1. Marotte D, Denoyer A, Pisella PJ.
Influence of the Compensation for Pupil Decentration and Ocular Rotation on the Residual Ocular Aberrations in Myopic Astigmatic Patients After Wavefront Guided Refractive Surgery
Marotte D, Denoyer A, Pisella PJ.
University François Rabelais
Hospital Bretonneau, Tours, France
No Financial interest

2. Does the iris recognition reduce the postoperative cylindrical error and treatment induced high order aberrations in the astigmatic patients undergoing W-G refractive surgery ?
Courtesy of D.Marotte

3. Alpins method
This method described by Dr Noel Alpins is a vector analysis tool which provides the ability to calculate
and statistically compare the magnitudes and axes of astigmatic change (vectors) separately.
This method can allow the analyses of mean and standard deviations of calculated index for the evaluation of errors, surgical success and secondary adjustments required for final results improvement..
Courtesy of D.Marotte

4. Study design
Prospective comparative study (University Hospital of Tours, France)
71 myopic eyes with astigmatism > |1 D| underwent WG photoablation ( Excimer Star S4-IR and CustomVue, Visx, USA)
32 with iris-guided compensation (IGC)
39 controls without IGC
6-month postoperative outcomes :
Main : Accuracy of cylindrical treatment using Alpins method taking into account magnitude and axis of error.
Others : UCVA, BCVA, induced ocular wavefront aberrations

5. Preoperative features
With IGC (n=32)
Without CC (n=39)
Age (years)
36.7 ± 9.9
31 ± 7
Sex Ratio (M/F)
0.54
0.80
Procedures (PRK/LASIK)
1.13
1.05
Sphere (D)
-3.4 ± 1.79
-3.9 ± 2.4
Preop Cylinder(D)
-1.34 ± 0.43
-1.44 ± 0.96
Postop Cylinder(D)
-0.22 ± 0.24
-0.61 ± 0.31
RMS HOA (µ)
0.32 ± 0.19
0.28 ± 0.18
Mean Torsion (°)
3.06 ± 2.3
None
Mean Pupil Decentration (mm)
0.34 ± 0.14

6. Cylindrical error (6 months)
§: Statistical difference in the achieved/intented vector magnitude ratio:
84.36±14,64 % vs 51±29.6 %, p<

7. Accuracy of Cylindrical Treatment using Alpins method
§:p<0.05
§:p<0.05
High statistical difference in the Magnitude and Axe of Error in the « All » group (p<0.0001)

8. Induced high order aberrations (6 months)
§ §
HOA induction is lower in the PRK-IGC+ group
§: Satistical difference in the Total Hoa and Trefoil induced for PRK group (p<0.05)

9. Conclusions
The accuracy of cylindrical treatment by compensating peroperative ocular torsions, is independent from the surgical procedure.
The treatment induced HOA(s) are more limited with the benefit of iris guided compensation after PRK .
Because of the flap and change of biophysical properties of the cornea (healing phenomena), the Lasik procedures induce more aberrations.
Compensating ocular misalignments during WG refractive surgery reduces the residual astigmatism,and optimises the treatment of higher-order aberrations in myopic astigmatic patients.