Influence of the Compensation for Influence of the Compensation for Pupil Decentration and Ocular Pupil Decentration and Ocular

Rotation on the Residual Ocular Rotation on the Residual Ocular Aberrations in Myopic Astigmatic Aberrations in Myopic Astigmatic Patients After Wavefront Guided Patients After Wavefront Guided

Refractive SurgeryRefractive SurgeryMarotte D, Denoyer A, Pisella PJ.

University François Rabelais

Hospital Bretonneau, Tours, France

No Financial interestNo Financial interest

Does Does the the iris recognition reduce the iris recognition reduce the postoperative cylindrical error and treatment postoperative cylindrical error and treatment

induced high order aberrations in induced high order aberrations in the the astigmatic patients astigmatic patients undergoing W-G refractive undergoing W-G refractive

surgery surgery ??

Courtesy of D.Marotte

Alpins methodAlpins method

This method described by Dr Noel Alpins is a vector analysis tool which provides the ability to calculateand 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

Study design

71 myopic eyes with astigmatism > |1 D| underwent WG photoablation ( Excimer Star S4Excimer Star S4-IR -IR andand CustomVue, CustomVue, Visx, USAVisx, 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

Prospective comparative study (University Hospital of Tours, France)

Preoperative featuresWith 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 None

Cylindrical error (6 months)

§: Statistical difference in the achieved/intented vector magnitude ratio:

84.36±14,64 % vs 51±29.6 %, p<0.000001

§

Accuracy of Cylindrical Treatment using Alpins method

§§

High statistical difference in the Magnitude and Axe of Error in the « All » group (p<0.0001)

§ § §

Magnitude of Error (D) With IGC Without IGC p

ALL 0,16 0,39 p<0.0005PRK 0,18 0,49 p<0.005

LASIK 0,14 0,27 p=0,063

Axe of Error (D)With IGC Without IGC p

ALL 2,83 10,07 p<0.00001PRK 2,48 10,52 p=0.002

LASIK 3,20 13,28 p<0.00001

§:p<0.05§:p<0.05

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)

§ § §

Conclusions

1. The accuracy of cylindrical treatment by compensating peroperative ocular torsions, is independent from the surgical procedure.

2. The treatment induced HOA(s) are more limited with the benefit of iris guided compensation after PRK .

3. 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 Compensating ocular misalignments during WG refractive surgery reduces the residual astigmatism,and optimises the treatment of reduces the residual astigmatism,and optimises the treatment of

higher-order aberrations in myopic astigmatic patients.higher-order aberrations in myopic astigmatic patients.