Caracterización morfológica de la superficie corneal posterior en córneas normales / Morphological characterization of the posterior corneal surface in normal corneas

OBJETIVO: describir las características de la superficie corneal posterior en córneas normales y las modificaciones de esta en pacientes a quienes se les realizó queratomileusis con láser in situ. MÉTODOS: fue realizado un estudio descriptivo, longitudinal y prospectivo en 282 ojos de pacientes que asistieron a la consulta de cirugía refractiva. Las variables estudiadas fueron: queratometría media central posterior, equivalente esférico, paquimetría óptica en la posición más delgada, astigmatismo topográfico anterior y posterior, astigmatismo refractivo y variación morfológica del mapa topográfico de elevación posterior respecto a la esfera de mejor ajuste. Fueron escogidos 27 ojos, los cuales reunían los criterios para cirugía refractiva láser y se les realizó la técnica queratomileusis con láser in situ. Se analizaron también las variables cantidad de ablación, estroma residual y diferencia de elevación posterior corneal, esta última obtenida del mapa de diferencia del tomógrafo Pentacam HR. RESULTADOS: la queratometría media posterior fue de -6,37 ± 0,22 dioptrías; la correlación entre la queratometría media posterior con respecto a la paquimetría óptica fue muy significativa (p= 0,008). La media de la diferencia de elevación máxima con respecto a la esfera de mejor ajuste posterior fue 5,33 µm; el 93,3 % de la muestra se encontraba dentro de valores normales. La diferencia de elevación posterior a través del tiempo fue de 18,38 µm ± 7,47 al mes y 14,95 µm ± 10,02. Se observó relación con la paquimetría y el estroma residual. CONCLUSIONES: la queratomileusis con láser in situ determina modificaciones en la superficie corneal posterior. El estroma residual es el factor más relacionado con estas modificaciones.

OBJECTIVE: to describe the characteristics of the posterior corneal surface in normal corneas and its changes in patients who underwent laser in situ keratomileusis. METHODS: prospective, longitudinal and descriptive study of 282 eyes from patients who went to the refractive surgery service. The studied variables were posterior central mean keratomery, spheral equivalent, optical pakimetry at the thinnest position, anterior and posterior topographic astigmatism, refractive astigmatism and morphological variation of the posterior elevation topographic map in relation to the best fit sphere. In this group, 27 eyes were selected, which met the criteria for laser refractive surgery using the laser in situ keratomileusis. Other analyzed variables were ablation amount, residual stroma and posterior corneal elevation difference, being the latter taken from the difference map outlined with the Pentacam HR tomography. RESULTS: mean posterior keratometry was -6,37 ± 0,22 dioptries; the correlation between mean posterior keratometry and optical pakimetry was very significant (p= 0,008). The mean difference of maximum elevation with respect to the best posterior fit sphere was 5,33 µm; 93,3 % of the sample was within the normal values. The correlation between the posterior elevation and the spheral equivalent was also significant (p= 0,019). The difference of the posterior elevation throughout the period was 18,38 µm ± 7,47 after a month and 14,95 µm ± 10,02 at the end of the period. There was correlation with pakimetry and residual stroma. CONCLUSIONS: laser in situ keratomileusis causes changes in the posterior corneal surface. The residual stroma is the factor most related with these changes.

Visual acuity and corneal topography stability after 5 years of laser-assisted in-situ keratomileusis

Corneal topographic analysis has been established as an invaluable tool for the refractive surgeon. The use of corneal topography in assessment of corneal surface has tremendously advanced the development and evaluation of refractive surgeries. The analysis of corneal topography permits the recognition of normal and abnormal patterns of ablation, documentation of decentrations following Laser-Assisted In-Situ Keratomileusis [LASIK] surgery and also allows the refractive surgeon to quantify irregularities of corneal surface. Despite numerous follow-up studies on incidence of refractive regression and other complications after LASIK ablation, little attention has been paid to the long-term effect of LASIK surgery on corneal surface remolding and the consequential effects on the stability of vision. To evaluate the postoperative corneal changes on patients at the risk, after 5 years of undergoing LASIK surgery. Also, we tried to assess the stability of vision within this period to determine if there was a significant topographic pattern changes. Methods: Subdividing our subjects [40 eyes] to three groups of risk factors depending on their corneal topographic patterns. Mean age of subjects were 32.3 +/- 5.5 years [range: 23 to 41 years] with a spherical equivalent manifest refraction [SEMR] ranging from -1.75 D to -13.75 D and a manifest refractive cylinder of less than 4.00D. Intended ablation depth ranged from 26.5 to 107.7 microns and the retrospective pachymetry value of 501 and 607m. There was a 100% improvement [p = 0.0001] in visual acuity in the groups with steep cornea and asymmetric bow tie, and a 60% improvement [p = 0.0001] in the inferior steepening cornea group. Also, there was a change in topographic pattern of each group with normal patterns being only associated with Steep Cornea and Asymmetric Bow tie groups while corneal ecstasies were observed in 3 eyes belonging to the inferior steepening group. Decreased thickness of residual Stroma, depth and width of ablation, older ages, increased myopic correction and abnormal corneal topography are some predisposing factors to unstable vision after LASIK correction. A significant change in VA and corneal topography were returned on assessment

Incidence, treatment and visual outcomes of non-infectious keratitis as a postoperative complication of laser-assisted in-situ keratomileusis [LASIK]

To study the incidence, treatment, and visual outcomes of Non-Infectious Keratitis as a Postoperative Complication of Laser in-Situ Keratomileusis [LASIK]. The files of 3500 post-LASIK patients [6326 eyes] were reviewed for the development of Non-Infectious Keratitis. Incidence, management regimens, and final best spectacle corrected visual acuity [BSCVA] were reported. Post-LASIK Non-Infectious Keratitis was diagnosed in 149 eyes [2.35%]. The Keratitis was classified as diffuse lamellar keratitis [DLK] in 89 eyes [1.4%] and 60 eyes [0.94%] as localized debris-related Keratitis [LDK]. The occurrence of post-LASIK Non-Infectious Keratitis was 2.35%, with DLK being the common diagnosis overall, with 92.6% of patients achieving < 20/20 BSCVA. The best way for prevention of DLK is to eliminate defined predisposing factors for DLK. Close follow-up during the early postoperative period

Cataract and Refractive Surgery in ; a Survey of KSCRS Members From 1995~2006

PURPOSE: This purpose of this report was to study trends in cataract and refractive surgeries conducted during the past twelve years and to compare results to previous reports from the ASCRS and New Zealand (NZ) in order to forecast future medical services. METHODS: We surveyed members of the Korean Society of Cataract and Refractive Surgery (KSCRS) every year from 1995 to 2006, and studied changes in cataract and refractive surgeries (RS). RESULTS: The duration of hospitalization has been gradually decreasing to the point that a one day hospitalization following surgery has become common. The rate of topical anesthesia use has significantly increased since 1998. Sutureless incision methods are now commonly practiced. The use of acryl IOL as an optic material has been gradually increasing for cataract surgeries. KSCRS members showed an interest in the special intraocular lenses as multifocal IOL. While Excimer laser PRK was the most popular refractive surgery during the first stage, KSCRS members increasingly prefer LASIK to the Excimer laser PRK. Regression of the corrected visual acuity, dry eye, night halo, and flashes were the most common complications following refractive surgeries. Medical disputes related to PRK and LASIK have been gradually increasing throughout the study period. CONCLUSIONS: We confirm that the KSCRS practice styles for cataract and RS are similar to those of the ASCRS and NZ. We infer a world-wide trend from the comparison of these three societies.

Corneal characteristics in myopic patients.

OBJECTIVES: To evaluate the characteristics of the cornea in myopic patients. MATERIAL AND METHOD: A retrospective study of 420 eyes in 210 patients who visited the Excimer Laser Surgery Clinic at Siriraj Hospital, Mahidol University from January 1999 to June 2002 was conducted. All cases that were eligible for myopic refractive surgery were included in the present study. A preoperative ocular examination was done in a fashionable method, including manifest refraction and Orbscan Topography to evaluate corneal thickness, corneal curvature and corneal diameter Statistical analysis was performed to identify the characteristics of the cornea in the patients. RESULTS: The mean age of the patients was 31.66 +/- 7.77 years. (ranging from 16-51). The mean manifest refraction (spherical equivalent) was -4.9 +/- 2.29 diopters (ranging from -0.50 to -13.75). The mean corneal diameter (white to white) was 11.60 mm +/- 0.37 mm (ranging from 10.8-12.9). The thinnest point of the cornea varied from 409 to 597 microns (mean = 522.55) and located mostly in the infero-temporal quadrant of the eye (23.69% in the right and 32.05% in the left). The mean curvature of the corneal was 44.6 +/- 13.8 diopters (ranging from 39.05-47.65). The mean corneal astigmatism was 1.34 +/- 0.71 diopters and 93.96% were with the rule astigmatism. Positive angle kappa was found in 408 eyes (97%) but all cases were within a 0.5 mm horizontal and 0.3 mm vertical radius from the pupillary axis. CONCLUSION: Characteristics of the cornea in Thai myopic patients were demonstrated in the present study. Most of the cornea showed with the rule astigmatism with positive angle kappa and the thinnest point, located at the infero-temporal quadrant.

Visual Quality after Wavefront-Guided LASIK for Myopia

This study evaluated the visual quality after wavefront-guided laser in situ keratomileusis (LASIK) for treating myopia. Thirty-two eyes with moderate myopia (-5.78~-2.17D) and 25 eyes with high myopia (-7.78~-6.17D) were prospectively reviewed. The contrast sensitivity (CS), glare and the total higher order aberrations (HOA) were measured before and 1 week, 1 month and 2 months after LASIK. The pupil diameter was measured at day- and night-time illumination. The CS and glare at all spatial frequencies were not reduced after wavefront-guided LASIK (p0.05). The area under the log contrast sensitivity function (AULCSF) showed no correlation with the total HOA (r2=-0.071, p=0.612, between the daytime AULCSF and the total HOA with a 4 mm entrance pupil, r2=-0.176, p=0.260, between the nighttime AULCSF and the total HOA with a 6 mm entrance pupil). There was no decrease in CS and glare after wavefront-guided LASIK for myopia. In conclusion, wavefront-guided LASIK based on the individual ablation patterns is a good option for refractive surgery to improve the visual quality in both moderate and high myopia cases.

Evaluación de factores pronósticos refractivos en lasik miópico / Evaluation of refractive prognostic factors in myopic lasik

Objetivo: Evaluar resultados y pronóstico de LASIK miópico, según refracción preoperatoria. Método: En 200 casos agrupados por esfera y cilindro preoperatorio, se comparó: esfera, cilindro , cambio astigmático, cilindro refractivo inducido (SIRC), astigmatismo residual, equivalente defocus, predictibilidad de corrección esférica y cilíndrica, agudeza visual (AV), índices de seguridad (IS) y eficacia (IE). Resultados: Ordenados por esfera: La esfera se corrige mejor que el cilindro, subcorrigiéndose las más miopes (p< 0.0171). El astigmatismo residual dio un centroide muy similar. La predictibilidad +/-1D va de 98 a 80 por ciento para la esfera y de 92 a 84 por ciento para el cilindro. Ordenados por cilindro alto se subcorrige (p< 0.05) e hipercorrige la esfera (p= 0.0469). El astigmatismo residual entre los grupos menores y mayores dio una diferencia de û0.32 x 90°. La predictibilidad +/- 1D va de 98 a 94 por ciento para esfera y de 96 a 88 por ciento para cilindro. El por ciento del Equivalente Defocus < 1D fue 74 y 46 por ciento por esfera y 82 y 38 por ciento por cilindro, para grupos menos y más miopes, respectivamente. Las AV pre y postoperatoria disminuyen a menor esfera o cilindro. IS > 1.0 e IE es similar (+/- 0.9), por Esf. y Cil . Preop. Predictibilidad de AV c/c 20/25 por esfera, va de 100 por ciento a 60 por ciento y por cilindro para 20/30 de 100 por ciento a 83 por ciento, de grupos menos a más miopes, respectivamente. Conclusiones: El análisis por grupo refractivos permite determinar su influencia para mejorar pronóstico y tratamiento. Es muy seguro y eficaz, para todos los grupo. Su inexactitud depende fundamentalmente del astigmatismo y menos de esfera preoperatoria. A mayor astigmatismo se debe disminuir ablación esférica y aumentar el cilindro.

Lasik miópico: en busca del nomograma ideal / Myopic Lasik: in search of ideal nomogram

Presentamos un estudio retrospectivos de 133 casos de LASIK miópico operados con el equipo VISX S2, con el objeto de obtener un nomograma ajustado a las características propias del equipo, Los pacientes fueron separados en dos grupos: bajas esferas con cilindros altos, y esferas mayores que los cilindros. Se pudo concluir, en forma preliminar, que: En el grupo 1 (cilindros mayor que esfera) la tendencia fue a la subcorrección cilíndrica. La corrección de cilindros altos no se acompañó de sobrecorrección esférica significativa. Los resultados refractivos en el grupo 2 (altas esferas, cilindros bajos) presentaron una distribución de tipo normal, con equilibrio entre la hipo e hipercorrección. La sobrecorrección severa que requirió retratamiento, mayor de 1 Diopatría, sólo alcanzó al 1 por ciento, siendo inferior a lo esperado. Es necesario mejorar el registro y seguimiento de los casos...