Bacterial keratitis in the critically ill

Development and Validation of Eyes Care Bundle for Mechanically Ventilated Patients

Lack of proper eye care (EC) for mechanically ventilated patients can lead to serious ocular complications. Objective of this study is to develop and validate eyes care bundle for mechanically ventilated patients. A Delphi design study was conducted between March and May 2021. The Content Validity Index (CVI) was used to calculate the degree of agreement among the experts to analyze the bundle. Content validity was determined by 5 experts using a 4-point Likert scale. They evaluated the items in terms of the following: 1 = "irrelevant," 2 = "somewhat relevant if the phrasing is profoundly adjusted," 3 = "relevant with some adjustment," and 4 = "very relevant." The CVI was applied, and the accepted value was ≥0.50. The validation of EC bundle was conducted through 3 rounds after developed it based on the evaluated research evidence. The items were reviewed for content and face validity. The bundle was validated with 5 items with a total CVI of 0.96, a face validity of 1, and a Scale-Level Content Validity Index/Universal Agreement calculation method value of 0.8. This bundle can help critical care nurses, doctors, academics, and students assess and provide standard EC for mechanically ventilated patients.

Study of Conjunctival Microbial Flora in Patients of Intensive Care Unit

Purpose

The objective of the study was to evaluate the type of conjunctival microbial flora in intensive care unit patients and their antimicrobial sensitivity pattern.

Methods

A total of 272 samples (conjunctival swabs) were taken from patients in various intensive care units and sent for culture and sensitivity. An ocular examination was done to look for lagophthalmos, conjunctival discharge, exposure keratitis, and corneal perforation.

Results

Majority (82.1%) of the samples showed at least one microbial isolate while 29 (10.7%) samples showed multiple microbial growth. The most common microbes were coagulase negative Staphylococcus spp. (41.5% of isolates), diphtheroids (11.0% of isolates), and Staphylococcus aureus (9.6% of isolates) which are the usual commensals of the ocular surface. Of the other microbes isolated, Pseudomonas aeruginosa (4.0%) was the most common. Eighty-four percent isolates of coagulase negative Staphylococcus sp., 81.8% isolates of diphtheroids and 100% isolates of Staphylococcus aureus were penicillin resistant. All isolates of Enterococcus fecalis were sensitive only to vancomycin. Two hundred and twenty eyes (80.9%) had varying degrees of lagophthalmos. Nineteen (7.0%) had severe corneal exposure changes leading to infectious corneal ulcer and perforation in all of them.

Conclusions

The isolates in patients of intensive care units were no different from the normal conjunctival flora though few pathogenic organisms such as Pseudomonas aeruginosa and Acinetobacter sp. were also isolated. Most of the isolates were penicillin resistant. This knowledge will help take appropriate prophylactic measures to contain ocular infections in the intensive care units.

Foundational concepts in the biology of bacterial keratitis

Bacterial infections of the cornea, or bacterial keratitis (BK), are notorious for causing rapidly fulminant disease and permanent vision loss, even among treated patients. In the last sixty years, dramatic upward trajectories in the frequency of BK have been observed internationally, driven in large part by the commercialization of hydrogel contact lenses in the late 1960s. Despite this worsening burden of disease, current evidence-based therapies for BK - including broad-spectrum topical antibiotics and, if indicated, topical corticosteroids - fail to salvage vision in a substantial proportion of affected patients. Amid growing concerns of rapidly diminishing antibiotic utility, there has been renewed interest in urgently needed novel treatments that may improve clinical outcomes on an individual and public health level. Bridging the translational gap in the care of BK requires the identification of new therapeutic targets and rational treatment design, but neither of these aims can be achieved without understanding the complex biological processes that determine how bacterial corneal infections arise, progress, and resolve. In this chapter, we synthesize the current wealth of human and animal experimental data that now inform our understanding of basic BK pathophysiology, in context with modern concepts in ocular immunology and microbiology. By identifying the key molecular determinants of clinical disease, we explore how novel treatments can be developed and translated into routine patient care.

Descemetocele and bilateral, severe Pseudomonas keratitis in an intensive care unit patient with Graves' orbitopathy: A case report

RATIONALE

Exposure keratopathy (EK) is common among intensive care unit (ICU) patients, especially those under sedation and with incomplete eyelid closure. EK can be mild punctate epithelial erosions exhibiting spontaneous recovery; rarely, severe complications including bacterial ulcers causing corneal perforation or opacity could occur. We describe a patient with pre-existing Graves' orbitopathy (GO) who developed bilateral, rapidly progressing bacterial keratitis due to EK with secondary aerosol inoculation from respiratory pathogens in ICU.

PATIENT CONCERNS

A 49-year-old intubated and sedated woman who underwent urgent craniotomy was admitted to ICU. The ophthalmology department was consulted for progressive chemosis. History of poorly controlled GO was revealed based on external ocular signs, including proptosis with lid retraction, and careful ophthalmological history taking. After 2 days of ICU admission, slit lamp examination revealed large inferior corneal epithelial defects and dellen (OU). Despite prescribing gentamicin ointment and lubricants, purulent discharge with corneal infiltration and thinning (OU) was observed 2 days later. Owing to a characteristic Pseudomonas odor from her endotracheal tube, corneal and endotracheal sputum cultures were obtained, which revealed Pseudomonas aeruginosa infection.

DIAGNOSIS

Pseudomonas keratitis secondary to EK INTERVENTIONS:: Topical fortified anti-Pseudomonas antibiotic eye drops with temporary tarsorrhaphy and lubricants OUTCOMES:: Despite multiple treatments, she developed enlarging descemetocele in the left eye with severe corneal stromal destruction and severe visual impairment due to central corneal scar formation in the right eye. After 2 months, the descemetocele ruptured owing to generalized tonic-clonic seizures after cranioplasty. Therefore, she underwent urgent penetrating keratoplasty in the left eye.

LESSONS

GO increases ocular surface inflammation and exposure, which may exacerbate EK and subsequent complication risks. Careful monitoring and aggressive treatment through appropriate eye care regimen are required in these patients.

Ocular Complications in the Prone Position in the Critical Care Setting: The COVID-19 Pandemic

PURPOSE

Ocular complications are common in the critical care setting but are frequently missed due to the focus on life-saving organ support. The SARS-CoV-2 (COVID-19) pandemic has led to a surge in critical care capacity and prone positioning practices which may increase the risk of ocular complications. This article aims to review all ocular complications associated with prone positioning, with a focus on challenges posed by COVID-19.

MATERIALS AND METHODS

A literature review using keywords of "intensive care", "critical care", "eye care", "ocular disorders", "ophthalmic complications," "coronavirus", "COVID-19," "prone" and "proning" was performed using the electronic databases of PUBMED, EMBASE and CINAHL.

RESULTS

The effects of prone positioning on improving respiratory outcomes in critically unwell patients are well established; however, there is a lack of literature regarding the effects of prone positioning on ocular complications in the critical care setting. Sight-threatening ophthalmic disorders potentiated by proning include ocular surface disease, acute angle closure, ischemic optic neuropathy, orbital compartment syndrome and vascular occlusions.

CONCLUSIONS

COVID-19 patients may be more susceptible to ocular complications with increased proning practices and increasing demand on critical care staff. This review outlines these ocular complications with a focus on preventative and treatment measures to avoid devastating visual outcomes for the patient.

Ocular Surface Disease in a PICU: Incidence and Outcomes With a Dynamic Eye Care Protocol

OBJECTIVES

Sedated intensive care patients have impaired ocular protective mechanisms putting them at risk for ocular surface disease with potential vision loss. Historically, routine eye care has been limited to critically ill patients receiving neuromuscular blockade. The aim of this project was to determine the occurrence rate of ocular surface disease in sedated and ventilated children, identify risk factors, and determine the progression of injury with routine eye care.

DESIGN

Prospective cohort study.

SETTING

A tertiary care medical-surgical PICU.

PATIENTS

All intubated patients admitted from May 2015 to December 2016.

INTERVENTIONS

Staff education regarding corneal examination with fluorescein, and routine eye care as per a PICU eye care protocol.

MEASUREMENTS AND MAIN RESULTS

We evaluated 479 patients (1,242 corneal exams) and found that 15% had ocular surface disease at admission to the PICU: keratopathy 62, abrasion 16. The highest incidence was in trauma patients (39.0%) and those intubated in the emergency department (22.2%) or prehospital setting (42.9%). Of the 245 patients with multiple ocular assessments, 32.2% displayed ocular surface disease at some point during their hospitalization: keratopathy 73, abrasion 24. Ourprotocol dictated increased frequency of eye care if ocular surface disease worsened. As a result, the overall incidence of ocular surface disease decreased to 8.6% by the last examination (keratopathy 19, mild abrasion 2), but more severe ocular abnormalities such as corneal infiltrates, ulcers, or scarring were not observed. Based on multivariate analysis, clinical factors associated with increased risk of ocular surface disease included primary diagnosis, and lagophthalmos (incomplete eyelid closure).

CONCLUSIONS

Ocular surface disease is an under-recognized process in critically ill pediatric patients. A standardized and dynamic protocol may improve corneal health, which in turn may reduce injury, pain, infection, and long-term vision loss.

Eye care in the intensive care unit

Ocular surface disease is common in the intensive care population with 20-42% of patients developing corneal epithelial defects. The ocular surface is normally protected by the ability to produce tears, to blink and to close the eyes with rest or sleep. All of these mechanisms can be disrupted in the intensive care population, increasing the risk of developing ocular surface disease. Despite the scale of the problem, eye-care protocols are commonly not instigated and documentation of eye care is often poor. This review details the risk factors for developing ocular surface disease. It also provides evidence-based guidance on protecting the eyes in vulnerable patients, identifying diseases affecting the eye in intensive care patients and delivering the best treatment to the eye. There is growing evidence that adherence to a correctly performed eye-care guideline prevents the majority of corneal problems encountered in the intensive care unit.

Intensive Care Nurses' Views and Practices for Eye Care: An International Comparison

Eye care is an important area of critical care. However, lack of eye care studies is a common issue across the globe. The aim of this study is to determine the views and practices of intensive care unit (ICU) nurses on eye care in Turkey and Palestine. This descriptive study was conducted using a self-administrated questionnaire. The data were collected from 111 nurses in nine kinds of ICUs in two education hospital. Normal saline (75.9%) was the most commonly reported solution for eye hygiene among the Palestinian nurses, and gauze soaked in normal saline or sterile water (64.3%) were the most frequently used supplies by the Turkish nurses. Although both Palestinian and Turkish ICU nurses took some precautions to prevent eye complications in critical patients, there were some gaps and insufficiencies in the eye care of ICU patients. There is a need for continuing training in this area.

Making a Difference in Eye Care of the Critically Ill Patients

Ocular surface disorders are frequently encountered in patients under sedation and paralyzed patients in intensive care units (ICUs). In the ICUs, treatment is usually focused on the management of organ failures, and eye care becomes a side issue. As a result, ophthalmological complications do occur (incidence ranges from 3.6% to 60%) and are frequently overlooked in this setting. To identify the best available evidence in providing the best eye care to prevent exposure keratopathy, a literature review was performed. The databases of PUBMED, COCHRAN, and EMBASE library were searched. We only looked at higher quality articles. Among various eye care measures that have been advocated to prevent exposure keratopathy, the most effective is the application of polyethylene covers. Early diagnosis and effective treatment will help prevent microbial keratitis and visual loss.

Keratitis after Corneal Projection of Biological Fluids: A Possible Occupational Prejudice?

This article describes a case of Pseudomonas aeruginosa keratitis resulting from projection of biological fluids (bronchial secretions) on the face, mainly in the right eye. The employee presented with keratitis complicated by a corneal abscess. Consequently, the employee had a chronic and severe ocular surface and stoma destruction, possibly due to microbial proliferation into the surface tissues exacerbated by contact lenses. The infection was determined to be work related by experts.

Virulence properties of multidrug resistant ocular isolates of Acinetobacter baumannii

PURPOSE

Acinetobacter (A.) baumannii is an opportunistic pathogen and has been reported as a causative agent of ocular infections. The aim of this study is to identify virulence properties (biofilm formation, adhesion, invasion and cytotoxicity) and antibiotic resistance among A. baumannii isolates recovered from the eye.

MATERIALS AND METHODS

The Microscan Walk-Away®, an automated bacterial identification and susceptibility testing system was used to determine antibiotic resistance. Clonal relatedness was assessed by Pulsed-field gel electrophoresis (PFGE) and plasmid profile analysis. Conjugation experiments were carried out to determine the transfer of antibiotic resistance genes and PCR was used to confirm gene transfer. Virulence properties of the isolates were determined by biofilm formation using crystal violet and immunofluorescence staining, adherence and internalization using cultured corneal epithelial cells, and cytotoxicity by TUNEL-staining and LDH release assays.

RESULTS

All ocular isolates (n = 12) exhibited multidrug resistant (MDR) phenotype and one of the isolate (AB12) was resistant to 18 antibiotics (β-lactam, aminoglycosides, tetracycline, chloramphenicol and quinolones). The plasmid profile analysis showed the presence of multiple plasmids in each isolate and a total of 10 different profiles were observed. However, PFGE analysis was more discriminatory which revealed 12 distinct genotypes. Antibiotic resistance (tetracycline and quinolone) was transferable from the isolate AB12 to a recipient Escherichia coli J53. Ten isolates were strong biofilm producers and the remaining two (AB5 and AB7) were moderate producers. All isolates demonstrated adherence and invasive properties towards HCECs. A similar trend was observed in their ability to cause cell death and toxicity.

CONCLUSIONS

Our results indicate that ocular isolates of A. baumannii are biofilm producers and adherent and invasive to corneal epithelium, a first step in the pathogenesis of ocular infection. In addition, they demonstrated plasmid-mediated transfer of MDR traits making them a reservoir of resistance genes at ocular surface.

Ocular surface disorders in intensive care unit patients

Patients in intensive care units (ICU) are at increased risk of corneal abrasions and infectious keratitis due to poor eyelid closure, decreased blink reflex, and increased exposure to pathogenic microorganisms. The aim of this retrospective study was to evaluate the ocular surface problems in patients who stayed in ICU more than 7 days and were consulted by an ophthalmologist. There were 26 men and 14 women with a mean age of 40.1 ± 18.15 years (range 17–74 years). Conjunctiva hyperemia, mucopurulent or purulent secretion, corneal staining, and corneal filaments were observed in 56.25%, 36.25%, 15%, and 5% of the eyes, respectively. Keratitis was observed in 4 patients (10%) who were treated successfully with topical antibiotics. Mean Schirmers test results were 7.6 ± 5.7 mm/5 min (median 6.5 mm/5 min) in the right, and 7.9 ± 6.3 mm/5 min (median 7 mm/5 min) in the left eyes. Schirmers test results were <5 mm/5 min in 40% of the subjects. The parameters did not show statistically significant difference according to mechanical ventilation, sedation, and use of inotropes. As ICU patients are more susceptible to develop dry eye, keratopathy, and ocular infections, they should be consulted by an ophthalmologist for early diagnosis of ocular surface disorders.

Risk factors for ophthalmic complications in patients with burns

A retrospective study of patients admitted to MetroHealth Medical Center was performed to identify the risk factors for short- and long-term ophthalmologic complications related to burn injury. From 2000 to 2007, the authors identified 293 patients with the inclusion criteria of facial burns, TBSA ≥20%, or smoke inhalation injury. Seventy (24%) developed ocular complications, and 16 (11%) developed long-term complications. Statistically significant risk factors identified for short-term complications were burn size, chemical burns, depth of facial burns, initial Glasgow Coma Scale, and need for mechanical ventilation/sedation. Risk factors for long-term complications included wound infection with Pseudomonas or Acinetobacter, third-degree burn size, hours to ophthalmology evaluation, LOS, time on mechanical ventilation, and need for STSG. In addition to facial burns, the requirement of mechanical ventilation, prolonged sedation, and presence of infection with Pseudomonas or Acinetobacter increase the risk of injury to the eye after burn injury, and these patients may benefit from serial eye examinations for early identification of ocular complications.

Ocular surface bacterial colonisation in sedated intensive care unit patients

We investigated the time-dependent ocular surface bacterial colonisation of sedated patients hospitalised in an intensive care unit and aimed to evaluate whether proper topical antibiotic prophylaxis could prohibit corneal infection. The study lasted 12 months and included 134 patients undergoing sedation and mechanical respiratory support for various medical reasons. Patients hospitalised for less than seven days and those with pre-existing ocular surface pathology were excluded. All patients were examined on admission by inspecting the cornea for erosions. Followup examinations were performed each subsequent day. Cultures were also obtained from the conjunctival sac of both eyes on admission and every seventh day until the end of sedation. Standard laboratory techniques were used for isolation, identification and antibiotic susceptibility testing of bacteria. Antibiotic treatment for prophylaxis was administered accordingly. Analysis was carried out for 70 patients. Duration of sedation ranged from seven to 122 days. Fifty-four (77%) patients were colonised by at least one bacterial species other than normal flora within seven to 42 days. Multiple bacteria were isolated from 28 patients undergoing prolonged sedation. Prevalent isolates were Pseudomonas aeruginosa, Acinetobacter spp. and Staphylococcus epidermidis. Infectious keratitis was prohibited in all cases. Ocular surface of long-term sedated patients was found to be colonised by various bacterial species and their isolation was closely associated with the time period of hospitalisation. The results of this study suggest that the early identification of ocular surface bacteria colonisation and the administration of topical antibiotics for prophylaxis can prohibit corneal infection in these patients.

Bioadhesive sulfacetamide sodium microspheres: evaluation of their effectiveness in the treatment of bacterial keratitis caused by Staphylococcus aureus and Pseudomonas aeruginosa in a rabbit model

The aim of this study was to prepare bioadhesive sulfacetamide sodium (SA) microspheres to increase their residence time on the ocular surface and to enhance their treatment efficacy on ocular keratitis. Microspheres were fabricated by spray drying method using mixture of polymers such as pectin, polycarbophil and hydroxypropylmethyl cellulose (HPMC) at different ratios. The particle size and distribution, morphological characteristics, thermal behavior, encapsulation efficiency, mucoadhesion and in vitro drug release studies on formulations have been investigated. After optimisation studies, SA-loaded polycarbophil microsphere formulation with polymer:drug ratio of 2:1 was found to be the most suitable for ocular application and used in in vivo studies. In vivo studies were carried out on New Zealand male rabbit eyes with keratitis caused by Pseudomonas aeruginosa and Staphylococcus aureus. Sterile microsphere suspension in light mineral oil was applied to infected eyes twice a day. Plain SA suspension was used as a positive control. On 3rd and 6th days of the antimicrobial therapy, the eyes were examined in respect to clinical signs of infection (blepharitis, conjunctivitis, iritis, corneal oedema and corneal infiltrates) which are the main symptoms of bacterial keratitis and then cornea samples were counted microbiologically. The rabbit eyes treated with microspheres demonstrated significantly lower clinical scores than those treated with SA alone. A significant decrease in the number of viable bacteria in eyes treated with microspheres was observed in both infection models when compared to those treated with SA alone. In conclusion, in vitro and in vivo studies showed that SA-loaded microspheres were proven to be highly effective in the treatment of ocular keratitis.

Bedside glue blepharorrhaphy for recalcitrant exposure keratopathy in immobilized patients

PURPOSE

To report the practical use and the effectiveness of cyanoacrylate glue blepharorrhaphy in immobilized patients with recalcitrant exposure keratopathy.

METHODS

Retrospective case series. Temporal two thirds of upper eyelid eyelashes were glued to lower eyelid skin with tissue adhesive n-butyl-2-cyanoacrylate (histoacryl blue) after application of a contact lens. The systemic condition for immobilization; duration of exposure signs in the ocular surface; location, depth, and dimensions of the corneal ulcer; duration of effective blepharorrhaphy; and the time to heal were recorded.

RESULTS

Twelve eyes of nine patients were treated. The reasons for immobilization were coma due to malignancy (3 patients), ischemic encephalopathy (2 patients), subarachnoid hemorrhage (2 patients), head trauma (1 patient), coma and hypotony of unknown cause (1 patient). All of the corneal ulcers healed within 4 to 11 days (mean: 5.5 days). Blepharorrhaphy opened spontaneously in 4 to 21 days (mean: 8.6 days).

CONCLUSIONS

Bedside glue blepharorrhaphy with tissue adhesive n-butyl-2-cyanoacrylate is a practical, economic, and effective procedure in the treatment of exposure keratopathy in immobilized patients.

Screening for ocular surface disease in the intensive care unit

PURPOSE

Ventilated patients in the intensive care unit (ICU) often develop exposure keratopathy. This predisposes to the development of bacterial keratitis, which in ICU is often bilateral, with a high risk of perforation. As regular examinations of all ventilated patients by ophthalmologists would be impractical, the purpose of this study was to assess whether ICU staff can screen reliably for keratopathy.

METHODS

A prospective study was performed in a general adult ICU. Twice each week, two junior ICU doctors examined the lid position and ocular surface of all patients who had been continuously sedated for more than 24 h, using fluorescein and a pen torch with a blue filter. An ophthalmologist performed similar examinations using a portable slit lamp.

RESULTS

A total of 48 ocular examinations were performed in 18 patients. Exposure keratopathy was found by the ophthalmologist in 37.5% of examinations and by ICU doctors in 31.3% of examinations. ICU doctors had a sensitivity of 77.8% and a specificity of 96.7% in detecting keratopathy, when compared with the findings of the ophthalmologist. All cases missed by ICU doctors had punctate erosions of less than 5% of the corneal surface. Keratopathy was significantly commoner in patients with incomplete lid closure than in patients with closed lids (70.0 vs 28.9%; two-tailed Fisher's exact test P=0.027).

CONCLUSIONS

ICU staff can perform screening examinations for exposure keratopathy with reasonable sensitivity and specificity. Regular screening by ICU staff would facilitate appropriate treatment of exposure keratopathy and promote earlier identification of cases of keratitis.

Effect of Head Position on Postoperative Chemosis After Prone Spinal Surgery

Conjunctival swelling is a common finding in patients positioned prone. The purpose of this study was to evaluate the effect of head position on postoperative chemosis after prone spinal surgery. On the basis of the head position, 108 patients scheduled for prone lumbar surgery were randomly allocated to 1 of 2 groups: head neutral group (n=54) versus head down (HD) group (n=54). Head position was defined as neutral when the imaginary line from the occipital protuberance to the top of C7 spine process is parallel to the operating table. HD position was maintained by adjusting the height of the prone headrest 5 cm lower than neutral position. Chemosis was evaluated after surgery. The severity of chemosis, which was graded as none, mild, moderate, and severe, showed statistically significant difference between the head neutral group [24 (44%), 25 (46%), 3 (6%), 2 (4%), respectively] and HD group [10 (19%), 23 (43%), 17 (31%), 4 (7%), respectively, P<0.01]. Positive fluid balance and duration of surgery were risk factors for the development of postoperative chemosis. This result suggested that neutral head position, smaller fluid administration, and shorter duration of surgery were useful in decreasing the development of postoperative chemosis after prone spinal surgery.

Development of a new eye care guideline for critically ill patients

Ventilated, critically ill patients have an increased risk of corneal exposure and microbial keratitis; however there is evidence that eye care is a neglected area of patient care. An audit of eye surface disease and eye care documentation revealed a problem within one general intensive care unit (GICU). An education programme was developed to highlight the incidence of eye surface disease and importance of eye care in the ventilated patient.

A randomised controlled study of the efficacy of hypromellose and Lacri-Lube combination versus polyethylene/Cling wrap to prevent corneal epithelial breakdown in the semiconscious intensive care patient

OBJECTIVE

To compare the efficacy of two forms of eye care (hypromellose and Lacri-Lube combination vs polyethylene/Cling wrap covers) for intensive care patients.

DESIGN

Randomised-controlled trial.

SETTING

University affiliated, tertiary referral hospital.

PATIENTS AND PARTICIPANTS

One hundred ten patients with a reduced or absent blink reflex were followed through until they regained consciousness, were discharged from the facility during study enrolment, died or developed a positive corneal ulcer or eye infection.

INTERVENTIONS

All patients received standard eye cleansing every 2 h. In addition to this, group one ( n=60) received a treatment combining hypromellose drops and Lacri-Lube (HL) to each eye every 2 h. Group two ( n=50) had polyethylene covers only placed over the eye to create a moisture chamber.

MEASUREMENTS AND RESULTS

Corneal ulceration was determined using corneal fluorescein stains and mobile slit lamp evaluation, performed daily. No patients had corneal ulceration in the polyethylene cover group, but 4 patients had corneal ulceration in the HL group.

CONCLUSIONS

Polyethylene covers are as effective as HL in reducing the incidence of corneal damage in intensive care patients.

Pseudomonas aeruginosa protease IV enzyme assays and comparison to other Pseudomonas proteases

Pseudomonas aeruginosa secretes multiple proteases that have been implicated as virulence factors and the detection of each specific enzyme can be difficult to determine. Unlike the three Pseudomonas enzymes that have been well characterized (elastase A, elastase B, and alkaline protease), the activity of protease IV in multiple assays has yet to be described. This study defines new assays for Pseudomonas proteases and compares protease IV activity to the activities of elastase A, elastase B, and alkaline protease. Six in vitro assays were studied: zymography, elastin congo red assay, staphylolytic assay, colorimetric peptide assay, solid-phase colorimetric peptide assay, and poly-l-lysine degradation. Casein zymography distinguished protease IV from elastase B and alkaline protease, and gelatin zymography differentiated all four proteases. The elastin congo red assay detected mainly elastase B while the staphylolytic assay was specific for elastase A. Protease IV activity was assayed specifically by the colorimetric assay and two new assays, the solid-phase colorimetric assay and degradation of poly-L-lysine in the presence of EDTA. Alkaline protease could be specifically assayed by poly-L-lysine degradation in the presence of N-alpha-p-tosyl-L-lysine chloromethyl ketone. The results identified three specific assays for protease IV, a new assay specific for alkaline protease, and showed that protease IV has a distinct enzymatic specificity relative to the three other Pseudomonas proteases.

Corneal biopsy with tissue micro-homogenisation for isolation of organisms in bacterial keratitis

PURPOSE

To evaluate a novel two-stage technique to increase yield of bacteria isolated from infected corneal ulcers.

METHODS

A new blade was designed to remove friable material from infected corneal ulcers. The new blade was used in combination with standard tissue micro-homogenisation equipment in a two-stage technique intended to distribute biopsy samples evenly between relevant agar plates. Patients with presumed-bacterial corneal ulcers underwent sequential corneal sampling using the new two-stage technique and a scalpel blade, used without micro-homogenisation (the order of sampling was varied between two groups). Bacterial isolation rates were compared using the chi-squared test.

RESULTS

Twenty-four patients with presumed-bacterial corneal ulcers were studied. The overall positive bacterial isolation rate was 88%, with identical bacterial isolation rates for the new two-stage technique and the scalpel blade (71%). The new technique isolated bacteria from three ulcers that had initially been 'sterile' when sampled with a scalpel blade. Polymicrobial infections were identified in two ulcers with the new blade where only a single organism had been identified using the scalpel blade (not significantly different).

CONCLUSIONS

The new two-stage technique shows promise for improving bacterial isolation rates from presumed-bacterial corneal ulcers.

Ocular surface disease in intensive care unit patients

PURPOSE

To assess the prevalence and natural history of ocular surface disease in patients in an intensive care unit (ICU) and to identify any predisposing factors in order to improve eye care management protocols.

METHODS

The eyes of all patients admitted to an ICU between February and May 1998 were examined at least weekly. The eyelid position, presence of conjunctival oedema, degree of keratopathy and sedation score were documented at every assessment.

RESULTS

Twenty-six patients in an ICU were followed throughout their stay, which ranged from 3 days to 10 weeks. Eleven patients (42%) had some degree of keratopathy, which was detected in the majority in the first week of their stay. The presence of ocular surface disease was closely correlated with the degree of lagophthalmos, which in turn is closely related to the depth of sedation or paralysis.

CONCLUSIONS

In this first ever longitudinal study it was found that assessment of lid position in ICU patients is the single most important observation to be carried out. A management algorithm derived from this evidence is based on daily observation and selective lid taping and shows encouraging early results.