Biomedical subjects

Roberto Roizenblatt

Publications and source records attributed to Roberto Roizenblatt.

5 recordsLinked to original sources

PubMed2005

Nanobiolistic delivery of indicators to the living mouse retina.

The development of a technique to load functional indicators into living neurons is an ongoing challenge in retinal neurophysiology. In a number of live-cell preparations, fluorescence-based indicators have been of particular importance for investigating ionic concentrations, protein localization, and other physiological parameters. In the present study, we demonstrate a novel technique that uses a modified gene gun to propel silver nanoparticles coated with indicators into live retinal neurons, and we highlight the advantages of using this technique to deliver these functional indicators.

Animals↗

PubMed2005

Implantation of an inactive epiretinal poly(dimethyl siloxane) electrode array in dogs.

The aim of this study is to investigate the long-term, mechanical biocompatibility of a polymer microtechnology that can be used to position electrodes in close proximity to the retina. Poly(dimethylsiloxane) (PDMS) arrays were manufactured by soft-lithography at Lawrence Livermore National Laboratory. The PDMS implant measured 4 mm x 40 mm x 55-60 microm and included 4-8 electrodes. Micromolded ribs were placed at the perimetry for strength and ease of manipulation. The PDMS arrays were implanted epiretinally in four normal dogs, with a single retinal tack used in each case to hold the device on the retina. The mechanical effects of the implant were followed up after surgical implantation by photography, fluorescein angiography, optical coherence tomography (OCT), and electrophysiologic tests. An intraoperative retinal tear occurred in the first implanted dog, causing retinal detachment and necessitating termination. The remaining dogs experienced no gross complications secondary to the array implantation procedure. During the follow-up period of 2 months in one eye and 6 months in three eyes, OCT demonstrated that the arrays were in close contact with the retina. Fluorescein angiography showed good perfusion of the retina under the array. At the end of 6 months, there was no statistical difference from baseline in mean retinal thickness under the array (P=0.43) or peripapillary retinal nerve fibre layer thickness corresponding to the implanted area (P=0.34). The mean distance between the array and the retinal surface varied from 32 to 68 microm throughout the follow-up. Histopathologic evaluation of the retinal implantation site in eyes followed for 6 months showed a general preservation of the normal, layered retinal structure, except for some localized retinal thinning in two eyes, where the array frame had been in direct retinal contact. The PDMS substrate micro array is a new and promising technology that can be scaled to support a high-density retinal stimulating array. Its implantation and handling is surgically manageable, and it forms a mechanically stable, acceptable interface with the inner retinal surface.

Animals↗

PubMed2005

Long-term stimulation by active epiretinal implants in normal and RCD1 dogs.

An epiretinal prosthesis, consisting of an extraocular microelectronic stimulator and an intraocular electrode array, was implanted in one eye of three blind and three sighted dogs. Three dogs (2 blind, 1 normal) were stimulated for 120 days, and two dogs (both normal) for 60 and 103 days respectively for 8-10 h/day at levels of 0.1 mC cm(-2) and 0.05 mC cm(-2), with each stimulus level presented to half of the array. One blind dog was kept as an inactive implant control. During the study period, electroretinograms (ERG) and fundus photographs were recorded. At the end of the study period, the dogs were sacrificed and histological and morphometric evaluation was made of the retina. No inflammatory reaction, neovascularization or hemorrhage was observed during the follow-up examinations. ERGs were unchanged. Stimulus levels used were of sufficient amplitude to elicit cortical evoked potentials. Histological evaluation showed no inflammatory infiltrates or changes in retina morphometry related to electrical stimulation when compared to the unstimulated control eye. Morphometric analysis revealed no consistent differences relating to electrical stimulation. In summary, chronic electrical stimulation of the dog retina at up to 0.1 mC cm(-2) with an epiretinal prosthesis does not appear to adversely affect the retina.

Animals↗

PubMed2004

Iris recognition as a biometric method after cataract surgery.

BACKGROUND: Biometric methods are security technologies, which use human characteristics for personal identification. Iris recognition systems use iris textures as unique identifiers. This paper presents an analysis of the verification of iris identities after intra-ocular procedures, when individuals were enrolled before the surgery. METHODS: Fifty-five eyes from fifty-five patients had their irises enrolled before a cataract surgery was performed. They had their irises verified three times before and three times after the procedure, and the Hamming (mathematical) distance of each identification trial was determined, in a controlled ideal biometric environment. The mathematical difference between the iris code before and after the surgery was also compared to a subjective evaluation of the iris anatomy alteration by an experienced surgeon. RESULTS: A correlation between visible subjective iris texture alteration and mathematical difference was verified. We found only six cases in which the eye was no more recognizable, but these eyes were later reenrolled. The main anatomical changes that were found in the new impostor eyes are described. CONCLUSIONS: Cataract surgeries change iris textures in such a way that iris recognition systems, which perform mathematical comparisons of textural biometric features, are able to detect these changes and sometimes even discard a pre-enrolled iris considering it an impostor. In our study, re-enrollment proved to be a feasible procedure.

Algorithms↗

PubMed2002

Therapeutic contact lens-related bilateral fungal keratitis.

PURPOSE: To describe a rare case of bilateral Candida keratitis after contact lens use following bilateral penetrating keratoplasty (PK). METHODS: A 40-year-old female with a clinical diagnosis of Sjögren's syndrome was being followed for corneal thinning in both eyes. She suffered a spontaneous bilateral perforation and underwent penetrating keratoplasty. Therapeutic contact lenses were prescribed for both eyes owing to persistent epithelial defects. Two months later, a biomicroscopic examination revealed corneal infiltrates. RESULTS: A corneal tissue sample, saline, and contact lens cultures were all positive for Candida albicans. Topical and systemic antifungal therapy successfully cleared the infection in the right eye; however, the left eye underwent another corneal graft surgery. CONCLUSIONS: Infectious fungal keratitis may be a complication of wearing therapeutic contact lenses after PK, in a patient with Sjögren's syndrome. The pre-existing eye disease is an important associated factor in cases of yeast infection; therefore, adequate care of these patients and careful follow-up after PK are indicated as measures to prevent early infections.

Adult↗