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Useful Vision (useful + vision)
Selected AbstractsRetinoblastoma: Review of 30 years' experience with external beam radiotherapyJOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 3 2003Claire Phillips Summary A review of the experience at the Peter MacCallum Cancer Centre (Peter Mac), Melbourne, Australia in treating retinoblastoma with external beam radiotherapy was conducted. Outcomes of particular interest were tumour control, vision preservation and treatment late effects. The review was restricted to patients that had intact eyes treated at Peter Mac from 1965 until 1997 with at least 2 years of follow up. Histories were reviewed regarding patient and tumour characteristics and treatment details. Thirty-five patients were identified in whom 47 eyes were treated. Of the tumours, 47% were Reese,Ellsworth stage IV or V and the majority of others were at high risk for vision loss because of tumour location. The radiation treatment technique became increasingly sophisticated during the study period. Radiation dose and fraction size have similarly evolved but most patients received 30,50 Gy. Since 1989, a highly accurate contact lens immobilization technique has been used to deliver 40 Gy in 20 fractions. Thirteen eyes required additional local therapy. Of the treated eyes, 34 (72%) remain intact and 74% of these have useful vision. One patient died from retinoblastoma and three from second malignant neoplasms. With modern radiotherapy, late toxicities other than growth arrest and non-progressive cataract did not occur during the study period. Tumour control was high and a very acceptable rate of organ and vision preservation was achieved in a relatively high-risk population. Modern radiotherapy continues to develop in an attempt to improve treatment accuracy and minimize late radiation toxicity. [source] Estimation of Phosphene Spatial Variability for Visual Prosthesis ApplicationsARTIFICIAL ORGANS, Issue 5 2010Iyad Obeid Abstract Visual prostheses are the focus of intensive research efforts to restore some measure of useful vision to blind or near-blind patients. The development of such technology is being guided to an extent by tools that simulate prosthesis behavior for healthy sighted subjects in order to assess system requirements and configurations. These simulators, however, typically assume purely deterministic phosphene properties and thus do not apply any variability to phosphene size, intensity, or location. We address this issue by presenting data on phosphene variability measured in a blind human subject fitted with an optic nerve prosthesis. In order to correct for normal limitations in human-pointing accuracy, the experimental conditions were repeated with sighted subjects. We conclude that identical optic nerve stimulations can result in phosphenes whose perceived locations vary by up to 5° of deviation angle and 10° of position angle. The consistency of phosphenes presented in the peripheral field of view can vary by an additional 3°. [source] Does delayed treatment shorten the life of patients with fatal choroidal melanoma?ACTA OPHTHALMOLOGICA, Issue 2009B DAMATO Purpose Metastatic death from uveal melanoma occurs in about 50% of patients many of whom experience a delay in treatment, either intentionally or accidentally. The aim of this study was to determine whether treatment delay shortens survival in patients with choroidal melanoma whose disease apparently proved fatal. Methods Patients with choroidal melanoma were included in the study if resident in mainland Britain and if deceased. Survival was analysed according to basal tumour diameter by Kaplan-Meier and Log rank analysis. Results A total of 696 patients with choroidal melanoma died. The patients had a median age of 65 years and a median basal tumour diameter of 15.0 mm. The basal tumour diameter was <10mm in 41 patients; 10-11mm in 88; 12-13mm in 108; 14-15mm in 165; 16-17mm in 123; and >17mm in 171 patients. Log-rank analysis showed no correlation between survival and basal tumour diameter in these patients (Log rank analysis, p = 0.5537). There was perhaps a trend towards longer survival in patients with a basal tumour diameter less than 10mm. Conclusion In patients with fatal uveal melanoma, there is no significant correlation between basal tumour diameter and survival time. Delay in treatment does not seem to worsen prognosis for survival significantly, except perhaps in patients with small tumours. This finding adds further support to the concept that the main objective of ocular treatment is to conserve the eye with as much useful vision as possible. Since ocular treatment can itself cause significant visual loss, the benefit of treating asymptomatic uveal melanomas is uncertain. There is scope for randomized, prospective studies of treatment versus non-treatment of patients with asymptomatic choroidal melanoma. [source] Electronic subretinal implants allow blind retinitis pigmentosa patients to read letters and recognize the direction of fine stripe patternsACTA OPHTHALMOLOGICA, Issue 2009E ZRENNER Purpose Restoration of letter reading and stripe pattern recognition in blind RP patients by placing subretinal implants transchoroidally near the macula, consisting of two arrays: 4x4 electrodes controlled retroauricularly via a subdermal line for direct stimulation ("DS array") and a "chip" (3x3x0,1 mm),1500 electrodes. Methods Letters and stripe pattern were presented to 3 patients via the light sensitive chip , by patterns steadily presented at a screen. On the DS array the sensation evoked by each individual pulse consists of whitish round dot, clearly separated from its neighbor. Patterns consisting of such 4 x 4 dots correspond to letters of approximately 5 cm diameter presented at 60 cm distance. Results Pat.1 correctly (20/24) recognized the direction of the letter "U", presented with the opening in four different directions (DS array). Pat.2 correctly (12/12) differentiated letters via DS array (e.g. COIL). With the light sensitive chip, he correctly (22/24) differentiated letters (e.g. LITZ; 8,5 cm high, 1.7 cm line width) steadily presented on a screen at 62 cm distance Pat.3 recognized (15/20 correct, 4AFC) the direction of lines or stripe patterns with the chip, as did Pat.1 (11/14, 2AFC) and Pat.2 (11/12 4AFC) up to 0.35 cycles/deg. Conclusion Active subretinal multielectrode implants with currents close to produce retinotopically correct patterns that allow for the first time recognition of individual letters and stripe patterns up to 0.35 cycles/deg clearly supporting the feasibility of light sensitive subretinal multi-electrode devices for restoration of useful vision. [source] | ||||||||||