Artificial Sight: Basic Research, Biomedical Engineering, and Clinical Advances

Artificial sight is a frontier area of modern ophthalmology combining the multidisciplinary skills of surgical ophthalmology, biomedical engineering, biological physics, and psychophysical testing. Many scientific, engineering, and surgical challenges must be surmounted before widespread practical applications can be realized. The goal of Artificial Sight is to summarize the state-of-the-art research in this exciting area, and to describe some of the current approaches and initiatives that may help patients in a clinical setting. The Editors are active researchers in the fields of artificial sight, biomedical engineering and biological physics. They have received numerous professional awards and recognition for their work. The artificial sight team at the Doheny Eye Institute, led by Dr. Mark Humayun, is a world leader in this area of biomedical engineering and clinical research. Key Features Introduces and assesses the state of the art for a broad audience of biomedical engineers, biophysicists, and clinical researchers Describes advances in microelectronics, microfabrication, surgical implantation, and psychophysical testing of visual prostheses Outlines the promise of artificial sight and the challenges that must be me

Clusterin protein diversity in the primate eye

Purpose: The clusterin gene encodes a multi-functional protein that has been identified in different tissues, including a number of different eye tissues, primarily in the mouse and to a much lesser extent in humans. Clusterin has been implicated in a number of cellular processes such as lipid transport, membrane integrity, apoptosis, and neurodegeneration, all of which could be important to the biology of the eye. In the current communication, we provide data that confirms the expression of clusterin in a number of different human eye tissues and establishes the expression profile of this gene in monkey derived eye tissues. The issue that we sought to examine is whether a broad profile of clusterin expression in the eye is consistent in primates (monkey and human). Methods: The majority of our study was done using monkey eye tissues. Where possible, we have used human tissues in order to confirm published findings. Northern and western analysis was performed using tissues derived from monkey eyes. In situ hybridization and immunochemistry were carried out on human eye sections. Results: Clusterin mRNA is expressed in primate lens, cornea, limbus, sclera, orbital muscle, ciliary body, retina, RPE/choroid, and RPE cells in culture. Western analysis revealed that two major groups of clusterin exist in the eye, a high molecular weight group (\u3e100 kDa) and a second group consisting of at least five clusterin species that are all approximately 80 kDa. Analysis of conditioned media from RPE cells cultured on permeable supports suggests that different forms of clusterin display alternative patterns of secretion. Conclusions: Clusterin is expressed in a broad range of eye tissues in both human and monkey, suggesting that this is a characteristic feature in primates. We demonstrate for the first time that a diverse number of clusterin isoforms were observed in monkey eye tissues by western analysis. Meanwhile, the molecular size of clusterin mRNA detected in the array of tissues are identical in size, suggesting that the nature of the diversity in clusterin forms is due to post-translational modifications. In addition, new insights were made in defining clusterin expression in ciliary body, cornea, and the retinal pigment epithelium

Acute variations in retinal vascular oxygen content in a rabbit model of retinal venous occlusion.

PURPOSE: To study the variation in intravascular oxygen saturation (oximetry) during an acute retinal vein occlusion (RVO) using hyperspectral computed tomographic spectroscopy based oximetry measurements. METHODS: Thirty rabbits were dilated and anesthetized for experiments. Baseline oximetry measurements were made using a custom-made hyperspectral computed tomographic imaging spectrometer coupled to a fundus camera. RVO were induced using argon green laser following an intravenous injection of Rose Bengal. RVO induction was confirmed by fluorescein angiography. Retinal oximetry measurements were repeated in arterial and venous branches one hour after RVO induction and up to 4 weeks afterwards. Comparison of retinal oximetry before and after vein occlusion was made using the Student T-test. RESULTS: One hour after RVO induction, we observed statistically significant reductions in the intravascular oxygen saturation in temporal retinal arteries (85.1 ± 6.1% vs. 80.6 ± 6.6%; p<0.0001) and veins (71.4 ± 5.5% vs. 64.0 ± 4.7%; p<0.0001). This decrease was reversible in animals that spontaneously recannulated the vein occlusion. There were no statistically significant differences in oxygen saturation in the nasal control arteries and veins before and after temporal vein RVO induction. CONCLUSIONS: We demonstrate, for the first time, acute changes in the intravascular oxygen content of retinal vessels 1 hour after RVO. These changes are reversible upon spontaneous recannulation of retinal vessels. This study demonstrates that hyperspectral computer tomographic spectroscopy based oximetry can detect physiological variations in intravascular retinal oxygen saturation. The study also provides the first qualitative and quantitative evidence of the variation in retinal vascular oxygen content directly attributable to an acute retinal vein occlusion