Introduction: The prevalence and diversity of methicillin-resistant Staphylococcus aureus (MRSA) virulent factors as well as the host inflammatory response makes managing MRSA keratitis challenging. Alternative treatments are being investigated that can both neutralize the MRSA toxins while also reducing the host immune response. One such alternative is Photodynamic Antimicrobial Therapy (PDAT); however, limited research has been performed to understand the impact of PDAT on the host immune response during MRSA-related infections.
Purpose: To measure the immune response (Interleukin(IL)-1, 6 and 8) of human corneal epithelial cells in an ex-vivo tissue model following MRSA infection and rose bengal PDAT.
Methods: EpiCorneal tissue models (Maktek) were prepared according to manufacturer’s protocol. All groups were tested in duplicate: Control, Infection, Infection-PDAT. Infections were created in the tissue with three separate MRSA inocula (10E5 CFU/mL). For the Infection-PDAT group, 0.1% rose bengal solution was applied and wells were irradiated with a custom-made green LED light source. After 30 minutes, fluid from all of the tissue model wells was collected and IL-1, 6 and 8 were quantified with ELISA kits (Thermo Fisher Scientific).
Results: The EpiCorneal Tissue model simulated the immune response of human corneal epithelial cells during MRSA infection and treatment with PDAT. Compared to the control, the immune response increased in all three MRSA infection groups. Of the cytokines tested, IL-8 showed the greatest response in the tissue models, followed by IL-6 and IL-1. In the Infection-PDAT groups, immune response was mixed depending on the MRSA strain. The largest downregulation of immune factors was observed in the community-associated MRSA strain.
Introduction: In the past 25 years, methicillin-resistant Staphylococcus aureus (MRSA) strains have grown in both magnitude and diversity, making it more difficult for healthcare providers to treat these types of infections. Virulence factors of MRSA allow it to adapt to its environment and develop antibiotic resistance rapidly. One alternative treatment to combat these resistant pathogens is PDAT. Previous studies demonstrated the inhibitory effect of PDAT against MRSA isolates; however, there is limited knowledge regarding the effect of PDAT on virulence factors (toxins, defense mechanisms, stress response).
Purpose: To evaluate the impact of rose bengal (RB) and riboflavin (RI) PDAT on the virulence factors of six different ocular species of MRSA.
Methods: Suspensions were made with six separate MRSA species inocula (108CFU/mL) with either water (control), 0.1% RB, or 0.1% RI solutions. Each suspension was aliquoted onto an agar plate and exposed to either dark or a 5.4J/cm2 irradiation dose with custom-made LED irradiation sources [λ= 525nm (RB) or 375nm (RI)]. Plates were incubated for 48 hours and then photographed for percent growth measurement. Microbial samples were collected from each plate from which DNA was extracted and sent for full genome sequencing at CosmosID.
Results: Rose bengal PDAT completely inhibited the growth of all six MRSA species within the irradiation zone, while riboflavin had minimal inhibition. The dark conditions for both photosensitizers showed minimal inhibition. Full genome sequencing revealed that the virulence factors had varying responses to PDAT, depending on the MRSA species, photosensitizer used, and light exposure.
Age-related changes in the crystalline lens shape and refractive index gradient produce changes in dioptric power and high-order aberrations that influence the optics of the whole eye and contribute to a decrease in overall visual quality. Despite their key role, the changes in lens shape and refractive index gradient with age and accommodation and their effects on high-order aberrations are still not well understood. The goal of this project was to develop a combined laser ray tracing (LRT) and optical coherence tomography (OCT) system to measure high-order aberrations, shape and refractive index gradient in non-human primate and human lenses. A miniature motorized lens stretching system was built to enable imaging and aberrometry of the lens during simulated accommodation. A positioning system was also built to enable on- and off-axis OCT imaging and aberrometry for characterization of the peripheral defocus of the lens. We demonstrated the capability of the LRT-OCT system to produce OCT images and aberration measurements of crystalline lens with age and accommodation in vitro. In future work, the information acquired with the LRT-OCT system will be used to develop an accurate age-dependent lens model to predict the role of the lens in the development of refractive error and aberrations of the whole eye.
Glaucoma is the leading cause of irreversible blindness worldwide. Due to its wide prevalence, effective screening tools are necessary. The purpose of this project is to design and evaluate a system that enables portable, cost effective, smartphone based visual field screening based on frequency doubling technology. The system is comprised of an Android smartphone to display frequency doubling stimuli and handle processing, a Bluetooth remote for user input, and a virtual reality headset to simulate the exam. The LG Nexus 5 smartphone and BoboVR Z3 virtual reality headset were used for their screen size and lens configuration, respectively. The system is capable of running the C-20, N-30, 24-2, and 30-2 testing patterns. Unlike the existing system, the smartphone FDT tests both eyes concurrently by showing the same background to both eyes but only displaying the stimulus to one eye at a time. Both the Humphrey Zeiss FDT and the smartphone FDT were tested on five subjects without a history of ocular disease with the C-20 testing pattern. The smartphone FDT successfully produced frequency doubling stimuli at the correct spatial and temporal frequency. Subjects could not tell which eye was being tested. All five subjects preferred the smartphone FDT to the Humphrey Zeiss FDT due to comfort and ease of use. The smartphone FDT is a low-cost, portable visual field screening device that can be used as a screening tool for glaucoma.
Fungal keratitis can lead to pain and impaired vision. Current treatment options include antifungal agents and therapeutic penetrating keratoplasty. An emerging option for the management of keratitis is photodynamic antimicrobial therapy (PDAT) which uses a photosensitizer rose bengal activated with green light. Utilizing a pulsed irradiation, rather than the standard continuous irradiation may have a similar antimicrobial effect with less total energy. This study is to compare pulsed and continuous rose bengal mediated PDAT for inhibition of six fungal isolates on agar plates: Fusarium solani, Fusarium keratoplasticum, Aspergillus fumigatus, Candida albicans, Paecilomyces variotti, and Pseudoallescheria boydii. Isolates were mixed with 0.1% rose bengal and exposed to three irradiation conditions: (1) 30-minute continuous (10.8J/cm2), (2) 15-minute continuous (5.4J/cm2), (3) 30-minute pulsed (5.4J/cm2). Plates were photographed at 72 hours and analyzed with custom software. At 72 hours, 30-minute continuous rose bengal mediated PDAT inhibited all six fungal species. Fungal inhibition was analogous between 30-minute continuous and 30-minute pulsed test groups, with the exception of A. fumigatus. The 15-minute continuous irradiation was less effective when compared to both 30-minute continuous and 30-minute pulsed groups. These in vitro results demonstrate the potential strength of pulsed rose bengal mediated PDAT as an adjunct treatment modality for fungal keratitis.
Keratitis associated with Pseudomonas aeruginosa is difficult to manage. Treatment includes antibiotic eye drops, however, some strains of Pseudomonas aeruginosa are resistant. Current research efforts are focused on finding alternative and adjunct therapies to treat multi-drug resistant bacteria. One promising alternate technique is photodynamic therapy (PDT). The purpose of this study was to evaluate the effect of riboflavin- and rose bengal-mediated PDT on Pseudomonas aeruginosa keratitis isolates in vitro. Two isolates (S+U- and S-U+) of Pseudomonas aeruginosa were derived from keratitis patients and exposed to five experimental groups: (1) Control (dark, UV-A irradiation, 525nm irradiation); (2) 0.1% riboflavin (dark, UV-A irradiation); and (3) 0.1% rose bengal, (4) 0.05% rose bengal and (5) 0.01% rose bengal (dark, 525nm irradiation). Three days after treatment, in dark conditions of all concentration of riboflavin and rose bengal showed no inhibition in both S+U- and S-U+ strains of Pseudomonas aeruginosa. In 0.1% and 0.05% rose bengal irradiated groups, for both S+U- and S-U+ strains, there was complete inhibition of bacterial growth in the central 50mm zone corresponding to the diameter of the green light source. These in vitro results suggest that rose bengal photodynamic therapy may be an effective adjunct treatment for Pseudomonas aeruginosa keratitis.
The purpose of this project is to design and evaluate a system that will enable objective assessment of the optical accommodative response in real-time while acquiring axial biometric information. The system combines three sub-systems which were integrated and mounted on a joystick x-y-z adjustable modified slit-lamp base to facilitate alignment and data acquisition: (1) a Shack-Hartmann wavefront sensor for dynamic refraction measurement, provided software calculates sphere, cylinder and axis values, (2) an extended-depth Optical Coherence Tomography (OCT) system using an optical switch records high-resolution cross-sectional images across the length of the eye, from which, dynamic axial biometry (corneal thickness, anterior chamber depth, crystalline lens thickness and vitreous depth) can be extracted, and (3) a modified dual-channel accommodation stimulus unit based on the Badal optometer for providing a step change in accommodative stimulus. The prototypal system is capable of taking simultaneous measurements of both the optical and the mechanical response of lens accommodation. These measurements can provide insight into correlating changes in lens shape with changes in lens power and ocular refraction and ultimately provide a more comprehensive understanding of accommodation, presbyopia and an objective assessment of presbyopia correction techniques.
Minimally invasive laser assisted surgery in ophthalmology is continuously developing in order to find new surgical
approaches, preserve patient tissue and improve surgical results in terms of cut precision, restoration of visual acuity, and
invasiveness. In order to achieve these goals, the current approach in corneal transplant is lamellar keratoplasty, where
only the anterior or posterior part of the patient’s cornea is substituted depending on the lesion or pathology. In this
work, we present a novel alternative approach: a case study of intrastromal sutureless transplant, where a portion of the
anterior stroma of a donor cornea was inserted into the stroma of the recipient cornea, aiming to restore the correct
thickness of the patient’s cornea. The patient cornea was paracentrally thin, as the result of a trophic ulcer due to ocular
pemphigoid. A discoid corneal graft from the anterior stroma of a donor eye was prepared: a femtosecond laser cut with
a trapezoidal profile (thickness was 300 μm, minor and major basis were 3.00 and 3.50 mm, respectively). In the
recipient eye, an intrastromal cut was also performed with the femtosecond laser using a specifically designed mask; the
cut position was 275 μm in depth. The graft was loaded into an injector and inserted as an intrastromal presbyopic
implant. The postoperative analysis evidenced a clear and stable graft that selectively restored corneal thickness in the
thinned area. Intrastromal corneal transplant surgery is a minimally invasive alternative to anterior or posterior lamellar
keratoplasty in select cases. We believe that Sutureless Intrastromal Laser Keratoplasty (SILK) could open up new
avenues in the field of corneal transplantation by fully utilizing the potential and precision of existing lasers.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.