder to fit than WTR- more effects from blink • OR sphere first, then sphere/cyl • Try to OR on axis • Use cross cyl calculator • 1.4-1.6 lenses /eye for successful result

  27. Fitting-Rotation • Quick rotational return • Try forced lid closure and see how lens rotates • >30degree rotation-get new lens • Inconsistent rotation-get new lens

  28. Rotation • Tends toward nasal due to temporal-nasal motion of upper lid • Higher outer canthus tends toward temporal rotation • Higher nasal canthus tends toward nasal rotation • Dial axis to proper location and see if VA improves

  29. Rotation • Large axis shifts cause minimal change, then insufficient cyl correction • Steep fit-Locks in at incorrect location, slow return when dialed off • Flat fit- Variable vision due to blink, unstable rotation

  30. High Astigmatism • Check Tyler’s Quarterly for cyl power & axis • (-1.75 and off 180 & 90 more than 20 degrees) • Consult with company • Available lenses: • CooperVision (Vertex XR, Proclear XR, Frequency XR, Preference XR, Hydrasoft Torics) • Bausch & Lomb (Optima Toric) • Ciba (Durasoft Optifit Toric)

  31. LARS • Left • Add • Right • Subtract • Add to Spectacle Rx, Dr’s perspective

  32. Ways to determine rotation: • Trial frame and low power cyl lens • Narrow slit and SL protractor scale • Measuring reticule in ocular • Clock dial-guesstimate

  33. Spec Rx -3.00 -1.00 X 180OR -0.50-1.00 X 40 Final Rx?

  34. Cross Cylinder Calculation • AOA CLS EZ fitter-Dr. Paul Whitten • www.eyedock.com • Check company websites for calculators • (Vistakon, CooperVision & Ciba) • Cylinder 90 degrees away means too much cyl, cyl at same axis add, cyl at oblique axis means change axis

  35. Common Mistakes

  36. LARS • Based on practitioner viewpoint • Based on base of lens • Scribe mark indicates base not axis • Make change from spectacle axis • After compensation, want new lens to rotate the same way • Vertex back both meridians

  37. Dispense lenses for 1 week trial

  38. Dispense when good vision and no rotation or good vision and some rotation

  39. Trouble-shooting • Blurry vision • Incorrect Rx, rotation, poor fit • Fluctuating vision • Poor stabilization, poor fit, rotation • Variable vision • Check fit, change design

  40. Trouble-shooting-Becherer • Consistent blur – adjust power/axis • Intermittent blur – adjust fitting

  41. Patient Education Nuggets • Use rewetting drop before lens removal • Twist lens one way to remove and the other the following night – alternating the spot that is pinched off

  42. Look for neo, dehydration, edema under inferior portion of lens

  43. Si Hy Torics

  44. Acuvue Advance & Oasys for Astigmatism • 2 week replacement • Laser markings at 6 & 12 • Accelerated Stabilization Design • UV inhibitor

  45. PureVision Toric • Anterior Aspheric Optics to reduce spherical aberration • Prism ballast with 360° comfort chamfer for enhanced rotational stability • Laser markings at 5,6,7 • Monthly replacement • DW or 30 day CW