Clinical research of changes in posterior corneal elevation after small incision lenticule extraction / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM:To assess the changes of posterior corneal elevation after small incision lenticule extraction(SMILE). <p>METHODS:A retrospective study was conducted on 120 patients(240 eyes)who underwent SMILE surgery with myopia. All patients were examined with the Pentacam of preoperation and 1d, 1wk, 1, 3, 6 and 12mo postoperatively, respectively. We analyze the change of the posterior corneal elevation of the apex, and the change of mean posterior corneal elevation in the circle of 2mm, and 6mm diameter.<p>RESULTS:Comparison among the three groups showed that the differences of apex and 2mm circle at a different time and between the groups were statistically significant(apex: <i>F</i>_time=30.09, <i>P</i>_time<0.01; <i>F</i>_group=7.29, <i>P</i>_group<0.01; 2mm circle: <i>F</i>_time=24.72, <i>P</i>_time<0.01; <i>F</i>_group=7.44, <i>P</i>_group=0.01), and there was no statistically significant difference in interaction time and groups(apex: <i>F</i>_time×group=1.65, <i>P</i>_time×group=0.15; 2mm circle: <i>F</i>_time×group=1.81, <i>P</i>_time×group=0.25). The difference of 6mm circle at different time points after the operation was statistically significant(<i>F</i>_time=18.34, <i>P</i>_time<0.01), while the difference in interaction time and groups was not statistically significant(<i>F</i>_group=2.21, <i>P</i>_group=0.12; <i>F</i>_time×group=1.34, <i>P</i>_time×group=0.25). In the low and moderate myopia groups, the changes of the apex, 2mm circle and 6mm circle in the posterior corneal elevation were statistically significant within 1mo after surgery(<i>P</i><0.05); In the high myopia group, there were statistically significant at the apex and 2mm circle within 3mo after surgery(<i>P</i><0.05); There was statistically significant after surgery at 6mm circle within 1mo(<i>P</i><0.05). In all cases, the difference of the posterior corneal elevation between 1wk and 1d was negative at the apex and 2mm circle, after that, the difference became positive and smaller. The reverse was true at the 6mm circle. <p>CONCLUSION:Among three groups after SMILE, the central posterior cornea was slightly backward, and the peripheral cornea was slightly forward, the changes were most obvious after 1wk and then returned gradually. It means the surgery was safe, stable, precise, and predictable.

Changes of anterior segment structure after sub-bowman keratomileusis / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To observe the effect of sub-bowman keratomileusis(SBK)on the posterior corneal curvature, posterior corneal elevation and anterior chamber parameters.<p>METHODS: Prospective self controlled study. Totally 49 patients(97 eyes)with myopia who had planned for SBK were included in this study, mean posterior corneal curvature, central posterior corneal elevation(PCE), anterior chamber volume(ACV), central and peripheral anterior chamber depth(ACD)were measured by Oculyzer before and 1wk, 1y, 3y after surgery. Repeated measure analysis of variance was adopted for data analysis.<p>RESULTS: There were no significant differences in mean posterior corneal curvature at any time point postoperatively compared with that preoperatively(<i>P</i>>0.05). However, central PCE, ACV and central ACD at 1wk, 1y and 3y postoperatively were all decreased(<i>P</i><0.01). Except for the anterior peripheral ACD at 3y after SBK, other peripheral ACD at any time point postoperatively were all decreased(<i>P</i><0.05).<p>CONCLUSION: The posterior corneal curvature remained stable after SBK, while the central PCE shifted slightly backward and the entire anterior chamber became shallow.

Early changes in posterior corneal elevation and related factors after femtosecond laser assisted LASIK and SBK / 中华实验眼科杂志

Objective To compare the early change of posterior corneal elevation with femtosecond laser assisted laser in situ keratomileusis (FS-LASIK) and sub-Bowman keratomileusis (SBK) by Oculyzer and analyze the related factors after FS-LASIK.Methods A longitudinal observational study was designed.Ninety-one eyes of 46 patients with myopia or myopic astigmatism in the First Affiliated Hospital of Anhui Medical University from January to April in 2016 were divided into FS-LASIK group (53 eyes of 27 patients),SBK group (38 eyes of 19 patients)according to the patients' wishes and each part of corneal elevation change values were explored after FS-LASIK and SBK surgeries.The posterior corneal elevation was measured at twenty-seven measuring points along the central,paracentral,midperipheral and peripheral zone (vertex and 1,2 and 3 mm radius) using Oculyzer preoperatively,l day,7 days and 1 month postoperatively,respectively.Written informed consent was obtained from each patient before the surgery.Results In the FS-LASIK group,the posterior corneal elevation difference values in the central zone were (-0.924± 1.859),(-1.151 ± 1.586) and (-0.940 ± 1.994) μm 1 day,7 days and 1 month postoperatively,respectively.In the periphery zone,the elevation difference values were (1.046 ± 1.667),(1.172 ± 1.566) and (1.023±1.622)μm.In the paracentral and midperipheral zone,the cornea displayed slightly backward or forward shift.In SBK group,the posterior corneal elevation difference values of the ve,ex were (-0.684 ± 1.454),(-1.053 ±1.723) and (-0.553 ± 1.572) μm 1 day,7 days and 1 month after operation,respectively.In the paracentral and midperipheral zone displayed the same trend with FS-LASIK group,and in the periphery,the values were (1.207 ±1.317),(1.327 ± 1.529) and (1.208 ± 1.415) μm.There were no statistically significant differences in posterior corneal elevation between the two surgery modes among the three time points (all at P ＞ O.05).At 1 month postoperatively,only two independent variables,which were spherical equivalent (SE) and ablation depth (AD)entered the regression in the central and paracentral zones.Independent variables,such as central thinnest corneal thickness (TCT),SE,AD,residual bed thickness (RBT) and the ratio of AD and TCT (AD/TCT) did not enter the regression in other two areas.Conclusions The posterior corneal elevation in the central 6 mm area shows tiny change in the early stage and the variation is larger 7 days after operation in the two groups,but it does not result in keratectasia.With the increase of SE and AD,the posterior corneal elevation is more likely to be affected.

A one-year follow-up study of posterior corneal elevation after FS-LASIK / 实用医学杂志

Objective To study the changes of posterior corneal elevation with one-year follow-up by using Allegro Oculyzer anterior segment diagnostic system in patients who had undergone laser in situ keratomileusis with femtosecond laser (FS-LASIK) for myopia. Methods Ninety eyes of forty-five patients who had undergone FS-LASIK for myopia were included in our study . The spherical equivalent of ametropia was-10.63D to -1.63D. The preoperative and postoperative corneal tomography (including 1, 3, 6 and 12 month after operation ) were collected by Allegro Oculyzer in the posterior corneal elevation and the thickness at central corneal thinnest point of each eye were measured , and the differences of the posterior corneal elevation were calculated. The data were analyzed with ANOVA and Pearson correlation analysis. Results There were no statistically significant differences in the changes of posterior corneal elevation from the preoperative time to the any postoperative follow-up time (F = 1.50, P > 0.05). There were no statistically significant changes of the posterior corneal elevation from the 1st month to 12th month postoperatively (F = 1.47, P > 0.05). There were statistically significant differences in the changes of thickness at central corneal thinnest point from the preoperative to the 12th month postoperative (F = 369.10, P 0.05). Conclusion After strictly followed surgical indications in FS-LASIK, the posterior corneal elevation can keep good stability and has no significant change. Thickness of central cornea thinnest point increases gradually and tends to stablity at the 3th months after surgery.

Modificaciones de la superficie corneal posterior al año de la cirugía / Changes in the posterior corneal surface one year after surgery

Objetivo: describir las modificaciones de la curvatura posterior corneal en pacientes sometidos a cirugía refractiva láser en el Instituto Cubano de Oftalmología Ramón Pando Ferrer en el período de enero-diciembre de 2011. Métodos: estudio descriptivo, longitudinal y prospectivo, con un universo de 257 pacientes (504 ojos) sometidos a cirugía refractiva láser. La muestra quedó conformada por 31 pacientes (59 ojos). Se analizaron las variables: edad, sexo, equivalente esférico, paquimetría preoperatoria, cantidad de ablación, estroma residual y diferencia de elevación posterior corneal, esta última obtenida del mapa de diferencia del tomógrafo Galilei con medición preoperatoria, al mes, 3 meses, 6 meses y 1 año de la cirugía. Con análisis de regresión múltiple se evaluaron dichos cambios con la paquimetría, cantidad de ablación, estroma residual y presión intraocular. Resultados: el equivalente esférico, paquimetría, cantidad de ablación, estroma residual y presión intraocular estaban dentro de los criterios de seguridad. La diferencia promedio de la elevación corneal posterior fue de 15,62 µm al mes y 11,78 µm a los 3 meses, 7,68 µm a los 6 meses y 3,22 µm al año con disminución significativa con el tiempo (p= 0,000). Se observó asociación con la paquimetría preoperatoria, el estroma residual y la presión intraocular. Conclusiones: la cirugía refractiva láser induce un aumento precoz en la elevación corneal posterior, con disminución progresiva en el tiempo. Los factores que más influyeron en estos cambios fueron el estroma residual, la paquimetría preoperatoria y la presión intraocular

Objective: to describe the changes of the posterior corneal curvature observed in patients who underwent laser-assisted refractive surgery at Ramón Pando Ferrer Cuban Institute ofOphthalmology from January through December 2011. Methods: a prospective, longitudinal and descriptive study of a sample of 31 patients (59 eyes) selected from a universe of 257 patients (504 eyes), who underwent laser-assisted refractive surgery. The analyzed variables were age, sex, spherical equivalent, pachymetry before surgery, ablation magnitude, residual stroma and difference in posterior corneal elevation. The latter was obtained from the Galilei´s tomograph difference map with measurements before surgery and one month, three months, six months and a year after surgery. Stepwise multiple regression analysis allowed evaluating such changes with pachymetry, ablation microns, residual stroma and intraocular pressure. Results: spherical equivalent, pachymetry, ablation microns, residual stroma and intraocular pressure were within the set safety criteria. The average difference of the posterior corneal elevation was 15,62 µm at one month, 15,62 µm three months, 7,68 µm six months and 3,22 µm one year after the surgery, with significant reduction as time goes by (p=0.000). Preoperative pachymetry, residual stroma and intraocular pressure were found to be related. Conclusions: laser-assisted refractive surgery causes an early increase of the posterior corneal elevation, with progressive reduction in time. The most influential factors were residual stroma, preoperative pachymetry and intraocular pressure

Modificaciones de la curvatura posterior corneal después de la cirugía refractiva láser / Modifications in the corneal posterior curve after laser refractive surgery

OBJETIVO: Describir las modificaciones de la curvatura posterior corneal en pacientes sometidos a cirugía refractiva láser en el Instituto Cubano de Oftalmología Ramón Pando Ferrer en el período de mayo a octubre de 2010. MÉTODOS: Se realizó un estudio descriptivo, longitudinal y prospectivo, con un universo de 257 pacientes (504 ojos) sometidos a cirugía refractiva láser. La muestra quedó conformada por 31 pacientes (59 ojos). Se analizaron variables como edad, sexo, equivalente esférico, paquimetría preoperatoria, cantidad de ablación, estroma residual y diferencia de elevación posterior corneal, esta última obtenida del mapa de diferencia del topógrafo Galilei, con medición preoperatoria al mes y a los tres meses de la cirugía. Mediante análisis de regresión múltiple fueron valorados dichos cambios de la paquimetría, la cantidad de ablación y el estroma residual. RESULTADOS: El equivalente esférico, la paquimetría, la cantidad de ablación y el estroma residual se encontraron dentro de los parámetros de seguridad establecidos. La diferencia promedio de la elevación corneal posterior fue de 15,62 Ám al mes y de 11,78 Ám a los tres meses, con disminución significativa con el tiempo (p= 0,000). Se observó asociación con la paquimetría preoperatoria y el estroma residual, y se encontró una correlación inversa entre este último y la elevación corneal posterior a los tres meses. CONCLUSIONES: La cirugía refractiva láser induce un aumento precoz en la elevación corneal posterior, con disminución progresiva hacia el tercer mes. Los factores que más influyeron en estos cambios fueron el estroma residual y la paquimetría preoperatoria

OBJECTIVES: To describe the modifications in the corneal posterior curve in patients underwent laser refractive surgery in the Ramón Pando Ferrer Cuban Institute of Ophthalmology from May to October, 2020. METHODS: A prospective, longitudinal and descriptive study was conducted in an universe of 257 patients (504 eyes) underwent to laser refractive surgery. Sample included 31 patients (59 eyes). Variables analyzed were: age, sex, spherical equivalent, preoperative pachymetry, ablation amount, residual stroma and difference of corneal posterior elevation, this latter achieved from the difference map of Galilei topography, with preoperative measurement at month and at three months after surgery. By multiple regression analysis the changes of pachymetry, the ablation amount and the residual stroma were assessed. RESULTS: The spherical equivalent, the pachymetry, the ablation amount and the residual stroma were within the established safety parameters. The mean difference of posterior corneal elevation was of 15,62 ?m at three months, with a significant decrease in time (p= 0,000). There was association with preoperative pachymetry and the residual stroma and also an inverse correlation between this latter and the posterior corneal elevation at three months. CONCLUSIONS: The laser refractive surgery produces an early increase in the posterior corneal elevation with a progressive decrease at third month. The factors that more influenced in such changes were the residual stroma and the preoperative pachymetry