Ablation Rate of Human Corneal Epithelium and Bowman's Layer With the Excimer Laser (193 nm)

Seiler, Theo; Kriegerowski, Martin; Schnoy, N.; Bende, Thomas

doi:10.3928/1081-597x-19900301-06

Cited by 83 publications

(10 citation statements)

References 5 publications

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“…The cornea is the most anterior optical component of the eye, which accounts for two thirds of its total refractive power of about 60 diopters ͑D͒. For surgical correction of refractive errors of the eye, the use of lasers to reshape the corneal surface ͓photorefractive keratectomy ͑PRK͔͒ by controlled and precise corneal stromal tissue removal 1,2 has been a major advancement in the field of refractive surgery. In PRK, an excimer laser operating at 193 nm is used to change the corneal curvature in an optical zone of 5-7 mm diameter for up to 10 diopters of refractive power ͑equivalent to about 100 m of ablation depth in the corneal center͒ with a precision that is unattainable with conventional surgery.…”

Section: Introductionmentioning

confidence: 99%

“…The suboptimum results obtained in 10%-30% of the patients are usually at-tributed to variations in epithelial and stromal wound healing including scar formation and, possibly, to small intersession changes of the ablation rate over a 1 day period. 2 The capacity to ablate stromal layers in the micron range has called for methods to measure the corneal thickness with high precision. Commonly used clinical methods for obtaining corneal thickness measurements on patients are ultrasound, 3 optical slit-lamp pachymetry, 4 and specular microscopy.…”

Section: Introductionmentioning

confidence: 99%

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Real-Time Pachymetry During Photorefractive Keratectomy Using Optical Low-Coherence Reflectometry

Böhnke

Widmer

Wälti³

2001

J. Biomed. Opt.

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Optical low-coherence reflectometry (OLCR) was used as a noncontact method to measure the central corneal thickness of three patients intraoperatively during photorefractive keratectomy. Continuous on-line measurements were performed on the intact cornea immediately before the beginning of surgery, after the removal of the corneal epithelium, during laser tissue photoablation, and for 3 min after the ablation process. Corneal thinning due to evaporation was studied on a separate patient with the OLCR instrument, and it was found to be -0.14 microm/s during the first 5 min after epithelium removal. This baseline corneal thinning rate was used as a fit parameter to calculate actual from measured ablation depths. The measurements showed a maximum difference of +/-10 microm between planned ablations (34-92 microm) and measured ablation depths.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Real-Time Pachymetry During Photorefractive Keratectomy Using Optical Low-Coherence Reflectometry

Böhnke

Widmer

Wälti³

2001

J. Biomed. Opt.

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“…Transepithelial approaches modify the cornea through the epithelium. The ablation rate is higher in the epithelium than in the stroma, and it increases with stromal depth [12]. The difficulty lies in performing corrections with TransPRK for low-myopia corrections, when the epithelial thickness cannot be measured, because if the epithelium is thicker than the standard given by the software (55 microns) at the center, the OZ may be smaller than the precalculated value, which can result in undercorrection [3].…”

Section: Discussionmentioning

confidence: 99%

Customized versus Standard Epithelium Profiles in Transepithelial Photorefractive Keratectomy

Ortueta¹,

Rüden²,

Arba-Mosquera

2021

Optics

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Transepithelial photorefractive keratectomy (TransPRK) is an established surface ablation technique used to correct refractive errors. Using anterior segment optical coherence (AS-OCT), it is now possible to measure the epithelium thickness and input these data into the laser platform. In this study, we explore whether better results were obtained in this way. To this end, we retrospectively analyze the results from a low-myopia group treated with a customized epithelium thickness, as measured using AS-OCT, and compare them with the results from a group treated with an optimized standard epithelium thickness. The customized epithelium profile group contains more eyes with vision better than 20/20, and more eyes in this group gain one line of corrected distance visual acuity (CDVA). In conclusion, with the customized epithelium thickness, we obtain superior results using TransPRK in low-myopia corrections.

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“…The ablation rate is higher in epithelium than in stroma, and it increases with the stromal depth. This ablation rate is also compensated by the laser system [33], and if we change the epithelium thickness to 5 microns deeper, it will, theoretically, ablate stroma where it should ablate epithelium. As this occurs on the entire surface, the final curvature of the surface will be the same.…”

Section: Surgical Techniquementioning

confidence: 99%

Comparison of Refractive and Visual Outcomes after Transepithelial Photorefractive Keratectomy (TransPRK) in Low versus Moderate Myopia

Ortueta¹,

Rüden²,

Arba-Mosquera

2021

Photonics

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Is it possible to obtain good results in myopia of 2 or fewer diopters (D) with transepithelial photorefractive keratectomy (TransPRK) changing the optical zone and epithelium thickness? We retrospectively analyzed two groups of 296 eyes with a minimum follow-up of 4 months. Group A had 2 or less D, treated with an optical zone (OZ) 0.2 mm bigger than recommended, and a central epithelium thickness of 60 microns, and group B had 2 D to 5 D, with the recommended optical zone, and a 55-micron epithelium ablation at the center. The outcomes were not different between the two myopic ranges; the postop uncorrected distance visual acuity was 20/20 ± 4 in both groups (p = 0.2), which was −0.3 ± 0.8 lines worse than the preoperative corrected distance visual acuity in both groups (p = 0.5). The safety of the treatments resulted in a change of 0.0 ± 0.7 lines in the low myopia group, versus a gain of +0.1 ± 0.8 lines in the moderate myopia group (p = 0.1). The deviation from the intended target was −0.04 ± 0.33 D in the low myopia group and +0.07 ± 0.32 D in the moderate myopia group (p < 0.0001); the postoperative spherical equivalent was 0.00 ± 0.33 D in the low myopia group and +0.10 ± 0.31 D in the moderate myopia group (p < 0.0001). The postop refractive astigmatism was 0.32 ± 0.16 D in both groups (p = 0.5). In conclusion, the refractive and visual outcomes after TransPRK are comparable in low myopia changing the optical zone and epithelium thickness versus moderate myopia with standard optical zone and epithelium thickness.

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Ablation Rate of Human Corneal Epithelium and Bowman's Layer With the Excimer Laser (193 nm)

Cited by 83 publications

References 5 publications

Real-Time Pachymetry During Photorefractive Keratectomy Using Optical Low-Coherence Reflectometry

Real-Time Pachymetry During Photorefractive Keratectomy Using Optical Low-Coherence Reflectometry

Customized versus Standard Epithelium Profiles in Transepithelial Photorefractive Keratectomy

Comparison of Refractive and Visual Outcomes after Transepithelial Photorefractive Keratectomy (TransPRK) in Low versus Moderate Myopia

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