Minor Influence of Myopic Laser In Situ Keratomileusis on the Posterior Corneal Surface

Pérez‐Escudero, Alfonso; Dorronsoro, Carlos; Sawides, Lucie; Remón, Laura; Merayo‐Lloves, Jesús; Marcos, Susana

doi:10.1167/iovs.09-3411

Cited by 44 publications

(43 citation statements)

References 36 publications

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“…The commercial software included correction routines but only for the cornea. 29 In addition, the edge detection routines of the software fail to detect the edges of some IOLs with scattering properties very different from the crystalline lens (that is, acrylic). Therefore, the algorithms for the estimation of tilt and decentration of the intraocular lenses were applied directly to the raw images.…”

Section: Tilt and Decentration From Scheimpflug Imagesmentioning

confidence: 99%

Intraocular lens alignment from Purkinje and Scheimpflug imaging

Rosales

Castro

Jiménez-Alfaro

et al. 2010

Clinical and Experimental Optometry

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The improved designs of intraocular lenses (IOLs) implanted during cataract surgery demand understanding of the possible effects of lens misalignment on optical performance. In this review, we describe the implementation, set-up and validation of two methods to measure in vivo tilt and decentration of IOLs, one based on Purkinje imaging and the other on Scheimpflug imaging. The Purkinje system images the reflections of an oblique collimated light source on the anterior cornea and anterior and posterior IOL surfaces and relies on the well supported assumption of the linearity of the Purkinje images with respect to IOL tilt and decentration. Scheimpflug imaging requires geometrical distortion correction and image processing techniques to retrieve the pupillary axis, IOL axis and pupil centre from the three-dimensional anterior segment image of the eye. Validation of the techniques using a physical eye model indicates that IOL tilt is estimated within an accuracy of 0.261 degree and decentration within 0.161 mm. Measurements on patients implanted with aspheric IOLs indicate that IOL tilt and decentration tend to be mirror symmetric between left and right eyes. The average tilt was 1.54 degrees and the average decentration was 0.21 mm. Simulated aberration patterns using custom models of the patients eyes, built using anatomical data of the anterior cornea and foveal position, the IOL geometry and the measured IOL tilt and decentration predict the experimental wave aberrations measured using laser ray tracing aberrometry on the same eyes. This reveals a relatively minor contribution of IOL tilt and decentration on the higher-order aberrations of the normal pseudophakic eye.

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Section: Tilt and Decentration From Scheimpflug Imagesmentioning

confidence: 99%

Intraocular lens alignment from Purkinje and Scheimpflug imaging

Rosales

Castro

Jiménez-Alfaro

et al. 2010

Clinical and Experimental Optometry

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“…Our results are similar to those reported in recent studies using the Pentacam system. P erez-Escudero et al 13 detected steepening of the posterior corneal surface and a shift toward prolateness after the first day that disappeared after 1 week. Zhang and Wang 12 also found time-dependent changes in the posterior corneal surface by measuring the posterior elevation changes in response to myopic LASIK and interpreted that as forward protrusion 1 month after surgery that returned to the original level after 6 months.…”

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confidence: 97%

“…11 To our knowledge, this study is the first to evaluate changes in the posterior corneal surface in response to myopic LASIK with a rotating dual Scheimpflug imaging-based device, although there have been studies using a single Scheimpflug device. 12,13 Our first objective was to analyze early changes in the posterior corneal curvature 1 day, 1 week, and 1 and 3 months postoperatively for different amounts of tissue ablated and to follow the progression over the various time points. Our second objective was to evaluate the relevance of the attempted percentage of anterior tissue severed during surgery as a new, useful variable for screening for the risk for post-LASIK ectasia in patients before refractive surgery.…”

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confidence: 99%

“…POSTERIOR CORNEAL RESPONSE TO MYOPIC LASIK reliability of the posterior corneal surface assessment with actual topographers remains controversial, P erez-Escudero et al 13 recently used a hybrid porcine plastic eye model to validate the accuracy of the posterior corneal surface geometry measurement with a Scheimpflug imaging-based device (Pentacam, Oculus, GmbH). Scheimpflug technology uses an algorithm to correct for optical distortions and compensate for the camera-viewing angle in the images by taking into account the Snell law of refraction at the anterior surface.…”

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confidence: 99%

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Response of the posterior corneal surface to myopic laser in situ keratomileusis with different ablation depths

Smadja¹,

Santhiago²,

Mello³

et al. 2012

Journal of Cataract and Refractive Surgery

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“…Increasing numbers of recent studies [15][16][17][18] have shown that the posterior corneal surface was barely changed by refractive surgery; therefore, we speculate that the anterior corneal surface alone is sufficient to reflect the surgically induced refractive changes. Therefore, only the radius change in the curvature of the anterior corneal surface was considered in the present study.…”

Section: Discussionmentioning

confidence: 82%

A new method to accurately assess post-laser-surgery refractive changes with the intrinsic corneal power changes

Liu

Wang

2015

BME

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Abstract.To evaluate the ability of assessing the refractive change induced by myopic laser surgery using the intrinsic data, obtained from a reference intrinsic to the cornea. Twenty-nine eyes with laser in situ keratomileusis for myopia were included in the study. Statistical analyses were performed to determine the relationship between refractive changes and two kinds of corneal power: KIP_value (obtained by keratometric index of 1.3375 and radius of curvature) and RIP_value (obtained by real corneal refraction index of 1.376 and radius of curvature). The comparisons were made between results given by intrinsic data and Pentacam HR. Preoperatively, the intrinsic radii of curvature are significantly less (p<<0.001) than those from Pentacam HR, while the intrinsic radii of curvature are significantly larger (p <<0.001) after surgery. The corneal power changes given by Pentacam HR always underestimate the refractive changes. However, the intrinsic data generally reduce the discrepancies between the corneal power and the refractive changes. The intrinsic KIP_value correlated best with the refractive changes at the corneal plane (p<<0.001) with a prediction error as low as 1.51%. The use of intrinsic data of the cornea can possibly provide an accurate estimation of surgically induced refractive changes.

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Minor Influence of Myopic Laser In Situ Keratomileusis on the Posterior Corneal Surface

Abstract: The Pentacam Scheimpflug system can be used reliably to assess changes in the posterior corneal radius of curvature after LASIK. There is no evidence of surgically induced changes in the corneal posterior surface beyond 1 week after surgery.

Cited by 44 publications

References 36 publications

Intraocular lens alignment from Purkinje and Scheimpflug imaging

Intraocular lens alignment from Purkinje and Scheimpflug imaging

Response of the posterior corneal surface to myopic laser in situ keratomileusis with different ablation depths

A new method to accurately assess post-laser-surgery refractive changes with the intrinsic corneal power changes

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