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IRTC Eye Microsurgery State Enterprise named after S.N. Fyodorov, Moscow, Russia

COMBINATION OF HYPEROPIC AND MYOPIC ABLATION ALGORYTHMS FOR CORRECTION OF SPHERIC ABERRATION APPEARING DURING CORNEA ABLATION FOR MYOPIA CORRECTION. Kh.P.Takhchidi , O.A. Kostin 1 , A.V.Doga , S.V. Rebrikov, 1 , A.A. Stepanov 1 , A.I. Ovchinnikov 1.

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IRTC Eye Microsurgery State Enterprise named after S.N. Fyodorov, Moscow, Russia

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  1. COMBINATION OF HYPEROPIC AND MYOPIC ABLATION ALGORYTHMS FOR CORRECTION OF SPHERIC ABERRATION APPEARING DURING CORNEA ABLATION FOR MYOPIA CORRECTION Kh.P.Takhchidi, O.A. Kostin1, A.V.Doga, S.V. Rebrikov,1, A.A. Stepanov1 , A.I. Ovchinnikov1. IRTC Eye Microsurgery State Enterprise named after S.N. Fyodorov, Moscow, Russia Ekaterinburg Branch1

  2. J Refract Surg. 2000 Jul-Aug;16(4):407-13

  3. AIM • To develop the technology for correction of spheric aberration appearing during excimer laser cornea ablation for myopia correction • To compare refraction, visual acuity, and spheric aberration after wavefront-guidedand combined excimer laser surgery

  4. PATIENTS AND METHODS • Aberrometrywith 6 mm diameter - WASCA aberrometer (Carl Zeiss Meditec) • Keratotopography – ATLASTM 995 (Carl Zeiss Meditec) • Flap formation - HansatomeExcellusmicrokeratome (B&L) • Excimer laser ablation with 6 mm diameter - MEL-80 excimer laser (Carl Zeiss Meditec) Wavefront-guided ablation was performed with the use of CRS-Master (Carl Zeiss Meditec) Combined ablation was performed in 2 steps during one operation: • Myopic ablation with the depth corresponding to the degree of myopia increased by 2.0 D for mild myopia and by 2.5 D for moderate myopia. • Hyperopic ablation with the depth corresponding to +1.0 D for mild myopia and +1.5 D for moderate myopia.

  5. PATIENTS AND METHODS Group 2 Group 1 wavefront-guided LASIK combined LASIK • 20 patients (40 eyes) • 14 patients (20 eyes) • SE– 4,67 D ± 1,94D (range, -1,5D to – 7,63D) • SE– 3,93 D ± 1,05D (range, -2,75 D to –7,00D) • UCVA 0,05±0,02 • BCVA 1,0±0,06 • Z (4,0) 0,08± 0,23 μm (Malacara notation) • RMS HO: 0,28 ± 0,21μm • UCVA0,05±0,02 • BCVA 1,00 • Z (4,0) 0,01 ± 0,19μm (Malacara notation) • RMSHO 0,24 ± 0,07μm Postoperative follow-up 6 months

  6. RESULTS REFRACTIVE EFFECT(6 months) Group 1 -wavefront-guidedLASIK Group 2 - combined LASIK a c h i e v e d p l a n n e d

  7. RESULTS REFRACTION CHANGES Group 1 -wavefront-guidedLASIK Group 2 - combined LASIK before 1 month 3 mos. 6 mos. before 1 month 3 mos. 6 mos.

  8. RESULTS VISUAL ACUITY CHANGES

  9. RESULTS HIGHER ORDER ABERRATIONS *p>0,05

  10. RESULTS WAVEFRONT-GUIDED LASIK OD COMBINED LASIK OS Numerical keratotopographic map 6 months after surgery. A significant increase of corneal refraction (marked with red oval) from cornea center (0 mm) to the periphery (6 mm) is seen in wavefront – guided LASIK group (∆ 0,94 D) while it is almost absent in combined LASIK group (∆ 0,17 D).

  11. RESULTS WAVEFRONT-GUIDED LASIK OD COMBINED LASIK OS The value of spheric aberration 6 months after surgery (red arrow indicates the numeric value of spheric aberration). A significant increase of negative spheric aberration in wavefront – guided group (Z(4,0) -0.674 µm, Malacara notation) compared to combined LASIK (Z(4,0) 0.000 µm, Malacara notation).

  12. CONCLUSIONS • During customized correction of higher order aberrations it is necessary to take into consideration not only preoperative wavefront aberration data, but also biomechanical changes of the cornea taking place during ablation • Combination of myopic and hyperopic ablation during correction of myopia is able to correct spheric aberration appearing due to ablation-induced biomechanical changes of the cornea

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