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R Folberg

Publications and source records attributed to R Folberg.

At least 19 recordsLinked to original sources
PubMed2006

Three-dimensional volume reconstruction of extracellular matrix proteins in uveal melanoma from fluorescent confocal laser scanning microscope images.

The distribution of looping patterns of laminin in uveal melanomas and other tumours has been associated with adverse outcome. Moreover, these patterns are generated by highly invasive tumour cells through the process of vasculogenic mimicry and are not therefore blood vessels. Nevertheless, these extravascular matrix patterns conduct plasma. The three-dimensional (3D) configuration of these laminin-rich patterns compared with blood vessels has been the subject of speculation and intensive investigation. We have developed a method for the 3D reconstruction of volume for these extravascular matrix proteins from serial paraffin sections cut at 4 microm thicknesses and stained with a fluorescently labelled antibody to laminin (Maniotis et al., 2002). Each section was examined via confocal laser-scanning focal microscopy (CLSM) and 13 images were recorded in the Z-dimension for each slide. The input CLSM imagery is composed of a set of 3D sub-volumes (stacks of 2D images) acquired at multiple confocal depths, from a sequence of consecutive slides. Steps for automated reconstruction included (1) unsupervised methods for selecting an image frame from a sub-volume based on entropy and contrast criteria, (2) a fully automated registration technique for image alignment and (3) an improved histogram equalization method that compensates for spatially varying image intensities in CLSM imagery due to photo-bleaching. We compared image alignment accuracy of a fully automated method with registration accuracy achieved by human subjects using a manual method. Automated 3D volume reconstruction was found to provide significant improvement in accuracy, consistency of results and performance time for CLSM images acquired from serial paraffin sections.

Extracellular Matrix Proteins↗
PubMed2002

[The Munich/San Diego/Iowa City Collaboration (MuSIC). MuSIC Report I: Design , characteristics of the collective and preliminary results].

BACKGROUND: We have previously shown that histologically described microcirculation patterns (MCP) can be visualized with indocyanine green (ICG) angiography. We have designed a prospective study to evaluate the prognostic value of these angiographically imaged MCP in small choroidal melanocytic lesions. In this report we describe the design of the study, characterize the patient collective, and present the first results. PATIENTS AND METHODS: In this prospective nonrandomized observational study, unilateral choroidal melanocytic lesions with 1.5-5.5 mm maximum apical height are observed until growth is determined according to defined criteria. Variables are demographic parameters, subjective symptoms, subretinal fluid, location and dimension of tumor, hemorrhage, color, orange pigment, and MCP determined by ICG angiography: normal, straight, parallel without crosslinking, parallel with crosslinking, arcs without branching, arcs with branching, loop, and network. RESULTS: Seventy patients (22 males, 48 females; age: 33-88 years, median: 64 years) have been included up to now: 19 tumors showed growth so far (time to growth: 51-946 days, median: 127 days). The following parameters were statistically significantly correlated with time to tumor growth: flashes (p = 0.082), orange pigment (p = 0.012), subretinal fluid (p < 0.001), maximum basal tumor diameter (p = 0.001), maximum apical tumor height (p < 0.001), parallel with crosslinking (p < 0.001), arcs with branching (p = 0.006), loop (p < 0.001), and network (p < 0.001). Of these, complex MCP (parallel with crosslinking, arcs with branching, loop and/or network) showed the strongest correlation with time to tumor growth in a Cox regression model. Based on our data, the positive predictive value of imaging complex MCP (for growth within 12 months) is 78% and the negative predictive value is 98%. CONCLUSION: Our patient collective demonstrates comparable prognostic parameters for time to growth as described in the literature. In addition, the ICG angiographic detection of complex MCP is more strongly predictive of the time to growth than other clinically determinable factors. Thus, we recommend this examination for patients with small choroidal melanocytic lesions, if the patient is to be counseled regarding the likely biologic behavior of his tumor.

Adult↗
PubMed2001

Comparison of microcirculation patterns and MIB-1 immunoreactivity in iris and posterior uveal melanoma.

PURPOSE: To compare melanomas confined to the iris and those involving either the ciliary body or choroid for the histologic features of microcirculation patterns and tumor cell proliferation indices. DESIGN: Retrospective comparative human tissue study. PARTICIPANTS: Ninety-eight uveal melanomas were studied, including 18 tumors confined to the iris, 30 tumors involving the ciliary body, and 50 tumors confined to the choroid. METHODS: Formalin-fixed, paraffin-embedded sections from each tumor were stained with hematoxylin-eosin and with periodic acid-Schiff. Adjacent histologic sections were stained with the MIB-1 antibody that reacts with the Ki-67 antigen. MAIN OUTCOME MEASURES: Microcirculation patterns were assessed in the periodic acid-Schiff-stained sections. Proliferative activity was assessed in the MIB-1-stained sections. The mean MIB-1 positive cell count per high-power field (HPF) was calculated in 10 HPF (x 40) in the area of maximal immunoreactivity. Two observers evaluated each MIB-1-stained section, and the interobserver reproducibility was assessed. RESULTS: Histologic microcirculation patterns associated with death from metastatic disease in ciliary body and choroidal melanomas (parallel vessels with cross-linking and networks of back-to-back loops) were not found in any of the iris melanomas. By contrast, 34% and 63% of the choroidal and ciliary body melanomas, respectively, showed at least one of these patterns. The mean positive cell count per HPF +/- standard error was 19.9 +/- 3.5, 27 +/- 5.3, and 1.9 +/- 0.4 in choroidal, ciliary body, and iris melanoma, respectively (P: = 0.003, Kruskal-Wallis test). CONCLUSIONS: Melanoma confined to the iris is characterized by a low rate of proliferation and the histologic absence of microcirculation patterns associated with metastatic posterior uveal melanoma. Both features are consistent with the relatively benign nature of iris lesions compared with melanomas involving the ciliary body or choroid.

Adult↗
PubMed2001

Microcirculation patterns other than loops and networks in choroidal and ciliary body melanomas.

PURPOSE: To provide ophthalmologists and pathologists with expanded criteria for separating patients at high risk of metastatic melanoma from those at low risk on the basis of microcirculation patterns in choroidal and ciliary body melanomas. DESIGN: Tissue culture studies and observational case series. PARTICIPANTS: The pattern-forming ability of four uveal melanoma cell lines of varying degrees of aggressive behavior was studied in vitro. Histologic sections of 234 eyes removed for choroidal or ciliary body melanoma were studied for the presence of microcirculation patterns. METHODS: The study was divided into two phases: the study of histologic sections of eyes removed for choroidal and ciliary body melanomas and observations on the in vitro behavior of cultured melanoma cells of varying degrees of invasive behavior. The presence or absence of each of nine microcirculation patterns was recorded from tissue sections, and interrelationships between different patterns were explored statistically. In vitro reconstitution of patterns and a study of the interrelationships of patterns in histologic sections was carried out. In the in vitro studies, uveal melanoma cell lines of varying degrees of aggressive potential were cultured to observe the development of architectural patterns other than loops and networks. MAIN OUTCOME MEASURES: In histologic studies, the outcome measure was the conditional probability of detecting loops or networks given the presence or absence of other patterns positive for periodic acid-SCHIFF: For tissue culture studies, the outcome measure was either the development or lack of development of patterns of different shapes in vitro. RESULTS: Histologic studies disclosed that given the presence of arcs without or with branching in a tissue section, it is likely that loops or networks will be detected in the same section plane, suggesting that the production of these patterns by aggressive tumor cells reflects a spectrum of architectural potential. In vitro studies confirmed this hypothesis by revealing that highly aggressive and metastatic uveal melanoma cell lines, but not poorly aggressive tumor cell lines, generated parallel channels with and without crosslinking and arcs with and without branching as well as loops and networks. CONCLUSIONS: The criteria for separating patients into low- and high-risk categories for metastasis from uveal melanoma should be expanded to include patterns other than loops or networks. In both the pathology laboratory as well as in a clinical setting, the detection of arcs or arcs with branching and parallel channels should prompt a careful search for loops and networks and for crosslinking parallel channels, respectively.

Choroid Neoplasms↗
PubMed2001

Safety levels for exposure of cornea and lens to very high-frequency ultrasound.

OBJECTIVE: Very high-frequency (50-MHz) ultrasound is widely used for imaging the anterior segment of the eye. Our aim was to determine whether exposures to ultrasound at and above those used in diagnostic imaging systems might cause bioeffects in ocular tissues. METHODS: We characterized the output parameters of a polyvinylidene difluoride transducer using a needle hydrophone. We exposed sites on the cornea or lens of rabbits for up to 30 minutes at a 10-kHz pulse repetition frequency. Tissue obtained immediately or 24 hours after exposure was examined by light microscopy. A numeric model was implemented to calculate expected temperature elevations in the cornea and lens under experimental conditions. RESULTS: No tissue changes were observed directly or by slit lamp. Light microscopy showed no abnormalities attributable to ultrasound exposure. Simulations showed that even long-term exposures should produce temperature elevations of less than 1 degree C in both the cornea and lens. CONCLUSION: With the use of exposure parameters 4 to 5 orders of magnitude greater than encountered in a clinical situation, no tissue changes were observed. This is consistent with the small (0.2 degrees C) temperature rises computed in simulations. The lack of biological effects is attributable to the small dimensions of the focal zone, allowing rapid dissipation of heat, and the low total acoustic power produced by the transducer.

Animals↗
PubMed2001

Prognostic significance of periodic acid-Schiff-positive patterns in primary cutaneous melanoma.

The patterns of periodic acid-Schiff (PAS) staining of extracellular matrix in histological sections of certain melanomas may be predictive of outcome. Recent in vitro and molecular genetic data suggest that the appearance of these patterns in both uveal and cutaneous melanoma is a function of aggressive tumor cells. We studied 96 patients with primary cutaneous melanomas treated at the University of Illinois at Chicago who were monitored for disease-free survival. Survival probabilities were determined by Kaplan-Meier estimates, and prognostic factors were evaluated by multivariate analysis. By univariate analysis, there was a significant decrease in disease-free survival among patients whose tumors contained parallel with cross-linking or network patterns (PXNs; P = 0.0070). Stepwise regression with Cox models that included the combinations of the PAS-positive patterns, tumor thickness, female gender, ulceration, and age yielded a model with thickness and the PAS-positive parallel with cross-linking or networks. Despite the relatively small sample size in this study, the detection of the PAS-positive parallel with cross-linking or networking in cutaneous melanoma was associated with a decrease in disease-free outcome. Additional studies of the prognostic significance of these patterns is warranted on larger data sets.

Adolescent↗
PubMed2000

Confirmation of confocal microscopy diagnosis of Acanthamoeba keratitis using polymerase chain reaction analysis.

BACKGROUND: Acanthamoeba keratitis has commonly been identified with in vivo confocal microscopy and confirmed with histologic examination of an epithelial biopsy specimen. OBJECTIVE: To determine if Acanthamoeba keratitis can be verified using polymerase chain reaction (PCR) of epithelial biopsy specimens. METHODS: Epithelial specimens from patients with suspected Acanthamoeba keratitis by confocal microscopy were tested for Acanthamoeba with PCR of Acanthamoeba ribosomal DNA. RESULTS: Twenty-four of 31 patients with evidence of Acanthamoeba keratitis were positive for Acanthamoeba on PCR analysis using 3 sets of primers. In 22 cases, the sequence obtained closely matched Acanthamoeba castellanii. CONCLUSIONS: This study demonstrates that PCR analysis of epithelial biopsy specimens can provide definitive verification of the confocal microscopic and histologic identification of Acanthamoeba organisms associated with keratitis. Acanthamoeba keratitis is probably quite common, especially in contact lens wearers, although more than half of the patients in this study did not wear contact lenses.

Acanthamoeba↗
PubMed2000

Vasculogenic mimicry and tumor angiogenesis.

Tumors require a blood supply for growth and hematogenous dissemination. Much attention has been focused on the role of angiogenesis-the recruitment of new vessels into a tumor from pre-existing vessels. However, angiogenesis may not be the only mechanism by which tumors acquire a microcirculation. Highly aggressive and metastatic melanoma cells are capable of forming highly patterned vascular channels in vitro that are composed of a basement membrane that stains positive with the periodic acid-Schiff (PAS) reagent in the absence of endothelial cells and fibroblasts. These channels formed in vitro are identical morphologically to PAS-positive channels in histological preparations from highly aggressive primary uveal melanomas, in the vertical growth phase of cutaneous melanomas, and in metastatic uveal and cutaneous melanoma. The generation of microvascular channels by genetically deregulated, aggressive tumor cells was termed "vasculogenic mimicry" to emphasize their de novo generation without participation by endothelial cells and independent of angiogenesis. Techniques designed to identify the tumor microcirculation by the staining of endothelial cells may not be applicable to tumors that express vasculogenic mimicry. Although it is not known if therapeutic strategies targeting endothelial cells will be effective in tumors whose blood supply is formed by tumor cells in the absence of angiogenesis, the biomechanical and molecular events that regulate vasculogenic mimicry provide opportunities for the development of novel forms of tumor-targeted treatments. The unique patterning characteristic of vasculogenic mimicry provides an opportunity to design noninvasive imaging techniques to detect highly aggressive neoplasms and their metastases.

Animals↗
PubMed1999

Evaluation of the human choroidal melanoma rabbit model for studying microcirculation patterns with confocal ICG and histology.

The aim of this study was to develop consistently focal elevated choroidal masses of human choroidal melanoma in immunosuppressed rabbits and to correlate the visualization of prognostically significant microcirculation patterns from confocal indocyanine green angiography with histologic microcirculation patterns. A human choroidal melanoma cell line (OCM1) was implanted in the choroid of 40 rabbit eyes using three different techniques: transscleral choroidal injection of a cell suspension, injection of a cell suspension in a surgically induced cyclodialysis cleft, and implantation of solid tumor fragments in a surgically induced cyclodialysis cleft. The rabbits were immunosuppressed with daily injections of Cyclosporin A to prevent host versus graft reaction. The eyes were studied weekly with indirect ophthalmoscopy and fundus photography to monitor tumor growth and indocyanine green angiography using a confocal scanning laser ophthalmoscope to identify microcirculation patterns in vivo and correlate these findings with the histologic demonstration of tumor microcirculation patterns. A tumor mass was identified by indirect ophthalmoscopy in 16 of the 40 implanted rabbit eyes (40%). Each of these tumors was confirmed histologically to represent a focal elevated choroidal mass. All 16 elevated choroidal masses grow in eyes in which solid tumor fragments were implanted. In total, a melanoma was identified histologically in 28 of the implanted 40 eyes (70%). In addition to the 16 eyes where the melanoma appeared as a focal elevated choroidal mass, 4 eyes contained a focal elevated mass in the sclera and 8 eyes contained a flat choroidal tumor. Histologically, microcirculation patterns were identified only in the 16 eyes with focal elevated choroidal masses. Confocal indocyanine green angiography imaged microcirculation patterns in 13 of these 16 eyes (81%). The surgical implantation of small solid fragments of human choroidal melanoma in immunosuppressed rabbit eyes provides the best method to consistently obtain focal elevated choroidal masses. These focal elevated choroidal masses resemble booth the localization and the growth pattern of choroidal melanomas in humans. In addition, they also contain microcirculation patterns similar to those seen in humans that are detectable with confocal indocyanine green angiography. The use of indocyanine green angiography with this animal model may be especially useful in designing and evaluating anti-microcirculation treatments directed at uveal melanoma.

Angiography↗
PubMed1999

Evaluation of microvascularization pattern visibility in human choroidal melanomas: comparison of confocal fluorescein with indocyanine green angiography.

BACKGROUND: The presence of specific microvascularization patterns (networks, parallel with and without crosslinking, silent) in histological sections of human choroidal melanomas has prognostic significance for survival. We showed previously in selected patients that the identification of these microvascularization patterns is possible in vivo by using confocal scanning laser indocyanine green angiography and that this technique is superior to fluorescein angiography using a conventional acquisition technique with a fundus camera. We now routinely use simultaneous confocal fluorescein/indocyanine green angiography to study microvascularization patterns in choroidal melanomas. The purpose of this study was to compare the visibility of tumor vessels and microvascularization patterns in fluorescein and indocyanine green angiography in simultaneous confocal series taken with the same instrument in a large prospective series of patients. PATIENTS AND METHODS: The simultaneously procured confocal fluorescein and indocyanine green angiograms of 50 patients with untreated choroidal melanomas (maximal apical height according to standardized A-scan between 2 and 8 mm) were studied for the visibility of tumor vessels and microvascularization patterns. At least one simultaneous confocal optical series (32 images in sequential depth order) during the early arterial venous phase was obtained per patient. RESULTS: Confocal forescein angiography disclosed signs of tumor vascularization in 12 (24%) of the 50 patients examined. However, in only 3 patients (6%) could microvascularization patterns be identified using confocal fluorescein angiography, and only in the very early arterial phase, which is often difficult to capture. In contrast, simultaneously obtained confocal indocyanine green angiograms disclosed tumor vessels in 47 (94%) of the examined 50 patients and microvascularization patterns could be identified in all of these cases. In 3 patients (6%) no tumor vessels could be detected within the tumor borders. CONCLUSION: This study demonstrates that confocal indocyanine green angiography images microvascularization patterns in choroidal melanomas better than fluorescein angiography, even when the images are acquired with the same technique. This can be explained with the different absorption, fluorescence and exudation characteristics of these dyes. In vivo imaging of these microvascularization patterns using confocal indocyanine green angiography offers the possibility of assessing the prognosis of choroidal melanomas without the removal of tissue.

Adult↗
PubMed1999

New technique for the cytologic identification of presumed Acanthamoeba from corneal epithelial scrapings.

PURPOSE: To describe a cytologic technique for the rapid identification of presumed Acanthamoeba organisms from corneal epithelial scrapings. METHODS: After administering topical anesthesia, we removed the affected corneal epithelium with a scalpel blade. The tip of the blade, containing the scrapings, was washed off into a cuvette with a solution of an alcohol-based fixative for cytology specimens. The blade was immersed in the cuvette and agitated to ensure that the sample was collected. The specimen was fixed for at least 10 minutes and processed by cytospin centrifugation. RESULT: Seventy-five patient samples have been studied with this technique, with excellent preservation of the organism. CONCLUSIONS: The organism preservation with this technique is superior to that of conventional smears and permits confirmatory organism identification by immunohistochemistry.

Acanthamoeba↗
PubMed1999

Vascular channel formation by human melanoma cells in vivo and in vitro: vasculogenic mimicry.

Tissue sections from aggressive human intraocular (uveal) and metastatic cutaneous melanomas generally lack evidence of significant necrosis and contain patterned networks of interconnected loops of extracellular matrix. The matrix that forms these loops or networks may be solid or hollow. Red blood cells have been detected within the hollow channel components of this patterned matrix histologically, and these vascular channel networks have been detected in human tumors angiographically. Endothelial cells were not identified within these matrix-embedded channels by light microscopy, by transmission electron microscopy, or by using an immunohistochemical panel of endothelial cell markers (Factor VIII-related antigen, Ulex, CD31, CD34, and KDR[Flk-1]). Highly invasive primary and metastatic human melanoma cells formed patterned solid and hollow matrix channels (seen in tissue sections of aggressive primary and metastatic human melanomas) in three-dimensional cultures containing Matrigel or dilute Type I collagen, without endothelial cells or fibroblasts. These tumor cell-generated patterned channels conducted dye, highlighting looping patterns visualized angiographically in human tumors. Neither normal melanocytes nor poorly invasive melanoma cells generated these patterned channels in vitro under identical culture conditions, even after the addition of conditioned medium from metastatic pattern-forming melanoma cells, soluble growth factors, or regimes of hypoxia. Highly invasive and metastatic human melanoma cells, but not poorly invasive melanoma cells, contracted and remodeled floating hydrated gels, providing a biomechanical explanation for the generation of microvessels in vitro. cDNA microarray analysis of highly invasive versus poorly invasive melanoma tumor cells confirmed a genetic reversion to a pluripotent embryonic-like genotype in the highly aggressive melanoma cells. These observations strongly suggest that aggressive melanoma cells may generate vascular channels that facilitate tumor perfusion independent of tumor angiogenesis.

Biomarkers, Tumor↗
PubMed1999

Cytologic changes in the conjunctiva mimicking malignancy after topical mitomycin C chemotherapy.

PURPOSE: To describe the epithelial changes observed in the conjunctiva secondary to the use of topical mitomycin C (MMC) for treatment of primary acquired melanosis with atypia. DESIGN: Retrospective comparative case series. PARTICIPANTS AND CONTROLS: Conjunctival biopsy specimens (18) were taken during the follow-up of ten patients treated with MMC drops (0.02% or 0.04%) during 14 or 21 days for primary acquired melanosis with atypia. An equal number of age- and sex-matched patients with normal conjunctival biopsy findings were included for control. Conjunctival biopsy specimens from patients treated with MMC were compared with the morphologic changes already described in the urothelium following the use of the same chemotherapeutic agent. METHODS: Hematoxylin and eosin-stained biopsy samples were evaluated for recurrent neoplasm and chemotherapeutic effect in the epithelium using the following criteria: nuclear enlargement, nuclear hyperchromasia, smudging of the chromatin, presence of nucleoli, cytoplasmic eosinophilia, and individual cell necrosis. MAIN OUTCOME MEASURES: The presence or absence of morphologic changes in the conjunctival epithelium related to the use of MMC. RESULTS: Morphologic features consistent with chemotherapy effect were seen in the biopsy specimens of nine patients. Nuclear enlargement and chromatin smudging-hyperchromasia localized in the superficial layers of the epithelium were the main features observed (9 patients). Cytoplasmic eosinophilia, single cell necrosis, and occasionally subepithelial chronic inflammation were also seen. CONCLUSIONS: Secondary changes with the topical use of MMC are seen in the conjunctival epithelium and are similar to the changes described in the urothelium. These changes are important to recognize and to differentiate from recurrent neoplasm. The localization of the described features in the superficial layers of the conjunctival epithelium is the key feature in the differential diagnosis.

Administration, Topical↗
PubMed1999

Association between keratin and vimentin expression, malignant phenotype, and survival in postmenopausal breast cancer patients.

Pathology observational reports and experimental data suggest that keratin and vimentin intermediate filament (IF) coexpression in breast cancer confers a more aggressive "interconverted" phenotype, expressing both epithelial and mesenchymal markers. In this study, we extended previous observations by measuring the expression of keratin and vimentin, in relation to other selected biomarkers of disease progression, in postmenopausal women with breast cancer. Using immunohistochemical analysis of 54 archival, formalin-fixed, paraffin-embedded invasive breast cancers from a well-defined cohort, we examined relative IF (keratin and vimentin) expression in a semiquantitative fashion and compared these results with other biological markers and survival. By univariate analysis, we found that vimentin expression was inversely associated with keratin expression alone (P = 0.0089) and directly related to histological grade (P = 0.017), nuclear grade (P = 0.027), Ki67 growth fraction (P = 0.024), and epidermal growth factor receptor immunostaining (P = 0.019). The relative expression of keratin and vimentin in approximately similar amounts characterized tumors with the poorest prognosis, as compared with keratin-high/vimentin-negative or keratin-low/vimentin-positive tumors. These latter two groups demonstrated similar Kaplan-Meier survival curves; the former group (keratin and vimentin in approximately similar amounts) demonstrated a poorer survival, with a hazard ratio of 2.1 (95% confidence interval, 0.5-9.6). These data suggest that relative keratin and vimentin IF expression is more indicative of prognosis and tumor phenotype than either IF marker detected independently.

Aged↗
PubMed1998

Imaging the microvasculature of choroidal melanomas with confocal indocyanine green scanning laser ophthalmoscopy.

OBJECTIVE: To image the microvasculature of choroidal melanoma with a new confocal scanning laser ophthalmoscope. METHODS: Eighteen consecutive patients, each with a unilateral choroidal melanoma, were examined prospectively. Indocyanine green angiography was performed with a new confocal scanning laser ophthalmoscope that enabled serial optical sectioning through the tumor. Two additional patients were studied with indocyanine green angiography and confocal scanning laser ophthalmoscopy just before enucleation for posterior choroidal melanomas. The histologic identification of microvasculature patterns was compared with the angiograms for these patients. RESULTS: In the series of 18 patients, 16 (89%) indocyanine green angiograms with optical sectioning revealed tubular structures within the melanoma that were identified as tumor vessels based on their angiographic appearance. The microvasculature patterns identified by indocyanine green angiography correlated well with the histologic appearance of these microvasculature patterns in both patients for whom histologic verification was available. CONCLUSIONS: This preliminary study suggests that indocyanine green angiography with confocal scanning laser ophthalmoscopy images the microvasculature of choroidal melanomas and may be capable of detecting microvasculature patterns that have been shown to be prognostically significant from histopathological studies.

Adult↗
PubMed1998

An epidemic of presumed Acanthamoeba keratitis that followed regional flooding. Results of a case-control investigation.

OBJECTIVES: To investigate an outbreak of presumed Acanthamoeba keratitis (AK), to identify risk factors associated with its development, and to characterize the changing epidemiology of AK. METHODS: We performed a pairwise-matched case-control study involving 31 patients who were diagnosed as having AK between July 1993 and December 1994. Risk factors were identified using conditional logistic regression analysis. To investigate the impact of regional flooding, we stratified counties within Iowa by whether their water facilities were affected and then calculated population-based estimates of the incidence of AK. RESULTS: During the study, 43 presumed incident cases of AK were diagnosed; 31 were included in the case-control study. Cases were diagnosed based on the clinical presentation of keratitis, positive tandem scanning confocal microscopy examination results, and confirmatory cytopathologic findings. There were no positive culture specimens. On average, cases had symptoms for 8 weeks before diagnosis, most notably photophobia (94%), red eyes (94%), and pain (80%). Contact lens use (odds ratio [OR] = 44.16; P = .02) and fishing (OR = 22.62; P = .04) were independent predictors of the development of AK. The presence of a humidifier in the home (OR = 0.08; P = .03) and having household water that originated from a private well instead of the municipal water supply (OR = 0.12; P = .08) were protective. Twenty-nine of 30 cases resided in counties in which the water supplies were affected by flooding as determined by the Department of Natural Resources, Des Moines, Iowa. The incidence of AK in these counties was more than 10 times higher than that in the unaffected counties (relative risk = 10.83, 95% confidence interval, 1.48-79.49; P < .003). CONCLUSIONS: We describe an epidemic of keratitis that, based on clinicopathologic and epidemiological evidence, is consistent with AK. As in previous outbreaks of culture-proven AK, contact lens use was the major risk factor. Both the results of the case-control study and the population-based incidence estimates suggest that the recent outbreak may be caused, in part, by the effects of regional flooding. However, because the outbreak also coincided with a change in diagnostic techniques, we cannot eliminate recognition bias as the reason for the apparently changing epidemiology.

Acanthamoeba Keratitis↗