Effect of Larger Ablation Zone and Transition Zone on Corneal Optical Aberrations After Photorefractive Keratectomy

Endl, Michael; Martínez, Carlos; Klyce, Stephen D.; McDonald, Marguerite B.; Coorpender, Steven J; Applegate, Raymond A.; Howland, Howard C.

doi:10.1001/archopht.119.8.1159

Cited by 98 publications

(48 citation statements)

References 13 publications

(18 reference statements)

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“…These post-LASIK trends are consistent with previously mentioned studies documenting that conventional PRK and LASIK procedures cause an increase in higher order aberrations. [5][6][7][8][9][10] Total rms wavefront error changed negligibly with the creation of the microkeratome flap, however, if the average preoperative total rms value of 3.55 Ϯ 2.159 m is compared with the average 2-month postoperative flap cut value of 3.44 Ϯ 2.421 m in the study group (Figure 1). Clinically, patients confirmed this observation by noting that they were able to see well with the same spectacle correction they had used preoperatively and that their manifest refractions postflap cut were similar.…”

Section: This Study Noted That There Was a Large Reductionmentioning

confidence: 99%

“…[1][2][3][4] It has been well established that conventional photorefractive keratectomy (PRK) and LASIK procedures induce higher order aberrations, including increased amounts of spherical aberration, despite their accurate correction of spherocylindrical errors. [5][6][7][8][9][10] To date, little evidence has been presented to determine the origins of these induced higher order aberrations. Consequently, not much is known about the importance or relative contribution of the two separate effects of creating a microkeratome flap and performing a subsequent laser ablation on the overall optical quality of an eye receiving a LASIK treatment.…”

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confidence: 99%

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Separate effects of the microkeratome incision and laser ablation on the eye’s wave aberration

Porter¹,

MacRae

Yoon

et al. 2003

American Journal of Ophthalmology

134

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• PURPOSE: To study the optical changes induced by the microkeratome cut, the subsequent laser ablation, and the biomechanical healing response of the cornea in normal laser in situ keratomileusis (LASIK) eyes.• DESIGN: Prospective randomized clinical trial.• METHODS: A Hansatome microkeratome was used to cut a corneal flap in one eye (study eye) of 17 normal myopic patients and a subsequent laser ablation was performed 2 months after this initial microkeratome incision. Control eyes received conventional LASIK treatments at the latter time point. The wave aberration of both the study and contralateral control eyes were measured over a 6-mm pupil with a Shack-Hartmann wavefront sensor for all preoperative, postflap cut, and postablation visits.• RESULTS: The eye's higher order aberrations had a small, but significant increase (P ‫؍‬ .03) of approximately 30% 2 months after cutting a flap. No systematic changes were observed in nearly all Zernike coefficients from their preoperative levels at 2 months postflap cut. A significant difference between the study and control eyes was observed for one trefoil mode, Z 3 3 (P ‫؍‬ .04).• CONCLUSIONS: There was a wide variation in the response of individual Zernike modes across patients after cutting a flap. The majority of spherical aberration induced by the LASIK procedure seems to be due to the laser ablation and not the microkeratome cut. In addition, the total and higher order root mean square of wavefront errors were nearly identical for both the study and control eyes 3-months after the laser ablation, indicating that a procedure in which the incision and the ablation are separated in time to better control aberrations does not compromise the outcome of a conventional LASIK treatment. ( have been encouraging, further refinements of wavefront-guided laser in situ keratomileusis (LASIK) procedures are needed to obtain an aberration-free ablative correction. 1-4 It has been well established that conventional photorefractive keratectomy (PRK) and LASIK procedures induce higher order aberrations, including increased amounts of spherical aberration, despite their accurate correction of spherocylindrical errors. [5][6][7][8][9][10] To date, little evidence has been presented to determine the origins of these induced higher order aberrations. Consequently, not much is known about the importance or relative contribution of the two separate effects of creating a microkeratome flap and performing a subsequent laser ablation on the overall optical quality of an eye receiving a LASIK treatment. Developing a firm understanding of the aberrations induced by these two processes is crucial for achieving an optimal, customized correction of the eye's higher order aberrations with laser refractive surgery.Studies have been conducted to investigate structural changes in corneal shape due to the laser ablation in refractive surgery procedures. Howland and coworkers 11 found that changes made in the midperipheral and peripheral cornea could create biomechanical changes in the central corn...

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Section: This Study Noted That There Was a Large Reductionmentioning

confidence: 99%

mentioning

confidence: 99%

Separate effects of the microkeratome incision and laser ablation on the eye’s wave aberration

Porter¹,

MacRae

Yoon

et al. 2003

American Journal of Ophthalmology

134

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“…Many patients with higher refractive errors are thus precluded from undergoing LASIK. Use of a small optical zone conserves corneal tissue but has been associated with increased postoperative higher order aberrations and poor quality vision outcomes [7][8][9][10] . The tissue-sparing algorithm such as that provided by Bausch & Lomb Zyoptix system (Surrey, UK) permits removal of less corneal tissue than conventional treatments.…”

Section: Introductionmentioning

confidence: 99%

Results of a 1-Year Comparative Study of Zyoptix Tissue-Sparing and Conventional Planoscan LASIK Treatments

Kirwan

O’Keefe

2009

Ophthalmologica

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“…In addition, the haze may be confined to the wound edge, and the central cornea may remain relatively clear and provide good vision. Endl et al revealed that corneal optical aberrations after photorefractive keratectomy with a larger ablation zone and a transition zone were less pronounced than those associated without transition zone [16]. In fact, the exact size, shape and the profile of transition zone have profound impacts on the residual optical aberrations and postoperative visual functions.…”

Section: Discussionmentioning

confidence: 99%

The influence of the aspheric profiles for transition zone on optical performance of human eye after conventional ablation

Fang

2014

JEOS:RP

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The analysis in the impact of transition zone on the optical performance of human eye after laser refractive surgery is important for improving visual correction technology. By designing the ablation profiles of aspheric transition zone and creating the ablation profile for conventional refractive surgery in optical zone, the influence of aspheric transition zone on residual aberrations was studied. The results indicated that the ablation profiles of transition zone had a significant influence on the residual wavefront aberrations. For a hyperopia correction, the profile #9 shows a larger induced coma and spherical aberration when the translation of the centre of pupil remains constant. However, for a myopia astigmatism correction, the induced coma and spherical aberration in profile #1 shows relatively larger RMS values than those in other profiles. Therefore, the residual higher order aberrations may be decreased by optimizing ablation profiles of transition zone, but they cannot be eliminated. In order to achieve the best visual performance, the design of ablation pattern of transition zone played a crucial role.

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Effect of Larger Ablation Zone and Transition Zone on Corneal Optical Aberrations After Photorefractive Keratectomy

Cited by 98 publications

References 13 publications

Separate effects of the microkeratome incision and laser ablation on the eye’s wave aberration

Separate effects of the microkeratome incision and laser ablation on the eye’s wave aberration

Results of a 1-Year Comparative Study of Zyoptix Tissue-Sparing and Conventional Planoscan LASIK Treatments

The influence of the aspheric profiles for transition zone on optical performance of human eye after conventional ablation

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