Differences in early biomechanical properties after myopic and hyperopic lasik using mechanical microkeratome Sub-Bowman's Keratomileusis (SBK)

Purpose: To evaluate biomechanical changes measured with the ORA (Ocular Response Analyzer (R); Reichert Ophthalmic Instruments, Buffalo, New York, USA) after Lasik with the Moria One Use Plus and to compare the biomechanics changes after myopic and hyperopic ablations. Methods: Fourteeneyes for hyperopia (H) and 19 eyes for myopia (M) were evaluated with the ORA preoperatively and 1 month after Lasik with thin flap (100 microns) using SBK-OUP (Sub-Bowman Keratomileusis-One Use Plus, Moria (R)). CH (Corneal Hysteresis), CRF (Corneal Resistance Factor), IOPg (gold-standard, Goldmann correlated Intraocular pressure), IOPcc (Corneal compensated Intraocular pressure) and more 38 variables derived from the corneal biomechanical response signal of the ORA were analyzed. The Wilcoxon test was used to assess differences between the variables before and after surgery for each group and the differences between the pre and postoperative (1 month) myopic eyes were compared with those obtained in hyperopic eyes, using the Mann-Whitney test. Results: There was a significant difference before and after Lasik in myopic and hyperopic eyes in IOPg (Wilcoxon, p<0.05), but not in IOPcc. Only myopic eyes showed a significant difference in CH and CRF measurements before and after LASIK, as well as 9 other biomechanical parameters (aspect1, h1, dive1, path1, p1area1, W11, H11, and w2 path11; Wilcoxon, p<0, 05), 8 of these being related to the first sign of flattening. Five parameters related to the sign of the second applanation showed significant variation only in the eyes before and after hyperopic Lasik (aspect2, h2, dive2, mslew2 and H21; Wilcoxon, p<0,05). There was a difference in both myopic and hyperopic on three parameters related to the applanation signal areas (p1area, and p2area p2area1; Wilcoxon, p<0.05). Differences in IOPg and p1area, before and after surgery were significantly higher in myopic eyes than in hyperopic eyes (Mann-Whitey, p<0.05). Conclusion: There are several significant differences in biomechanical parameters after Lasik with Moria OUP_SBK. Overall, the impact of myopic LASIK on corneal biomechanics is higher than of hyperopic Lasik. The parameters derived from the first sign of the ORA are more affected in myopic LASIK, whereas parameters derived from the second applanation are more affected in hyperopic LASIK.

The Endothelial Sample Size Analysis in Corneal Specular Microscopy Clinical Examinations

Purpose: To evaluate endothelial cell sample size and statistical error in corneal specular microscopy (CSM) examinations. Methods: One hundred twenty examinations were conducted with 4 types of corneal specular microscopes: 30 with each BioOptics, CSO, Konan, and Topcon corneal specular microscopes. All endothelial image data were analyzed by respective instrument software and also by the Cells Analyzer software with a method developed in our lab(US Patent). A reliability degree (RD) of 95% and a relative error (RE) of 0.05 were used as cut-off values to analyze images of the counted endothelial cells called samples. The sample size mean was the number of cells evaluated on the images obtained with each device. Only examinations with RE<0.05 were considered statistically correct and suitable for comparisons with future examinations. The Cells Analyzer software was used to calculate the RE and customized sample size for all examinations. Results: Bio-Optics: sample size, 97 +/- 22 cells; RE, 6.52 +/- 0.86; only 10% of the examinations had sufficient endothelial cell quantity (RE<0.05); customized sample size, 162 +/- 34 cells. CSO: sample size, 110 +/- 20 cells; RE, 5.98 +/- 0.98; only 16.6% of the examinations had sufficient endothelial cell quantity (RE<0.05); customized sample size, 157 +/- 45 cells. Konan: sample size, 80 +/- 27 cells; RE, 10.6 +/- 3.67; none of the examinations had sufficient endothelial cell quantity (RE>0.05); customized sample size, 336 +/- 131 cells. Topcon: sample size, 87 +/- 17 cells; RE, 10.1 +/- 2.52; none of the examinations had sufficient endothelial cell quantity (RE>0.05); customized sample size, 382 +/- 159 cells. Conclusions: A very high number of CSM examinations had sample errors based on Cells Analyzer software. The endothelial sample size (examinations) needs to include more cells to be reliable and reproducible. The Cells Analyzer tutorial routine will be useful for CSM examination reliability and reproducibility.

Influence of the magnetization damping on dynamic hysteresis loops in single domain particles

This article reports on the influence of the magnetization damping on dynamic hysteresis loops in single-domain particles with uniaxial anisotropy. The approach is based on the Neel-Brown theory and the hierarchy of differential recurrence relations, which follow from averaging over the realizations of the stochastic Landau-Lifshitz equation. A new method of solution is proposed, where the resulting system of differential equations is solved directly using optimized algorithms to explore its sparsity. All parameters involved in uniaxial systems are treated in detail, with particular attention given to the frequency dependence. It is shown that in the ferromagnetic resonance region, novel phenomena are observed for even moderately low values of the damping. The hysteresis loops assume remarkably unusual shapes, which are also followed by a pronounced reduction of their heights. Also demonstrated is that these features remain for randomly oriented ensembles and, moreover, are approximately independent of temperature and particle size. (C) 2012 American Institute of Physics. [doi:10.1063/1.3684629]

Importance of anterior segment tomography for the diagnosis of corneal ectasia

Purpose: The methodology currently used for interpretation of the cornea and anterior segment tomography for the diagnosis of corneal ectasia and its susceptibility. Methods: Description of the methodology and clinical interpretation of corneal and anterior segment tomography indexes; report of three cases demonstrating the importance of this new diagnostic tool (Pentacam HR (R)) in ophthalmological practice. Conclusion: The use of corneal and anterior segment tomography seems to be an effective method to increase the sensitivity and specificity for the diagnosis and early detection of corneal ectasia.

Restoration of the rabbit corneal surface after total epithelial debridement and complete limbal excision

How is the corneal epithelium restored when all of it plus the limbus have been eliminated? This investigation explored the possibility that this may be achieved through the conjunctival epithelium. The corneal epithelium of the right eye of 12 rabbits (Oryctolagus cuniculus) was totally scraped followed by surgical excision of the limbus plus 1.0-1.5 mm of the adjacent conjunctiva. Antibiotics and corticosteroids were applied for 1 week after surgery. Histological and immunohistochemical techniques were used to monitor the events taking place on the eye surface 2 weeks and 1, 3 and 6 months thereafter. Initially, the corneal surface was covered by conjunctival-like epithelium. After 1 month and more prominently at 3 and 6 months an epithelium displaying the morphological features of the cornea and reacting with the AE5 antibody was covering the central region. It is likely that the corneal epithelium originated from undifferentiated cells of the conjunctiva interacting with the corneal stroma.

Subdivision of Hysteresis Loss in Mn-Zn Ferrite Toroidal Cores

The hysteresis loss subdivision method proved to be a strong tool to help in the analysis of different energy dissipation mechanisms along the quasi-static hysteresis loop measured on electrical steels. This paper used the samemethod to discuss the mechanisms involving the energy loss dissipation in Mn-Zn ferrite toroidal cores. The samples, sintered under controlled atmosphere in industrial conditions, were measured under triangular waveform excitation at very low frequency (5 mHz) and peak flux densities varying from 0.05 T to 0.45 T. The results show a different behavior between the low inductions hysteresis loss (WLI) and the high induction hysteresis loss (WHI) which proves the existence of different energy dissipation mechanisms affecting these loss components.

Corneal wavefront-guided photorefractive keratectomy with mitomycin-C for hyperopia after radial keratotomy: Two-year follow-up

PURPOSE: To assess corneal wavefront-guided photorefractive keratectomy (PRK) to correct hyperopia after radial keratotomy (RK). SETTING: Sadalla Amin Ghanem Eye Hospital, Joinville, Santa Catarina, Brazil. DESIGN: Case series. METHODS: Excimer laser corneal wavefront-guided PRK with intraoperative mitomycin-C (MMC) 0.02% was performed. Main outcome measures were uncorrected (UDVA) and corrected (CDVA) distance visual acuities, spherical equivalent (SE), corneal aberrations, and haze. RESULTS: The mean time between RK and PRK in the 61 eyes (39 patients) was 18.8 years +/- 3.8 (SD). Before PRK, the mean SE was +4.17 +/- 1.97 diopters (D); the mean astigmatism, -1.39 +/- 1.04 D; and the mean CDVA, 0.161 +/- 0.137 logMAR. At 24 months, the mean values were 0.14 +/- 0.99 D (P<.001), -1.19 +/- 1.02 D (P=.627), and 0.072 +/- 0.094 logMAR (P<.001), respectively; the mean UDVA was 0.265 +/- 0.196 (P<.001). The UDVA was 20/25 or better in 37.7% of eyes and 20/40 or better in 68.9%. The CDVA improved by 1 or more lines in 62.3% of eyes. Two eyes (3.3%) lost 2 or more lines, 1 due to corneal ectasia. Thirty eyes (49.2%) were within +/- 0.50 D of intended SE and 45 (73.8%) were within +/- 1.00 D. From 6 to 24 months, the mean SE regression was +0.39 D (P<.05). A significant decrease in coma, trefoil, and spherical aberration occurred. Three eyes developed peripheral haze more than grade 1. CONCLUSION: Corneal wavefront-guided PRK with MMC for hyperopia after RK significantly improved UDVA, CDVA, and higher-order corneal aberrations with a low incidence of visually significant corneal haze.

Magnetic hyperthermia investigation of cobalt ferrite nanoparticles: Comparison between experiment, linear response theory, and dynamic hysteresis simulations

Considerable effort has been made in recent years to optimize materials properties for magnetic hyperthermia applications. However, due to the complexity of the problem, several aspects pertaining to the combined influence of the different parameters involved still remain unclear. In this paper, we discuss in detail the role of the magnetic anisotropy on the specific absorption rate of cobalt-ferrite nanoparticles with diameters ranging from 3 to 14 nm. The structural characterization was carried out using x-ray diffraction and Rietveld analysis and all relevant magnetic parameters were extracted from vibrating sample magnetometry. Hyperthermia investigations were performed at 500 kHz with a sinusoidal magnetic field amplitude of up to 68 Oe. The specific absorption rate was investigated as a function of the coercive field, saturation magnetization, particle size, and magnetic anisotropy. The experimental results were also compared with theoretical predictions from the linear response theory and dynamic hysteresis simulations, where exceptional agreement was found in both cases. Our results show that the specific absorption rate has a narrow and pronounced maxima for intermediate anisotropy values. This not only highlights the importance of this parameter but also shows that in order to obtain optimum efficiency in hyperthermia applications, it is necessary to carefully tailor the materials properties during the synthesis process. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729271]

Dynamic symmetry loss of high-frequency hysteresis loops in single-domain particles with uniaxial anisotropy

Understanding how magnetic materials respond to rapidly varying magnetic fields, as in dynamic hysteresis loops, constitutes a complex and physically interesting problem. But in order to accomplish a thorough investigation, one must necessarily consider the effects of thermal fluctuations. Albeit being present in all real systems, these are seldom included in numerical studies. The notable exceptions are the Ising systems, which have been extensively studied in the past, but describe only one of the many mechanisms of magnetization reversal known to occur. In this paper we employ the Stochastic Landau-Lifshitz formalism to study high-frequency hysteresis loops of single-domain particles with uniaxial anisotropy at an arbitrary temperature. We show that in certain conditions the magnetic response may become predominantly out-of-phase and the loops may undergo a dynamic symmetry loss. This is found to be a direct consequence of the competing responses due to the thermal fluctuations and the gyroscopic motion of the magnetization. We have also found the magnetic behavior to be exceedingly sensitive to temperature variations, not only within the superparamagnetic-ferromagnetic transition range usually considered, but specially at even lower temperatures, where the bulk of interesting phenomena is seen to take place. (C) 2011 Elsevier B.V. All rights reserved.

Peripheral Sterile Corneal Ring Infiltrate After Riboflavin-UVA Collagen Cross-Linking in Keratoconus

Purpose: To present 7 cases of peripheral sterile corneal infiltrates that occurred after corneal cross-linking (CXL) for progressive keratectasia. Methods: Seven patients who had their progressive keratoconus documented underwent corneal deepithelization and subsequently CXL, which was performed with the application of 0.1% riboflavin with 20% dextran, and exposure to UVA light (370 nm, 2.9-3.1 mW/cm(2)) for 30 minutes. Results: Nearly a week after the procedure, the patients presented with peripheral stromal infiltrates. The ring-like infiltrates were superficial and were present at the 9.0-mm zone. Sterile infiltration was diagnosed. Patients were treated with topical corticosteroids, and complete resolution was achieved after a few weeks of treatment. Conclusions: We hypothesize that the phototoxic effect on the corneal stroma may be the main mechanism that triggers these infiltrates. Alternatively, alterations in antigenicity that occur in native proteins after CXL could result in patients recognizing the proteins as nonself and mounting immune responses.

Longitudinal dynamic hysteresis in single-domain particles

We present results for longitudinal dynamic hysteresis in single domain particles with uniaxial anisotropy. The combined influence of temperature, field-sweeping frequency, and field amplitude is discussed in detail. A novel and efficient numerical method is proposed, based on the direct solution of the infinite hierarchy of differential recurrence relations obtained from averaging over the stochastic realizations of the magnetic Langevin equation. (C) 2012 American Institute of Physics. [doi:10.1063/1.3676416]

Topical Brazilian propolis improves corneal wound healing and inflammation in rats following alkali burns

Abstract Background The objective of this study was to investigate the effects of the Brazilian Scaptotrigona sp propolis, a widely used folk medicine, in corneal wound healing and inflammation. Methods Corneal epithelial defects of 1 mm in diameter were made in the right eyes of Wistar male adult rats by cauterization with silver nitrate sticks. Subsequently, they were divided in two groups (n = 40 rats/group): Brazilian propolis (BP) group was topically treated with a microemulsion containing 1% Brazilian propolis; vehicle (VH) group received the same formulation without propolis. The epithelial defect area was photographed and measured at t = 0 (wound induction), and after 12, 24, 48 and 120 h of treatment. The inflammatory response was evaluated based on counting of neutrophils. Epithelial regeneration rates were determined based on Ki-67 expression in basal epithelial cells. Comparisons were made using the Kruskal-Wallis and the Mann–Whitney U test. Results The BP group presented both smaller epithelial defect areas at 12, 24 and 48 h and fewer corneal infiltrating neutrophils at 24 and 48 h (P < 0.01) than the VH group. These effects were associated with more pervasive Ki-67 staining in the BP group at 12 and 24 h (P < 0.05). Conclusions Topically applied BP accelerated wound healing and reduced the inflammatory response to silver nitrate-induced corneal alkali burns in rats.