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CATz for Highly Irregular Corneas after Keratorefractive Surgery

CATz for Highly Irregular Corneas after Keratorefractive Surgery. Hamed M. Anwar, MD, FRCS Alaa El- Danasoury , MD, FRCS 1 Institutional affiliation: Magrabi Eye Hospital, Jeddah, Saudi Arabia. 1 . Dr. Alaa El-Danasoury is a consultant to Nidek Co. Ltd, Gamagori, Japan. Introduction.

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CATz for Highly Irregular Corneas after Keratorefractive Surgery

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  1. CATz for Highly Irregular Corneas after Keratorefractive Surgery Hamed M. Anwar, MD, FRCS Alaa El-Danasoury, MD, FRCS1 Institutional affiliation: Magrabi Eye Hospital, Jeddah, Saudi Arabia. 1 . Dr. Alaa El-Danasoury is a consultant to Nidek Co. Ltd, Gamagori, Japan.

  2. Introduction Keratorefractive surgery such as LASIK and radial keratotomy can reduce visual acuity due to induction of higher order aberrations. Decreased visual acuity in such cases is due to an irregular corneal surface. Management modalities include: Extensive postoperative counseling, Pharmacologic intervention Contact lens therapy Topography-guided retreatment

  3. Topography guided retreatments may be a better option compared to wavefront guided treatments in such patients as: Quality of topographic images can be checked Data limited to pupillary area. Shack-Hartmaannaberrometry Data isn’t limited to pupillary area. Questionable reliability of data in highly aberrated eyes

  4. CATz Key concepts • Uses scanning spot for irregular ablation • Uses scanning slit for sphere & Cylinder • Corneal topography guided ablation The basic treatment in CATz is the aspheric ablation Prolate cornea: Aspheric ablation Oblate cornea: Conventional ablation The “red ring” indicating the transition zone (TZ) is more peripheral and less pronounced in the CATz ablation Conventional ablation CATz

  5. Methods • Corneal topography, wavefront data, and pupillometry were acquired using the OPD-Scan II • All surgeries were planned using Nidek Final Fit 1.13 software • Ablation performed with Nidek EC-5000 CXIII excimer laser 100% treatment rate of all irregularities Corneal wavefront mode used Ablation centered midway between corneal vertex and pupil center (50% PDist on FinalFit) No treatment of spherical or cylindrical error due to the high degree of corneal irregularity

  6. Results – 8 eyes at 1 year Postoperatively 50% of all eyes saw  20/20 All eyes saw better than 20/30 Improvement in modulation transfer frequency values postoperatively Cumulative BSCVA of patients before and after CATz treatment Mean HO MTF over time The higher order MTF plots the effect on visual performance of the higher order aberrations, not sphere and cylinder.

  7. Results (cont) 0.45m decrease in the mean higher order spherical aberration postoperatively 0.45m decrease in the mean coma postoperatively Spherical aberration (Z12) over time (m) Coma RMS over time [m]

  8. Topography: • Small EOZ = 4 mm • Well centered ablation OPD HO: Coma RMS = 1.83 • Case example • 1 year after LASIK (2006 Flying spot laser): • Night Vision symptoms (Starbursts ) • UCVA: 20/20 • MR: 0.00 -0.25 x 20 • BSCVA: 20/16 • Pachymetry 450 • Mesopic pupil 6.7 mm MTF: Poor quality of vision A/B = 0.197 H/B = 0.363 PSF: Poor quality WF error: 1.28 Strehl Ratio: 0.01

  9. Difference map shows the targeted area of localised ablation Enlargement of functional optical zone from 4mm to 6mm Decrease in OPD HO coma RMS from 2.07D to 1.2D

  10. Modulation transfer function (MTF) shows an improvement on the higher spatial frequencies. A/B and H/B ratios increase. Point spread function (PSF) improvement shown by the Strehl ratio increase from 0.01 to 0.04 and WF error decrease from 1.28m to 0.6m

  11. Conclusion • Customized Topography Guided Ablation using Final Fit 1.13 & the CATz profile is safe and effective in the treatment of corneas with high irregularities after keratorefractive procedure.

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