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Papers by Giuseppe Lombardo

Research paper thumbnail of Interocular high-order corneal wavefront aberration symmetry

Journal of The Optical Society of America A-optics Image Science and Vision, 2006

The interocular symmetry of the high-order corneal wavefront aberration (WA) in a population of m... more The interocular symmetry of the high-order corneal wavefront aberration (WA) in a population of myopic eyes was analyzed before and after photorefractive keratectomy (PRK). The preoperative and one-year postoperative corneal aberration data (from third to seventh Zernike orders) for 4-and 7-mm pupils from right and left eyes were averaged after correcting for the effects of enantiomorphism to test for mirror symmetry. Also, the mean corneal point-spread function (PSF) for right and left eyes was calculated. Preoperatively, a moderate and high degree of correlation in the high-order corneal WA between eyes was found for 4-and 7-mm pupils, respectively. Myopic PRK did not significantly change the interocular symmetry of corneal high-order aberrations. No discernible differences in the orientation PSF between eyes were observed one year after surgery in comparison with the preoperative state over the two analyzed pupils.

Research paper thumbnail of Differences in nasal and temporal responses of the cornea after photorefractive keratectomy

Journal of Cataract and Refractive Surgery, 2005

Methods: Preoperative and 1-, 3-, 6-, and 12-month postoperative corneal topographies of 70 eyes ... more Methods: Preoperative and 1-, 3-, 6-, and 12-month postoperative corneal topographies of 70 eyes that had PRK with the Technolas 217C excimer laser (Bausch & Lomb) were obtained. The eyes were divided into 4 groups according to the preoperative spherical equivalent refraction. Preoperative and follow-up topographic data were imported into custom software that computed the average composite corneal map and difference maps in each group to scientifically evaluate the corneal response to the surgery. The software was also used to analyze regional corneal changes after the laser ablation. Corneal peripheries up to 9.0 mm were evaluated.

Research paper thumbnail of Relative Contribution of Central and Peripheral Aberrations to Overall High Order Corneal Wavefront Aberration

To analyze the influence of specific combinations of corneal high order aberrations on the optica... more To analyze the influence of specific combinations of corneal high order aberrations on the optical image quality of the cornea before and after photorefractive keratectomy (PRK) for low to high myopia and myopic astigmatism. Corneal topography was obtained for 80 eyes that underwent PRK using a scanning-spot excimer laser. The eyes were subdivided into three groups according to the preoperative refraction. The topographical data were imported into a custom software program that combined the Zernike high order terms having the same sign and angular frequency up to seventh order for 4-mm and 6-mm pupils, ie, coma and spherical aberrations, and midperipheral and peripheral high order aberrations. Photorefractive keratectomy induced a significant amount of the root-mean-square (RMS) values of the combinations of midperipheral and peripheral high order aberrations over the smaller pupil size for deeper myopic ablations (P<.05). Over the larger pupil, spherical myopic ablations showed a significant increase (P<.05) of the RMS values of coma and spherical aberrations. In the astigmatism group, the combination of terms having higher angular frequency increased significantly (P<.05) after surgery both over 4-mm and 6-mm pupils. After surface ablation, ablation depth and profile significantly influence the distribution and contribution of determined combinations of high order aberrations to the overall high order corneal wavefront aberration. Terms having high angular frequency were increased following large myopic correction and wide treatment zone. Quality of the whole corneal optics will be enhanced by designing future ablation profiles to compensate for peripheral high order optical aberrations.

Research paper thumbnail of Atomic force microscopy analysis of normal and photoablated porcine corneas

Journal of Biomechanics, 2006

We showed the capabilities and accuracy of atomic force microscopy (AFM) techniques for imaging a... more We showed the capabilities and accuracy of atomic force microscopy (AFM) techniques for imaging and analyzing the corneal epithelium and the photoablated corneal stroma. Eight normal porcine corneas, half of which were ablated using a scanning-spot excimer laser, were examined. All the corneas were imaged in balanced salt solution after fixation in glutaraldehyde. In the normal untreated corneas we observed the epithelial surface showing the typical polygonal cells and presenting numerous microprojections. The superficial epithelial cells were classified in three types as a result of the anterior-surface roughness measurements. AFM images of the photoablated corneal specimens showed undulations and granule-like features on the ablated stromal surface, specific to 193nm ArF laser irradiation. Nevertheless, the quantitative analysis confirmed the precision of excimer laser surgery in removing submicrometric amounts of tissue. AFM showed to be a high-resolved imaging tool for the scanning of both native as well as photoablated corneal specimens. Also, this technique permits precise topographic analysis of the corneal plane, in the nanometric scale, of which smoothness is an important physical characteristic and necessary to achieve an optimal optical quality of the eye. r

Research paper thumbnail of Analysis of intraocular lens surface properties with atomic force microscopy

Journal of Cataract and Refractive Surgery, 2006

PURPOSE: To analyze the surface optics of 4 currently available intraocular lenses (IOLs) with at... more PURPOSE: To analyze the surface optics of 4 currently available intraocular lenses (IOLs) with atomic force microscopy.

Research paper thumbnail of Mechanically Induced Biaxial Transition in a Nanoconfined Nematic Liquid Crystal with a Topological Defect

Physical Review Letters, 2009

Using an atomic force microscopy, we have measured the separation dependence of the force between... more Using an atomic force microscopy, we have measured the separation dependence of the force between an atomically flat mica sheet and a micrometer-sized glass sphere immersed in the nematic liquid crystal. As the mica surface induces a strong parallel alignment and the treated glass sphere induces a strong perpendicular alignment on the liquid crystal, a repulsive force is observed due to the elastically deformed nematic liquid crystal. We observe that below a critical separation d th % 10 nm, the system undergoes a structural transition, thus relaxing the distortion. The results are interpreted within the eigenvalue exchange mechanism using the Landau-de Gennes tensorial approach.

Research paper thumbnail of Analysis of intraocular lens surface adhesiveness by atomic force microscopy

Journal of Cataract and Refractive Surgery, 2009

PURPOSE: To analyze intraocular lens (IOL) optic surface adhesiveness using atomic force microsco... more PURPOSE: To analyze intraocular lens (IOL) optic surface adhesiveness using atomic force microscopy (AFM).

Research paper thumbnail of Interocular high-order corneal wavefront aberration symmetry

Journal of The Optical Society of America A-optics Image Science and Vision, 2006

The interocular symmetry of the high-order corneal wavefront aberration (WA) in a population of m... more The interocular symmetry of the high-order corneal wavefront aberration (WA) in a population of myopic eyes was analyzed before and after photorefractive keratectomy (PRK). The preoperative and one-year postoperative corneal aberration data (from third to seventh Zernike orders) for 4-and 7-mm pupils from right and left eyes were averaged after correcting for the effects of enantiomorphism to test for mirror symmetry. Also, the mean corneal point-spread function (PSF) for right and left eyes was calculated. Preoperatively, a moderate and high degree of correlation in the high-order corneal WA between eyes was found for 4-and 7-mm pupils, respectively. Myopic PRK did not significantly change the interocular symmetry of corneal high-order aberrations. No discernible differences in the orientation PSF between eyes were observed one year after surgery in comparison with the preoperative state over the two analyzed pupils.

Research paper thumbnail of Differences in nasal and temporal responses of the cornea after photorefractive keratectomy

Journal of Cataract and Refractive Surgery, 2005

Methods: Preoperative and 1-, 3-, 6-, and 12-month postoperative corneal topographies of 70 eyes ... more Methods: Preoperative and 1-, 3-, 6-, and 12-month postoperative corneal topographies of 70 eyes that had PRK with the Technolas 217C excimer laser (Bausch & Lomb) were obtained. The eyes were divided into 4 groups according to the preoperative spherical equivalent refraction. Preoperative and follow-up topographic data were imported into custom software that computed the average composite corneal map and difference maps in each group to scientifically evaluate the corneal response to the surgery. The software was also used to analyze regional corneal changes after the laser ablation. Corneal peripheries up to 9.0 mm were evaluated.

Research paper thumbnail of Relative Contribution of Central and Peripheral Aberrations to Overall High Order Corneal Wavefront Aberration

To analyze the influence of specific combinations of corneal high order aberrations on the optica... more To analyze the influence of specific combinations of corneal high order aberrations on the optical image quality of the cornea before and after photorefractive keratectomy (PRK) for low to high myopia and myopic astigmatism. Corneal topography was obtained for 80 eyes that underwent PRK using a scanning-spot excimer laser. The eyes were subdivided into three groups according to the preoperative refraction. The topographical data were imported into a custom software program that combined the Zernike high order terms having the same sign and angular frequency up to seventh order for 4-mm and 6-mm pupils, ie, coma and spherical aberrations, and midperipheral and peripheral high order aberrations. Photorefractive keratectomy induced a significant amount of the root-mean-square (RMS) values of the combinations of midperipheral and peripheral high order aberrations over the smaller pupil size for deeper myopic ablations (P<.05). Over the larger pupil, spherical myopic ablations showed a significant increase (P<.05) of the RMS values of coma and spherical aberrations. In the astigmatism group, the combination of terms having higher angular frequency increased significantly (P<.05) after surgery both over 4-mm and 6-mm pupils. After surface ablation, ablation depth and profile significantly influence the distribution and contribution of determined combinations of high order aberrations to the overall high order corneal wavefront aberration. Terms having high angular frequency were increased following large myopic correction and wide treatment zone. Quality of the whole corneal optics will be enhanced by designing future ablation profiles to compensate for peripheral high order optical aberrations.

Research paper thumbnail of Atomic force microscopy analysis of normal and photoablated porcine corneas

Journal of Biomechanics, 2006

We showed the capabilities and accuracy of atomic force microscopy (AFM) techniques for imaging a... more We showed the capabilities and accuracy of atomic force microscopy (AFM) techniques for imaging and analyzing the corneal epithelium and the photoablated corneal stroma. Eight normal porcine corneas, half of which were ablated using a scanning-spot excimer laser, were examined. All the corneas were imaged in balanced salt solution after fixation in glutaraldehyde. In the normal untreated corneas we observed the epithelial surface showing the typical polygonal cells and presenting numerous microprojections. The superficial epithelial cells were classified in three types as a result of the anterior-surface roughness measurements. AFM images of the photoablated corneal specimens showed undulations and granule-like features on the ablated stromal surface, specific to 193nm ArF laser irradiation. Nevertheless, the quantitative analysis confirmed the precision of excimer laser surgery in removing submicrometric amounts of tissue. AFM showed to be a high-resolved imaging tool for the scanning of both native as well as photoablated corneal specimens. Also, this technique permits precise topographic analysis of the corneal plane, in the nanometric scale, of which smoothness is an important physical characteristic and necessary to achieve an optimal optical quality of the eye. r

Research paper thumbnail of Analysis of intraocular lens surface properties with atomic force microscopy

Journal of Cataract and Refractive Surgery, 2006

PURPOSE: To analyze the surface optics of 4 currently available intraocular lenses (IOLs) with at... more PURPOSE: To analyze the surface optics of 4 currently available intraocular lenses (IOLs) with atomic force microscopy.

Research paper thumbnail of Mechanically Induced Biaxial Transition in a Nanoconfined Nematic Liquid Crystal with a Topological Defect

Physical Review Letters, 2009

Using an atomic force microscopy, we have measured the separation dependence of the force between... more Using an atomic force microscopy, we have measured the separation dependence of the force between an atomically flat mica sheet and a micrometer-sized glass sphere immersed in the nematic liquid crystal. As the mica surface induces a strong parallel alignment and the treated glass sphere induces a strong perpendicular alignment on the liquid crystal, a repulsive force is observed due to the elastically deformed nematic liquid crystal. We observe that below a critical separation d th % 10 nm, the system undergoes a structural transition, thus relaxing the distortion. The results are interpreted within the eigenvalue exchange mechanism using the Landau-de Gennes tensorial approach.

Research paper thumbnail of Analysis of intraocular lens surface adhesiveness by atomic force microscopy

Journal of Cataract and Refractive Surgery, 2009

PURPOSE: To analyze intraocular lens (IOL) optic surface adhesiveness using atomic force microsco... more PURPOSE: To analyze intraocular lens (IOL) optic surface adhesiveness using atomic force microscopy (AFM).