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Biomedical subjects

Fiona Stapleton

Publications and source records attributed to Fiona Stapleton.

At least 19 recordsLinked to original sources
PubMed2006

Prospective controlled study of vapor pressure tear osmolality and tear meniscus height in nasolacrimal duct obstruction.

PURPOSE: To determine tear osmolality (TO) and tear meniscus height (TMH) in patients with functional (FNLDO) and primary acquired (PANDO) nasolacrimal duct obstruction. Additionally, to determine the effect of successful dacryocystorhinostomy surgery on these tear parameters. DESIGN: Prospective case-controlled interventional case series. METHODS: Up to 20 microl of basal tears were collected from 20 age- and gender-matched control subjects, 33 patients with FNLDO, 28 patients with PANDO, and 31 patients after successful dacryocystorhinostomy. TMH was measured with videoreflective dacryomeniscometry, and TO was measured with vapor pressure osmometry. RESULTS: Thirty-nine percent of the patients with FNLDO (13/33) elected to undergo dacryocystorhinostomy surgery, compared with 64% of the patients with PANDO (18/28; P = .09). TMH was significantly higher in the disease groups (FNLDO median, 630 +/- 187 microm; PANDO median, 620 +/- 210 microm) compared with the control subjects (median 262 +/- 50 microm; P < .01). In those patients who underwent surgery, TMH was slightly higher in FNLDO than PANDO (P = .08), and TMH reduced significantly after surgery (P < .05). Mean TO in the control subjects was 313 +/- 17 mmol/kg, in FNLDO was 309 +/- 19 mmol/kg, and in PANDO was 315 +/- 24 mmol/kg (P > .05). TO was similar in those patients who progressed to surgery compared with the total group and was unaffected by surgery. CONCLUSION: TO was similar in normal control subjects and in the watery eye group and was unchanged after dacryocystorhinostomy surgery. Despite the slightly higher TMH in patients with FNLDO, a higher proportion of patients PANDO elected to have surgery. Relative to FNLDO, patients with PANDO who progressed to surgery had lower TMH and normal TO, which suggests that a complete lacrimal drainage obstruction induces negative feedback that results in no reduction in TO.

Aged↗
PubMed2006

Silicone hydrogel contact lenses and the ocular surface.

For 30 years, contact lens research focused on the need for highly oxygen-permeable (Dk) soft lens materials. High Dk silicone hydrogel contact lenses, made available in 1999, met this need. The purpose of this review is to examine how silicone hydrogel lens wear affects the ocular surfaces and to highlight areas in which further research is needed to improve biocompatibility. Silicone hydrogel lenses have eliminated lens-induced hypoxia for the majority of wearers and have a less pronounced effect on corneal homeostasis compared to other lens types; however, mechanical interaction with ocular tissue and the effects on tear film structure and physiology are similar to that found with soft lens wear in general. Although the ocular health benefits of silicone hydrogel lenses have increased the length of time lenses can be worn overnight, the risk of infection is similar to that found with other soft lens types, and overnight wear remains a higher risk factor for infection than daily wear, regardless of lens material. Future contact lens research will focus on gaining a better understanding of the way in which contact lenses interact with the corneal surface, upper eyelid, and the tear film, and the lens-related factors contributing to infection and inflammatory responses.

Contact Lenses, Extended-Wear↗
PubMed2006

Type III secretion system-associated toxins, proteases, serotypes, and antibiotic resistance of Pseudomonas aeruginosa isolates associated with keratitis.

The association between possession of toxin gene-related type III secretory system, protease profiles, O serotypes, and antibiotic resistance patterns was characterized genetically and phenotypically in 46 keratitis isolates of Pseudomonas aeruginosa. There was no significant difference in exoU or exoS prevalence among the keratitis strains. Distinct protease profiles were seen in isolates harboring either exoU or exoS genes. One hundred percent (13/13) of serotype E (O:11) strains contained type III secretion system-associated cytotoxin gene exoU. Multidrug resistance was identified in 4% of Australian and 29% of Indian isolates. None of the Australian isolates was resistant to ciprofloxacin. In general, the rate of multidrug resistance in the exoU positive cytotoxic and serotype E (O:11) strains was significantly higher than in exoS positive invasive strains (p < 0.01). The results suggest that multidrug resistance may be more commonly associated with the corneal isolates of P. aeruginosa having type III secretion system-associated cytotoxin gene exoU and belonging to serotype E (O:11) group.

ADP Ribose Transferases↗
PubMed2006

Evaluation of corneal sensitivity to mechanical and chemical stimuli after LASIK: a pilot study.

PURPOSE: To evaluate the effect of laser in situ keratomileusis (LASIK) on corneal sensitivity, nerve morphology, and tear film characteristics. METHODS: A cross-sectional study design was used. Eighteen patients (eight men and 10 women with a mean age of 36.9 +/- 11.2 years) who had undergone bilateral LASIK for low myopia within 18 months of the study and 28 control subjects (16 men and 12 women with a mean age of 27.2 +/- 7.7 years) were enrolled. Central and inferior corneal thresholds to mechanical (air) and chemical (air plus carbon dioxide) stimuli were determined by using a staircase technique. Stimuli of a 1-second duration at 34 degrees C were delivered with a CRCERT-Belmonte aesthesiometer. Images of subbasal nerves in the central cornea were captured with confocal microscopy. Nerve morphology was classified as no nerves, short nerves (<175 microm), or long nerves (>175 microm), with or without interconnections. Noninvasive tear break up time was measured. The phenol red thread test was used to indicate basal tear secretion. Differences between groups were evaluated with analysis of variance, and associations between variables were evaluated with parametric or nonparametric correlation, when appropriate. RESULTS: Central corneal mechanical sensitivity was significantly reduced in the post-LASIK group compared with the control subjects (P < 0.001). Nerve morphology was associated with mechanical threshold. Nerve morphology, mechanical sensitivity, and tear breakup time improved during the first 1 to 3 months after surgery, with little change thereafter. Chemical sensitivity was associated with tear secretion (P < 0.05). CONCLUSIONS: Central corneal mechanical sensitivity is reduced in patients after LASIK, with partial recovery seen 3 months after surgery. A similar recovery trend is seen for nerve morphology.

Adult↗
PubMed2006

Factors affecting the morbidity of contact lens-related microbial keratitis: a population study.

PURPOSE: To examine factors influencing the severity of soft contact lens (SCL)-related microbial keratitis. METHODS: Cases were detected via surveillance studies in Australia and New Zealand. Factors affecting disease severity (costs, days of symptoms, and 2 or more lines of vision loss) were examined and included age; gender; delay in SCL removal, seeking consultation, or receiving treatment; overnight wear; SCL material (hydrogel or silicone hydrogel [SiH]); and causative organism. RESULTS: Two hundred ninety-seven cases were identified: 61% female, age: 35 +/- 13 years (mean +/- SD). Treatment costs were (median [interquartile range]) $760 [1859] and indirect costs were $468 [1810]. Patients were symptomatic for 7 [11] days, and vision loss occurred in 14.3% of cases. Cases with pathogenic causative organisms (66/297, 22%) were 11.4 times (95% confidence interval [CI], 4.2-30.9) more likely to result in vision loss, had longer duration of symptoms (21 [40] vs. 6 [8] days, P < 0.001) and incurred higher costs (5,512 [14,733] vs. 1,048[8,325], P < 0.001). Delays (>12 hours) before treatment increased the likelihood of vision loss (P = 0.048) disease duration (P = 0.004), and associated costs (P = 0.009). Remoteness increased the risk of vision loss (odds ratio [OR] = 5.1; 95% CI 1.6-16.6), and individuals over 28 years of age had longer disease duration (P = 0.02). In overnight wear and after adjustment for culture result and treatment delays, SiH wearers had slightly shorter disease duration (4 [4] vs. 7 [10] days, P = 0.02) but a rate of vision loss and cost similar to those of hydrogel wearers. CONCLUSIONS: The causative organism was the major determinant of severity; however, modifiable factors such as delays in treatment had considerable influence. Duration of symptoms was shorter in SiH wearers, but other factors dominated disease outcome in this population study.

Adolescent↗
PubMed2005

Microbial keratitis predisposing factors and morbidity.

PURPOSE: To examine predisposing factors, treatment costs, and visual outcome of microbial keratitis in an ophthalmic casualty and inpatient population. DESIGN: Retrospective medical records review. PARTICIPANTS: Fifteen- to 64-year-olds with microbial keratitis treated at the Royal Victorian Eye and Ear Hospital between May 2001 and April 2003 (n = 291). METHODS: Risk factors were identified from patient files. Demographic, clinical, and microbiological data; severity; outpatient visits; hospital bed days; and vision loss were examined. MAIN OUTCOME MEASURES: Cost to treat (Australian dollars), vision loss, and factors influencing these outcomes. RESULTS: Ocular trauma (106/291 [36.4%]) and contact lens (CL) wear (98/291 [33.7%]) were the most commonly identified predisposing factors; 18 (6.1%) had multiple predisposing factors; 17 (5.8%), ocular surface disease; 20 (6.9%), herpetic eye disease; 4 (1.4%), systemic associations; 5 (1.7%), other; and 23 (7.9%), unknown cause. Of trauma cases, 90.6% involved males, compared with 44% to 57% for other groups (P<0.001). Contact lens wearers were younger than the other groups--mean age 30 years, compared with 40 to 47 years (P<0.01). Gram-negative organisms were isolated more frequently in CL wearers than trauma cases (18.7% vs. 6.5%, P = 0.01). The number of outpatient visits was 4+/-1 (median +/- interquartile range), and 19.6% (57/291) were hospitalized for 5+/-2 days. Hospital resource use and vision loss were similar for predisposing factors but differed by causative microorganism. Eighty-eight percent of cases were scraped: acanthamoeba keratitis was the most expensive to treat, followed by fungal and herpetic keratitis and, lastly, culture-proven bacterial keratitis or culture-negative cases (P<0.0001). After treatment, 21.7% exhibited >2 lines of vision loss, and 1.6% of cases had > or =10 lines of vision loss. Vision loss was associated with clinical severity (P = 0.005). CONCLUSIONS: Ocular trauma and CL wear are the major predisposing factors for microbial keratitis in this age range. These cases require significant hospital resources during treatment, and the keratitis may result in loss of vision.

Acanthamoeba Keratitis↗
PubMed2005

Videoreflective dacryomeniscometry in normal adults and in patients with functional or primary acquired nasolacrimal duct obstruction.

PURPOSE: Videoreflective dacryomeniscometry (VRD) for evaluation of marginal tear film has not been performed in patients with watery eye or in a controlled study. We used VRD to evaluate the height of the central marginal lower lid tear film in normal adults and compared it with two watery-eye groups and a postoperative dacryocystorhinostomy (DCR) group. DESIGN: Case-controlled interventional case series. METHODS: We evaluated with VRD 20 subjects with normal lacrimal drainage function, 21 patients with primary acquired nasolacrimal duct obstruction (PANDO), 28 patients with functional nasolacrimal duct obstruction (FNLDO), and a postoperative group of 14 patients derived from the previous two pathologic groups. Comparison between the four groups was performed to determine statistically significant differences between tear film height. RESULTS: PANDO and FNLDO groups were shown to have significantly greater median tear meniscus heights ([TMH] PANDO: 620 microm, interquartile range [IQR] 453 microm; FNLDO: 731 microm, IQR 529 microm) than normal subjects (296 microm, IQR 214 microm; P < .001) and postoperative PANDO patients (265 microm, IQR 159 microm). There was no significant difference in TMH between PANDO and FNLDO groups preoperatively (P = .275). There was a reduction in median TMH postoperatively of 355 microm (P = .008) in PANDO and 360 microm (P = .068) in FNLDO. CONCLUSIONS: PANDO and FNLDO patients have similar preoperative TMH. In both these groups, TMH is significantly greater than in normal control subjects. Lacrimal drainage surgery substantially reduces TMH as measured using VRD in PANDO.

Aged↗
PubMed2005

Effects of alpha-toxin-deficient Staphylococcus aureus on the production of peripheral corneal ulceration in an animal model.

PURPOSE: To examine the role of Staphylococcus aureus alpha-toxin in contact lens-induced peripheral ulceration (CLPU). MATERIALS AND METHODS: Proteolytic enzyme, hyaluronidase, alpha-toxin, and beta-toxin production by S. aureus 8325-4 and its alpha-toxin-deficient mutant (S. aureus DU1090) were examined. Using a rabbit model of CLPU, animals were fitted with hydrogel contact lenses colonized by either S. aureus 8325-4 or the mutant strain. The clinical presentation, bacterial cultures, and histology of the ulceration were examined. RESULTS: Both strains of S. aureus produced similar levels of caseinase, gelatinase, elastase, hyaluronidase, and beta-toxin. S. aureus DU1090 induced weaker haemolysis of rabbit blood cells than S. aureus 8325-4. Ulceration in the S. aureus DU1090 eye was less frequent and less severe than that caused by S. aureus 8325-4. CONCLUSIONS: The enzyme production profile of S. aureus DU1090 was similar to the parent strain. S. aureus strains may produce CLPU-like lesions irrespective of alpha-toxin production, but severe infectious lesions are produced only in the presence of alpha-toxin.

Animals↗
PubMed2005

Corneal mechanical sensitivity measurement using a staircase technique.

PURPOSE: To determine the repeatability of an unequal staircase technique (Garcia-Perez Staircase, GPS) to measure corneal mechanical threshold using the CRCERT-belmonte Aesthesiometer, and to compare this with a previously-reported psychophysical method (method of constant stimuli, MOCS). METHODS: The GPS, utilising unequal ascending and descending steps, was used to obtain a threshold measurement from the mean of six response reversals. repeatability was determined for the GPS and MOCS methods (N = 14), and threshold results obtained with each method were compared (N = 10). RESULTS: The GPS (65.0 +/- 16.9 mL min(-1); CoR +/- 18.3 mL min(-1)) method was more repeatable than the MOCS (64.0 +/- 15.7 mL min(-1); CoR +/- 37.3 mL min(-1)) and the absolute values obtained with the two methods were not significantly different. CONCLUSIONS: Although each method gave equivalent threshold results, the GPS method was more repeatable and quicker to apply and hence should reduce the influence of patient fatigue and help to minimise possible carry-over effects.

Adult↗
PubMed2004

The corneal stroma during contact lens wear.

Recent technological advances have lead to novel descriptions of the microanatomy of the corneal stroma. In the first section of this review, these findings and the role they play in the maintenance of vital properties such as corneal transparency, mechanical strength, homeostasis, wound-healing response and metabolism are described. In the second part, contact lens induced stromal alterations such as acidosis, oedema, striae, thinning and opacities are reviewed as well as the more recently described phenomenon of microdot deposits and keratocyte loss with an emphasis on how lens wearing stromal effects can be minimised.

Animals↗
PubMed2004

Induction of cytokines from polymorphonuclear leukocytes and epithelial cells by ocular isolates of Serratia marcescens.

PURPOSE: During contact lens wear, bacterial contamination of the lens can lead to the development of microbial keratitis (MK) or contact lens induced acute red eye (CLARE). Inflammatory mediators released by the host may heighten the response. We have examined the ability of human corneal epithelial cells and polymorphonuclear leukocytes (PMNs) to release cytokines upon stimulation with bacteria. METHODS: Serratia marcescens strains were added to corneal epithelial cells or PMNs. After incubations of up to 20 hours, supernatants were assayed for the presence of inflammatory mediators by ELISA. RESULTS: All strains stimulated PMNs to release IL-8 and LTB(4). Epithelial cells did not release LTB(4). IL-8 was released after exposure to most S. marcescens isolates. A sub-group of strains stimulated the release of TNF-alpha from corneal epithelial cells. CONCLUSIONS: S. marcescens can stimulate the release of inflammatory mediators from both PMNs and corneal epithelial cells. This release could be important in the progression and resolution of MK and CLARE.

Cells, Cultured↗
PubMed2004

Development and validation of a multidimensional quality-of-life scale for myopia.

BACKGROUND: Five dimensions of health-related quality of life in myopia were hypothesized to affect satisfaction with visual correction modality. Items on these dimensions reflected the frequency of visual compromise and ocular symptoms; individual tolerance of these compromises and symptoms; cosmesis; psychological constructs (including situation-dependent characteristics such as adaptability, self-efficacy, and subjective well-being); and personality traits such as extraversion and introversion. METHODS: Psychologically oriented items and visually oriented items were developed in two stages involving 1,647 participants. Item development was based on a comprehensive literature review, interviews with experts, myopic subjects, and graduate students, and written feedback. Items were selected through factor analysis and the examination of their ability to discriminate between treatment conditions (spectacle wear, daily use of contact lenses, continuous use of contact lenses, or laser-assisted in-situ keratomileusis for myopia). After development, selection, and validation of the psychological items and then the vision items, a final multidimensional scale combining both types of items was designed. The scale was administered to 124 subjects whose myopia was corrected by one of several treatment modalities to determine final construct validity. RESULTS: Using principal axis factoring and oblimin with Kaiser normalization rotation methods, five factors with strong item loadings evolved as hypothesized. The final multidimensional scale consisted of 13 items related to specific aspects of frequency of visual compromise and ocular symptoms with 13 corresponding items for level of tolerance for these problems; three items related to cosmesis; 10 items related to psychological characteristics; and six items related to personality traits. Good internal consistency in each factor (Cronbach's alpha range, 0.76 to 0.92) for the scale was evident. DISCUSSION: This report describes the development and validation of an easily administered, short, effective multidimensional health-related quality-of-life questionnaire for use in selecting and measuring success of methods for correcting myopia.

Adult↗
PubMed2004

Evaluation of surveillance methods for an epidemiological study of contact lens related microbial keratitis.

PURPOSE: To evaluate surveillance methods in a pilot epidemiological study of contact lens related microbial keratitis (MK) cases identified by ophthalmic practitioners in Australia and New Zealand between May and August 2003 inclusive. METHODS: Twelve ophthalmologists and 55 optometrists from rural and metropolitan locations were sent a study information pack with postal reporting forms. After 2 months, practitioners were emailed a link to a website for Internet reporting. After 4 months, practitioners were prompted by email and then by telephone if a response was not received. Passive response rates were the rate of returns after posting information and emailing the website link. Active response rates included personalized email and telephone follow-up. RESULTS: Ten cases of MK were identified by optometrists and five by ophthalmologists. The passive response rates were 79% and 58% for the first and second reporting periods, respectively. There was a lower response rate in the second reporting period compared to the first (P = 0.02). With active surveillance the response rate increased to 97% and 96%. A large proportion of optometrists (62%) and ophthalmologists (55%) used the website for at least one reporting period. Internet reporting was used by all New Zealand practitioners (5/5). CONCLUSIONS: A surveillance study to estimate the incidence of contact lens related MK in Australia and New Zealand is feasible and acceptable. Internet-based reporting offers a reliable, rapid and cost-effective means of running a large scale, international surveillance study. Active surveillance methods are necessary to enhance reporting rates.

Adolescent↗
PubMed2003

Hypersensitivity responses and contact lens wear.

Hypersensitivity diseases that involve the eye are common reasons why patients present to eyecare practitioners. Common ocular hypersensitivity disorders include allergic conjunctivitis, giant or contact lens induced papillary conjunctivitis and atopic keratoconjunctivitis. The diagnosis and management of ocular hypersensitivity can present a challenge to eyecare practitioners and an understanding of the mechanisms that underlie the signs and symptoms of such conditions is necessary for their appropriate management. This article reviews the mechanisms by which the eye responds to antigenic challenges, the pathogenesis of ocular hypersensitivity responses, particularly in relation to contact lens wear, and illustrates possible management strategies.

Journal Article↗
PubMed2003

Altered conjunctival response after contact lens-related corneal inflammation.

PURPOSE: Corneal inflammation in overnight contact lens (CL) wear is not fully understood. We designed a masked study to examine the impact of overnight CL wear on clinical variables in subjects who had previously experienced corneal inflammatory disease. METHODS: Forty-four subjects were entered into the study: Nine subjects who had previously experienced CL-associated acute red eye (CLARE) and nine controls; 13 subjects who had previously experienced CL-induced peripheral ulceration (CLPU) and 13 controls, respectively. Controls were matched for age, gender, CL wear experience, and refractive error. Subjects wore bilateral disposable CLs (-3.00 DS). Corneal, conjunctival, and CL fitting variables were assessed prior to sleep, after a single night of CL wear, at 1, 2, and 4 hours after waking by clinicians who were masked to group membership. Retrospective analysis of prewear corneal and conjunctival variables for CLARE subjects and their respective controls was also performed. RESULTS: Contact lens-associated acute red eye subjects consistently showed higher limbal redness (p < 0.05), bulbar redness (p < 0.05), and conjunctival staining (p < 0.005) compared with controls. Lens fitting and corneal variables were not significantly different at any time point for CLARE subjects. Contact lens-induced peripheral ulceration subjects were not different from matched controls for any variable at any time point. Limbal redness varied significantly over time among controls, with highest values measured at eye opening (p < 0.05). Retrospective analysis of prewear variables showed no significant differences between CLARE and control subjects. CONCLUSIONS: Wearers who previously experienced CLARE had a greater conjunctival response to CL wear compared with wearers who had no previous inflammatory disease. Clinical observations, however, were not helpful in predicting wearers who were predisposed to CLARE.

Adult↗
PubMed2003

The causes of and cures for contact lens-induced peripheral ulcer.

PURPOSE: Contact lens-induced peripheral ulceration (CLPU) is a relatively common adverse response associated with wearing hydrogel lenses, especially on an extended wear schedule. Bacteriologic examination of lenses at the time of an event has demonstrated an association with Staphylococci spp. We sought to investigate the causes of CLPU in a rabbit model of contact lens wear. METHODS: Rabbits wore contact lenses for a period of 24 hr in the presence or absence of bacteria or in presence or absence of epithelial scratches made in the periphery of the cornea before lens wear. Bacteria tested were a strain of Staphylococcus aureus or a strain of Staphylococcus epidermidis isolated from human CLPUs. Rabbits were also challenged with S. aureus in the presence of an epithelial defect and in the absence of a contact lens. Corneas were monitored by slitlamp, histology, and microbial culture after 24 hr. RESULTS: No CLPU-like lesions were detected under the following conditions: corneal scratch plus lens wear with no bacteria; corneal scratch plus S. epidermidis colonized lenses; corneal scratch without lens wear and with S. aureus applied to eyes; no scratch plus S. aureus colonized lenses; and corneal scratch plus contact lenses colonized by dead S. aureus. CLPU-like lesions were found only when the corneas were scratched and contact lenses colonized by viable S. aureus were applied to the eye. The histology of the lesions demonstrated a frank epithelial break with underlying stromal infiltration. Only low numbers of bacteria could be cultivated from the corneas with CLPU-like lesions. The CLPU-like lesions shared many similarities with CLPU in humans. CONCLUSION: CLPU-like lesions were only produced by S. aureus and not S. epidermidis in the presence of an epithelial abrasion and contact lens. Thus, we hypothesize that to reduce the incidence of CLPU, contact lenses designed to reduce corneal interaction and repel microbial colonization should be produced.

Animals↗
PubMed2003

Contact lens-related microbial keratitis: what can epidemiologic studies tell us?

Since the publication of large-scale population based studies to estimate the risks of contact lens-related microbial keratitis, the lens types and modes of wear have changed considerably, with the introduction of silicone hydrogel contact lenses for continuous wear of up to 30 nights and daily disposable contact lenses. It is time to consider epidemiologic studies to estimate the absolute and relative risk of microbial keratitis associated with these new exposures. This article summarizes current knowledge of the estimates and determinants of risk associated with re-useable hydrogel lenses and discusses study design considerations for future studies. The absolute risk of microbial keratitis to the wearer has been remarkably stable since 1989. Risk factors consistently associated with increased risk have included overnight wear, the duration of continuous overnight wear, lower socioeconomic class, smoking, and lens hygiene practice, specifically in daily wear lenses. Men seem to be at a slightly higher risk compared to women. Factors such as the lens age, duration of wear or wear history, and time since the last aftercare visit do not seem to modulate risk. Outstanding questions include whether the risk has changed over time, whether the risk is modified with daily disposable or silicone hydrogel wear, whether the risk is different for 6 or 30 nights of continuous wear, or whether the severity of the disease or spectrum of causative organisms has been modified with new lens types. Different study designs have been used to derive risk data in contact lens wear, including cohort, surveillance, and case-control designs. An appreciation of the advantages and limitations of each of these approaches will assist in the planning of future studies to address these outstanding questions.

Contact Lenses, Hydrophilic↗