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Biomedical subjects

Fiona Stapleton

Publications and source records attributed to Fiona Stapleton.

26 records · Page 2Linked to original sources
PubMed2003

Microbial keratitis and vision loss with contact lenses.

PURPOSE: Microbial keratitis is the only sight-threatening adverse event that occurs with contact lens wear. This article gives a preliminary estimation of the incidence of microbial keratitis and vision loss with continuous-wear contact lenses made from highly oxygen permeable (Dk) materials. METHODS: The most up-to-date data available on microbial keratitis and vision loss are collected from a range of sources including industry, private practice, and publications and is reviewed. RESULTS: There have been 16 cases of microbial keratitis with high-Dk silicone hydrogel lenses. Of the 13 where data are available, none have lost two or more lines of best-corrected visual acuity (BCVA). CONCLUSION: First approximation indicates that the incidence of microbial keratitis with high-Dk silicone hydrogel lenses may be lower than the incidence with low-Dk soft lenses during extended wear. The rate of loss of more than two lines of BCVA is low in patients that develop microbial keratitis with low- and high-Dk soft lenses.

Adult↗
PubMed2003

Evasion of cellular ocular defenses by contact lens isolates of Serratia marcescens.

PURPOSE: Contact lens contamination by Serratia marcescens can lead to the development of microbial keratitis and contact lens-induced acute red eye, particularly during overnight contact lens wear. The aim of this study was to investigate the interaction of S. marcescens with polymorphonuclear leukocytes (PMNs), which occur in closed-eye tears. METHODS: The respiratory burst of PMNs, when incubated with S. marcescens, was measured using chemiluminescence. Phagocytosis of planktonic and biofilm-grown bacteria by PMNs was also determined. RESULTS: Some strains of S. marcescens did not induce a respiratory burst from PMNs and resisted phagocytosis regardless of opsonization. Phagocytic resistance and growth in the presence of PMNs was markedly increased when bacteria were grown as a biofilm on a contact lens. CONCLUSIONS: The ability of S. marcescens to resist phagocytosis and grow to high levels in the presence of PMNs, particularly when grown as a biofilm on contact lenses, may be a mechanism by which this bacterium can survive the ocular host defense system, grow, and cause keratitis or other adverse responses.

Bacteriological Techniques↗
PubMed2003

Experimental Pseudomonas aeruginosa keratitis in interleukin-10 gene knockout mice.

Pseudomonas aeruginosa keratitis is one of the most destructive diseases of the cornea. The host response to this infection is critical to the outcome. The cytokine interleukin-10 (IL-10) is thought to play an important role in modulating excessive inflammation and antimicrobial defenses. We have found that in IL-10(-/-) mice there is a significant decrease in bacterial load in corneas at 7 days postchallenge with P. aeruginosa. This decrease was accompanied by a reduction in neutrophil numbers in the cornea and changes in cytokine levels compared to those of wild-type mice. A characteristic increase in neovascularization in the cornea was found in the IL-10(-/-) mice. This increased angiogenesis correlated with an increased expression of KC, whereas the kinetics of macrophage inflammatory peptide 2 expression correlated with neutrophil numbers. This finding suggests that KC may play a role in corneal angiogenesis. The source of IL-10 in mouse corneas was identified as a subpopulation of infiltrating cells and keratocytes. This study demonstrates that IL-10 plays an important role in regulating the balance of inflammatory mediators during P. aeruginosa infection of the cornea.

Animals↗
PubMed2003

Pseudomonas aeruginosa keratitis in IL-6-deficient mice.

BACKGROUND: Pseudomonas aeruginosa infection is one of the most destructive diseases of the eye. The host response to this infection is critical to the outcome. Interleukin-6 (IL-6) is implicated in this response; however, the mechanisms by which IL-6 contributes to the host defences in corneal infection remain unclear. Using IL-6-/- mice, we have explored the role of IL-6 in P. aeruginosa keratitis. METHODS: The eyes of IL-6 gene knockout and wild-type mice were challenged topically with P. aeruginosa and examined on days 1-7. Keratitis was examined clinically and histologically. Cytokine, chemokine and complement 3 levels were determined by ELISA and ICAM-1 by immunohistochemistry. RESULTS: Clinically, the IL-6-/- mice showed more severe disease than wild-type mice and this was supported by the histological findings. More than 2-fold higher bacterial load was detected in the eyes of the IL-6-/- mice than in those of the wild-type mice. Neutrophil infiltration to the central cornea of the IL-6-/- mice failed to occur in response to infection, although a greater number of neutrophils were present in the whole eye. This may in part be due to the reduced expression of the adhesion molecule ICAM-1 in the cornea, but does not appear to stem from insufficient production of chemokines or complement 3. CONCLUSIONS: Our findings indicate that IL-6 is critical to the host defence of the cornea during P. aeruginosa infection. Pharmacological manipulation of the IL-6 response may represent a rational strategy for new interventions.

Animals↗
PubMed2003

Differences in clinical parameters and tear film of tolerant and intolerant contact lens wearers.

PURPOSE: To determine whether intolerance to contact lens wear is attributable to clinical or protein characteristics of the tear film. METHODS: Thirty-eight subjects participated; 20 were successful contact lens wearers and 18 had discontinued contact lens wear because of discomfort. Baseline tear film (no lens wear) was analyzed with a range of clinical measurements and protein analyses (lactoferrin, sIgA, and lysozyme). Comfort was determined after 6 hours of lens wear, and differences in tear film characteristics between subject groups were determined. In half of the subject group (n = 19), discriminant analysis was used to develop an equation for predicting the likelihood of intolerance to lens wear. Sensitivity and specificity were determined by testing the formula on the remaining subjects. These formulas were also tested on a separate group of subjects enrolled in a contact lens-wearing trial. RESULTS: Tear volume (meniscus height and phenol red thread test) and tear stability (noninvasive tear break up time [NI-TBUT]) were significantly reduced in intolerant wearers (P < 0.05). A greater number of symptoms were reported by intolerant than by tolerant wearers (P < 0.05). Tolerance was associated with clinical but not protein characteristics of the tear film. Formulas best able to predict contact lens intolerance included NI-TBUT, number of symptoms experienced, and tear film meniscus height. Formulas had high sensitivity, and specificity which ranged from 29% to 57%. CONCLUSIONS: Contact lens intolerance appears to be best predicted by a combination of clinical variables, including tear film stability, tear volume, and symptom reporting.

Adult↗
PubMed2002

The effect of water content on the 193 nm excimer laser ablation.

BACKGROUND: Water content of the corneal stroma may influence excimer laser ablation and may therefore affect residual refractive error following laser in situ keratomileusis. This study reports associations between water content of hydrogel materials and laser ablation depth. METHODS: Hydrated (n = 4) and dehydrated (n = 4) hydrogel buttons of 38%, 45%, 55% and 69% water content were ablated with the Nidek EC-5000 ArF 193 nm excimer laser, set to deliver a -6.00 DS curvature. Central curvature, optical quality and water content were measured before and after ablation. Hydrated buttons were rehydrated postablation and prior to measurement, to eliminate the effect of water removal during the procedure. The ablation depth per pulse was calculated. RESULTS: The average ablation rate for fully hydrated buttons was 0.51 +/- 0.17 microm. The ablation rate for hydrated materials (dry component ablation) reduced with increasing water content (P < 0.001). Dry hydrogel materials (0% water content) had an average ablation rate of 0.23 +/- 0.06 microm per pulse. CONCLUSIONS: For a constant laser energy output, lower water content materials ablated to a greater extent than higher water content materials. This model provides a simple way to assess the effect of water content and dehydration on myopic laser in situ keratomileusis.

Contact Lenses↗