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Introduction to Custom Ablations

Introduction to Custom Ablations. Eric Polk, OD, FAAO Adjunct Assistant Professor UMSL College of Optometry. Special Thanks To…. David Hardten, M.D., Mark Whitten , M.D. Dawn Holsted, OD Tom Gilbert, O.D., F.A.A.O. For text materials, photographs, and final editing.

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Introduction to Custom Ablations

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  1. Introduction to Custom Ablations Eric Polk, OD, FAAO Adjunct Assistant Professor UMSL College of Optometry

  2. Special Thanks To… David Hardten, M.D., Mark Whitten , M.D. Dawn Holsted, OD Tom Gilbert, O.D., F.A.A.O. For text materials, photographs, and final editing.

  3. Standard Laser Ablation • In the beginning • Laser ablation diameters were smaller • 1996: Diameters were as small as 5.0mm and correct up to -6.00 diopters • 1997: Astigmatism treatment was FDA approved up to -4.00 diopters • Laser ablations evolved with larger ablation diameters • 6.0-6.5mm • Higher parameters were introduced (~-11.00 sph) • Correction of hyperopia and mixed astigmatism

  4. Standard (Traditional) Laser Ablation • Standard laser ablation • Patients Rx is programmed into the laser • Each patient receives the same laser ablation • Diameter of laser ablation can be adjusted to fit the patients need • For myopia • 6.0 mm optical zone • 6.5 mm optical zone • 8.0 mm blend • No iris registration

  5. Standard Laser Ablation • Problems with Standard • Treatment was not customized to visual system • High order aberrations are not corrected • Night Vision Problems • Glare and Halo • Irregular ablations (dishomogenous ablations) • Reports of ghost imaging, diplopia, decreased contrast sensitivity

  6. Advantages of Custom Wavefront Ablation • Custom Wavefront ablations were introduced in 2004 • Wavefront ablations customized to patients RX • Increases the chance of 20/20 vision • Better contrast sensitivity • Better chance of improving BCVA • Lessens the chance of visual side effects • Glare • Halo • Diplopia • Ghost Images

  7. Why is Custom Wavefront Better? • Custom Wavefront ablations • Treatment is customized to each patient with wavefront mapping • Larger ablation zones with high astigmatism • Iris registration • Pupil tracking • Flying spot lasers • Leaves cornea more prolate

  8. Wavefront Analyzer • Wavefront analyzer captures the image • Wavefront analyzer examines the visual system of the eye. • The Wavefront analyzer uses the information to suggest a programmable ablation pattern

  9. Patient Presents for Exam • 3-5 Wavefront maps capture image on each eye • Mapping of aberrations • Approximation of RX • Percentage of aberrations

  10. Wavefront Assessment Derived wavefront shape Hartmann ShackWavefront Data Algorithm Each dot represents a tiny lens

  11. Hartmann Shack Aberrometer Measures the ray pattern as it emerges from the eye to see what changes in the cornea will make those rays absolutely straight. Outcoming Wave CCD-Image CCD-Camera Lens Array

  12. Spherical Cornea Ideal wavefront: - Spherical: rays converge on retina - Regular: all rays converge at one point plane wavefront Refracting medium in focus image C. of Austin Roorda

  13. Irregular Cornea plane wavefront Distorted (irregular) wavefront: - Myopic: most rays converge anterior to retina - Irregular: all rays do not converge at one point C. of Austin Roorda

  14. Hartmann-Shack Image • Cornea must be normal before image is taken • Dryness • CL Distortion Poor Tear Film distorts the image • Each dot represents a lenslet that measures the visual system • Accommodation during testing can also be a problem

  15. Percentage of High Order Aberrations compared to RX RMS Error of all aberrations RX & HOA RX RMS Error of High Order Aberrations Quantity of Individual Aberrations

  16. Custom LASIK • Traditional lasers correct low order aberrations • Low-order aberrations: • Sphere, Cylinder • Custom wavefront correct high order aberrations • High-order aberrations: • Coma, Spherical Aberration, Trefoil, • proportional to refractive error and pupil size

  17. Zernike Polynomials Shapes Sphere Cylinder Tilt Spherical Aberration Coma Higher Astigmatism

  18. Higher Order Aberrations: Examples

  19. Subjective Visual Symptoms: Glare

  20. Subjective Visual Symptoms: Monocular Diplopia

  21. Subjective Visual Symptoms:Night Vision Disturbances

  22. Subjective Visual Symptoms: Starbursts

  23. Custom WavePrint • % of Aberrations • Percentage of patients prescription that is made up of high order aberrations versus low order aberrations (myopia, astigmatism, ….) • Acuity Map RMS Error • Total of all aberrations (Low order and High Order) • High Order Aberrations RMS Error • Amount of high order aberrations • <0.5 is significant • Zernike Coefficient Table • Quantifies individual aberrations • Wavefront refraction is basically the patients RX (auto refractor)

  24. Custom LASIK • The Wavefront Analyzer/Aberrometer takes into account: • Corneal curvature • Corneal smoothness • SPK • Astigmatism • Pupil size • Crystalline lens and media • Cataract • Retinaand Vitreous • PVD • Each laser manufacturer has a different wavefront analyzer.

  25. Wavefront Refraction • Manifest and cycloplegic refraction is performed • Ideally the refractions will match up with the wavefront refraction • Wavefront Refraction +0.19-0.97X 099 • Manifest Refraction +0.25-1.00X 100 • The wavefront mapping is downloaded onto the laser • Fourier analysis • Zernike polynomials • Lessens chance of user error: transcribing RX • Laser treatment is customized to the patient’s eye

  26. Prolate Versus Oblate Cornea • Wavefront Technology Leaves Cornea More Prolate • Prolate: Shape is steeper in center and progressively flattens toward the periphery. • Typical of a normal cornea • Conventional LASIK ablations are spherical and only correct lower order aberrations -- myopia, hyperopia, astigmatism • Conventional ablations leave the cornea Oblate • Oblate: Shape is flatter in the center and steepens out toward the periphery. • Alegretto laser leaves cornea more prolate then other laser platforms

  27. Wavefront – Diagnostic Tool • Wavefront – Diagnostics • Can be used to determine if a patient has irregular corneas. High RMS error indicates irregularity • Wavefront mappings have been used as a diagnostic tool to determine risk for keratoconus • High coma is a indication of keratectasia • High coma is also associated with diplopia and ghost images • Spherical aberration is associated with halos at night

  28. Custom Ablations • Custom Wavefront allows for larger ablations especially with higher astigmatism (< 1.50) • Advantages • Less chance of glare and halo • Disadvantage • Larger diameters = Greater ablation depth • Flying spot lasers (smaller spot lasers used to create blend zones, correction of high order aberrations, creation of large diameter ablations)

  29. Iris Registration • Wavefront analyzer captures image with patient sitting up • Laser ablation: Supine position • Finds landmarks on the iris • Before laser ablation the laser looks for landmarks • Prevents cyclorotation • Especially important with high astigmatic patients

  30. Iris Registration

  31. Wavefront Technology Custom wavefront platforms • Autonomous: • LADARWave • CustomCornea • VISX : • CustomVue – Wavefront treatment • B&L Chiron: • ZyWave II • Nidek Laser • Final Fit custom wavefront ablation • Wavelight “Allegretto” • AllegrettoWave Analyzer • Recently Purchased by Alcon

  32. Excimer Laser Most Commonly Used * DUFFEY Survey 2008

  33. Custom LASIK • FDA Approved Analyzer and Treatment Systems: • Alcon Autonomous LADARVision with the LadarWave Analyzer • “CustomCornea” - approved October, 2002, expanded parameters in July, 2004 - • Treats up to - 9.75 D of Myopia with up to 5.00 D of Cylinder – allows for a 10% adjustment to the sphere • Treats up to – 10.63 Manifest Refraction Spherical Equivalent (MRSE) • No Physician Adjustment on the Cylinder, No Monovision

  34. Custom LASIK • VISX S4 IR with CustomVue with the Fourier WaveScan • Expanded parameters in October, 2005 • Treats up to – 11.00 D of Myopia with up to 3.50 D of Cylinder – allows for a 10% adjustment to the sphere up to -0.75. • No monovision with custom treatments • Treats up to +3.00 diopters of hyperopia • Treats up to – 11.00 Manifest Refraction Spherical Equivalent (MRSE) • Optical Zone - 5-7mm

  35. Custom LASIK • FDA Approved Analyzer and Treatment Systems: • B & L “Zyoptix” with the ZyWave Analyzer • Treats up to – 7.00 D of Myopia with up to 3.00 D of Cylinder – allows for no adjustments

  36. Custom LASIK • FDA Approved Analyzer and Treatment Systems: • Wavelight “Allegretto” with the AllegrettoWave Analyzer • Wavefront optimized laser ablation • Leaves cornea more prolate • Treats up to – 12.00 D of Myopia with up to 6.00 D of Cylinder • Treats up to + 6.00 D of Hyperopia with up to + 5.00 Cylinder.

  37. HOA RMS Pre and Post LASIK Higher Order Aberrations Custom Wavefront Ablations do not eliminate high order aberrations. Custom wavefront does reduce the amount of aberrations that are formed compared to a traditional standard ablation.

  38. Custom LASIK Goals • Vision Better than 20/20 when possible • Better Contrast Sensitivity • Less complaints of night glare, starbursts, distortion • Repair Refractive Surgery Problems • Customized ablations for irregular corneas

  39. Case Example • 50 Year old male wants laser surgery for better distance vision • Manifest RX +1.75 SPH • Standard or Custom? • Reasons?

  40. Case Example • 28 year old female wants enhancement surgery. • MR: +0.25-1.25X 170 • 6.5mm Pupils • Complains of monocular ghost image day and night • Custom or Standard? • Reasons?

  41. Case Example • 45 year old male wants LASIK surgery to improve his night vision • WR: -1.75-2.89 X 176 • MR: -2.00-3.00 X 180 20/20 • CR: -2.00-3.00 X 180 20/20 • 8.0 mm Pupils • Currently experiences halos • Custom or Standard? • Reasons?

  42. Case Example • 40 year old white female wants LASIK Surgery • Wavefront Refraction: -3.75-0.25X090 • Manifest Refraction: -2.50-0.25 X 090 • Cycloplegic Refraction -2.00-0.25X 90 • 5.0mm pupils • 0.4 RMS of High Order Aberrations • Custom or Standard • Reasons

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