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Biomedical subjects

Minas T Coroneo

Publications and source records attributed to Minas T Coroneo.

At least 37 records · Page 2Linked to original sources
PubMed2004

Crystalline lens capsule staining with trypan blue.

A 1-step method for staining the anterior lens capsule with trypan blue is described. The dye is instilled via a paracentesis port at the start of cataract extraction. As aqueous humor is allowed to exit the anterior chamber (AC), which consequently shallows, the resulting pupil block confines the dye to the AC. An ophthalmic viscosurgical device (OVD) is used to flush dye-stained aqueous from the AC, circumventing the need for AC washout. Although the OVD may be tinged with dye, this does not impede performing capsulorhexis. This method does not add to the surgical time, requires no additional instruments or materials, and is safe.

Capsulorhexis↗
PubMed2004

Surface stimulation of the brain with a prototype array for a visual cortex prosthesis.

We are developing a neural prosthesis to electrically stimulate the visual cortex to restore basic visual perceptions to blind patients. The effects on cortical excitation of different stimulus configurations using a prototype electrode array are presented. Cats underwent a bilateral craniotomy to expose the cortex. An array for brain stimulation was placed on the surface of the right hemisphere. Cortical stimulation was undertaken in a variety of configurations while measuring the evoked responses that propagated through transcallosal pathways, at a homologous region on the contralateral hemisphere. Cortical excitation elicited by stimulation with a particular paradigm could be assessed by measuring the spatial spread and amplitudes of evoked responses in the contralateral hemisphere. Results from this transcallosal model have allowed us to examine the spatial and amplitude effects of cortical stimulation with our prototype electrode array and will aid in developing a neuroprosthesis for blind patients.

Animals↗
PubMed2004

Pathogenesis of pterygia: role of cytokines, growth factors, and matrix metalloproteinases.

Pterygium is a common ocular surface disease apparently only observed in humans. Chronic UV exposure is a widely accepted aetiological factor in the pathogenesis of this disease and this concept is supported by epidemiological data, ray tracing models and histopathological changes that share common features with UV damaged skin. The mechanism(s) of pterygium formation is incompletely understood. Recent data have provided evidence implicating a genetic component, anti-apoptotic mechanisms, cytokines, growth factors, extracellular matrix remodelling (through the actions of matrix metalloproteinases), immunological mechanisms and viral infections in the pathogenesis of this disease. In this review, the current knowledge on pterygium pathogenesis is summarised, highlighting recent developments. In addition, we provide novel data further demonstrating the complexity of this intriguing disease.

Animals↗
PubMed2004

An in-vivo paradigm for the evaluation of stimulating electrodes for use with a visual prosthesis.

BACKGROUND: Electrical stimulation of the visual cortex with surface electrodes is able to elicit basic visual perceptions in blind patients. The development of a visual prosthesis for the blind will require an in-vivo model for the optimization of cortical neurostimulation with multielectrode arrays. METHODS: In anaesthetized cats a bilateral craniotomy was performed and the dura was removed to expose the cerebral cortex. A prototype stimulating electrode array was placed on a gyrus in one hemisphere, and the transcallosal evoked response (TER) to cortical stimulation by this electrode array was recorded at a homologous region in the contralateral hemisphere. RESULTS: The stimulating electrode array elicited TER of short latency (6.9 ms) in the contralateral hemisphere. Bipolar stimulation of adjacent electrodes on the array evoked similar TER regardless of the polarity of stimulation. Electrodes spread apart on the array caused higher amplitude TER than electrodes placed close together. Multielectrode stimulation evoked lower amplitude TER than bipolar stimulation. CONCLUSIONS: This transcallosal model of cortical neurostimulation is a useful method to evaluate electrode arrays and stimulation techniques in the development of a visual prosthesis.

Animals↗
PubMed2004

Peripheral light focusing as a potential mechanism for phakic dysphotopsia and lens phototoxicity.

Our aim was to examine secondary image formation in the anterior segment caused by peripheral light focusing (PLF) in the human cornea, and in particular the crystalline lens. Non-sequential ray-tracing (OptiCAD) was applied to an anatomically based human eye model, which incorporates a gradient index crystalline lens. For analysis of the limbal effect, we varied the incident angle from 100 to 122 degrees, while for the crystalline lens effect, the incident angle was varied from 60 to 90 degrees. The corneal shapes studied included central radii from 7.4 to 8.2 mm with a range of shape factors. In each case, we computed the peak and average intensities, and the area of exposure at the limbus or lens periphery. The computation was repeated with a previous model eye for comparison. For the limbal effect, a peak intensity gain of x22.5 was found at an incident angle of 104 degrees which compares well with previous results. The average intensity gain at this angle was x7.5 over an area of 0.23 mm2. Steeper corneal curvature produced a greater PLF effect. For the crystalline lens effect, maximum UVA (365 nm) intensity gain peaked at x8.6 at 84 degrees with average intensity gain of x2.3. The area of UVA exposure peaked at 4.7 mm2 at 70 degrees. A relatively wide range (30 degrees ) of incident angles produced peak PLF gains of x3 or more in the lens. Significant focusing of light is directed to the nasal limbus, and to a lesser extent to the crystalline lens over a broad range of incident angles. PLF in the nasal cornea is reduced by an order of magnitude when a UV-blocking soft contact lens is used. The concentration levels and intraocular sites of PLF action on UV and visible light suggest a new mechanism of phakic dysphotopsia and lens phototoxicity.

Anterior Chamber↗
PubMed2004

Proliferative effects of heparin-binding epidermal growth factor-like growth factor on pterygium epithelial cells and fibroblasts.

PURPOSE: To investigate the growth promoting and chemotactic effects of heparin binding epidermal growth factor-like growth factor (HB-EGF), recently shown to be upregulated by ultraviolet irradiation in pterygium-derived epithelium cells (PECs) and pterygium fibroblasts (PFs). METHODS: PECs and PFs were incubated with various concentrations of HB-EGF. Cell proliferation was evaluated by measurement of [3H]thymidine incorporation. The potential chemotactic effect of HB-EGF on these two cell lines was assessed with migration assays, using modified Boyden chambers and checkerboard analysis. RESULTS: Incubation of PECs and PFs with HB-EGF resulted in a significant increase in [3H]thymidine incorporation compared with that of control cells. HB-EGF stimulated chemotaxis of both PECs and PFs. Maximum stimulation occurred at 1 ng/mL for PFs and 10 ng/mL for PECs. These effects were abolished by the addition of a neutralizing antibody to HB-EGF. CONCLUSIONS: The findings demonstrate the potential proliferative and chemotactic effects of HB-EGF on both PECs and PFs. This is the first study to illustrate the positive effect of a specific growth or chemotactic factor on the cellular elements of a pterygium.

Cell Division↗
PubMed2004

Matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases in the human lens: implications for cortical cataract formation.

PURPOSE: To characterize the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) in human cortical cataract and to determine whether there is a correlation with the localization of cortical cataract. To evaluate the expression and activity of MMPs and TIMPs after cytokine and UV-B exposure in a human lens epithelial cell line. METHODS: Twenty-eight human donor eyes with cortical cataract and 21 normal human donor eyes were photographed. Thirteen cortical cataract and six normal lenses were immunohistochemically analyzed for MMP-1, -2, -3, and -9 and TIMP-1, -2, and -3. Twelve fresh cortical cataract and 12 normal lenses were divided into quadrants to quantify, by ELISA, the expression of MMP-1, -2, -3, and -9 and TIMP-1. Three fresh cortical cataract and three control lenses were assessed for MMP-1, -2, and -9 activity by SDS-PAGE zymography. Human lens epithelial cells (HLE-SRA-01/04) were exposed to proinflammatory cytokines and UV-B radiation to determine the protein expression profiles of MMP-1, -2, -3, and -9 and TIMP-1 and -2. RESULTS: Immunohistochemical analysis revealed specific localization of MMP-1 within lens epithelium and cortical lens fibers of cortical cataract. Normal lenses had equally low MMP-1, -2, -3, and -9 and TIMP-1, -2, and -3 immunoreactivity, expression, and activity in all lens quadrants. IL-1 and TNF-alpha upregulated the expression of MMP-2, -3, and -9, and UV-B upregulated the expression of MMP-1 in the SRA-01/04 HLE cell line. CONCLUSIONS: This is the first study to localize the expression of MMP-1 in cataracts with clinically observed opacification in vivo and to examine the expression induced by UV-B, in vitro.

Adult↗
PubMed2003

The role of ultraviolet irradiation and heparin-binding epidermal growth factor-like growth factor in the pathogenesis of pterygium.

Ultraviolet (UV) light is one of the major factors implicated in the pathogenesis of pterygium. The mechanism by which UV light induces this disease remains elusive. The aim of this study was to evaluate the effects of UVB irradiation on the expression of growth factors in cultured pterygium epithelial cells and to demonstrate their distribution within pterygium. We cultured pterygial epithelial cells from pterygium explants and these cells were exposed to 20 mJ/cm(2) of UVB. Total RNA was extracted at 0, 6, and 12 hours after irradiation. (32)P-labeled cDNA was synthesized and analyzed using microarray technology to determine the differential expression of 268 growth factor and cytokine related genes. Semiquantitative reverse transcriptase-polymerase chain reaction was used to corroborate this data. Conditioned media derived from cells exposed to UVB irradiation was analyzed for protein expression by enzyme-linked immunosorbent assay. Immunohistochemistry was used to evaluate the distribution of heparin-binding epidermal growth factor-like growth factor (HB-EGF) in pterygium tissue. Analysis of the hybridization signals revealed that the genes encoding HB-EGF, fibroblast growth factor 3, and cytotoxic trail ligand receptor were consistently elevated at 6 and 12 hours after UVB treatment. HB-EGF mRNA was elevated 6.8-fold at 6 hours after irradiation and was augmented in culture supernatants after the same treatment. Furthermore, HB-EGF reactivity was identified in the epithelium and vasculature of pterygium by immunohistochemistry. HB-EGF was present in normal limbal epithelium, although it was not induced in cultured limbal epithelial cells by UV irradiation. HB-EGF is a potent mitogen, localized in pterygium tissue, and significantly induced by UVB in pterygium-derived epithelial cells. We postulate that this growth factor is a major driving force in the development of pterygia and a means by which UV irradiation causes the pathogenesis of pterygium.

Cell Culture Techniques↗
PubMed2003

Off-axis edge glare in pseudophakic dysphotopsia.

PURPOSE: To characterize peripheral light focusing of oblique off-axis light in the edge-glare phenomenon associated with pseudophakic dysphotopsia. SETTING: Department of Ophthalmology, Prince of Wales Hospital, The University of New South Wales, Sydney, Australia. METHODS: Nonsequential optical ray-tracing (OptiCAD) was performed on a model pseudophakic human eye with an intraocular lens (IOL). The acrylic IOL had an anterior radius of 14.23 mm, posterior radius of 25.00 mm, center thickness of 0.72 mm, diameter of 6.00 mm, and refractive index of 1.5597. Peripheral light focusing caused by off-axis light was calculated for light rays incident on the temporal cornea at angles between 0 degrees and 120 degrees to the sagittal plane. RESULTS: Light incident on the temporal cornea at oblique angles was able to strike the nasal portion of the IOL and the nasal retina. The focusing gain was 2.56 times the incident intensity. The critical incidence window at the temporal cornea was between 71 degrees and 89 degrees to the sagittal plane. The light-focusing effect created foci of light in the nasal edge region of the IOL. In the mid range of permissive angles, up to 3 secondary images were formed, some of which may be apparent only under scotopic conditions. CONCLUSION: Off-axis light incident at the temporal cornea formed intense foci in the nasal edge of the IOL. Multiple secondary images can be formed. These spots constitute glare sources and may be of sufficient intensity to disturb vision. These findings indicate that off-axis light may be an important contributor to some disability glare problems and that IOL edge design should be reevaluated to minimize dysphotopsia associated with peripheral focusing effects.

Computer Simulation↗
PubMed2003

Bilateral microsporidial keratoconjunctivitis in an immunocompetent non-contact lens wearer.

PURPOSE: To describe an immunocompetent male with bilateral microsporidial keratoconjunctivitis who responded to treatment with albendazole, propamidine, and fumagillin. METHODS: Corneal and conjunctival epithelial scrapings from a man with bilateral keratoconjunctivitis previously treated with topical corticosteroids were evaluated by Gram stain and by fluorescence microscopy. RESULTS: Gram stain and fluorescence microscopy of corneal epithelial scraping revealed organisms characteristic of microsporidia. Results of human immunodeficiency virus antibody testing were reported as nonreactive. Symptoms of ocular discomfort and clinical signs of keratoconjunctivitis resolved after five weeks of treatment that included systemic albendazole and topical propamidine isethionate 0.1% and fumagillin bicyclohexylammonium salt. A follow-up conjunctival scraping failed to detect any residual organisms 2 weeks after cessation of all treatment. CONCLUSION: Microsporidial ocular infection occurred in an immunocompetent non-contact lens wearer. Microsporidial keratoconjunctivitis should be considered in any individual with atypical multifocal diffuse epithelial keratitis, regardless of immune status or recent history of contact lens wear.

Adult↗
PubMed2003

Prevention of the adverse photic effects of peripheral light-focusing using UV-blocking contact lenses.

PURPOSE: Peripheral light-focusing (PLF) is an occult form of ultraviolet radiation (UVR) hazardous to the human eye. In PLF, obliquely incident light is refracted from the peripheral cornea to concentrated sites inside the anterior segment. In the current study, the directionality of this phenomenon for UVR and whether PLF is established in outdoor settings exposed to sunlight were investigated. The protection provided by a UV-blocking contact lens was also evaluated. METHODS: UVA and UVB sensors were placed on the nasal limbus of an anatomically based model eye. The temporal limbus was exposed to a UV light source placed at various angles behind the frontal plane. PLF was quantified with the sensor output. The ensemble was mounted in the orbit of a mannequin head and exposed to sunlight in three insolation environments within the region of Sydney, Australia. PLF for UVA and UVB was determined with no eyewear or with sunglasses and commercially available soft contact lenses, with and without UV-blocking capability. RESULTS: The intensity of UVA peaked at approximately 120 degrees incidence, the level at which the UVB response was also at its maximum. The intensification of UVA was up to x18.3. The intensity of PLF for UVA and UVB was reduced by an order of magnitude by a UV-blocking contact lens, whereas a clear contact lenses had a much lesser effect. Only the UV-blocking contact lens achieved a significant effect on UVA and UVB irradiance in the urban, beach, and mountain locales (P < 0.056). CONCLUSIONS: The results identify another type of sunlight hazard: the peripheral focusing of obliquely incident light. UVR from albedo (reflected ambient light) is capable of establishing PLF in the anterior segment, but this can be shielded by UV-blocking soft contact lenses. Sunglasses may be unable to shield oblique rays, unless side protection is incorporated. Contact lenses can offer UVR protection against all angles of incidence, including the peak-response angle. They can also protect the eye in settings in which the wearing of sunglasses is not feasible or convenient.

Contact Lenses↗
PubMed2003

UVB-elicited induction of MMP-1 expression in human ocular surface epithelial cells is mediated through the ERK1/2 MAPK-dependent pathway.

PURPOSE: Pterygia are common, frequently recurring ocular surface lesions characterized by tissue remodeling, cellular proliferation, angiogenesis, and inflammation. The increased incidence of pterygia in persons exposed to excessive solar radiation suggests that ultraviolet (UV) light may play a critical role in the pathogenesis of this disease. These investigations were focused on the expression of collagenase-1 (matrix metalloproteinase [MMP]-1) in pterygia and cultured pterygium epithelial cells, to determine whether the expression of this protease could be modified after exposure to UVB. METHODS: Pterygium, conjunctival, and limbal epithelial cells were subcultured and exposed to various amounts of UVB. The conditioned medium and RNA were harvested for analysis by gelatin zymography, Western blot analysis, ELISA, and RT-PCR. Furthermore, whole pterygium specimens were irradiated to determine secreted MMP-1 levels. RESULTS: Immunohistochemical analysis revealed enhanced MMP-1 expression in pterygia that corresponded precisely with p63-positive epithelial cells. In contrast, significantly less MMP-1 reactivity was found in normal conjunctiva, limbus, and cornea. A dose- and time-dependent increase in MMP-1 was observed when pterygium epithelial cells were exposed to UVB with no significant modulation of inhibitor activity. MMP-1 was not affected in irradiated normal conjunctival epithelial cells or in pterygium fibroblasts but was induced in limbal epithelial cells. Although the induction of MMP-1 after UVB was not mediated by an intermediate soluble factor, the extracellular signal-regulated kinase (ERK)1/2 mitogen-activated protein kinase (MAPK) intracellular pathway was involved. CONCLUSIONS: Collectively, these data support the hypothesis of the involvement of UV light and MMPs in the development of pterygia and may assist in devising new therapeutic approaches for the treatment and prevention of pterygia.

Blotting, Western↗
PubMed2003

Retinal detachment in cytomegalovirus retinitis: intravenous versus intravitreal therapy.

PURPOSE: To compare the rate of retinal detachment in a group of patients treated with intravitreal ganciclovir to the rate of retinal detachment in a group of patients treated with systemic ganciclovir. METHODS: A retrospective non-randomized comparative case series was conducted. The participants were 186 consecutive patients with cytomegalovirus (CMV) retinitis treated at two centres over the period from June 1990 to May 1997. Of the 186, 133 patients had systemic therapy of whom 113 had intravenous ganciclovir or foscarnet and 20 had oral ganciclovir, and 53 patients had intravitreal induction and maintenance therapy. The main outcome measure was the rate of retinal detachment, which was calculated using person-months-at-risk denominators. The effect measure used in the main comparative analysis was the hazard ratio obtained from multiple regression using the Cox proportional hazards model. RESULTS: Retinal detachment occurred in three of 53 patients in the intravitreal therapy group, one of 20 patients receiving oral maintenance therapy and 21 of 113 patients receiving intravenous maintenance therapy. The risk of retinal detachment with systemic therapy was 14-fold higher than with intravitreal therapy (P < 0.001)and up to fourfold higher with oral maintenance therapy. CONCLUSIONS: Intravitreal therapy offers a significant advantage over systemic therapy in the treatment of CMV retinitis by substantially reducing the risk of CMV-related retinal detachment.

AIDS-Related Opportunistic Infections↗
PubMed2002

Acute haptic-induced pigmentary glaucoma with an AcrySof intraocular lens.

A 49-year-old man had uneventful endocapsular phacoemulsification with in-the-bag implantation of an AcrySof SA60AT single-piece intraocular lens (IOL) (Alcon) in the right eye. Twenty-seven days postoperatively, he presented with ocular pain, intraocular pressure of 48 mm Hg, 360 degrees of hyperpigmentation of the trabecular meshwork, and iris pigment epithelial atrophy in the region of the upper temporal haptic, which had dislocated into the sulcus. The patient made an excellent recovery following IOL removal and exchange. Scanning electron microscopy of the explanted IOL demonstrated that the haptic had a rough lateral surface and anterolateral edge. We do not think this IOL should be implanted in the sulcus placement of the heptics. In this article, we report the case of a patient with an AcrySof SA60ATIOL (Alcon) who developed acute pigmentary glaucoma when the inferior haptic slipped out of the bag and came into contact with the pigmented iris and ciliary body.

Acrylic Resins↗
PubMed2002

Hypersensitivity reaction to intravitreal clindamycin therapy.

A Caucasian woman presenting with recurrence of intra-ocular toxoplasmosis was given intravitreal clindamycin. She subsequently developed a hypersensitivity reaction in the form of a generalized erythematous rash. To the authors' knowledge, hypersensitivity reactions to an antibiotic given by the intra-vitreal route have not previously been reported.

Anti-Bacterial Agents↗
PubMed2002

Development and surgical implantation of a vision prosthesis model into the ovine eye.

PURPOSE: A surgical technique was designed and tested to enable the implantation of an intraocular electrical retinal stimulator. METHOD: An inoperative perspex and silicone model was constructed to closely resemble the anticipated properties of the proposed visual prosthesis. The animal model chosen for these experiments was the sheep, because the dimensions of its ocular anatomy are approximately 30% larger than the human's, being otherwise grossly similar. The surgical method involved transplanar port-hole lensectomy and vitrectomy, insertion of the model implant through a limbal incision, and fixation of the perspex subunit close to the location of the native crystalline lens, by way of trans-pars plana fixation sutures. Adequate pre-retinal positioning of the implant's silicone extension was obtained by way of its inherent elastic recoil. RESULTS: The procedure was performed without macroscopic evidence of undue surgical trauma. CONCLUSION: Although further long-term experiments are required to fully assess the surgical procedure and biocompatibility of the implant, intraoperative assessment and postmortem computed tomographic imaging of the globe has confirmed the successful intraocular positioning and fixation of the implant.

Animals↗