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Corneal Wave Front- DOES IT REALLY EXIST ? Dr Kumar Doctor Mumbai India NO FINANCIAL INTEREST CORNEAL ABBEROMETRY Purpose • To Evaluate Corneal Wave Front treatment • KERATRON SCOUT • • TOPOGRAPHER USES A SMALL CONE AND 28 RINGS ,PLACIDO DISC PRINCIPLE CONCEPT OF ARC STEP RECONSTRUCTION OF THE CORNEAL SURFACE PROFILE,VERY ACCURATE TO A MICRON CORNEAL ABBEROMETRY OPTICAL PATH DIFFERENCE(OPD) • LIGHT RAYS THAT EXIT FROM THE CORNEA TRAVEL FASTER IN AIR THAN THOSE STILL IN THE CORNEAL SUBSTANCE DUE TO THE DIFFERENCE IN RI OF AIR AND CORNEA • EMERGING RAYS FORM A WAVEFRONT WHICH HAS A SHAPE EQUAL AND OPPOSITE TO THE CORNEAL SURFACE BUT ABOUT 1/3RD MAGNITUDE • OPTICAL PATH DIFERANCE IS THE DIFERANCE BETWEEN THIS NEW WAVEFRONT AND THE IDEAL OPTICAL PATH DIFFERENCE(OPD) “Rule of 3”: Every 3 micron distortion on the Cornea creates 1 micron of Wavefront Error “Corneal Wavefront” is the component of eye refraction owed to the cornea (or OPTICAL PATH DIFFERENCE OPD) Aberrations: “Ocular” = “Corneal” + “Internal” (or “Total”) From WA From TC (100%) (80%) ADVANTAGES OF USING A CORNEAL DERIVED WAVEFRONT-WHY NOT JUST USE A WAVEFRONT ABBEROMETER? • OPTICAL ZONE IS NOT RESTRICTED BY PUPIL SIZE.WE CAN DO A 8.5 MM ABLATION • ABBERATIONS ARE EXCLUSIVELY CORNEAL AND DO NOT DEPEND ON ACCOMODATION,LENS, OR PUPIL SIZE • CORNEA IS RESPONSIBLE FOR OVER 80% OF THE TOTAL ABBERATIONS OF THE EYE METHOD - CORNEAL WAVEFRONT LASIK FOR A DECENTERED CORNEAL GRAFT Preop corneal • PATIENT OPERATED • • FOR PENETRATING KERATOPLASTY 5 YEARS AGO BCVA WITH -4 SPH 5CYL,6/12 POST LASIK RESULT 0.5 CYL,6/6 Preop bcva 6/12 Ablation shotfile wavefront RESULT This is only possible with corneal wavefront which breaks down any surface distortion into a combination of zernicke polynomials which can then be treated with the software on the schwind ESIRIS laser POSTOP TOPOGRAPHY 6/6 UCVA!! Conclusion Patient Treated By MEL 70 in 1999 Post op Refraction before Retreatment OD -0.75 D Sph. 6/6 Patient treated in November 2006 Post Op Corneal WF image Post op image on 28/10/06 Post op Corneal WF image Conclusion – CORNEAL WF WORKS VERY WELL WITH SCHWIND ESIRIS LASER • Add –on aspheric Rx to improve night Quality vision in previously treated eyes • Works very well in High corneal Astigmatism