Document Detail


Phosphenes electrically evoked with DTL electrodes: a study in patients with retinitis pigmentosa, glaucoma, and homonymous visual field loss and normal subjects.
MedLine Citation:
PMID:  17065515     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
PURPOSE: To develop an improved, easy, and safe method for reliably eliciting electrical phosphenes and to compare reported perceptions and values of chronaxie and rheobase in healthy individuals and patients with distinct ophthalmic diseases. METHODS: DTL electrodes were used with a four-alternative, forced-choice method to determine psychophysically the strength-duration curves by using the Weiss model of electrical tissue stimulation in 47 subjects: healthy individuals (n = 17; n = 6 under light- and dark-adapted conditions), patients with open-angle glaucoma (n = 9), retinitis pigmentosa (RP; n = 14), amblyopia (n = 3), or homonymous visual field loss (n = 4). RESULTS: In all subjects, thresholds were safely determined without side effects. Subjects reported a homogenous, central, white, steady phosphene. The rheobase was higher in glaucoma and patients with RP than in healthy subjects (0.1129 +/- 0.0314 and 0.6868 +/- 0.1054 vs. 0.0383 +/- 0.0057 mA; P = 0.05 and <0.00001, respectively), and it increased with age (r = 0.51; P = 0.038). The rheobase was lower in light- than in dark-adapted conditions (difference 0.015 mA; P = 0.016). In patients with RP, no correlation was found between rheobase or chronaxie and retinal thickness (in OCT) or number of years after reading loss, but there was a correlation between rheobase and visual acuity (P = 0.014). In patients with RP or glaucoma, no inhomogeneity of phosphenes was reported, but all patients with homonymous visual field loss reported lateralization of the phosphene into the area of visual loss. CONCLUSIONS: Use of DTL electrodes to elicit electrical phosphenes is safe, fast, and reliable. It bears significant advantages over corneal electrodes and provides a valuable tool to elucidate ophthalmologic disease processes and to screen candidates for retinal prostheses.
Authors:
Florian Gekeler; Andre Messias; Max Ottinger; Karl Ulrich Bartz-Schmidt; Eberhart Zrenner
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Investigative ophthalmology & visual science     Volume:  47     ISSN:  0146-0404     ISO Abbreviation:  Invest. Ophthalmol. Vis. Sci.     Publication Date:  2006 Nov 
Date Detail:
Created Date:  2006-10-26     Completed Date:  2006-12-08     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7703701     Medline TA:  Invest Ophthalmol Vis Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  4966-74     Citation Subset:  IM    
Affiliation:
Centre for Ophthalmology, University of Tübingen, Schleichstrasse 12-16, D-72076 Tübingen, Germany. gekeler@uni-tuebingen.de
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MeSH Terms
Descriptor/Qualifier:
Adult
Aged
Dark Adaptation
Electric Stimulation / methods*
Feasibility Studies
Glaucoma, Open-Angle / physiopathology*
Hemianopsia / physiopathology*
Humans
Microelectrodes*
Middle Aged
Phosphenes / physiology*
Retinitis Pigmentosa / physiopathology*
Visual Perception / physiology*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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