1 / 53

Clinical electrophysiology:

Clinical electrophysiology:. Plugging into the visual system. Marlee M. Spafford, OD, MSc, PhD, FAAO. COPE Personal Disclosure. For this lecture, I have: developed the course material independently developed the course material without commercial interests

saeran
Download Presentation

Clinical electrophysiology:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Clinical electrophysiology: Plugging into the visual system Marlee M. Spafford, OD, MSc, PhD, FAAO

  2. COPE Personal Disclosure For this lecture, I have: • developed the course material independently • developed the course material without commercial interests • no personal conflicts of interest • no financial relationship with a commercial interest

  3. Basic Electrodiagnostic Equipment • Specialized computer hardware & software • >$100,000 Cn Pattern stimulator Ganzfeld (flash stimuli) http://www.diagnosysllc.com/home/

  4. Visual Electrodiagnostic Tests • Electroretinogram (ERG) • Electro-oculogram (EOG) • Visually Evoked Potential (VEP)

  5. Electroretinogram (ERG) • Reflects global changes in retinal electrical potential in response to flash or pattern stimuli http://webvision.med.utah.edu/ClinicalERG.html

  6. Electro-oculogram (EOG) • Records the ocular standing electrical potential • Dark-adapted with light-adapted • Reflects gross outer retina/RPE function + - http://webvision.med.utah.edu/ClinicalERG.html http://brainconnection.positscience.com/med/medart/l/eye-xsection-side.gif

  7. Visually Evoked Potential (VEP) • Assess macular-cortical pathway’s gross integrity Record http://www.metrovision.fr http://www.aph.org/cvi/brain.html

  8. Patient #1: 6-yr-old male • VEP referral (family OD): • Reduced VA, not corrected by spectacles: meridional amblyopia? • OD: -1.00/-3.00 x 170 6/12 • OS: -2.00/-3.50 x 180 6/15 • Interview: • Ocular Hx: • 1st Rx@ 4 yrs • Nyctalopia: “always trips in the dark” • Health Hx: • Unremarkable • Birth Hx: • Polydactyl (surgery @ 1 yr) • Negative family hx of eye disease • 1 step-brother (“normal” vision) • No parental consanguinity http://www.medes-salud.com.ar/causas.htm

  9. Nyctalopia • Causes: • Retinitis pigmentosa (RP) • Choroideremia • Congenital stationary night blindness (CSNB) • Pan-retinal laser surgery • Vitamin A deficiency • Non-retinal • Night myopia • Optical defects (e.g., cataract) • Problem Specific Testing: • DFE • Visual fields • Automated > 30o; Goldmann • ERG (full field ERG) • Colour Vision • adults; B-Y & R-G defects

  10. DFE http://www.scielo.br.proxy.lib.uwaterloo.ca/scielo.php?script=sci_arttext&pid=S0004-27492009000500019&lng=en&nrm=iso&tlng=en

  11. Bardet-Biedl Syndrome Cardinal Features (4 of 6) • Retinal dystrophy (RP) • Polydactyly • Obesity • Cognitive impairment • Hypogonadism • Nephropathy • AR inheritance • 1/179 carry gene • Progressive vision loss • Nyctalopia • Constricted Fields • Acuity loss • Optometrist duties: • Low vision care • Referral for genetic work-up • Referral to nephrologist

  12. Retinal-based Function Tests • ERG • Full-field ERG: fERG (typical referral) • Pattern ERG: pERG • Multi-focal ERG: mfERG • EOG

  13. Full-field ERGs • Assess the gross integrity of the outer 2/3rds of the neural retina • Good test for: • widespread retinal diseases • vision loss that changes with lighting conditions fERG http://webvision.med.utah.edu/ClinicalERG.html

  14. fERGs • Standardized fERG protocol exists: • ISCEV standard: 2008 (International Society for Clinical Electrophysiology of Vision) • Dark adapt (>20 min): scotopic ERGs (rod-isolated & rod-cone mixed) • Light adapt (>3 min): photopic ERGs (cone-isolated) http://webvision.med.utah.edu/ClinicalERG.html

  15. Measuring fERGs • a-wave: Amplitude & implicit time • b-wave: Amplitude & implicit time http://webvision.med.utah.edu/ClinicalERG.html

  16. fERG Components • a-wave:Photoreceptors • b-wave:Müllers & On-Bipolars • Oscillatory potentials (OPs):Amacrines http://webvision.med.utah.edu/ClinicalERG.html

  17. ISCEV Recording Electrodes • Gold Standard • Contact lens electrode (e.g., Burian-Allen Speculum Contact Lens Electrode) • Bipolar electrode design • CL: active • Speculum: reference http://fn.bmjjournals.com/content/82/3/F233.abstract

  18. ISCEV Recording Electrodes • Other ISCEV Electrodes • DTL Fiber • Gold foil • HK loop http://www.nature.com/eye/journal/v21/n6/fig_tab/6702309f2.html http://www.diagnosysllc.com/products/product5.php

  19. DTL Fiber Electrode Insertion

  20. Ganzfeld View

  21. Chin Rest Prep

  22. ERG Recording

  23. ERG Recording

  24. Simulated fERG Normative Database(Amplitude [µV]: 20-39 yrs) S P Supernormal = > 100th percentile WNL = ≥ 5th percentile Diminished = < 5th percentile

  25. Diagnostic Uses of fERG • Inherited retinal disorders • RPE photoreceptor disease, photoreceptor disease, chorioretinal dystrophies, vitreoretinal dystrophies • Retinal ischemic disease • diabetic retinopathy, central retinal vein occlusion, carotid artery stenosis, sickle cell retinopathy • Pre-surgical evaluation • obstructed retina due to cataract, hemorrhage or penetrating injury • Retinal toxicity • hydroxychloroquine • Unexplained vision loss

  26. fERG: RPE-Photoreceptor Disease rod maximal flicker cone http://webvision.med.utah.edu/ClinicalERG.html

  27. fERG: Photoreceptor Disease rod maximal flicker cone http://webvision.med.utah.edu/ClinicalERG.html

  28. fERG: Photoreceptor Disease rod maximal flicker cone http://webvision.med.utah.edu/ClinicalERG.html

  29. pERG(seldom done) • Reflects central retinal response (incl. ganglion cell) • Macular disease • Toxic/nutritional disease • Unexplained central vision loss • 2012 ISCEV standard http://www.diagnosysllc.com/home/ http://www.iscev.org/standards/perg.html

  30. mfERG • 2011 ISCEV standard • Topographical measure of outer 2/3rds of retina • ~60-100 small retinal areas • Local ERGs are mathematical extractions of the signal • Dilated pupils; fiber electrode www.Cephalon.dk http://webvision.med.utah.edu/ClinicalERG.html

  31. Diagnostic Uses of mfERG • Macular disease • e.g., Stargardt Disease, ARMD • Unexplained central vision loss

  32. mfERG ARMD mfERG Normal mfERG

  33. Electro-oculogram (EOG) • Seldom done • 2010 ISCEV standard • Reflects global outer retina/RPE function • Clinical diagnostic use: • Bestvitelliform macular dystrophy (rare, AD inheritance) EOG http://img.medscape.com/pi/emed/ckb/ophthalmology/1189694-1227128-71.jpg

  34. EOG • Eyes have a ‘standing potential’ • Cornea positive; RPE negative • Derived from RPE; changes with retinal illumination • Potential decreases in dark; increases in light • Test involves: • Making lateral saccades through a dark & light phases + - http://www.iscev.org/standards/pdfs/eog-standard-2006.pdf http://brainconnection.positscience.com/med/medart/l/eye-xsection-side.gif

  35. EOG Arden Ratio • Light peak (LP)/dark trough (DT) • >2.0: normal • 1.5 to 2.0: borderline • <1.5: abnormal http://www.iscev.org/standards/pdfs/eog-standard-2006.pdf

  36. Patient #2: 9-yr-old male • VEP referral (family OD): • Fine, mostly pendular, horizontal nystagmus, photodysphoria & reduced VA: albinism? • OD: +3.00/-1.00 x 150 6/24 • OS: +2.50/-0.50 x 020 6/21 • Interview: • Ocular Hx: • Congenital nystagmus • Health Hx: • Unremarkable • Negative family hx of eye disease/low vision • No parental consanguinity http://www.kilgorevision.com/stories.htm

  37. Ocular Albinism (OA) Main Features • Sl. lighter hair & skin complexion (not necessary) • Nystagmus(most horizontal & pendular) • Iris tranillumination • Macular hypoplasia • Fundushypopigmentation • Visual pathway decussation abnormality • X-linked recessive (GPR143 mutation at Xp22.3-22.2) • Evidence of carrier status • iris illumination • ‘mud-spattered’ fundus • hypopigmented skin macules • Optometrist duties: • Strabismus Dx/Mx • Low vision care • Referral for genetic work-up

  38. Albinism: Problem Specific Testing • Ocular Motility • Iris tranillumination • DFE • VEP • OCT (nystagmus preclude?) http://journals1.scholarsportal.info/tmp/1186526813808035824.pdf

  39. Visually Evoked Potential (VEP) • Assess macular-cortical pathway’s gross integrity Record http://www.metrovision.fr NOTE: VEP = VER = VECP (latter 2: older terms) http://www.aph.org/cvi/brain.html

  40. Visually Evoked Potentials (VEPs) • Types of clinical-based VEPs • Pattern: pVEP • 2009 ISCEV standard • Full-field: fVEP • 2009 ISCEV standard • One example of research-based VEPs • Sweep: sVEP • No ISCEV standard yet

  41. VEP Stimuli pVEP fVEP NOTE: pVEPscan be reversing checkerboards or gratings http://www.metrovision.fr http://webvision.med.utah.edu/ClinicalERG.html

  42. ISCEV Recording Electrodes • Scalp silver-silver chloride or gold disc surface electrodes • ISCEV standard: • 1 active (3 better) plus 1 reference electrode www.lkc.com

  43. VEP Electrode Placement • International 10-20 system for electrode placement ISCEV Ref ISCEV Active z http://www.brainmaster.com

  44. VEP Electrode Placement • Multi-channel placement • Pre-chiasmal: Better • Post-chiasmal: Required OZ http://www.opt.indiana.edu http://www.brainmaster.com

  45. Measuring pVEPs P100: • Cortical response (Amplitude in μv) to checkerboard reversal (IT: Implicit time ~100ms) Transient VEP (<4Hz) Amp IT http://www.iscev.org/standards/pdfs/vep-standard-2004.pdf

  46. Simulated pVEP Normative Database(Implicit Time [ms]: 20-39 yrs) WNL = ≤ 5th percentile Delayed = > 5th percentile

  47. Measuring fVEPs P2: • Cortical response to 1 Hz flash stimulus (amplitude in μv; IT: Implicit time ~100ms) • fVEP useful when pVEP fails Amp IT http://www.iscev.org/standards/pdfs/vep-standard-2004.pdf

  48. Diagnostic Uses of pVEP • Optic nerve disease • Optic neuritis (recovery more than dx); compressive optic neuropathy; Leber’s hereditary optic neuropathy (LHON) • Post-chiasmal disease (with multiple-channels) • Demylinating disease; ocular albinism • Amblyopia • Psychogenic vision loss • Unexplained vision loss

  49. Optic Neuritis http://opt.pacificu.edu/test/index.html

  50. Visual Pathway Asymmetry Albinism ~55% decussate ~80% decussate ++ ++ ++ + ++ +++ http://www.nature.com/eye/journal/v21/n10/images/6702839f3.jpg

More Related