Polymerase Chain Reaction and Its Application in the Diagnosis of Infectious Keratitis

PCR involves a repeating cycle of replication to amplify small segments of deoxyribonucleic acid (DNA). A novel application of this technique is microbial identification in infectious keratitis, one of the leading causes of blindness in the world. PCR is more sensitive than biological stains and culture, which are considered the current gold standards for diagnosing infectious keratitis. The diagnosis and treatment of infectious keratitis cost the United States millions of dollars in health expenditure. PCR may help offset that cost by allowing for individualized disease management and screening for multiple antibiotic-resistant genes. While beneficial, PCR demonstrates lower specificity rates compared to culture and stain, indicating its shortcomings; this can be overcome by performing PCR after narrowing the pool of potential microorganisms. This article examines the clinical utility of PCR in cases of infectious keratitis by evaluating its reliability, validity, associated costs, and indications

EOS-AM1 Nickel Hydrogen Cell

This paper reports the interim results of the Earth Observing System AM-1 project (EOS-AM-1) nickel hydrogen cell life test being conducted under contract to National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) at the Lockheed Martin Missile and Space (LMMS) facility in East Windsor, NJ; and at COMSAT Labs., Clarksburg, MD. The purpose of die tests is to verify that the EOS-AM-1 cell design can meet five years of real-time Low Earth Orbit (LEO) cycling. The tests include both real-time LEO and accelerated stress tests. At LMMS, the first real-time LEO simulated 99 minute orbital cycle started on February 7, 1994 and the test has been running continuously since that time, with 18,202 LEO cycles completed as of September 1, 1997. Each cycle consists of a 64 minute charge (VT at 1.507 volts per cell, 1.06 C/D ratio, followed by 0.6 ampere trickle charge) and a 35 minute constant power discharge at 177 watts (22.5% DOD). At COMSAT, the accelerated stress test consists of 90 minute orbital cycles at 60% DOD with a 30 minute discharge at 60 amperes and a 60 minute charge at 40 amperes (VT at 1.54 volts per cell to 1.09 C/D ratio, followed by 0.6 ampere trickle charge). The real-time LEO life test battery consists of seven, 50AH (nameplate rating) Eagle-Picher, Inc. (EPI) Mantech cells manufactured into three, 3-cell pack assemblies (there are two place holder cells that are not part of the life test electrical circuit). The test pack is configured to simulate the conductive thermal design of the spacecraft battery, including: conductive aluminum sleeves, 3-cell pack aluminum baseplate, and honeycomb panel all mounted to a liquid (-5 C) cold plate. The entire assembly is located in a thermal chamber operating at +30 C. The accelerated stress test unit consists of five cells mounted in machined aluminum test sleeves and is operating at +10 C. The real-time LEO life test battery has met all performance requirements through the first 18,202 cycles, including: end of charge mid discharge cell voltages and voltage gradients; end of charge and discharge cell pressures; within cell and between cell temperature gradients; discharge capacity; current and power levels; and all charge parameters. The accelerated stress test battery has completed 11,998 cycles when the test was terminated. The stress test unit met all test parameters. This paper reports battery perfortnances as a funcfion of cycle life for both the real-time LEO and the accelerated life test regimes

Biological Staining and Culturing in Infectious Keratitis: Controversy in Clinical Utility

Infectious keratitis causes significant, financial burden and is only increasing in frequency with contact lens use. Despite this, no retrospective studies, prospective studies, or clinical trials have evaluated the diagnostic validity of clinical guidelines in cases of infectious keratitis. Currently, standard of care recommends that corneal samples be obtained for staining and culturing in select patients showing evidence of corneal ulceration. Ideally, diagnostic information from corneal sampling is thought to help guide therapeutic interventions, prevent disease progression, reduce antibiotic resistance, and decrease overall expenditures for the management and treatment of infectious keratitis. However, current staining and culturing methods are limited by poor sensitivity in non-bacterial cases (i.e. fungal, viral) and lengthy turnaround times, and these methods do not frequently change clinical decision making. Newer fluoroquinolones and broad-spectrum antibiotics resolve the vast majority of cases of infectious keratitis, rendering cultures less essential for management. We studied the clinical utility of obtaining corneal samples for culturing and staining and the need for future research to establish superior diagnostic guidelines for their use in infectious keratitis

Persistent Corneal Epithelial Defects: A Review Article

Persistent corneal epithelial defects (PEDs or PCEDs) result from the failure of rapid re-epithelialization and closure within 10-14 days after a corneal injury, even with standard supportive treatment. Disruptions in the protective epithelial and stromal layers of the cornea can render the eye susceptible to infection, stromal ulceration, perforation, scarring, and significant vision loss. Although several therapies exist and an increasing number of novel approaches are emerging, treatment of PEDs can still be quite challenging. It is important to treat the underlying causative condition, which may include an infection, limbal stem cell deficiency, or diabetes, in order to facilitate wound healing. Standard treatments, such as bandage contact lenses (BCLs) and artificial tears (ATs), aim to provide barrier protection to the epithelial layer. Recently-developed medical treatments can target the re-epithelialization process by facilitating access to growth factors and anti-inflammatory agents, and novel surgical techniques can provide re-innervation to the cornea. PEDs should be treated within 7-10 days to avoid secondary complications. These interventions, along with a step-wise approach to management, can be useful in patients with PEDs that are refractory to standard medical treatment. In this review, we discuss the epidemiology, etiology, diagnosis, current and novel management, and prognosis of persistent epithelial defects

Persistent Corneal Epithelial Defects: A Review Article

Persistent corneal epithelial defects (PEDs or PCEDs) result from the failure of rapid re-epithelialization and closure within 10-14 days after a corneal injury, even with standard supportive treatment. Disruptions in the protective epithelial and stromal layers of the cornea can render the eye susceptible to infection, stromal ulceration, perforation, scarring, and significant vision loss. Although several therapies exist and an increasing number of novel approaches are emerging, treatment of PEDs can still be quite challenging. It is important to treat the underlying causative condition, which may include an infection, limbal stem cell deficiency, or diabetes, in order to facilitate wound healing. Standard treatments, such as bandage contact lenses (BCLs) and artificial tears (ATs), aim to provide barrier protection to the epithelial layer. Recently-developed medical treatments can target the re-epithelialization process by facilitating access to growth factors and anti-inflammatory agents, and novel surgical techniques can provide re-innervation to the cornea. PEDs should be treated within 7-10 days to avoid secondary complications. These interventions, along with a step-wise approach to management, can be useful in patients with PEDs that are refractory to standard medical treatment. In this review, we discuss the epidemiology, etiology, diagnosis, current and novel management, and prognosis of persistent epithelial defects

Diagnosis and Management of Pseudoguttata: A Literature Review

Corneal pseudoguttata (PG), also known as pseudoguttae or secondary guttata, is a transient, reversible endothelial edema commonly associated with anterior segment pathology. While considered rare, PG presents on slit-lamp examination more commonly than originally thought. We have clinically observed PG after refractive surgeries, in association with infectious keratitis, and following medication use. PG presents as dark lesions on slit-lamp exam with specular illumination, similar to primary corneal guttata. PG is distinct from guttata because PG resolves over time and does not involve Descemet’s membrane. Other ocular findings that may be confused with guttata include endothelial blebs (EB) and endothelial denudation (ED). EB are possibly a type of PG that present after contact lens use or hypoxia. ED is a distinct entity that is characterized by loss of endothelial cells without involvement of Descemet’s membrane. Confocal microscopy may be useful in differentiating these four endothelial lesions, with differences in border definition and the presence of hyperreflective areas two main distinctions. PG presents as a hyporeflective, elevated shape without clear borders on confocal microscopy. PG, EB, and ED can resolve with time without the need for surgical intervention, unlike corneal guttata. Treatment of the underlying condition will lead to resolution of both PG and EB

Diagnosis and Management of Pseudoguttata: A Literature Review

Corneal pseudoguttata (PG), also known as pseudoguttae or secondary guttata, is a transient, reversible endothelial edema commonly associated with anterior segment pathology. While considered rare, PG presents on slit-lamp examination more commonly than originally thought. We have clinically observed PG after refractive surgeries, in association with infectious keratitis, and following medication use. PG presents as dark lesions on slit-lamp exam with specular illumination, similar to primary corneal guttata. PG is distinct from guttata because PG resolves over time and does not involve Descemet’s membrane. Other ocular findings that may be confused with guttata include endothelial blebs (EB) and endothelial denudation (ED). EB are possibly a type of PG that present after contact lens use or hypoxia. ED is a distinct entity that is characterized by loss of endothelial cells without involvement of Descemet’s membrane. Confocal microscopy may be useful in differentiating these four endothelial lesions, with differences in border definition and the presence of hyperreflective areas two main distinctions. PG presents as a hyporeflective, elevated shape without clear borders on confocal microscopy. PG, EB, and ED can resolve with time without the need for surgical intervention, unlike corneal guttata. Treatment of the underlying condition will lead to resolution of both PG and EB