Induced optical aberrations following formation of a laser in situ keratomileusis flap

Pallikaris, Ioannis G.; Kymionis, George D.; Panagopoulou, Sophia I; Siganos, Charalambos S.; Theodorakis, Michalis A; Pallikaris, Aristofanis I.

doi:10.1016/s0886-3350(02)01507-9

Cited by 178 publications

(107 citation statements)

References 13 publications

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“…For 5.0 mm pupils, PRK induces more coma and third-order aberrations, although the low pr 2 (less than 0.01) indicates that the percentage of unexplained variance that can be attributed to surgical method (PRK versus LASIK) was very low. Flap production in LASIK induces higher-order aberrations, including coma and spherical aberrations, 7,8,27,28 which were consistent in part with our findings. Also, most of the patients in the present study were highly myopic with mean spherical equivalent of -7.32 D. Even so, post-operative higherorder aberrations in patients receiving PRK or LASIK differed little.…”

Section: Discussionsupporting

confidence: 91%

“…For example, some studies showed that all laser refractive surgery, including PRK and LASIK, will increase both higher-order aberrations of the corneal surface and the total wavefront aberrations even with a flying-spot excimer laser. [2][3][4][5][6] Furthermore, flap creation during LASIK can induce aberrations 7,8 and some other studies have shown that LASIK induces more aberrations than PRK and laser epithelial keratomileusis (LASEK). 3,9,10 These studies focused on the cornea because it is the target for laser ablation and accounts for most induced higher-order aberrations.…”

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confidence: 99%

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Anterior corneal optical irregularity measured by higher‐order aberrations induced by a broad beam excimer laser

Hsieh

Wang

2012

Clinical and Experimental Optometry

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Background:The aim was to analyse anterior corneal optical irregularity in patients receiving photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with a conventional broad beam laser. Methods: Pre-and post-operative anterior corneal aberrations including Zernike coefficients and root mean squares of higher-order aberrations were measured and derived with a Placido-ring-based corneal topographer and wavefront software, respectively, from 768 right eyes of patients receiving either PRK or LASIK for myopia with a conventional broad beam excimer laser in National Taiwan University Hospital, Taipei, Taiwan. Multiple linear regression models selected by Mallows' Cp criteria were used to evaluate predictability of surgically induced aberrations and relevant factors. Results: Mean attempted spherical equivalent correction was -7.37 Ϯ 2.33 D (range: -16.5 to -1.95). Root mean squares of higher-order aberrations and variances of Zernike coefficients all increased significantly after surgery (p < 0.01). All post-operative higherorder aberrations increased with the amount of attempted myopic correction and secondary astigmatism increased with attempted cylindrical correction. LASIK surgery induced less coma and third-order aberrations but more fifth-and sixth-order aberrations than PRK, although squared partial correlation coefficients were low. Larger optic and transitional zones meant fewer higher-order aberrations after surgery. Younger patients tended to have more surgically induced aberrations in the 3.0 mm pupil zone. Conclusions: Anterior corneal optical irregularity increased tremendously after refractive surgery by conventional broad beam lasers and correlated with greater attempted myopic correction, younger age and a smaller treatment zone. The effect of corneal flaps on post-operative corneal irregularity differed trivially.

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Section: Discussionsupporting

confidence: 91%

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confidence: 99%

Anterior corneal optical irregularity measured by higher‐order aberrations induced by a broad beam excimer laser

Hsieh

Wang

2012

Clinical and Experimental Optometry

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“…2,3 Laser ablation methods also find widespread use in the micro-structuring and patterning of polymers and wide band gap materials like silicon and fused silica, in removal of biological (e.g. corneal) tissue, 4 and are now even being applied to surface cleaning of delicate artwork. 5 The realisation that laser ablation methods could provide a means of ejecting intact molecules -even large biomolecules -into the gas phase helped spawn novel analytical techniques like matrix assisted laser desorption/ionisation (MALDI) which has now come to be seen as essential in broad areas of the life sciences.…”

Section: Simon Henley Completed His Phd In the Physics Department Of mentioning

confidence: 99%

Pulsed laser ablation and deposition of thin films

et al. 2004

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Pulsed laser ablation is a simple, but versatile, experimental method that finds use as a means of patterning a very diverse range of materials, and in wide areas of thin film deposition and multi-layer research. Superficially, at least, the technique is conceptually simple also, but this apparent simplicity hides a wealth of fascinating, and still incompletely understood, chemical physics. This overview traces our current physico-chemical understanding of the evolution of material from target ablation through to the deposited film, addressing the initial laser-target interactions by which solid material enters the gas phase, the processing and propagation of material in the plume of ejected material, and the eventual accommodation of gas phase species onto the substrate that is to be coated. It is intended that this Review be of interest both to materials scientists interested in thin film growth, and to chemical physicists whose primary interest is with more fundamental aspects of the processes of pulsed laser ablation and deposition.

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“…Vertical coma decreased in the study group and was not significant when compared with the control group at 2 months after the flap cut and 3 months postablation. Pallikaris and coworkers 21 noted an increase in horizontal coma after using a microkeratome that created a nasal hinge, suggesting the position of the flap hinge may influence the type(s) of aberrations induced after the incision. An analogous finding of induced vertical coma was not found for our cohort of patients after creating a flap with a superiorly located hinge.…”

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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

135

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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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Induced optical aberrations following formation of a laser in situ keratomileusis flap

Abstract: Flap formation during LASIK can modify the eye's existing natural higher-order aberrations (especially spherical and coma-like aberrations along the axis of the flap's hinge), while visual acuity and refractive error remain unaffected.

Cited by 178 publications

References 13 publications

Anterior corneal optical irregularity measured by higher‐order aberrations induced by a broad beam excimer laser

Anterior corneal optical irregularity measured by higher‐order aberrations induced by a broad beam excimer laser

Pulsed laser ablation and deposition of thin films

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

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