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Biomedical subjects

C M Kirkness

Publications and source records attributed to C M Kirkness.

At least 19 recordsLinked to original sources
PubMed2003

Residual debris as a potential cause of postphacoemulsification endophthalmitis.

AIM: To examine residual debris within sterilised instruments prior to cataract surgery. METHODS: (i) Flushings from 32 sets of phacoemulsification instruments, sterilised according to hospital routine protocols, were taken preoperatively and analysed by scanning electron microscopy (SEM). (ii) A total of 16 sets of flushings from a different institute were collected-with separation of samples collected from phacoemulsification and those from irrigation-aspiration (IA) instruments-and analysed in the same way. (iii) A total of 15 sets of flushings were collected from instruments where an automated flushing system was used prior to sterilisation. RESULTS: (i)In the first study, 62% were clean, 16% were moderately contaminated and 22% were severely contaminated. Various contaminants were identified including lens capsule and cells, man-made fibres, squamous cells, bacteria, fungal elements, diatoms, red blood cells and proteinaceous material. (ii) In the second study, the results were similar and contamination of both phacoemulsification and IA instruments was shown. (iii) The third study showed that although a decrease in contamination followed automated flushing, contamination was not completely eliminated. CONCLUSIONS: Although all equipment had been sterilised, pyrogenic material was still present. These findings emphasise the importance of meticulous cleaning of all surgical equipment in which biological debris can remain.

Endophthalmitis↗
PubMed2002

Instrumental debris.

Explore the source record for details and available documents.

Equipment Contamination↗
PubMed2001

A new surgical technique for keratoglobus-tectonic lamellar keratoplasty followed by secondary penetrating keratoplasty.

PURPOSE: To develop a technique that achieves satisfactory visual rehabilitation in keratoglobus, without the problems of re-epithelialization failure and with minimal risk of graft rejection. METHODS: A patient with bilateral keratoglobus and visual acuities of light perception in the right eye and 6/60 in the left underwent a tectonic lamellar keratoplasty to the right eye. The cornea was first trephined to the depth of the anterior stroma within the limbus. A lamellar dissection technique then was used to tunnel into sclera under the limbus to preserve stem cells. The host corneal epithelium was completely débrided, and a donor corneoscleral button, denuded of its endothelium, was laid on top. A paracentesis was made, and aqueous was aspirated until the anterior chamber had collapsed enough to take up a more physiologic shape. The donor corneoscleral graft was sutured into the prefashioned scleral bed with long, interrupted sutures. Once in situ, the donor graft was débrided of epithelium, and the host limbus was sutured on to it, covering its scleral component. Six months later, a penetrating keratoplasty was performed. The same procedure was performed on the left eye 2 years later. RESULTS: The right eye maintained a best-corrected visual acuity of 6/60 for 16 months after the penetrating graft until the graft decompensated, leaving a final acuity of counting fingers. The left eye maintained a best-corrected visual acuity of 6/18. CONCLUSION: Tectonic lamellar keratoplasty to preserve the host limbus, followed by secondary penetrating keratoplasty, is a realistic alternative to other procedures for the surgical management of keratoglobus.

Cornea↗
PubMed1999

Traumatic wound rupture after penetrating keratoplasty in Africa.

AIM: To investigate risk factors, visual outcome, and graft survival for traumatic wound rupture after penetrating keratoplasty. METHODS: A retrospective analysis of 336 patients who underwent penetrating keratoplasty from 1988 to 1995. RESULTS: 19 patients (5.7%) suffered traumatic postoperative wound rupture requiring surgical repair. They were younger (mean age 16.6 years, 95% CI 13.2-20.6) and more frequently keratoconic (p = 0.01) than other patients (mean age 28.9 years, 95% CI 26.-31.0). Mean postoperative follow up was 37.7 (SD 22.9) months and 24.5 (18.9) months for the rupture and non-rupture patients. Mean interval between keratoplasty and rupture was 18 (21) weeks. The lens was damaged and removed in 37% of ruptured eyes. For keratoconics, the probability of graft survival at 5 years was lower (p = 0.03) in the ruptured eyes (75%) than in the non-ruptured eyes (90%). Endothelial failure was a more common (p <0.05) cause of graft opacification in ruptured grafts than in intact grafts. Of the ruptured eyes, 53% achieved a final corrected acuity of at least 6/18 and 63% achieved at least 6/60 compared with 48% and 71% of the intact eyes respectively (both p >0.1). The proportion of keratoconic eyes which achieved at least 6/60 was lower (p = 0.02) in the ruptured eyes (67%) than the non-ruptured eyes (87%). Eyes with wound ruptures of 5 clock hours or greater were less likely (p <0.05) to achieve an acuity of 6/18 and were more likely (p <0.05) to have an associated lens injury. CONCLUSIONS: Graft rupture is relatively common in African practice, particularly in young keratoconics. Visual outcome and graft survival are not significantly worse than for other grafted eyes, but are significantly worse than for other grafted keratoconic eyes.

Adolescent↗
PubMed1998

Lack of evidence for systemic toxicity following topical chloramphenicol use.

There has been considerable controversy regarding the safety of topical chloramphenicol in ophthalmic practice. The evidence for associated haematopoietic toxicity in idiosyncratic and dose-dependent forms was reviewed. The 7 cases of idiosyncratic haematopoietic reactions associated with topical chloramphenicol reported in the literature are refutable evidence for the existence of such a response. In Scotland, despite extensive prescription of topical chloramphenicol, the incidence of acquired aplastic anaemia was found to be low, as were associated reports of blood dyscrasias throughout the UK. The epidemiology of acquired aplastic anaemia failed to make an association with topical chloramphenicol use. High-performance liquid chromatography (minimum detection limit 1 mg/l) was used to investigate whether serum accumulation of chloramphenicol occurred after topical therapy in 40 patients. The mean dose of chloramphenicol eye drops used after 1 week of treatment was 8.0 mg, and after 2 weeks, 15.3 mg. As expected, chloramphenicol failed to accumulate to detectable levels. This supported the view that topical chloramphenicol was not a risk factor for inducing dose-related bone marrow toxicity. Calls for the abolition of treatment with topical chloramphenicol based on current data are not supported.

Adult↗
PubMed1998

Antimicrobial management of presumed microbial keratitis: guidelines for treatment of central and peripheral ulcers.

AIMS: To determine the quantitative relation between the major risk factors for microbial keratitis of previous ocular surface disease and contact lens wear and central and peripheral infiltration, often associated with ulceration, in order to establish a rational chemotherapeutic management algorithm. METHODS: Data from 55 patients were collected over a 10 month period. All cases of presumed microbial keratitis where corneal scrapes had been subjected to microbiological examination were included. Risk factor data and laboratory outcome were recorded. Antimicrobial regimens used to treat each patient were documented. RESULTS: 57 episodes of presumed microbial keratitis were identified from 55 patients, 24 male and 31 female. There were 30 central infiltrates and 27 peripheral infiltrates of which 28 were culture positive (73% of central infiltrates, 22% of peripheral infiltrates). 26 patients had worn contact lenses of whom 12 had culture positive scrapes (9/14 for central infiltrates, 3/12 for peripheral infiltrates). 31 patients had an ocular surface disease of whom five previous herpes simplex virus keratitis patients developed secondary bacterial infection. Anterior chamber activity and an infiltrate size > or = 4 mm2 were more common with culture positive central infiltrates than peripheral infiltrates (chi 2 test = 11.98, p < 0.001). CONCLUSIONS: Predisposing factors for "presumed" microbial keratitis, either central or peripheral, were: ocular surface disease (26/57 = 45.6%), contact lens wear (26/57 = 45.6%), and previous trauma (5/57 = 8.8%). Larger ulceration (> or = 4 mm2) with inflammation was more often associated with positive culture results for central infiltration. None of these four variables (contact lens wear, ocular surface disease, ulcer size, anterior chamber activity) were of intrinsic value in predicting if a peripheral infiltrate would yield identifiable micro-organisms. Successful management of presumed microbial keratitis is aided by a logical approach to therapy, with the use of a defined algorithm of first and second line broad spectrum antimicrobials, for application at each stage of the investigative and treatment process considering central and peripheral infiltration separately.

Acanthamoeba Keratitis↗
PubMed1996

Amebic keratitis in a wearer of disposable contact lenses due to a mixed Vahlkampfia and Hartmannella infection.

PURPOSE: To support the hypothesis that Acanthamoeba is not a unique cause of amebic keratitis, we report a case of amebic keratitis in which viable Acanthamoeba could not be isolated from corneal tissue. Vahlkampfia and Hartmannella, two other genera of free-living ameba, were isolated, however, using prolonged culture. METHODS: A 24-year-old wearer of soft contact lenses had keratitis. Extensive histologic and microbiologic investigations were performed on corneal scrape, biopsy, and keratoplasty tissue. Contact lenses, storage case, and the home water supply, where contact lens hygiene was practiced, were examined for the presence of micro-organisms. RESULTS: No viruses, pathogenic bacteria, or fungi were detected from corneal tissue samples. Amebae were observed using light and electron microscopy, but these could not be unequivocally classified using immunocytochemical staining. Viable Vahlkampfia and Hartmannella, but no Acanthamoeba, were isolated from the corneal biopsy sample. Indirect immunofluorescence with a range of polyclonal rabbit antisera raised against axenically cultivated stains of the three amebal genera was unhelpful because of cross-reactivity. A diverse range of micro-organisms was present within the storage case, including the three amebal species. Amebic cysts also were associated with the contact lens. CONCLUSION: A mixed non-Acanthamoeba amebic keratitis has been identified in a wearer of soft contact lenses where lack of storage case hygiene provided the opportunity for the free-living protozoa Vahlkampfia and Hartmannella to be introduced to the ocular surface. When Acanthamoeba-like keratitis occurs, but where Acanthamoeba cannot be isolated using conventional laboratory culture methods, alternate means should be used to identify other amebae that may be present. Polyclonal immunofluorescent antibody staining was unreliable for generic identification of pathogenic free-living amebae in corneal tissue.

Adult↗
PubMed1996

Storage of donor corneas, surgery, outcome, and complications of penetrating keratoplasty.

A review of current literature reveals continuing concerns regarding the safety and success of penetrating keratoplasty. Quality assurance within eyebanks is directed inter alia at the prevention of transmission of infection from donor to host. Recent controversy in the United Kingdom regarding the transmission of Creutzfeldt-Jakob disease underscores the need for constant vigilance and regular review of eyebank standards. The improvement of the success rates for keratoplasty in difficult cases and the elimination or reduction of side effects assume increasing importance as the technical difficulties in more straightforward cases are solved. This review discusses some recent publications in this field.

Cornea↗
PubMed1996

Acanthamoeba griffini. Molecular characterization of a new corneal pathogen.

PURPOSE: Acanthamoeba was isolated from the cornea of a soft contact lens wearer who had keratitis. The protozoan was also isolated from the contact lens storage case and the domestic water supply used to clean the case. Using morphologic features, all three isolates were identified tentatively as A. griffini, a species not previously associated with keratitis. Complete small subunit ribosomal RNA gene (18S rDNA) sequence analysis was used to characterize further the three isolates. METHODS: 18S rDNA was polymerase chain reaction-amplified from whole cell DNA derived from amoebal lysates. The genes were cloned and sequenced. Complete sequences of approximately 2800 base pairs were obtained from each culture and compared wih those stored in a data base for homologous Acantamoeba sequences. RESULTS: The isolates were unequivocally identified as A. griffini both by comparison of the gene sequence available for the type strain of the species and the presence of a unique group I intron located within the small subunit rDNA. Sequences obtained for the three isolates were identical, indicating that they were the same strain. CONCLUSIONS: The first direct connection between human disease and A. griffini is reported from a case of Acanthamoeba keratitis. The type strain of this species was isolated from a marine environment, but the disease-causing strain ws isolated from a domestic water supply. The DNA sequences obtained confirmed unequivocally the epidemiologic association between a keratitis-causing strain of Acanthamoeba, the contact lens storage case, and the domestic water supply.

Acanthamoeba↗
PubMed1996

The histopathology of the iridocorneal-endothelial syndrome.

The iridocorneal-endothelial (ICE) syndrome is characterised clinically by a "hammered-silver" appearance of the corneal endothelium, corneal failure, glaucoma, and iris destruction. Specular photomicroscopic studies of the corneal endothelium have demonstrated a population of abnormal cells termed "ICE cells." The purpose of this study was to define the histological appearances typical of this disease and in particular the ultrastructural morphology of the ICE cell. Thirty-five corneas, 11 trabeculectomy specimens, and 3 failed corneal grafts taken from patients with the ICE syndrome were examined by transmission and scanning electron microscopy. Comparison was made with seven normal corneas. Ten corneas and two trabeculectomy specimens demonstrated a population of well-differentiated cells with epithelial features such as desmosomes, tonofilaments, and microvilli. Other cell types identified were cells that resembled those of normal corneal endothelium, inflammatory cells, and cells with a fibroblast-like morphology. It seems likely that the epithelial cells of our specimens are the histological equivalent of the ICE cell seen by specular photomicroscopy. The other cell types may be either residual normal endothelial cells or else arise from secondary phenomena of various kinds.

Cornea↗
PubMed1995

Advances in rapid laboratory diagnosis of infectious endophthalmitis.

Infectious endophthalmitis is a serious ocular condition which always requires rapid medical or surgical intervention. At present this, in a number of situations, remains empirical as a consequence of problems inherent in unequivocal identification of the causative organism, should one be present. Aqueous humor smears and culture have limited value in diagnosis. Vitreous samples can often reveal the presence of microbes, but these may not necessarily be detected in all cases, principally due to suboptimal sampling or pretreatment with antimicrobials which render microbes non-culturable on routine media. Use of electron microscopy and/or immunocytochemistry offers an alternative means of identification, but these approaches have drawbacks principally associated with interpretation. Molecular methods which identify conserved sequences from common causative microbes of endophthalmitis, or which can specify whether the organism is a bacterium or a fungus may become especially important as diagnostic tools in this clinical scenario.

Bacteria↗
PubMed1995

On the pathology of the iridocorneal-endothelial syndrome: the ultrastructural appearances of 'subtotal-ice'.

The iridocorneal-endothelial syndrome (ICE syndrome) is characterised by corneal failure, glaucoma and iris destruction. Specular photomicroscopical and histological studies of the corneal endothelium in this disease show a population of abnormal cells named 'ICE-cells'. In many patients some areas of the endothelium are occupied by ICE-cells and others by normal cells, an appearance described as 'subtotal-ICE'. Specular photomicroscopical observations suggest that ICE-cells and normal endothelial cells may actively interact at the boundary zone where they meet. The purpose of this study was to examine the ultrastructural appearances of the boundary zone to gain insight into the cellular pathology of this region. Thirty-five corneas taken from patients with the ICE syndrome were examined by light, transmission and scanning electron microscopy. The subtotal-ICE appearance was demonstrated in four specimens. The morphology of ICE-cells at the boundary zone suggests that they are non-motile but also implies a general state of high metabolic activity. Many of the normal endothelial cells in this region are damaged, an appearance which may result from a toxic effect from the nearby ICE-cells.

Atrophy↗