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The Visual Field for Technicians

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Visual Field for Technicians.

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The Visual Field for Technicians

  1. 1. Dwight Thibodeaux, OD THE VISUAL FIELD
  2. 2. VISUAL FIELDS Localized measurement of visual perception using manual or automated methods to determine normal status or to evaluate and track an ocular or neurological disease state.
  3. 3. NORMAL FIELDS • Visual Field - Roughly 140 degrees monocularly and just over 180 degrees binocularly • Field of Gaze – Over 200 deg • Field of View – Over
  4. 4. COMMON METHODS OF FIELDS TESTING • Confrontation –gross target movement - in from periphery • Manual kinetic central fields – Tangent screen, Autoplot • Microperimetry – Amsler Grid, automated units • Manual kinetic widefield perimetry – Goldmann • Automated static perimetry – Computer algorithm, tester independent Humphries HFA and FDT/Matrix Haag-Streit Octopus Oculus and others
  5. 5. HISTORICAL FIELD TESTS
  6. 6. CONFRONTATION FIELD TESTING Technique Targets
  7. 7. GOLDMANN KINETIC FIELD TESTER
  8. 8. GOLDMANN KINETIC PERIMETRY
  9. 9. OCTOPUS AND OCULUS
  10. 10. ZEISS/HUMPHRIES HUMPHRIES FIELD ANALYZER (HFA) FDT and MATRIX
  11. 11. TEST STRATEGIES • Suprathreshold – usually full field - 60 degrees • 24 degree central field 24-2 • 30 degree central 30-2 • 10 degree 10-2
  12. 12. SUPRATHRESHOLD • Targets set at moderate brightness (above threshold) with wide field • Either seen or not seen • Useful for lid/ptosis evaluation • Two field tests, taped and untaped
  13. 13. THRESHOLDING • First stimuli presented in each of the 4 quadrants • Lowered by 3-4 Db until not seen and vise versa • Moves to different area and repeats process • Cloverleaf pattern in poor pt. management and cooperation
  14. 14. SITA / SITA FAST (HFA) Swedish Interactive Thresholding Algorithm SITA 50% faster than standard, but 90% accuracy SITA FAST 70% faster, 80% as accurate
  15. 15. FDT/FDP • Frequency Doubling Technology (Perimetry) • For early detection of glaucoma • Resistant to blur (Rx) and pupil size effects
  16. 16. MATRIX FDT • Hybrid of FDT and SAP • Even more sensitive to early glaucoma defects • Too hypersensitive for neuro field testing and poor for tracking glaucoma progression • Best for glaucoma suspects / pre-perimetric glaucoma
  17. 17. SWAP – SHORT WAVELENGTH AUTO PERIMETRY • Yellow background and large blue stimulus on HFA • Catches early defects in pre-perimetric glaucoma • Very time consuming and sensitive to media opacities • Matrix now more commonly used
  18. 18. 30-2 VS 24-2 • 30-2 = 76 test locations Most accurate, 0.2 sec. stimulus vs. 0.25 sec latency for eye movements • 24-2 = 54 test locations Used for the difficult patient
  19. 19. HFA 10-2 • 10 deg. central field for macular toxicity and end stage glaucoma or RP • Plaquenil – hydroxychloroqui ne • OCT of macula also part of new protocol
  20. 20. MICROPERIMETRY • Amsler Grid • Automated
  21. 21. WHAT FIELD IS INDICATED? • Glaucoma suspect or pre-perimetric pt. • Established glaucoma patient with field loss • Neuro patient • Ptosis patient • High risk meds patient
  22. 22. GLAUCOMA SUSPECT • Minimal or no nerve head cupping – Matrix/FDT • Obvious nerve damage – SITA Standard 30-2 • Difficult patient w/ damage– SITA Fast 24-2
  23. 23. ESTABLISHED GLAUCOMA • SITA Standard 30-2 • Difficult / older patient SITA Fast 24-2
  24. 24. NEURO FIELDS • SITA Fast 30-2 • Used for unexplained vision loss or neuro signs • Matrix oversensitive
  25. 25. PTOSIS OR BLEPHAROCHALASIS • Suprathreshold automated or kinetic fields • Wider field to catch more peripheral defects
  26. 26. HIGH RISK MEDS SITA 10-2 • For subtle central defects from retinal toxicity
  27. 27. INTERPRETATION • Quality measures and errors • Plots • Glaucoma Hemifield Test • Global indices
  28. 28. QUALITY MEASURES • Fixation losses – targets blind spot, need <15%, ? misaligned • False positives – positive response when no target is shown, need < 20% • False negatives – <33% • Gaze tracker - camera notes eye movement
  29. 29. COMMON ARTIFACTS AND ERRORS • Ptosis • Prominent brows • Lens holder positioning—ring scotoma • Patient positioning—high FL, ring scotoma • False positives based on patient expectations of stimulus timing
  30. 30. GREY SCALE PLOT • Quickly identifies overall depressions • Good for patient education • No comparison for age related normals • No adjustment for media opacities • Under represents shallow gen. depression and overemphasizes midperipheral non- significant defects
  31. 31. TOTAL DEVIATION PLOT • Graph and numeric representation • Compared to age-matched normals
  32. 32. PATTERN DEVIATION PLOT • Probably the most important data • Takes total deviation and filters out overall depression (cataracts) • Looks for focal damaged areas pertinent to glaucoma
  33. 33. GLOBAL INDICES • Mean Deviation (MD) • Positive Standard Deviation (PSD) • Glaucoma Hemifield Test (GHT)
  34. 34. GLOBAL INDICES • Single number representations of the visual field • Overall guidelines to help assess the field • Probability values when numbers reach significant levels
  35. 35. MEAN DEVIATION (MD) • Overall level of sensitivity compared to age-matched normals • Not corrected for generalized depression from media opacities • Important for following diffuse loss in glaucoma • MD of -2.00 or worse is suspicious • Mild damage at <-6 • Moderate at -6 to-12 severe >-12
  36. 36. PATTERN STANDARD DEVIATION (PSD) • Sensitive measurement of localized loss • Especially useful in glaucoma evaluation/progression • The higher the number, the greater the loss
  37. 37. GLAUCOMA HEMIFIELD TEST GHT • Compares top and bottom half of field • General reduction in sensitivity • Abnormally high sensitivity • ONL – difference not found in 99% of patients without glaucoma • Borderline – difference not found in 97% of normals
  38. 38. VISUAL FUNCTION INDEX (VFI) AND PROGRESSION ANALYSIS Seen in newer units VFI similar in meaning to MD but easier to conceptualize-- 100% is normal 75-80% is approaching significant loss = -6 or worse on MD
  39. 39. COMMON GLAUCOMA SCOTOMAS • Arcuate • Nasal step • Temporal wedge • Localized paracentral • Generalized depression
  40. 40. ARCUATE OR NERVE FIBER BUNDLE DEFECT
  41. 41. NASAL STEP
  42. 42. LOCALIZED PARACENTRAL SCOTOMAS
  43. 43. SECTOR OR WEDGE DEFECTS
  44. 44. GENERALIZED DEPRESSION
  45. 45. FUNCTIONAL VISION LOSS • Most common in young girls • Emotional trauma • Also called hysterical fields • Spiral and variable in nature • Treat with education of parents and counseling
  46. 46. NEURO FIELDS Unilateral – usually involves the retina or optic nerve Bilateral – involves both nerves or the optic chiasm/tract/brain Homonymous – alike, same side on both eyes Heteronomous – different, opposite sides Congruous – symmetric in both eyes Hemianopia – defect respects vertical midline
  47. 47. MRI CHIASM
  48. 48. HOMONYMOUS • Hemianopsia – homonymous, congruous, points to cerebral cortex lesion such as stroke • Quadranopsia or sectoranopsia– cerebral cortex (congruous) or lateral geniculate nucleus
  49. 49. HETERONOMOUS Hemianopsia- bitemporal, congruous- points to chiasmal lesion such as a pituitary tumor Quadranopsia- very rare, points to different area of chiasm
  50. 50. BINOCULAR FIELDS
  51. 51. ALTITUDINAL • Almost always unilateral • Associated with AION – stroke at the optic disc
  52. 52. CENTRAL SCOTOMA • More commonly unilateral as in: optic neuritis macular degeneration early AION, cerebro-vascular blood loss retinal dystrophy Bilateral – toxic, nutritional, heriditary optic neuropathy and maculopathy
  53. 53. QUESTIONS? DRTHIB@MSN.COM

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