The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Steven E. Wilson - One of the best experts on this subject based on the ideXlab platform.
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phototherapeutic keratectomy science and art
Journal of Refractive Surgery, 2017Co-Authors: Steven E. Wilson, Gustavo K Marino, Carla S Medeiros, Marcony R. SanthiagoAbstract:Purpose To describe, with videos, the principles of excimer laser phototherapeutic keratectomy (PTK) for the treatment of corneal scars, corneal Surface Irregularity, and recurrent corneal erosions. Methods Depending on the pathology in a treated cornea, the epithelium is removed either by transepithelial PTK ablation with the excimer laser or thorough scraping with a scalpel blade. Stromal PTK can be performed with or without photorefractive keratectomy (PRK), depending on the refractive status of both eyes. Residual Surface Irregularity is treated with masking-smoothing PTK. Typically, 0.02% mitomycin C treatment is applied for 30 seconds to corneas treated with PTK for scars and Surface Irregularity. Results Transepithelial PTK with masking-smoothing typically improves corrected distance visual acuity in the eye even if the entire stromal opacity cannot be removed and can be used to debulk Surface Irregularity to facilitate subsequent therapeutic customized wavefront-guided or optical coherence tomography-guided PTK or PRK. PTK for recurrent erosion is performed after thorough mechanical epithelial debridement of redundant epithelial basement membrane (EBM) with a scalpel and should only include a dusting of excimer laser to remove residual EBM without inducing central irregular astigmatism or damaging limbal tissues. Meta-analyses are provided for PTK treatment for corneal scars, corneal dystrophies, and recurrent corneal erosions. Conclusions Excimer laser PTK is a highly effective treatment for superficial corneal scars, central corneal irregular astigmatism, and recurrent corneal erosions unresponsive to medical treatment or mechanical epithelial debridement alone. [J Refract Surg. 2017;33(3):203-210.].
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phototherapeutic keratectomy science and art
Journal of Refractive Surgery, 2017Co-Authors: Steven E. Wilson, Gustavo K Marino, Carla S Medeiros, Marcony R. SanthiagoAbstract:Purpose To describe, with videos, the principles of excimer laser phototherapeutic keratectomy (PTK) for the treatment of corneal scars, corneal Surface Irregularity, and recurrent corneal erosions. Methods Depending on the pathology in a treated cornea, the epithelium is removed either by transepithelial PTK ablation with the excimer laser or thorough scraping with a scalpel blade. Stromal PTK can be performed with or without photorefractive keratectomy (PRK), depending on the refractive status of both eyes. Residual Surface Irregularity is treated with masking-smoothing PTK. Typically, 0.02% mitomycin C treatment is applied for 30 seconds to corneas treated with PTK for scars and Surface Irregularity. Results Transepithelial PTK with masking-smoothing typically improves corrected distance visual acuity in the eye even if the entire stromal opacity cannot be removed and can be used to debulk Surface Irregularity to facilitate subsequent therapeutic customized wavefront-guided or optical coherence tomography-guided PTK or PRK. PTK for recurrent erosion is performed after thorough mechanical epithelial debridement of redundant epithelial basement membrane (EBM) with a scalpel and should only include a dusting of excimer laser to remove residual EBM without inducing central irregular astigmatism or damaging limbal tissues. Meta-analyses are provided for PTK treatment for corneal scars, corneal dystrophies, and recurrent corneal erosions. Conclusions Excimer laser PTK is a highly effective treatment for superficial corneal scars, central corneal irregular astigmatism, and recurrent corneal erosions unresponsive to medical treatment or mechanical epithelial debridement alone. [J Refract Surg. 2017;33(3):203-210.].
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stromal haze myofibroblasts and Surface Irregularity after prk
Experimental Eye Research, 2006Co-Authors: Marcelo V Netto, Rajiv R Mohan, S Sinha, Ajay Sharma, William J Dupps, Steven E. WilsonAbstract:In conclusion, these results demonstrated a relationship between the level of corneal haze formation after PRK and the level of stromal Surface Irregularity. PTK-smoothing with methylcellulose was an effective method to reduce stromal Surface Irregularity and decreased both haze and associated myofibroblast density. We hypothesize that stromal Surface Irregularity after PRK for high myopia results in defective basement membrane regeneration and increased epithelium-derived TGFβ signalling to the stroma that increases myofibroblast generation. Late apoptosis appears to have a role in the disappearance of myofibroblasts and haze over time.
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stromal haze myofibroblasts and Surface Irregularity after prk
Experimental Eye Research, 2006Co-Authors: Marcelo V Netto, Rajiv R Mohan, S Sinha, Ajay Sharma, William J Dupps, Steven E. WilsonAbstract:The aim of this study was to investigate the relationship between the level of stromal Surface Irregularity after photorefractive keratectomy (PRK) and myofibroblast generation along with the development of corneal haze. Variable levels of stromal Surface Irregularity were generated in rabbit corneas by positioning a fine mesh screen in the path of excimer laser during ablation for a variable percentage of the terminal pulses of the treatment for myopia that does not otherwise generate significant opacity. Ninety-six rabbits were divided into eight groups: [see table in text]. Slit lamp analysis and haze grading were performed in all groups. Rabbits were sacrificed at 4 hr or 4 weeks after surgery and histochemical analysis was performed on corneas for apoptosis (TUNEL assay), myofibroblast marker alpha-smooth muscle actin (SMA), and integrin alpha4 to delineate the epithelial basement membrane. Slit-lamp grading revealed severe haze formation in corneas in groups IV and VI, with significantly less haze in groups II, III, and VII and insignificant haze compared with the unwounded control in groups I and V. Analysis of SMA staining at 4 weeks after surgery, the approximate peak of haze formation in rabbits, revealed low myofibroblast formation in group I (1.2+/-0.2 cells/400x field) and group V (1.8+/-0.4), with significantly more in groups II (3.5+/-1.8), III (6.8+/-1.6), VII (7.9+/-3.8), IV (12.4+/-4.2) and VI (14.6+/-5.1). The screened groups were significantly different from each other (p < 0.05), with myofibroblast generation increasing with higher Surface Irregularity in the -4.5 diopter PRK groups. The -9.0 diopter PRK group VI had significantly more myofibroblast generation than the -9.0 diopter PRK with PTK-smoothing group VII (p < 0.01). Areas of basement membrane disruption were demonstrated by staining corneas for integrin alpha4 and were prominent in corneas with grade I or higher haze. SMA-positive myofibroblasts tended to be present sub-adjacent to basement membrane defects. Late apoptosis was detected at 1 month after surgery within clusters of myofibroblasts in the sub-epithelial stroma. In conclusion, these results demonstrated a relationship between the level of corneal haze formation after PRK and the level of stromal Surface Irregularity. PTK-smoothing with methylcellulose was an effective method to reduce stromal Surface Irregularity and decreased both haze and associated myofibroblast density. We hypothesize that stromal Surface Irregularity after PRK for high myopia results in defective basement membrane regeneration and increased epithelium-derived TGFbeta signalling to the stroma that increases myofibroblast generation. Late apoptosis appears to have a role in the disappearance of myofibroblasts and haze over time.
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epithelial growth within the lamellar interface after laser in situ keratomileusis lasik
Cornea, 1997Co-Authors: Marco C Helena, David M Meisler, Steven E. WilsonAbstract:Purpose To report the occurrence and follow-up of ec-topic, interface, epithelial growth after laser in situ keratomileusis (LASIK) in four eyes (three patients) and provide suggestions for management. Methods Each eye was examined by slit-lamp biomicroscopy, and corneal topography was obtained with the Tomey TMS-1 instrument. Results Each eye with epithelium within the interface after LASIK developed interface opacities and Surface Irregularity. One eye had an early surgical intervention, and three eyes were observed. Each eye lost at least one line of best spectacle-corrected visual acuity and had visual disturbance at the last follow-up visit. Conclusions The presence of epithelium within the lamellar interface is a significant complication after LASIK. In some cases, interface epithelium may be associated with early postoperative inflammation. When reoperation is required to treat this complication, we suggest scraping of both sides of the interface with a metal blade. In some cases, light excimer laser treatment can be used to facilitate epithelial removal.
James H. Burge - One of the best experts on this subject based on the ideXlab platform.
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process optimization for polishing large aspheric mirrors
Proceedings of SPIE, 2014Co-Authors: James H. Burge, Dae Wook Kim, Hubert M MartinAbstract:Large telescope mirrors have stringent requirements for Surface Irregularity on all spatial scales. Large scale errors, typically represented with Zernike polynomials, are relatively easy to control. Errors with smaller spatial scale can be more difficult because the specifications are tighter. Small scale errors are controlled with a combination of natural smoothing from large tools and directed figuring with precisely controlled small tools. The optimization of the complete process builds on the quantitative understanding of natural smoothing, convergence of small tool polishing, and confidence in the Surface measurements. This paper provides parametric models for smoothing and directed figuring that can be used to optimize the manufacturing process.
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orthonormal curvature polynomials over a unit circle basis set derived from curvatures of zernike polynomials
Optics Express, 2013Co-Authors: Chunyu Zhao, James H. BurgeAbstract:Zernike polynomials are an orthonormal set of scalar functions over a circular domain, and are commonly used to represent wavefront phase or Surface Irregularity. In optical testing, slope or curvature of a Surface or wavefront is sometimes measured instead, from which the Surface or wavefront map is obtained. Previously we derived an orthonormal set of vector polynomials that fit to slope measurement data and yield the Surface or wavefront map represented by Zernike polynomials. Here we define a 3-element curvature vector used to represent the second derivatives of a continuous Surface, and derive a set of orthonormal curvature basis functions that are written in terms of Zernike polynomials. We call the new curvature functions the C polynomials. Closed form relations for the complete basis set are provided, and we show how to determine Zernike Surface coefficients from the curvature data as represented by the C polynomials.
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super smooth optical fabrication controlling high spatial frequency Surface Irregularity
Proceedings of SPIE, 2013Co-Authors: Javier Del Hoyo, Dae Wook Kim, James H. BurgeAbstract:Modern advanced optical systems often require challenging high spatial frequency Surface error control during their optical fabrication processes. While the large scale Surface figure error can be controlled by directed material removal processes such as small tool figuring, Surface finish (<<1mm scales) is controlled with the polishing process. For large aspheric optical systems, Surface shape irregularities of a few millimeters in scale may cause serious performance degradation in terms of scattered light background noise and high contrast imaging capability. The conventional Surface micro roughness concept in Root Mean Square (RMS) over a very high spatial frequency range (e.g. RMS of 0.5 by 0.5 mm local Surface map with 500 by 500 pixels) is not sufficient to describe or specify these Surface characteristics. For various experimental polishing conditions, we investigate the process control for high frequency Surface errors with periods up to ~2-3mm. The Power Spectral Density of the finished optical Surfaces has been measured and analyzed to relate various computer controlled optical surfacing parameters (e.g. polishing interface materials) with the high spatial frequency errors on the Surface. The experiment-based optimal polishing conditions and processes producing a super smooth optical Surface while controlling Surface Irregularity at the millimeter range are presented.
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orthonormal vector polynomials in a unit circle part ii completing the basis set
Optics Express, 2008Co-Authors: Chunyu Zhao, James H. BurgeAbstract:Zernike polynomials provide a well known, orthogonal set of scalar functions over a circular domain, and are commonly used to represent wavefront phase or Surface Irregularity. A related set of orthogonal functions is given here which represent vector quantities, such as mapping distortion or wavefront gradient. Previously, we have developed a basis of functions generated from gradients of Zernike polynomials. Here, we complete the basis by adding a complementary set of functions with zero divergence – those which are defined locally as a rotation or curl.
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orthonormal vector polynomials in a unit circle part i basis set derived from gradients of zernike polynomials
Optics Express, 2007Co-Authors: Chunyu Zhao, James H. BurgeAbstract:Zernike polynomials provide a well known, orthogonal set of scalar functions over a circular domain, and are commonly used to represent wavefront phase or Surface Irregularity. A related set of orthogonal functions is given here which represent vector quantities, such as mapping distortion or wavefront gradient. These functions are generated from gradients of Zernike polynomials, made orthonormal using the Gram-Schmidt technique. This set provides a complete basis for representing vector fields that can be defined as a gradient of some scalar function. It is then efficient to transform from the coefficients of the vector functions to the scalar Zernike polynomials that represent the function whose gradient was fit. These new vector functions have immediate application for fitting data from a Shack-Hartmann wavefront sensor or for fitting mapping distortion for optical testing. A subsequent paper gives an additional set of vector functions consisting only of rotational terms with zero divergence. The two sets together provide a complete basis that can represent all vector distributions in a circular domain.
Chunyu Zhao - One of the best experts on this subject based on the ideXlab platform.
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orthonormal curvature polynomials over a unit circle basis set derived from curvatures of zernike polynomials
Optics Express, 2013Co-Authors: Chunyu Zhao, James H. BurgeAbstract:Zernike polynomials are an orthonormal set of scalar functions over a circular domain, and are commonly used to represent wavefront phase or Surface Irregularity. In optical testing, slope or curvature of a Surface or wavefront is sometimes measured instead, from which the Surface or wavefront map is obtained. Previously we derived an orthonormal set of vector polynomials that fit to slope measurement data and yield the Surface or wavefront map represented by Zernike polynomials. Here we define a 3-element curvature vector used to represent the second derivatives of a continuous Surface, and derive a set of orthonormal curvature basis functions that are written in terms of Zernike polynomials. We call the new curvature functions the C polynomials. Closed form relations for the complete basis set are provided, and we show how to determine Zernike Surface coefficients from the curvature data as represented by the C polynomials.
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orthonormal vector polynomials in a unit circle part ii completing the basis set
Optics Express, 2008Co-Authors: Chunyu Zhao, James H. BurgeAbstract:Zernike polynomials provide a well known, orthogonal set of scalar functions over a circular domain, and are commonly used to represent wavefront phase or Surface Irregularity. A related set of orthogonal functions is given here which represent vector quantities, such as mapping distortion or wavefront gradient. Previously, we have developed a basis of functions generated from gradients of Zernike polynomials. Here, we complete the basis by adding a complementary set of functions with zero divergence – those which are defined locally as a rotation or curl.
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orthonormal vector polynomials in a unit circle part i basis set derived from gradients of zernike polynomials
Optics Express, 2007Co-Authors: Chunyu Zhao, James H. BurgeAbstract:Zernike polynomials provide a well known, orthogonal set of scalar functions over a circular domain, and are commonly used to represent wavefront phase or Surface Irregularity. A related set of orthogonal functions is given here which represent vector quantities, such as mapping distortion or wavefront gradient. These functions are generated from gradients of Zernike polynomials, made orthonormal using the Gram-Schmidt technique. This set provides a complete basis for representing vector fields that can be defined as a gradient of some scalar function. It is then efficient to transform from the coefficients of the vector functions to the scalar Zernike polynomials that represent the function whose gradient was fit. These new vector functions have immediate application for fitting data from a Shack-Hartmann wavefront sensor or for fitting mapping distortion for optical testing. A subsequent paper gives an additional set of vector functions consisting only of rotational terms with zero divergence. The two sets together provide a complete basis that can represent all vector distributions in a circular domain.
Kazuo Tsubota - One of the best experts on this subject based on the ideXlab platform.
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the relation of ocular Surface Irregularity and visual disturbance in early stage acanthamoeba keratitis
Eye & Contact Lens-science and Clinical Practice, 2017Co-Authors: Yukihiro Matsumoto, Asako Kodama, Eiki Goto, Tetsuya Kawakita, Murat Dogru, Kazuo TsubotaAbstract:Purpose:To evaluate the relation between ocular Surface Irregularity and visual disturbance in early stage Acanthamoeba keratitis (AK).Methods:Fifteen patients with culture-proven AK underwent routine ophthalmic examinations, including best-corrected visual acuity (BCVA) measurement, slitlamp biomic
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comparison of anterior and posterior corneal Surface Irregularity in descemet stripping automated endothelial keratoplasty and penetrating keratoplasty
Cornea, 2010Co-Authors: Takefumi Yamaguchi, Murat Dogru, Kazuno Negishi, Kazuko Yamaguchi, Yuichi Uchino, Shigeto Shimmura, Kazuo TsubotaAbstract:PURPOSE To evaluate the Irregularity of the anterior and posterior cornea after Descemet stripping automated endothelial keratoplasty (DSAEK) and penetrating keratoplasty (PK). METHODS This clinical study comprised 39 eyes: 13 consecutive eyes after DSAEK, 13 consecutive eyes after PK, and 13 age-matched normal eyes. Corneal elevation data were acquired using a rotating Scheimpflug camera 1 and 3 months after DSAEK and PK. Anterior and posterior corneal elevation data were decomposed into a set of Zernike polynomials up to eighth order. Total higher-order root mean square (RMS) and RMS from third to eighth order were calculated. The astigmatism and Irregularity of the anterior and posterior Surfaces were compared between DSAEK and PK. RESULTS The regular astigmatism and tilt components of the anterior Surface were significantly lower after DSAEK than after PK at 1 and 3 months (P < 0.001), whereas there was no difference in astigmatism of the posterior Surface between the groups (P = 0.07, 0.22). The higher-order RMS and RMSs of third- to eighth-order components of the anterior Surface were significantly larger after PK than those after DSAEK at 1 and 3 months (P < 0.01), whereas there were no significant differences between DSAEK and PK in higher-order aberration RMS and RMSs of third- to eighth-order components of the posterior Surface. CONCLUSIONS Postoperative corneal Irregularity of the anterior Surface was greater after PK than after DSAEK, whereas there was no significant difference in posterior Surface Irregularity. DSAEK is superior to PK in terms of the higher-order Irregularity of the anterior Surface.
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effect of anterior and posterior corneal Surface Irregularity on vision after descemet stripping endothelial keratoplasty
Journal of Cataract and Refractive Surgery, 2009Co-Authors: Takefumi Yamaguchi, Kazuno Negishi, Kazuko Yamaguchi, Dogru Murat, Yuichi Uchino, Shigeto Shimmura, Kazuo TsubotaAbstract:Purpose To evaluate Irregularity of the anterior and posterior cornea before and after Descemet-stripping endothelial keratoplasty (DSEK) and its effect on visual acuity. Setting Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan. Methods Corneal data were acquired using a rotating Scheimpflug camera before and 1 month and 3 months after DSEK. Anterior and posterior corneal elevation data were decomposed into a set of Zernike polynomials up to the 8th order within a 4.0 mm diameter region. Total higher-order root mean square (HO-RMS) and RMS from the 3rd to 8th order were calculated. The effects of anterior and posterior Surface Irregularity on visual acuity were evaluated. Results This clinical study comprised 13 consecutive eyes of 12 bullous keratopathy patients. The mean best corrected visual acuity (BCVA) was 1.11 logMAR ± 0.5 (SD) preoperatively, 0.49 ± 0.49 logMAR 1 month postoperatively, and 0.27 ± 0.32 logMAR at 3 months. The HO-RMS of the anterior Surface 1 month ( P = .040) and 3 months ( P = .048) postoperatively was significantly lower than preoperatively. There were no significant differences in posterior Surface HO-RMS between preoperatively and 1 month ( P = .45) and 3 months ( P = .054). The postoperative BCVA was significantly correlated with HO-RMS ( P P = .354). Conclusion Postoperative BCVA correlated with Irregularity of the anterior Surface but not the posterior Surface. In addition to corneal transparency, regularity of the anterior Surface is an important factor in visual acuity after DSEK.
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impaired functional visual acuity of dry eye patients
American Journal of Ophthalmology, 2002Co-Authors: Eiki Goto, Yukihiro Matsumoto, Yukiko Yagi, Kazuo TsubotaAbstract:Abstract PURPOSE: To report dry eye patients' functional visual acuity, which was measured after sustained eye opening for 10–20 seconds, as a simulation of visual function of daily acts of gazing, which is defined as looking at an object with involuntary blink suppression. METHODS: Interventional clinical nonrandomized comparative trial. We measured ordinary best-corrected visual acuity and functional visual acuity in non-Sjogren's syndrome (non-SS, N=10) and Sjogren's syndrome (SS, N=12) patients and in normal controls (N = 8), prospectively. Surface regularity index (SRI) of corneal topography was also measured under routine circumstances and after sustained eye opening. Blink rates while gazing were measured during reading in another 28 dry eye patients and during driving in another 8 normal controls. RESULTS: Functional visual acuity did not change (1.27–1.16) in normal controls, but decreased significantly from 1.18–0.336 in non-SS patients ( P = .0007) and from 1.15–0.228 ( P P = .032) and SS patients ( P = .0007), but not in the normal controls. Blink rates during reading ( P P = .012) were significantly decreased from baseline blink rates. CONCLUSIONS: This study shows that the visual function of dry eye patients becomes abnormal with ocular Surface Irregularity when the eye is kept open for 10–20 seconds. Our data indicate impaired visual function in dry eye patients while gazing. Functional visual acuity may be important in daily activities.
Marcelo V Netto - One of the best experts on this subject based on the ideXlab platform.
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stromal haze myofibroblasts and Surface Irregularity after prk
Experimental Eye Research, 2006Co-Authors: Marcelo V Netto, Rajiv R Mohan, S Sinha, Ajay Sharma, William J Dupps, Steven E. WilsonAbstract:In conclusion, these results demonstrated a relationship between the level of corneal haze formation after PRK and the level of stromal Surface Irregularity. PTK-smoothing with methylcellulose was an effective method to reduce stromal Surface Irregularity and decreased both haze and associated myofibroblast density. We hypothesize that stromal Surface Irregularity after PRK for high myopia results in defective basement membrane regeneration and increased epithelium-derived TGFβ signalling to the stroma that increases myofibroblast generation. Late apoptosis appears to have a role in the disappearance of myofibroblasts and haze over time.
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stromal haze myofibroblasts and Surface Irregularity after prk
Experimental Eye Research, 2006Co-Authors: Marcelo V Netto, Rajiv R Mohan, S Sinha, Ajay Sharma, William J Dupps, Steven E. WilsonAbstract:The aim of this study was to investigate the relationship between the level of stromal Surface Irregularity after photorefractive keratectomy (PRK) and myofibroblast generation along with the development of corneal haze. Variable levels of stromal Surface Irregularity were generated in rabbit corneas by positioning a fine mesh screen in the path of excimer laser during ablation for a variable percentage of the terminal pulses of the treatment for myopia that does not otherwise generate significant opacity. Ninety-six rabbits were divided into eight groups: [see table in text]. Slit lamp analysis and haze grading were performed in all groups. Rabbits were sacrificed at 4 hr or 4 weeks after surgery and histochemical analysis was performed on corneas for apoptosis (TUNEL assay), myofibroblast marker alpha-smooth muscle actin (SMA), and integrin alpha4 to delineate the epithelial basement membrane. Slit-lamp grading revealed severe haze formation in corneas in groups IV and VI, with significantly less haze in groups II, III, and VII and insignificant haze compared with the unwounded control in groups I and V. Analysis of SMA staining at 4 weeks after surgery, the approximate peak of haze formation in rabbits, revealed low myofibroblast formation in group I (1.2+/-0.2 cells/400x field) and group V (1.8+/-0.4), with significantly more in groups II (3.5+/-1.8), III (6.8+/-1.6), VII (7.9+/-3.8), IV (12.4+/-4.2) and VI (14.6+/-5.1). The screened groups were significantly different from each other (p < 0.05), with myofibroblast generation increasing with higher Surface Irregularity in the -4.5 diopter PRK groups. The -9.0 diopter PRK group VI had significantly more myofibroblast generation than the -9.0 diopter PRK with PTK-smoothing group VII (p < 0.01). Areas of basement membrane disruption were demonstrated by staining corneas for integrin alpha4 and were prominent in corneas with grade I or higher haze. SMA-positive myofibroblasts tended to be present sub-adjacent to basement membrane defects. Late apoptosis was detected at 1 month after surgery within clusters of myofibroblasts in the sub-epithelial stroma. In conclusion, these results demonstrated a relationship between the level of corneal haze formation after PRK and the level of stromal Surface Irregularity. PTK-smoothing with methylcellulose was an effective method to reduce stromal Surface Irregularity and decreased both haze and associated myofibroblast density. We hypothesize that stromal Surface Irregularity after PRK for high myopia results in defective basement membrane regeneration and increased epithelium-derived TGFbeta signalling to the stroma that increases myofibroblast generation. Late apoptosis appears to have a role in the disappearance of myofibroblasts and haze over time.