Characterization of optical performance with defocusing curve: Analysis of two refractive intraocular lens models with high and medium addition / Caracterización del comportamiento óptico mediante curva de desenfoque: análisis de dos modelos de lentes intraoculares refractivas con adición alta y media

PURPOSE: To characterize the optical performance of two models of refractive bifocal intraocular lenses, with medium and high addition, using defocus curves. METHODS: 20 eyes from 20 subjects were included in this study. 10 eyes underwent caratact surgery with an implant of a medium addition refractive bifocal intraocular lens (IOL) (Lentis LS-313 MF20) and the other 10 eyes underwent cataract surgery with an implant of a high addition refractive bifocal IOL (Lentis LS-313 MF30). Six weeks after surgery, subjective refraction and defocus curve were made. RESULTS: Mean final residual refraction in spherical equivalent was +0.10 ± 0.07 D in the LS-313MF30 group and +0.12 ± 0.10 D in the LS-313MF20 group. Defocus curve showed a different optical performance in intermediate/near distance depending on the IOL model. The medium addition IOL provided good visual acuity (VA) at far and intermediate distance up to 50 cms, and the high addition IOL provided better VA in near distance up to 25 cms. CONCLUSIONS: The high addition intraocular lens provides better visual acuity in the spatial range from infinity to the point close to 25 cm. The medium addition intraocular lens provides excellent visual acuity in far and intermediate vision. The defocus curve seems to be a valid and reproducible tool for evaluating the optical behavior of multifocal sector refractive lenses

OBJETIVO: Caracterizar el comportamiento óptico de dos modelos de lentes intraoculares bifocales refractivas, con adición media y alta, utilizando curvas de desenfoque. MÉTODOS: Se incluyó en este estudio a 20 ojos de 20 sujetos: 10 ojos sometidos a cirugía de cataratas con implante de lentes intraoculares (LIO) bifocales refractivas con adición media (Lentis LS-313 MF20), y los 10 ojos restantes sometidos a cirugía de cataratas con implante de LIO bifocales refractivas de adición alta (Lentis LS-313 MF30). Transcurridas seis semanas de la cirugía, se realizó refracción subjetiva y curva de desenfoque. RESULTADOS: La refracción residual final media en el equivalente esférico fue de +0,1 ± 0,07 D en el grupo LS-313MF30, y de +0,12 ± 0,1 D en el grupo LS-313MF20. La curva de desenfoque mostró un comportamiento óptico diferente en la distancia intermedia/de cerca, dependiendo del modelo de LIO. La LIO de adición media aportó buena agudeza visual (AV) en la distancia de lejos e intermedia, de hasta 50 cm, y la LIO de adición alta aportó mejor AV en la distancia de cerca de hasta 25 cm. CONCLUSIONES: Las lentes intraoculares de adición alta aportan mejor agudeza visual en el rango espacial comprendido entre el infinito y el punto próximo a 25 centímetros. Las lentes intraoculares de adición media aportan una agudeza visual excelente en la visión de lejos e intermedia. La curva de desenfoque parece ser una herramienta válida y reproducible para evaluar el comportamiento óptico de las lentes refractivas multifocales

Characterization of optical performance with defocusing curve: Analysis of two refractive intraocular lens models with high and medium addition.

PURPOSE: To characterize the optical performance of two models of refractive bifocal intraocular lenses, with medium and high addition, using defocus curves. METHODS: 20 eyes from 20 subjects were included in this study. 10 eyes underwent caratact surgery with an implant of a medium addition refractive bifocal intraocular lens (IOL) (Lentis LS-313 MF20) and the other 10 eyes underwent cataract surgery with an implant of a high addition refractive bifocal IOL (Lentis LS-313 MF30). Six weeks after surgery, subjective refraction and defocus curve were made. RESULTS: Mean final residual refraction in spherical equivalent was +0.10±0.07D in the LS-313MF30 group and +0.12±0.10D in the LS-313MF20 group. Defocus curve showed a different optical performance in intermediate/near distance depending on the IOL model. The medium addition IOL provided good visual acuity (VA) at far and intermediate distance up to 50cms, and the high addition IOL provided better VA in near distance up to 25cms. CONCLUSIONS: The high addition intraocular lens provides better visual acuity in the spatial range from infinity to the point close to 25cm. The medium addition intraocular lens provides excellent visual acuity in far and intermediate vision. The defocus curve seems to be a valid and reproducible tool for evaluating the optical behavior of multifocal sector refractive lenses.

Accuracy of Cirrus HD-OCT and Topcon SP-3000P for measuring central corneal thickness / Precisión de Cirrus HD-OCT y Topcon SP-3000P en la medición del espesor corneal central

Purpose: To compare and analyze the interchangeability of three measuring systems, each based on a different technique, for central corneal thickness (CCT) analysis. Methods: CCT measurements were measured using optical coherence tomography (OCT), non-contact specular microscopy (NCSM), and ultrasonic pachymetry (USP) in 60 eyes of 60 healthy patients with a mean age of 66.5 ± 15.0 years and a mean spherical equivalent of 0.43 ± 1.14 D. Analysis of variations in measurement concordance and correlation among the three different methods were performed. Comparison of CCT measurements were done using Bland-Altman plots (with bias and 95% confidence intervals), intraclass correlation coefficient (ICC), and paired t-student analysis. Results: Mean CCT values were: 549.20 ± 26.91μm for USP (range 503-618μm), 514.20 ± 27.49μm for NCSM (range 456-586μm) and 542.80±25.56μm for OCT (range 48-605μm). CCT values obtained with NCMS were significantly lower than those obtained with OCT and USP methods. NCMS CCT value was 36.08 ± 10.72μm lower than USP value (p < 0.05), and NCMS CCT value was 7.88 ± 8.86 μm lower than OCT value (p < 0.05). ICC between USP-NCSM pair was 0.488 and 0.909 between USP-OCT pair. Conclusion: OCT and UPS offered highly comparable results, whereas NCSM offered lower mean CCT values compared to the other two methods. Therefore, NCSM should not be considered a reliable method for measuring CCT and should rather be considered for assessing longitudinal changes in the same patient

Objetivo: Comparar y analizar la intercambiabilidad de tres sistemas de medición, basado cada uno de ellos en una técnica diferente, para estudiar el espesor corneal central (ECC). Métodos: Se realizaron mediciones del ECC utilizando tomografía de coherencia óptica (OCT), microscopía especular (NCSM), y paquimetría ultrasónica (USP) en 60 ojos de 60 pacientes sanos, con una edad media de 66,5 ± 15 años y un equivalente esférico medio de 0,43 ± 1,14 D. Se realizaron análisis de las variaciones de concordancia de las mediciones, y correlación entre los tres métodos diferentes. Se compararon las mediciones del EEC utilizando gráficos de Bland-Altman (con desviaciones, e intervalos de confianza del 95%), coeficiente de correlación intra-clase (ICC), y análisis de t pareada de Student. Resultados: Los valores medios de ECC fueron: 549,2 ± 26,91μm para USP (rango 503-618 μm), 514,2 ± 27,49μm para NCSM (rango 456-586 μm) y 542,8 ± 25,56 μm para OCT (rango 486-605 μm). Los valores de ECC obtenidos con NCMS fueron significativamente inferiores que los obtenidos con los métodos OCT y USP. El valor de ECC obtenido mediante NCMS fue inferior en 36,08±10,72μm al valor obtenido mediante USP (p < 0,05), y el valor de ECC obtenido mediante NCMS fue inferior en 7,88 ± 8,86 μm al obtenido mediante OCT (p < 0,05). El ICC entre el par USP-NCSM fue de 0,488, y de 0,909 entre el par USP-OCT. Conclusión: Los métodos OCT y UPS aportaron resultados altamente comparables, mientras que NCSM aportó unos valores medios de ECC inferiores a los aportados por los otros dos métodos. Por tanto, NCSM no debería considerarse un método fiable en la medición del ECC, debiéndose utilizar en la valoración de los cambios longitudinales del mismo paciente

Intraocular lens bicylindric power calculation method: Using both flat and steep K readings to improve intraocular lens power prediction.

PURPOSE: To compare and analyze the accuracy of the refractive outcomes obtained in intraocular lens power calculation using the classical calculation method with mean keratometry (K) and the calculation method with both K meridians presented in this article. METHODS: A total of 62 eyes of 62 subjects who were undergoing cataract surgery were included in this study. Optical biometry was performed using mean K and Haigis formula for classical intraocular lens calculation methods to achieve intraocular lens power; 4 weeks after surgery, prior to medical discharge, subjective refraction was made. Alternatively, intraocular lens power was calculated with bicylindric method using both keratometry readings, obtaining spherocylindrical refractive expected outcomes. Finally, results obtained with intraocular lens calculation methods, bicylindric method, and Haigis formula were compared. RESULTS: Spherical equivalent calculated by classical intraocular lens calculation methods using Haigis formula (H-SE) was -0.027 ± 0.115 D and using bicylindric method (B-SE) was -0.080 ± 0.222 D. Achieved spherical equivalent obtained 4 weeks after surgery (A-SE) was -0.144 ± 0.268 D. Difference between H-SE and A-SE was -0.117 D (p = 0.002). Difference between B-SE and A-SE was not significant (-0.054 D, p = 0.109). Analysis in refraction groups showed a positive correlation between A-SE confronted to B-SE and H-SE (r = 0.313; p = 0.013 and r = 0.562; p < 0.001, respectively). This indicated a reliability in ametropic group prediction of 0.767 in H-SE and 0.843 in B-SE. CONCLUSION: Intraocular lens calculation with bicylindric method could be more accurate and had more reliability than classical intraocular lens calculation method. Bicylindric method adds astigmatism control and provides a reliable expected spherocylindrical refraction.

Accuracy of Cirrus HD-OCT and Topcon SP-3000P for measuring central corneal thickness.

PURPOSE: To compare and analyze the interchangeability of three measuring systems, each based on a different technique, for central corneal thickness (CCT) analysis. METHODS: CCT measurements were measured using optical coherence tomography (OCT), non-contact specular microscopy (NCSM), and ultrasonic pachymetry (USP) in 60 eyes of 60 healthy patients with a mean age of 66.5±15.0 years and a mean spherical equivalent of 0.43±1.14 D. Analysis of variations in measurement concordance and correlation among the three different methods were performed. Comparison of CCT measurements were done using Bland-Altman plots (with bias and 95% confidence intervals), intraclass correlation coefficient (ICC), and paired t-student analysis. RESULTS: Mean CCT values were: 549.20±26.91µm for USP (range 503-618µm), 514.20±27.49µm for NCSM (range 456-586µm) and 542.80±25.56µm for OCT (range 486-605µm). CCT values obtained with NCMS were significantly lower than those obtained with OCT and USP methods. NCMS CCT value was 36.08±10.72µm lower than USP value (p<0.05), and NCMS CCT value was 7.88±8.86µm lower than OCT value (p<0.05). ICC between USP-NCSM pair was 0.488 and 0.909 between USP-OCT pair. CONCLUSION: OCT and UPS offered highly comparable results, whereas NCSM offered lower mean CCT values compared to the other two methods. Therefore, NCSM should not be considered a reliable method for measuring CCT and should rather be considered for assessing longitudinal changes in the same patient.

Ocular Surface Disease Parameters After Collagen Cross-Linking for Keratoconus.

PURPOSE: To analyze the variations in tear quantity and quality after corneal collagen cross-linking (CXL) in patients with keratoconus. METHODS: This is a prospective observational study of 24 eyes with keratoconus that underwent epithelium-off CXL. The variables studied were tear film osmolarity, subjective symptoms (Ocular Surface Disease Index), tear breakup time, Schirmer test (SCH) score, tear clearance, fluorescein staining, and lissamine green staining. Variables were determined preoperatively and 3, 6, and 12 months after CXL. RESULTS: All the studied variables remained stable after 1-year follow-up (no significant difference in comparison with baseline values; Mann-Whitney U test). There was a positive paired correlation between the SCH score and tear clearance at 3; 0.532 (P < 0.01), 6; 0.434 (P = 0.04), and 12 months; 0.675 (P < 0.01). There was no correlation between the SCH score and tear breakup time, apart from a positive correlation at 12 months; 0.601 (P = 0.05). A negative correlation was found between osmolarity and the SCH score at 3; -0.589 (P < 0.01) and 12 months; -0.049 (P = 0.04). The Ocular Surface Disease Index did not correlate with any of the studied variables (Spearman test). CONCLUSIONS: CXL, at least during the first postoperative year, does not modify the parameters currently used to evaluate tear film function. There is no correlation between objective and subjective parameters in the analysis of the tear film function.