Slit Scanning Research Articles

Effectiveness and biocompatibility of a novel Schlemm’s canal microstent for glaucoma management

To evaluate the effectiveness and biocompatibility of Wistend, a novel Schlemm’s canal (SC) microstent made of Nitinol designed to improve aqueous humor outflow. New Zealand white (NZW) rabbits were divided into blank, sham-operated and Wistend groups. ICare® Tonovet Plus®, swept-source optical coherence tomography (SS-OCT), slit lamp biomicroscopy, retinal camera and scanning electron microscopy (SEM) were used for preoperative and postoperative observations. Hematoxylin and Eosin (H&E) tissue staining was adopted for biocompatibility. A significant difference in intraocular pressure (IOP) between the Wistend group and the control groups was observed during the six-month follow-up. SS-OCT identified arc line internal reflections within the SC in the anterior chamber angle. Conjunctival congestion and edema gradually diminished in the early stages. No corneal vascularization, no anterior chamber inflammatory response and no significant tissue reactions were noted in any groups. SEM showed the Wistend’s windows and orifices remained clear, encircled by minimal incidental ocular tissue and free from blockage. Histopathological examination revealed no discernible differences between the Wistend-implanted and sham-operated eyes. These in vivo studies demonstrate the effectiveness and biocompatibility of the microstent. Our findings suggest a promising potential for Wistend in significantly reducing IOP and effectively facilitating the outflow of aqueous humor.

High-resolution calibration and data reconstruction method for image mapping spectrometer

The image mapping spectrometer (IMS) is a kind of snapshot spectral imaging system that modulates the 3D spatial-spectral datacube (x,y,λ) to a 2D sensor for simultaneous measurement. Since the IMS utilizes an image mapper for mapping the spatial information, a calibration method is required to generate the lookup table between the measured raw image pixels and the desired datacube voxels. However, the current calibration methods are either time-consuming or low-accurate. We present a combined slit scan calibration and data processing approach that can balance the calibration efficiency and accuracy, by taking in account the irregularity of field of view (FOV) of the image mapper in the calibrating setup. Additionally, we analyze the spatial-spectral mixing phenomenon of the IMS datacube recovered from the calibrated lookup table. To reconstruct high-quality spectral datacube from the spatial-spectral mixed datacube, a spatial-spectral unmixing network (SSUNet) based on multi-head multi-attention mechanism is presented. Experimental results validated the effectiveness of both the calibration strategy and the datacube restoration network.

Construction and dosimetric characterization of a motorized scanning-slit system for electron FLASH experiments.

Beam scanning is a useful technique for the treatment of large tumors when the primary beam size is limited, which is the case with radiation beams used in FLASH radiotherapy. To optimize beam scanning as a dose delivery method for FLASH radiotherapy, it is necessary to first understand the effects of beam scanning on the FLASH effect. To do so, biological FLASH experiments need to be done using defined beam parameters with beam scanning and compared to the situation without beam scanning. In this regard, we propose implementation of a simple slit scanning system with an electron FLASH beam to obtain a scanned radiation field that closely resembles a static field. A pulsed electron linear accelerator (linac) was used in combination with a scanning slit system in order to simulate a scanned electron beam. Three configurations that produced homogeneous lateral profiles and high enough doses per pulse for FLASH experiments were established. The optimal scanning parameters were found for each configuration by examining the flatness of the obtained lateral dose profiles. Using the optimal scanning parameters, the scanned FLASH beams were dosimetrically characterized and compared to non-scanned open field beam. A final electron FLASH beam scanning configuration was found for a 1mm wide slit at a distance of 350mm from the linac and a 2mm wide slit at distances of 350 and 490mm from the linac. The lateral profiles for these final configurations were found to have a homogeneity that is comparable to the open field profiles. The percentage depth dose (PDD) values found for these final configurations closely matched (by a few percentage) the PDD of the open field beam. Three electron FLASH beam scanning configurations achieved by the motorized slit system were found to produce radiation fields similar to a non-scanned open field electron beam. These final configurations can therefore be used in future biological FLASH experiments to compare to non-scanned beam experiments in order to optimize beam scanning as a technique permitting the treatment of larger tumors with FLASH radiotherapy.

Norepinephrine as an Enhancer Promoting Corneal Penetration of Riboflavin for Transepithelial Corneal Crosslinking.

Previously, we found norepinephrine (NE) could affect the corneal epithelial integrity, herein we investigated the feasibility and safety of NE serving as a chemical enhancer to promote corneal penetration of riboflavin during transepithelial corneal crosslinking (CXL). The dosage of NE that could promote riboflavin diffusion through the healthy epithelial barrier without inducing epithelial damage in C57BL/6 mice was determined. The safety of NE treatment was confirmed by morphological and histological examinations of the whole cornea. The efficacy of NE in promoting riboflavin penetration was verified by slit lamp and scanning electron microscope (SEM), and corneal biomechanical measurement after CXL. To better fit the clinical scenario, increased NE dosage and shortened riboflavin infiltration time were further evaluated. The lowest dosage of NE (1 mg/mL) that facilitated transepithelial riboflavin permeation was 2 µL. No visible corneal structure alteration was observed after NE treatment. SEM indicated dissociation of intercellular junctions among corneal epithelial cells. Homogenous distribution of riboflavin throughout corneal stroma was observed. NE-treated corneas reached comparable biomechanical properties after CXL, including stress-relaxation curve and elastic modulus, with corneas treated with the commercially available transepithelial drug Peschke TE. To better fit the clinical scenario, increasing NE up to 5.5 µL helped riboflavin infiltrate the corneal stroma within 30 minutes. After CXL with 9 mW/cm2 ultraviolet-A (UVA) for 2.5 minutes, the cornea showed significantly enhanced corneal biomechanical properties with undisturbed corneal endothelium. NE serves as an effective enhancer in increasing riboflavin diffusion with limited impairment on corneal epithelium and has great potential for clinical application. NE serves as an effective enhancer for riboflavin penetration and clinical transepithelial CXL.

Sub-micron normalized emittance measurement for a MeV continuous-wave electron gun

Continuous-wave (CW) electron sources with sub-micron normalized emittance are of critical importance for advanced linear accelerator based light sources. The DC-SRF-II gun, designed as such a source, has been newly constructed and brought into operation. To characterize the performance of the gun, we have developed an emittance measurement system based upon single slit scanning method under a dedicated beam diagnostics mode. With this system, the measurement of sub-micron normalized emittance, together with a reconstruction of the phase space distribution, has been achieved with high reproducibility. This paper presents a detailed description of the system.

Angle Kappa agreement between Scheimpflug tomography, combined placido Scheimpflug and combined slit scanning placido systems

PurposeTo compare the measured or calculated angle Kappa using Oculus pentacam HR, Sirius and Orbscan III devices.Patients and methodsA prospective randomized cohort study, conducted on 47 eyes of 47 healthy orthotropic individuals, with an age range of 18–50 years and a corrected Snellen’s distance visual acuity (CDVA) of 0.8 decimal or better. Angle Kappa is assessed directly using Orbscan® III software version 1.8.165.1. (Bausch and Lomb Rochester, New York, United States), while Pentacam® HR 1.21r.65 (Oculus Optikgeräte GmbH, Wetzlar, Germany) and Sirius device (CSO, version 3.2.1.60, Costruzione Strumenti Oftalmici, Florence, Italy) were used to calculate angle kappa indirectly.ResultsLeast mean difference of estimated angle Kappa was between Orbscan and Pentacam devices (− 0.18° ± 1.8), and it was statistically insignificant (p value = 0.1294). Differences between both Orbscan and Sirius, and Pentacam and Sirius were statistically significant (p value = 0.0004 and < 0.0001 consecutively). Bland Altman analysis showed a 95% confidence interval between Orbscan III and Pentacam of − 3.76 to 3.4 and between Orbscan III and Sirius of − 3.79 to 2.26.ConclusionPentacam parameters can be used as a reliable method to calculate angle kappa indirectly, without usage of any additional measurements from other machine. Sirius device parameters could also be used, but with less accurate results. A simple modification to those devices’ software to calculate it, and incorporate it in the printout is possible, and highly recommended.

Empirical scatter correction: CBCT scatter artifact reduction without prior information.

The image quality of cone beam CT (CBCT) scans severely suffers from scattered radiation if no countermeasures are taken. Scatter artifacts may induce cupping and streak artifacts and lead to a reduced image contrast and wrong CT values of the reconstructed volumes. Established software-based approaches for a correction of scattered radiation typically rely on prior knowledge of the CT system, scan parameters, the scanned object, or all of theaforementioned. This study proposes a simple and effective postprocessing software-based correction method of scatter artifacts in CBCT scans without specific priorknowledge. We propose the empirical scatter correction (ESC), which generates scatter-like basis images from each projection image by convolution operations. A linear combination of these basis images is subtracted from the original projection image. The logarithm is taken and an FDK reconstruction is performed. The coefficients needed for the linear combination are determined automatically by a downhill simplex algorithm such that the resulting reconstructed images show no scatter artifacts. We demonstrate the potential of ESC by correcting simulated volumes with Monte Carlo scatter artifacts, a head phantom scan performed on our table-top CBCT, and a pelvis scan from a Varian Edge CBCTscanner. ESC is able to improve the image quality of CBCT scans, which is shown on the basis of our simulations and on measured data. For a simulated head CT, the CT value difference to the scatter-free reference image was as low as -6 HU after using ESC, whereas the uncorrected data deviated by more than -200 HU from the reference data. Simulations of thorax and abdomen CT scans show that although scatter artifacts are not fully removed, anatomical features which were hard to discover prior to the correction become clearly visible and better segmentable with ESC. Similar results are obtained in the phantom measurement, where a comparison to a slit scan of our head phantom shows only small differences. The CT values in soft tissue are improved in this measurement, as well. In soft tissue areas with severe scatter artifacts, the CT values agree well with those of the slit scan (difference to slit scan: 35HU corrected and -289 HU uncorrected). Scatter artifacts in measured patient data can also be reduced using the proposed ESC. The results are comparable to those achieved with designated correction algorithms installed on the Varian Edge CBCT system. ESC allows to reduce artifacts caused by patient scatter solely based on the projectiondata.

Infrared slit light-based scanning type portable device for monitoring of cataract

Age-related cataracts are reported to be responsible for over 50% of world blindness and are considered a priority eye disease by the World Health Organization. Cataracts progress slowly and often have no subjective symptoms, so regular examination is required for early detection and treatment. We report on the design and development of a portable slit-light-based cataract detection device using near-infrared light and a scanning mirror. Imaging results were obtained by scanning cataract model eyes made from dimethylpolysiloxane and starch mixture and enucleated swine eye with induced cataracts. The fabricated system has adequate sensitivity to detect the smallest cataract formation and progress of cataract in the induced cataract eye and such measurements are useful for early detection of cataract. The results indicate that our fabricated slit-light device could be an easy-to-handle and low-cost tool for remote/routine detection and diagnosis of ocular diseases (like cataracts) without a need for an ophthalmologist.

Research on X-ray Fluorescence Enhanced Fluoroscopy Imaging Technology

Chest X-ray fluoroscopy is a commonly used medical imaging method, which has a wide range of applications in the diagnosis of lung diseases and other fields. However, due to low contrast and relatively close linear attenuation coefficients, some early small lesions are difficult to detect in time. Using the X-ray fluorescent effect of high atomic number metal elements and metal atom-containing agents that can be enriched in the lesion, the fluoroscopy signal and the fluorescent signal emitted by the metal atoms can be detected at the same time during the fluoroscopy, and the images of the two can be integrated, which can theoretically enhance the contrast between the lesion and the surrounding tissue. Based on GEANT4, this paper conducts Monte Carlo simulations to explore the feasibility and enhancement effects of three enhancement schemes: the pencil beam spot scanning method, cone-beam collimation method, and slit scanning method, and discusses the specific geometric structure and material selection.

Optimal extraction of echelle spectra: Getting the most out of observations

Context. The price of instruments and observing time on modern telescopes is quickly increasing. Therefore, it is worth revisiting the data reduction algorithms to extract every bit of scientific information from available observations. Echelle spectrographs are typical instruments used in high-resolution spectroscopy, but attempts to improve the wavelength coverage and versatility of these instruments has resulted in a complicated and variable footprint of the entrance slit projection onto the science detector. Traditional spectral extraction methods generally fail to perform a truly optimal extraction when the slit image is not aligned with the detector columns and, instead, is tilted or even curved. Aims. Here, we present the mathematical algorithms and examples of their application to the optimal extraction and the following reduction steps for echelle spectrometers equipped with an entrance slit that is imaged with various distortions. The new method minimises the loss of spectral resolution, maximises the signal-to-noise ratio, and efficiently identifies local outliers. In addition to the new optimal extraction, we present order splicing and a more robust continuum normalisation algorithm. Methods. We developed and implemented new algorithms that create a continuum-normalised spectrum. In the process, we account for the (variable) tilt or curvature of the slit image on the detector and achieve optimal extraction without prior assumptions about the slit illumination. Thus, the new method can handle arbitrary image slicers, slit scanning, and other observational techniques aimed at increasing the throughput or dynamic range. Results. We compare our methods with other techniques for different instruments to illustrate the superior performance of the new algorithms compared to commonly used procedures. Conclusions. Advanced modelling of the focal plane requires significant computational effort but it has proven worthwhile thanks to the retrieval of a greater store of science information from every observation. The described algorithms and tools are freely available as part of our PyReduce package.

In vivo Slit Scanning Confocal Microscopic Observation in a Patient with Keratoconus Wearing Miniscleral Contact Lens for One Year: A Case Report

The purpose of the present case report was to evaluate corneal microstructure in a patient with keratoconus wearing miniscleral contact lens (MS CL) for 1 year. A 38 years old patient diagnosed with stage III keratoconus in right eye and corneal graft (penetrating keratoplasty) in left eye was referred to optometry department of a public hospital in Malaysia. Based on the MS CLs fitting performance on the patient’s eye, MS CLs were prescribed in both eyes. However, patient opted for MS CL only in the right eye. In vivo slit scanning confocal microscopy was performed at baseline and after 1 year of contact lens wear in right eye. Qualitative analysis was done using a grading scale designed by Hollingsworth et al. (2005a), while quantitative analysis was performed using NAVIS software in a fixed frame of 0.06 mm². After 1 year of MS CL wear, qualitative observation of right cornea showed no change in stromal haze and architecture of nerve fibers. However, morphological alterations like dark bands were observed both in anterior and posterior stroma along with tendency of clustering keratocyte nuclei in posterior stroma. Quantitative analysis showed that anterior and posterior stroma keratocyte density and endothelium cell density were relatively low after 1 year of MS CL wear (817.3, 667.2, and 2577 cells/mm², respectively) caompared to baseline observation (850.7, 705.0, and 2666 cells/mm², respectively). Mean cell area of anterior stroma, posterior stroma and endothelium were also different in post MS CL wear. Polymegathism and pleomorphism calculated by NAVIS software were varied after 1 year (49.6% and 37.5%, respectively) compared to baseline (67.1% and 29.6%, respectively). In the discussed case, noticeable changes were observed in corneal microstructure after 1 year of MS CL wear. Thereby, in conclusion we recommend future studies with more number of keratoconic eyes wearing MS CLs to emphasize the findings on microstructural changes in keratoconic cornea wearing MS CLs.

Calibration of programmable spectral imager with dual disperser architecture

We present a hyperspectral imager with a dual disperser architecture, which is highly re-configurable thanks to the use of a digital micro-mirror device (DMD). The system has over 200 spectral bands in the range 400–700 nm, and 2048 by 2048 spatial pixels. We describe a method to calibrate the instrument and quantify its performance using a simple slit scanning acquisition scheme, and discuss various methods to remove artifacts in the spectral datacube via post-processing. This prototype instrument is designed for simplicity, and aims to explore new acquisition schemes that exploit the property of colocation and use the programmable nature of the DMD to increase the speed of datacube retrieval and the quality of the hyperspectral data.

Research on measurement method of laser beam quality with orthogonal slit scanning

Research on measurement method of laser beam quality with orthogonal slit scanning

Area scanning method for 3D surface profilometry based on an adaptive confocal microscope

Conventional confocal 3D microscopes suffer from a slow measurement speed due to its requirement of scanning in three directions. Although lateral slit scanning has been proven to perform similarly to single point scanning, a direct area confocal scanning microscope is commonly considered impossible as the system is reduced into a wide-field microscope and loses its depth discerning capability. In this article, a direct area scanning method is proposed for 3D surface profilometry based on a tilted focal field. To demonstrate the underlying principle, theoretical analysis is conducted with simulation result, showing that depth discerning capability can be maintained in area scanning when the tilting angle is specifically chosen according to the numerical aperture of the system. An adaptive experimental setup is constructed based on a programmable light source and a programmable array microscope with chromatic axial encoding. Measurement result of a test target using the proposed method is comparable to the result of conventional array scanning. Although the axial uncertainty is increased by a factor of approximately 2.5, the direct area scanning method is more than 300 times faster than the conventional array scanning mode of the same setup.

Development of quantitative HPTLC-densitometry methods following a model process for transfer of TLC screening methods for pharmaceutical products containing moxifloxacin HCl, ofloxacin, amoxicillin trihydrate, acetylsalicylic acid + acetaminophen + caffeine, nimesulide, irbesartan, and pantoprazole

Transfer of thin-layer chromatography (TLC) Global Pharma Health Fund E.V. Minilab Manual and U.S. Food and Drug Administration (FDA) Compendium protocols for detecting falsified or substandard drugs in pharmaceutical products to quantitative high-performance TLC (HPTLC)-densitometry methods suitable for support of regulatory authorities was performed following a previously published model process for moxfloxacin HCl, ofloxacin, and amoxicillin trihydrate. In addition, the guidelines of the process were followed to develop and validate HPTLC-densitometry methods for pharmaceutical products containing acetylsalicylic acid + acetaminophen + caffeine, nimesulide, irbesartan, and pantoprazole that are not included in the Minilab Manual or FDA Compendium. The new methods involved silica gel 60 F254 plates; semiautomated bandwise sample and standard solution application; ascending mobile phase development of plates in a glass chamber; and automated slit scanning densitometry for detection, identification, and quantification. Data for standard and sample solution preparation, calibration curves, assay of pharmaceutical products compared to label declarations, standard addition validation, and peak purity and peak identity are provided. Supplemental FDA Compendium screening methods corresponding to the HPTLC-densitometry methods for caffeine, nimesulide, irbesartan, pantoprazole, and acetylsalicylic acid co-formulated with acetaminophen and caffeine were developed and published online with open access on the website www.layloff.net.

Peculiarities of Laue Diffraction of Neutrons in Strongly Absorbing Crystals

Well-known Kato's theory of the Laue diffraction of spherical x-ray waves is generalized to the case of the neutron diffraction in strongly absorbing crystals, taking into consideration both the potential and the resonant scattering of neutrons by nuclei as well as a realistic angular dispersion of incident neutrons. The saddle-point method is applied for estimation of the angular integrals, being more adequate in the case of strongly absorbing crystals than the usually used stationary-phase approximation. It is found that the intensity distribution of the diffracted and refracted beams along the basis of the Borrmann triangle significantly depends on the deviation of the neutron energy from the nuclear resonant level. When comparing our calculations with the Shull's experimental data on neutron diffraction in silicon we regard also the role of finite width of the collimating and scanning slits.

Real-time scatter estimation for medical CT using the deep scatter estimation: Method and robustness analysis with respect to different anatomies, dose levels, tube voltages, and data truncation.

X-ray scattering leads to CT images with a reduced contrast, inaccurate CT values as well as streak and cupping artifacts. Therefore, scatter correction is crucial to maintain the diagnostic value of CT and CBCT examinations. However, existing approaches are not able to combine both high accuracy and high computational performance. Therefore, we propose the deep scatter estimation (DSE): a deep convolutional neural network to derive highly accurate scatter estimates in real time. Gold standard scatter estimation approaches rely on dedicated Monte Carlo (MC) photon transport codes. However, being computationally expensive, MC methods cannot be used routinely. To enable real-time scatter correction with similar accuracy, DSE uses a deep convolutional neural network that is trained to predict MC scatter estimates based on the acquired projection data. Here, the potential of DSE is demonstrated using simulations of CBCT head, thorax, and abdomen scans as well as measurements at an experimental table-top CBCT. Two conventional computationally efficient scatter estimation approaches were implemented as reference: a kernel-based scatter estimation (KSE) and the hybrid scatter estimation (HSE). The simulation study demonstrates that DSE generalizes well to varying tube voltages, varying noise levels as well as varying anatomical regions as long as they are appropriately represented within the training data. In any case the deviation of the scatter estimates from the ground truth MC scatter distribution is less than 1.8% while it is between 6.2% and 293.3% for HSE and between 11.2% and 20.5% for KSE. To evaluate the performance for real data, measurements of an anthropomorphic head phantom were performed. Errors were quantified by a comparison to a slit scan reconstruction. Here, the deviation is 278HU (no correction), 123HU (KSE), 65HU (HSE), and 6HU (DSE), respectively. The DSE clearly outperforms conventional scatter estimation approaches in terms of accuracy. DSE is nearly as accurate as Monte Carlo simulations but is superior in terms of speed (≈10ms/projection) by orders of magnitude.

Effect of detruncation on the accuracy of Monte Carlo-based scatter estimation in truncated CBCT.

The purpose of this study is to investigate the necessity of detruncation for scatter estimation of truncated cone-beam CT (CBCT) data and to evaluate different detruncation algorithms. Scattered radiation results in some of the most severe artifacts in CT and depends strongly on the size and the shape of the scanned object. Especially in CBCT systems the large cone-angle and the small detector-to-isocenter distance lead to a large amount of scatter detected, resulting in cupping artifacts, streak artifacts, and inaccurate CT-values. If a small field of measurement (FOM) is used, as it is often the case in CBCT systems, data are truncated in longitudinal and lateral direction. Since only truncated data are available as input for the scatter estimation, the already challenging correction of scatter artifacts becomes even more difficult. The following detruncation methods are compared and evaluated with respect to scatter estimation: constant detruncation, cosine detruncation, adaptive detruncation, and prior-based detruncation using anatomical data from a similar phantom or patient, also compared to the case where no detruncation was performed. Each of the resulting, detruncated reconstructions serve as input volume for a Monte Carlo (MC) scatter estimation and subsequent scatter correction. An evaluation is performed on a head simulation, measurements of a head phantom and a patient using a dental CBCT geometry with a FOM diameter of 11cm. Additionally, a thorax phantom is measured to assess performance in a C-Arm geometry with a FOM of up to 20cm. If scatter estimation is based on simple detruncation algorithms like a constant or a cosine detruncation scatter is estimated inaccurately, resulting in incorrect CT-values as well as streak artifacts in the corrected volume. For the dental CBCT phantom measurement CT-values for soft tissue were corrected from -204HU (no scatter correction) to -87HU (no detruncation), -218HU (constant detruncation), -141HU (cosine detruncation), -91HU (adaptive detruncation), -34HU (prior-based detruncation using a different prior) and -24HU (prior-based detruncation using the identical prior) for a reference value of -26HU measured in slit scan mode. In all cases the prior-based detruncation results in the best scatter correction, followed by the adaptive detruncation, as these algorithms provide a rather accurate model of high-density structures outside the FOM, compared to a simple constant or a cosine detruncation. Our contribution is twofold: first we give a comprehensive comparison of various detruncation methods for the purpose of scatter estimation. We find that the choice of the detruncation method has a significant influence on the quality of MC-based scatter correction. Simple or no detruncation is often insufficient for artifact removal and results in inaccurate CT-values. On the contrary, prior-based detruncation can achieve a high CT-value accuracy and nearly artifact-free volumes from truncated CBCT data when combined with other state-of-the-art artifact corrections. Secondly, we show that prior-based detruncation is effective even with data from a different patient or phantom. The fact that data completion does not require data from the same patient dramatically increases the applicability and usability of this scatter estimation.

Development of quantitative HPTLC-densitometry methods following a model approach for transfer of TLC screening methods for pharmaceutical products of atenolol, chloramphenicol, furosemide, glibenclamide, penicillin V potassium, and praziquantel

ABSTRACTTransfer of six thin-layer chromatography (TLC) Global Pharma Health Fund E.V. Minilab manual protocols for detecting fake drugs in pharmaceutical products to quantitative high-performance TLC (HPTLC)-densitometry methods was performed following a previously published model process. The developed and validated methods for tablets or capsules containing atenolol, chloramphenicol, furosemide, glibenclamide, penicillin V potassium, and praziquantel involved use of a limited list of inexpensive, relatively nontoxic, readily available solvents and other reagents; silica gel 60 F254 plates; automated bandwise sample and standard solution application; ascending mobile phase development of plates in a chamber; and automated slit scanning densitometry for detection, identification, and quantification. Validation data for methods developed in an early version of the transfer model process that did not include standard addition validation are reported for pharmaceutical products containing amitriptyline HCl, amodiaquine, diphenhydramine HCl, and mebendazole.

Cornea and anterior eye assessment with placido-disc keratoscopy, slit scanning evaluation topography and scheimpflug imaging tomography.

Current corneal assessment technologies make the process of corneal evaluation extremely fast and simple and several devices and technologies allow to explore and to manage patients. The purpose of this special issue is to present and also to update in the evaluation of cornea and ocular surface and this second part, reviews a description of the corneal topography and tomography techniques, providing updated information of the clinical recommendations of these techniques in eye care practice. Placido-based topographers started an exciting anterior corneal surface analysis that allows the development of current corneal tomographers that provide a full three-dimensional reconstruction of the cornea including elevation, curvature, and pachymetry data of anterior and posterior corneal surfaces. Although, there is not an accepted reference standard technology for corneal topography description and it is not possible to determine which device produces the most accurate topographic measurements, placido-based topographers are a valuable technology to be used in primary eye care and corneal tomograhers expanding the possibilities to explore cornea and anterior eye facilitating diagnosis and follow-up in several situations, raising patient follow-up, and improving the knowledge regarding to the corneal anatomy. Main disadvantages of placido-based topographers include the absence of information about the posterior corneal surface and limited corneal surface coverage without data from the para-central and/or peripheral corneal surface. However, corneal tomographers show repeatable anterior and posterior corneal surfaces measurements, providing full corneal thickness data improving cornea, and anterior surface assessment. However, differences between devices suggest that they are not interchangeable in clinical practice.