Changes in corneal asphericity after laser in situ keratomileusis

Anera, Rosario G.; Jiménez, José María López; Barco, Luis Jiménez del; Bermúdez, Javier; Hita, E.

doi:10.1016/s0886-3350(02)01895-3

Cited by 101 publications

(68 citation statements)

References 14 publications

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“…The conic constants show the typical well-known trend in LASIK surgery. 13,24 Normal corneas have negative Q values: in this case −0.36 and −0.39, which are close to average values. 2 However, the sign becomes positive after LASIK surgery, which is patent even for the monozone analysis ͑+0.41, + 0.37͒.…”

Section: One Examplesupporting

confidence: 65%

Multizone model for postsurgical corneas: analysis of standard and custom LASIK outcomes

González¹,

Hernández-Matamoros²,

Navarro

2008

J. Biomed. Opt.

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Abstract. A multizone model for postsurgical corneal topography is presented and applied to a comparative analysis of the outcome of standard and customized myopic LASIK. The different zones are segmented automatically by a clustering algorithm. The algorithm uses a set of three local descriptors, which correspond to normalized physical magnitudes computed for each point of the corneal topography map: Gauss curvature, root-mean-square ͑RMS͒ fit error to an ellipsoid surface model, and distance to the center of the topographic map. Both presurgical and post-LASIK corneal topographies of 31 eyes were analyzed using monozone and multizone models. The patients were classified into three groups according to the different LASIK treatments applied: Allegretto, Zyoptix, and PlanoScan. For post-LASIK corneas, the multizone model provided a lower fit error, an average of 1.2± 0.4 m versus 2.4± 0.7 m ͑monozone͒. The comparative analysis of the three different LASIK treatments showed no improvement of custom over standard treatments. The outcomes of Zyoptix and PlanoScan were basically equivalent and consistent with previous findings: The higher-order aberration ͑HOA͒ increased by a factor of two. The increase in HOA was higher, by a factor of three, after the Allegretto treatment. The mutizone model shows a higherfidelity representation and permits a deeper understanding of the postsurgical cornea.

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Section: One Examplesupporting

confidence: 65%

Multizone model for postsurgical corneas: analysis of standard and custom LASIK outcomes

González¹,

Hernández-Matamoros²,

Navarro

2008

J. Biomed. Opt.

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“…En la mayoría de los casos, los resultados evaluados de la asfericidad corneal mostraron que después de la cirugía refractiva el cambio de la córnea anterior presentó valores de córneas que pasaban de prolatas a oblatas (20,21). Como lo mencionan Marcos y colaboradores (22), la media preoperatoria de asfericidad corneal fue negativa (-0,14 ± 0,14) y aumentó a los valores positivos después de LASIK (1,1 ± 1,3).…”

Section: Discussionunclassified

Variación de la asfericidad corneal en pacientes miopes sometidos a cirugía refractiva LASIK (Laser-Assisted in Situ Keratomileusis) o LASEK (Laser-Assisted Subepithelial Keratomileusis)

Rivera¹,

Mayorga²

2016

Cienc. Tecnol. Salud Vis. Ocul.

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Variación de la asfericidad corneal en pacientes miopes sometidos a cirugía refractiva LASIK (Laser-Assisted in Situ Keratomileusis) o LASEK (Laser-Assisted Subepithelial Keratomileusis)Variation in corneal asphericity in myopic patients undergoing refractive LASIK (laser-assisted in-situ keratomileusis) or LASEK (laser-assisted subepithelial keratomileusis) surgery RESUMEn Objetivo: analizar, por medio de una revisión sistemática de la literatura, la variación de la asfericidad corneal en pacientes miopes corregidos con cirugía LASIK (Laser-Assisted in Situ Keratomileusis) o LASEK (Laser-Assisted Subepithelial Keratomileusis). Métodología: se realizó una búsqueda de estudios primarios en las bases de datos PubMed, Scopus y Science Direct, a través del software Vantage Point; se recolectaron 229 publicaciones, de las cuales se seleccionaron diecinueve que cumplían con los criterios de inclusión. La calidad de los diecinueve artículos se evaluó mediante la plataforma FLC Web 2.0 para fichas de lectura crítica, con base en la declaración STROBE. La búsqueda se ejecutó con palabras clave como: corneal asphericity, corneal shape factor, Q-value, LASIK (Laser-Assisted in Situ Keratomileusis), LASEK (Laser-Assisted Subepithelial Keratomileusis), refractive surgery. Resultados: dieciocho de los artículos evaluados presentaron calidad media y uno, baja. Los artículos analizados coinciden en que se presentan cambios en la asfericidad corneal después de la cirugía refractiva, al pasar de prolatas a oblatas, que afectan notablemente los resultados visuales. Conclusiones: el análisis de los diecinueve artículos demostró el cambio en la asfericidad de prolata a oblata y reveló los factores que influyen en estas variaciones, al igual que la necesidad de mejorar las técnicas quirúrgicas y las falencias de las investigaciones, dado que el 95 % de los artículos analizados presentaron una calidad media. IntroduccIónLa asfericidad corneal es uno de los factores que se modifican por procedimientos como LASIK (Laser-Assisted in Situ Keratomileusis) o LASEK (Laser-Assisted Subepithelial Keratomileusis), como métodos de corrección de ametropías. El valor Q mide el índice de asfericidad corneal (Q = 0 en córneas esféricas, Q < 0 en córneas prolatas y Q > 0 en córneas oblatas). La córnea humana tiene una forma prolata (valor Q negativo promedio de -0,27). El valor Q se basa en una curvatura central de 3 a 4 mm de la córnea; este es un coeficiente que describe la tasa de cambio en la curvatura de la córnea desde su centro hasta la periferia, a través de valores de radio corneal (1-3). La forma normal de la córnea no es la de una esfera, sino la de una elipse prolata, que indica que su curvatura va aplanándose según nos alejamos del centro hacia la periferia. La cuantificación de ese aplanamiento se representa mediante el valor excentricidad (e), que en córneas normales es de 0,45 ± 0,10 (4). La excentricidad se puede definir como el alejamiento de la forma de una superficie asférica, respecto de la misma superficie circular (5); es una ...

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“…Before refractive surgery, the corneal anterior surface is prolate [12], which means the lowest of the radius of curvature is at the apex of the cornea. However, after refractive surgery, the corneal anterior surface is oblate [13,14], meaning that the highest radius of curvature is at the apex of the cornea. The difference in the radius of curvature between intrinsic data and Pentacam HR data is vital as it leads to a difference in the corneal power changes.…”

Section: Discussionmentioning

confidence: 99%

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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Changes in corneal asphericity after laser in situ keratomileusis

Cited by 101 publications

References 14 publications

Multizone model for postsurgical corneas: analysis of standard and custom LASIK outcomes

Multizone model for postsurgical corneas: analysis of standard and custom LASIK outcomes

Variación de la asfericidad corneal en pacientes miopes sometidos a cirugía refractiva LASIK (Laser-Assisted in Situ Keratomileusis) o LASEK (Laser-Assisted Subepithelial Keratomileusis)

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

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