A review of corneal biomechanics: Mechanisms for measurement and the implications for refractive surgery

Detailed clinical assessment of corneal biomechanics has the potential to revolutionize the ophthalmic industry through enabling quicker and more proficient diagnosis of corneal disease, safer and more effective surgical treatments, and the provision of customized and optimized care. Despite these wide-ranging benefits, and an outstanding clinical need, the provision of technology capable of the assessment of corneal biomechanics in the clinic is still in its infancy. While laboratory-based technologies have progressed significantly over the past decade, there remain significant gaps in our knowledge regarding corneal biomechanics and how they relate to shape and function, and how they change in disease and after surgical intervention. Here, we discuss the importance, relevance, and challenges associated with the assessment of corneal biomechanics and review the techniques currently available and underdevelopment in both the laboratory and the clinic

Measuring Dose and Teaching Moment Cues in Speech Sound Disorder

Speech sound disorder (SSD) occurs when children have difficulties saying sounds appropriately and need specialized instruction by a speech-language pathologist (SLP) to be understood. The best treatment approach is not always known to SLPs due to the individual needs of a client and the effects of different elements within interventions. By researching teaching strategies and dose in therapy, we can explore procedures that result in better outcomes and speed the learning process (Baker et al., 2018). Thus, the purpose of this research is to describe and quantify the elements that occurred within treatment of SSD to answer: How can we measure (a) dose and (b) modalities of cues in speech therapy? The participants included two boys aged 6;2 and 3;8 with SSD who were observed via video recording during speech sound treatment. A coding scheme was developed to track dosage and the different types of cues used in each therapy session; both were counted in one-minute increments. Quantifying dosage consisted of tallying the prompts given by the clinician, the client\u27s response, and whether the client responded correctly or incorrectly. Documenting modalities of cues consisted of tallying multiple forms of cues given by the clinician: pause, verbal model, pointing, visual cue, prolongation/segmentation, tactile, and instruction. The results for dosage and modalities of cues will be presented across participants and sessions, and the clinical implications will be discussed. This research is clinically significant because increasing our understanding of treatment elements that occur within sessions may inform our understanding of treatment outcomes and help speech-language pathologists design more effective therapies

Interferometric Ex Vivo Evaluation of the Spatial Changes to Corneal Biomechanics Introduced by Topographic CXL: A Pilot Study

PURPOSE: To determine the efficacy of interferometry for examining the spatial changes to the corneal biomechanical response to simulated intraocular pressure (IOP) fluctuations that occur after corneal cross-linking (CXL) applied in different topographic locations. METHODS: Displacement speckle pattern interferometry (DSPI) was used to measure the total anterior surface displacement of human and porcine corneas in response to pressure variations up to 1 mm Hg from a baseline pressure of 16.5 mm Hg, both before and after CXL treatment, which was applied in isolated topographic locations (10-minute riboflavin soak [VibeX-Xtra; Avedro, Inc], 8-minute ultraviolet-A exposure at 15 mW/cm2). Alterations to biomechanics were evaluated by directly comparing the responses before and after treatment for each cornea. RESULTS: Before CXL, the corneal response to loading indicated spatial variability in mechanical properties. CXL treatments had a variable effect on the corneal response to loading dependent on the location of treatment, with reductions in regional displacement of up to 80% in response to a given pressure increase. CONCLUSIONS: Selectively cross-linking in different topographic locations introduces position-specific changes to mechanical properties that could potentially be used to alter the refractive power of the cornea. Changes to the biomechanics of the cornea after CXL are complex and appear to vary significantly depending on treatment location and initial biomechanics. Hence, further investigations are required on a larger number of corneas to allow the development of customized treatment protocols. In this study, laser interferometry was demonstrated to be an effective and valuable tool to achieve this

Biomechanical Evaluation of Decellularized and Crosslinked Corneal Implants Manufactured From Porcine Corneas as a Treatment Option for Advanced Keratoconus

Currently corneal transplantation is the main treatment for late-stage keratoconus; however, transplantation procedures are accompanied by significant risk of post-surgical complications; this in addition to supply limitations imposed by a worldwide shortage of human donor corneas, has driven the development of alternative therapies. One such therapy is the use of corneal implants derived from porcine corneas (Xenia®, Gebauer Medizintechnik GmbH, Neuhausen, DE). In contrast to human donor tissue, these implants can be produced on demand and due to the processes used pose no risks for host-immune rejection. Their use has already been demonstrated clinically in patients for preventing the progression of topographic changes in keratoconus whilst improving visual acuity. The implants are derived from natural tissue and not standardised synthetic material, whilst this likely reduces the risk of issues with bio-incompatibility, there is inevitably variability in their intrinsic mechanical properties which requires investigation. Here, speckle interferometry is employed to examine the biomechanical properties, in response to physiologically representative forces, of native porcine corneal tissue prior to processing and after a proprietary 4-stage process involving decellularization, washing, compression and crosslinking. The control lenticules had an average Young’s modulus (E) of 11.11 MPa (range 8.39–13.41 MPa), following processing average E of the lenticules increased by 127% over that of the unprocessed tissue to 25.23 MPa (range 18.32–32.9 MPa). The variability in E of the lenticules increased significantly after processing suggesting variability in the propensity of the native tissue to processing. In summary, it is possible to produce thin (<90 µm) lenticules from porcine corneas with enhanced stiffness that are effective for treating late-stage keratoconus. Due to the observed variability in the responses of lenticules to processing, interferometry could be a useful technique for ensuring quality control in commercial production via biomechanical screening

The role of light in measuring ocular biomechanics

The cornea is a highly specialised tissue with a unique set of biomechanical properties determined by its complex structure. The maintenance of these mechanical properties is fundamental to maintain clear vision as the cornea provides the majority of the focussing power of the eye. Changes to the biomechanics of the cornea can occur during ageing, disease, and trauma, or as a result of surgery. Recently there has been increased interest in the mechanical properties of the cornea as knowledge of these properties has significant implications for the improvement of current ocular treatments including PRK and LASIK, and for the diagnosis and tracking of corneal diseases and therapy such as keratoconus and crosslinking. Biomechanics are also important for the development of artificial corneal replacements. This paper describes the use of a novel, non-destructive lateral electronic speckle pattern shearing interferometer (ESPSI). The data generated via this technique give a full-field view of the mechanical response of the cornea under simulated physiological loading conditions, and enables strain and displacement to be determined in three planes. The technique allows corneal stiffness to be quantified and enables changes and non-homogeneities that occur due to surgery or disease to be detected.Eye advance online publication, 15 January 2016; doi:10.1038/eye.2015.263

Caldwell-Dennis House Adaptive Reuse Feasibility Study

Professor JP Halls ARCH 607- Historic Preservation Studio course created an adaptive reuse plan to examine the feasibility of rehabilitating the historic Caldwell-Dennis residence into transitional housing for women reentering society

Understanding direct and indirect driver vision in heavy goods vehicles

The research described in this report has been performed by Loughborough Design School (LDS) under the CLOCS programme funded by TfL. The project was specified to allow an understanding of the variability of blind spots in direct vision through windows and indirect vision through mirrors for the top selling HGVs in the UK. The impetus for the research was the increasing number of accidents between Vulnerable Road Users (VRUs) and HGVs in London. The aim was to compare the manufacturers’ most sold vehicle specifications to determine which vehicle design variables can affect the size of blind spots, and to explore issues that have been raised in previous research including the potential for construction HGVs to be involved in more accidents with VRUs than distribution variants of HGV designs. The LDS team have utilised a virtual modelling technique to explore this issue. This virtual approach allows multiple accident scenarios to be modelled and simulated. In order to allow the analysis of vehicle blind spots 19 vehicle models have been created by digitally scanning the real world vehicles. The vehicles that have been modelled include construction, distribution and long haul HGV designs, as well as ‘high vision’ low entry cab designs. These models have been used in combination with simulations of cyclist and pedestrian VRUs in a manner which recreates critical accident scenarios that have been defined through the analysis of accident data. This involves placing the simulated VRUs in a number of defined locations adjacent to the vehicle. Subsequently the simulated VRUs are moved away from the vehicle into a position where they ‘just can’t be seen’ by the driver of the vehicle, i.e. moving them further away would allow them to be partially visible. The distance that the VRU is away from the side or front of the vehicle cab determines the size of the direct vision blind spot. In this way vehicle designs and configurations can be compared. In addition to this further testing was performed to determine if the VRUs located in the direct vision blind spots could be viewed by the driver through the use of mirrors. A further analysis technique utilised a method which projects the volume of space that can be seen by a driver through the windows and mirrors on to the surface of sphere. This provides a field of view value which can be used to compare the glazed area of HGVs and provides a method to distinguish between vehicles that perform at the same level in the VRU simulation. The results of the work highlight the follow key issues. 1. All standard vehicle configurations have blind spots which can hide VRUs from the driver’s direct vision 2. The height of the cab above the ground is the key vehicle factor which affects the size of direct vision and indirect vision blind spots 3. The design of window apertures and the driver location in relation to these window apertures can reduce the size of the identified blind spots. i.e. two different vehicle designs with the same cab height can have different results for blind spot size due to window design and driver seat location 4. Low entry cab designs, which are the lowest of the 19 vehicles tested, demonstrated real benefits in terms of reducing direct vision blind spots when compared to standard vehicle designs 5. The construction vehicles assessed in the project are on average 32% higher than the same cab design in the distribution configuration 6. For construction vehicles the distance away that a pedestrian in front of the vehicle can be hidden from the driver’s view is on average nearly three times greater than the distribution vehicles 7. For the construction vehicles the distance away that a cyclist to the passenger side of the vehicle can be hidden is on average more than two times greater than the distribution vehicles 8. The work has highlighted the need for a new standard which defines what should be visible through direct vision from the vehicle. Such a standard does not currently exist, and is seen as a key mechanism for improving future vehicle design

The definition, production and validation of the direct vision standard (DVS) for HGVS. Final Report for TfL review

This report presents research performed by Loughborough Design School (LDS) on behalf of Transport for London. The research has been conducted against a background of over representation of heavy goods vehicles (HGVs) being involved in road traffic accidents with vulnerable road users (VRUs) where ‘failed to look properly’ and ‘vehicle blind-spot’ are often reported as the main casual factors in the accident data. Previous work by LDS on driver’s vision from HGVs has identified the need to reduce reliance on indirect vision via mirrors through the specification of a direct vision standard (DVS) for HGVs. Recent work commissioned by TfL and performed by the Transport Research Laboratory (TRL) resulted in a draft DVS. This draft DVS has been evaluated and reworked by the LDS team to produce a viable and robust method to quantify direct vision performance of an HGV together with a means to rate that vision performance against a star rating standard. Throughout this process significant stakeholder consultation has been used to support the development of the DVS. A total of 27 vehicles representing the majority of the current Euro 6 N3 HGV fleet have been modelled in CAD. Where data were available these have been mounted at the highest, lowest and most sold heights to produce a sample of 54 test vehicles. A methodology has been developed that utilises volumetric projection of the field of view of the driver via the windows in the cab. This projection is then intersected with an assessment volume. The result is a volumetric representation of the space around a HGV cab that the driver can see to the front, driver and passenger sides. The volume of this space can be calculated to provide a rating of direct vision performance. An iterative design process was followed that explored different specifications of the assessment zone around the cab, factoring in the collision data with VRUs and the use of weightings to prioritise what needs to be seen. Two weighting schemes were evaluated one prioritising the volumes vertically, recognising the importance of being able to see closer to the ground, and a second prioritising the volumes directionally to address the prevalence of accidents being greater to the front and passenger side when compared to the driver’s side. The final specification of the volumetric assessment consists of a single, unweighted zone around the cab, informed by the current coverage of mirrors specified in UNECE regulation 46. This was done to foster direct vision that aims to remove the reliance on mirrors and thus should focus on providing direct vision of the areas currently covered by mirrors. The vehicle sample was then evaluated for its performance using this assessment, providing a volumetric score for each vehicle. These volumetric scores were then quantified by correlating them with a VRU simulation. Thirteen 5th %ile Italian female VRUs were placed around the vehicle and moved laterally to a point at which their head and shoulders could be seen. This served to provide context for the volumetric results such that a particular volume could be equated to an average distance at which the small adult could be seen. Furthermore, the VRU simulations provided a means to translate the volumetric performance into star ratings. Four star rating specifications were produced following an absolute (based on risk/safety) and a relative (based on the performance of the current fleet) approach. For both absolute and relative two iterations were proposed: 1. the VRU simulation distances were used to establish a threshold value, 2. the median volumetric result was used to establish a threshold value. The final option taken forwards used the VRU simulation distances for a 5th %ile Italian female to define the 1 star boundary. Vehicles able to provide direct vision of the VRUs at an average of <2m to the front, <4.5m to the passenger side and <0.6m to the driver’s side achieved a star rating 1 star or above. All others achieved a rating of zero star. Star ratings from 1 to 5 star were sub divided equally. The final result consists of three main outcomes: The definition, production and validation of the direct vision standard (DVS) for HGVs December 2018 Transport for London 4 Loughborough Design School © 1. A robust, repeatable and validated method for the volumetric analysis of direct vision performance using a CAD based process 2. A process to map a volumetric score for a given vehicle onto the 5 star rating scale to produce a DVS rating for any vehicle. 3. Star ratings for the majority of the Euro 6 N3/N3G HGV fleet showing that of the 41 configurations analysed, two vehicles are rated 5 star, no vehicles are rated 4 star, five vehicles are able to achieve 3 star, three vehicles are able to achieve 2 star, and six vehicles are able to achieve 1 star, the remainder 25 vehicles were rated as zero star

Riverside-Normal City Historic Design Guidelines

Professor JP Halls ARCH 441/541 Preservation policy course compiled a set of historic design guidelines as neighborhood stakeholders plan to create a local historic district for a portion of the neighborhood and to assist in the continued long-term architectural preservation of the Riverside neighborhood