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Topography-guided PRK with Fourier analysis combined with CXL for early keratoconus

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Session Details

Session Title: Advanced Surface Photoablation I

Session Date/Time: Sunday 08/10/2017 | 08:00-09:30

Paper Time: 08:57

Venue: Meeting Center Room I

First Author: : A.Assaf EGYPT

Co Author(s): :                        

Abstract Details


To evaluate visual acuity, visual quality, and corneal aberrations after topography-guided PRK based on Fourier analysis followed by immediate CXL for early keratoconus.


Al Watany Eye Hospital and Ain Shams University


This study is prospective non-randomized interventional case series. Inclusion criteria: keratoconus 1&2, BCVA; 0.4 or less, Kmax; 50D or less, irregular corneal astigmatism between 1-5D, central corneal thickness> 465 microns Data acquisition was obtained by Scheimflug rotating camera (Oculyzer II) or Placido disc topographer (Topolyzer Vario). The treatment plan was based on Fourier analysis for corneal astigmatism to separate regular astigmatism and decentration. 75% of regular corneal astigmatism on Fourier analysis was entered manually in the correction plan for topography-guided PRK by Wavelight EX500. Steps of surgery was PRK, PTK (50 microns), Mitomycin application, and finally corneal cross linking


Thirty-four eyes of 20 patients were included. Preoperative UCVA improved from 0.81 LogMAR to 0.34 LogMAR at three months after the surgery. BCVA improved from 0.39 LogMAR preoperatively to 0.11 LogMAR 12 months postoperatively. Preoperative vertical (1.2 microns) and horizontal (0.4 microns) corneal coma were significantly reduced to 0.34 microns and 0.01 microns respectively. Total ocular coma on OPD scan reduced from 0.64 microns preoperatively to 0.19 microns at 12 postoperatively. Strehl ratio improved from 0.012 to 0.036 postoperatively. Corneal haze noted in 14 eyes and improved gradually during 6 months after the surgery.


Fourier Analysis allows for better evaluation of corneal astigmatism in cases of early keratoconus. It helps to reduce irregular corneal astigmatism and improve visual quality when incorporated with simultaneous topography-guided PRK and CXL

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