Effect of 3 excimer laser ablation frequencies (200 Hz, 500 Hz, 1000 Hz) on the cornea using a 1000 Hz scanning-spot excimer laser

. Purpose: To evaluate the safety, efficacy, predictability and stability of laser in situ keratomileusis (LASIK) with a 1000‐Hz scanning spot excimer laser (Concept System 1000; WaveLight GmbH, Erlangen, Germany). Methods: LASIK was performed on twenty eyes with myopia or myopic astigmatism (mean spherical equivalent refraction: −3.97 ± 1.72 dioptres (D); mean cylinder: −0.84 ± 0.77 D) using a microkeratome for flap creation and the Concept System 1000 for photoablation. Patients were examined preoperatively as well as 1, 3 and 6 months after the treatment. Manifest sphere and cylinder, uncorrected (UCDVA) and best corrected (BCDVA) distance visual acuity, corneal topography and pachymetry were analysed. Results: We observed no adverse events that might have been associated with the use of a repetition rate of 1000 Hz. All eyes maintained or had improved BCDVA at 6 months after treatment when compared to preoperative values. Six months after LASIK, UCDVA was 20/20 or better in 85% and 20/25 or better in 100% of the eyes. The spherical equivalent refraction was within ±0.50 D in 95% of the eyes at 6 months after surgery. The refraction stayed stable over time; 95% of the eyes changed <0.5 D postoperatively. Conclusion: LASIK with the prototype 1000‐Hz excimer laser was safe, efficient and predictable. The postoperative refraction was stable over time. There were no specific clinical side‐effects that might be associated with the use of such a high repetition rate.

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“…Previously, our study group evaluated the Concept System 1000 in a laboratory setting (Khoramnia et al. 2010).…”

Section: Discussionmentioning

confidence: 99%

Safety, efficacy, predictability and stability of laser in situ keratomileusis (LASIK) with a 1000‐Hz scanning spot excimer laser

Khoramnia

Salgado

Wuellner³

et al. 2011

Acta Ophthalmologica

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“…Nach Angaben des Herstellers erreicht das Lasersystem MEL90 bei einer Ablationsfrequenz von 500 Hz eine intraoperative Abtragsgeschwindigkeit von bis zu 1,3 Sekunden pro Dioptrie. Über eine ähnliche Geschwindigkeit wurde bei einem Lasersystem berichtet, das mit einer Repetitionsrate von 1000 Hz arbeitet [24]. Eine mögliche Erklärung für die vergleichbare Abtragsgeschwindigkeit trotz geringerer Ablationsfrequenz ist, dass beim System MEL90 der Durchmesser des Laserstrahls bei der 500-Hz-Einstellung im Vergleich zur 250-Hz-Einstellung trotz doppelter Pulsfrequenz nicht reduziert wird.…”

Section: Diskussionunclassified

Einfluss unterschiedlicher Ablationsfrequenzen auf die klinischen Ergebnisse bei photorefraktiver Keratektomie unter Verwendung derselben Excimer-Laser-Plattform: Ein kontralateraler Vergleich

Tandogan

Khoramnia

Gye

et al. 2016

Klin Monatsbl Augenheilkd

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The objective of this study was to evaluate postoperative clinical outcomes of photorefractive keratectomy (PRK) using different ablation frequencies. In this prospective, contralateral eye study, 56 eyes of 28 patients with myopia or myopic astigmatism were included. PRK was performed using the MEL90 excimer laser system (Carl Zeiss Meditec, Germany). One eye of each patient was treated with a repetition rate of 250 Hz, while the other one was treated with a repetition rate of 500 Hz. The treatment pattern in the 250 Hz and 500 Hz group only differed in terms of ablation frequency; there was no difference in laser pulse energy, spot size or ablation profile. Postoperative follow-ups were at 3 and 7 days and 1, 3 and 6 months. The following parameters were assessed: Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), higher-order aberrations (HOAs), corneal re-epithelisation time and corneal haze. Ablation depth was proportional to laser pulse counts at both frequencies. At 6 months, 100.0% of the eyes in the 250 Hz group and 96.4% in the 500 Hz group had a UDVA of 0.00 logMAR or better; 100% of the eyes in both groups were within ± 1.00D of the attempted correction. All eyes had a postoperative CDVA of 0.00 logMAR or better. There was no difference between the groups in postoperative HOAs, corneal re-epithelisation time or corneal haze. Photorefractive keratectomy with a repetition rate of 250 Hz and 500 Hz showed comparable efficacy, safety and predictability in the correction of myopia. There were no significant complications due to the high repetition rate, such as postsurgical corneal haze.

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“…Three local frequency controls (10,40, and 1000 Hz) were tested with a system repetition rate of 1050 Hz. The change in peak corneal temperature progressed logarithmically with respect to the increasing local frequencies (Fig.…”

Section: Local Frequencymentioning

confidence: 99%

“…Other studies, however, also undermine the impact of ablation frequency regarding their clinical side effects. Khoramnia et al 40 evaluated the effect of three excimer laser ablation frequencies (200, 500, and 1000 Hz) on the cornea using a 1000-Hz scanning-spot excimer laser and found no specific side effects associated with the high-repetition rates based on structural and ultrastructural evaluation of corneas. The ablation quality was comparable in the three frequency groups with the fastest treatment times with 1000 Hz.…”

Section: Effect Of Epitheliummentioning

confidence: 99%

Analysis of the change in peak corneal temperature during excimer laser ablation in porcine eyes

Arba-Mosquera

Verma

2015

J. Biomed. Opt.

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The objective is to characterize the impact of different ablation parameters on the thermal load during corneal refractive surgery by means of excimer laser ablation on porcine eyes. One hundred eleven ablations were performed in 105 porcine eyes. Each ablation was recorded using infrared thermography and analyzed mainly based on the two tested local frequencies (40 Hz, clinical local frequency; 1000 Hz, no local frequency). The change in peak corneal temperature was analyzed with respect to varying ablation parameters [local frequency, system repetition rate, pulse energy, optical zone (OZ) size, and refractive correction]. Transepithelial ablations were also compared to intrastromal ablations. The average of the baseline temperature across all eyes was 20.5°C±1.1 (17.7°C to 22.2°C). Average of the change in peak corneal temperature for all clinical local frequency ablations was 5.8°C±0.8 (p=3.3E-53 to baseline), whereas the average was 9.0°C±1.5 for all no local frequency ablations (p=1.8E-35 to baseline, 1.6E-16 to clinical local frequency ablations). A logarithmic relationship was observed between the changes in peak corneal temperature with increasing local frequency. For clinical local frequency, change in peak corneal temperature was comparatively flat (r 2 =0.68 with a range of 1.5°C) with increasing system repetition rate and increased linearly with increasing OZ size (r 2 =0.95 with a range of 2.4°C). Local frequency controls help maintain safe corneal temperature increase during excimer laser ablations. Transepithelial ablations induce higher thermal load compared to intrastromal ablations, indicating a need for stronger thermal controls in transepithelial refractive procedures.

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Effect of 3 excimer laser ablation frequencies (200 Hz, 500 Hz, 1000 Hz) on the cornea using a 1000 Hz scanning-spot excimer laser

Abstract: No author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.

Cited by 12 publications

References 27 publications

Safety, efficacy, predictability and stability of laser in situ keratomileusis (LASIK) with a 1000‐Hz scanning spot excimer laser

Safety, efficacy, predictability and stability of laser in situ keratomileusis (LASIK) with a 1000‐Hz scanning spot excimer laser

Einfluss unterschiedlicher Ablationsfrequenzen auf die klinischen Ergebnisse bei photorefraktiver Keratektomie unter Verwendung derselben Excimer-Laser-Plattform: Ein kontralateraler Vergleich

Analysis of the change in peak corneal temperature during excimer laser ablation in porcine eyes

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