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Visual field testing and interpretation

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Useful for Optometry Students and Optometrist involved in Clinical Practice

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Visual field testing and interpretation

  1. 1. Visual Field Testing and Interpretation Raman P Shah Optometrist B. P. Koirala Lions Center for Ophthalmic Studies
  2. 2. References and recommended readings • Walsh TJ. Visual fields Examination and Interpretation, Ophthalmology monographs, AAO • J Boyd Eskridge. Clinical procedures in Optometry. Mosby • Automated Perimetry; Visual Field Digest: 5th edition • David O. Harrington, Michael V. Drake. The visual fields .7th edition
  3. 3. Presentation layout • Introduction on Visual field • Normal limits of Visual field • Short overview on history of VF • Terminologies related to VF • Visual field testing methods – Kinetic, static • Interpretation of VF reports
  4. 4. Introduction Visual Field • The visual area that is perceived simultaneously by a fixating eye.
  5. 5. Retina Vs Visual Field Optic disc Nasal to the fovea – Seen in temporal VF as a Blind spot
  6. 6. Traquairs field of vision
  7. 7. Hill of Vision
  8. 8. Normal limits of visual field
  9. 9. Short History of Visual Field • In B.C 150, Ptolemy: used some form of perimetric device to measure extend of VF • First clinical investigation of VF defect – Hippocrates in 5th century, hemianopic field defect • Finally in 1604 Kepler explained the principle of sight in term of an inverted retinal image – – an stage for modern investigation of VF
  10. 10. History…. • In 1666, Mariotte discovered physiological blind spot • In 1801, Young stated the normal extend of VF of an eye • Von Graefe mapped out blind spot, central scotomas, construction of isopter. – Introduced VF in clinical medicine for the first time • Until 1869, Foerester invented arc perimeter, till then VF plotted on flat surface Thomas Young Von Graefe
  11. 11. History…… • In 1880, Bjerrum developed Tangent screen • In 1940, Marc Amsler introduced Amsler grid • In 1939 Sloan described static perimetry • In 1945 Goldman Perimeter • In 1960 Tubinger- manual testing of both static and JannikPetersonBjerrum HenningRønne Dr.HansGoldman
  12. 12. Few Terminologies • Threshold: The weakest test stimulus that is just visible in a particular location under the specific testing condition. – Varies across the visual field. • Sensitivity: most subtle characteristics of a stimulus that is visible at a specific point in space. • Fixation: that part of visual field corresponding to fovea centralis.
  13. 13. Terminologies… • Isopter: – Line connecting all points in the visual field with the same threshold ( for a given test spot) – Boundary between area of visibility to the area of non- visibility for a particular stimulus
  14. 14. Terminologies… • Scotoma: Localized defectsdepressions surrounded by normal visual field. – Absolute: defect that persists when the maximum stimulus is used e. g blind spot. – Relative : defect that is present to weaker stimulus but disappears with brighter stimulus.
  15. 15. Location of Visual field defects • Central – 5 degrees or less from the point of fixation • Paracentral – >5 degress – 30 degrees – Ceacal, paraceacal, periceacal – Centrocecal • Peripheral – >30 degrees
  16. 16. Descriptive components of VF defects • Monocular descriptions – Density • Absolute (no visual sensation) or relative (depressed visual sensation) – Area • General or local – Shape • Sectorial (hemianopic) or non-sectorial (regular or irregular) – Extent • Total or Partial – Position • Rt. Or Lt. . Temporal, nasal, superior, inferior
  17. 17. Descriptive components of VF defects •Binocular description • Laterality •Unilateral or bilateral (homonymous/heteronymous) •Equalness •Congruous or incongruous •Additional description •Awareness •Positive (defect perceived) or negative (defect not perceived)
  18. 18. Significance of Visual field testing • Find out the extent of VF • To diagnose and detect diseases as well as extent of damage caused in VF by the disease • To locate possible lesion in neurological disorder • To find out the progression of diseases
  19. 19. Visual field testing methods/tools • Central – Amsler Grid: 200 – Tangent (Bjerrum screen): 300 – Goldmann – Automated (Octopus / Humphery) :300 • Peripheral – Confrontation – Goldmann – Automated 900 programme
  20. 20. Perimetry • Systematic measurement of VF by the use of a perimeter • Modern Perimeter – Consist of a bowl positioned at a fixed distance from the eye, • enable the controlled presentation of stimuli with in the bowl • Enables assessment of the visual function through out the visual field • Detection & quantification of damage to the visual field • Monitoring the change over a time
  21. 21. Perimetry types Kinetic Static • measures extent of visual field by plotting isopters ( locus of retinal points having same sensitivity) •Stimulus moves from non- seeing to seeing area. •Result depends upon the experience of the operator. • e.g, Goldman perimetry, confrontation, Tangent screen, Arc perimetry • measures the sensitivity of each retinal points. •The stimulus is stationary but increases in luminance. • Mostly automatic, very little role of the operator. •e. g, Automated perimetry, Goldman perimetry
  22. 22. Goldman Perimetry • The most widely used instrument for manual perimetry. • Has a calibrated bowl projection instrument – with a background intensity of 31.5 apostilbs (asb), • Test Targets: dots – Varying size and illumination
  23. 23. Perimetry Bowl • Background luminance 31.5 asb Radius of the bowl 30 cm Patient side
  24. 24. Goldmann Targets • The stimuli (Dot) used to plot an isopter denoted by – Roman numeral, a number, and a letter. • Roman Numerals = 0 to V (Size) • Number = 1 to 5 (Luminance) use of Filter • Alphabet = a to e ( ‘’) use of filter V4e , I4e, IV3e
  25. 25. Goldmann Perimetry: Roman numeral • Sizes of Stimuli [0...V scale] • Each size increment equals • a twofold increase in diameter and a fourfold increase in area. Diameter (mm) Area (mm2 ) 0 0.28 1/16 I 0.56 ¼ II 1.13 1 III 2.26 4 IV 4.51 16 V 9.03 64
  26. 26. Target illumination • Luminance settings • Expressed in units called Apostilbs (candela/m2 ) • 2 sets of filters – 5 each – 10 steps • Standard Vs Fine settings • (1...5 and a...e scales) • 1, 2, 3, 4 settings represent 0.5 log unit changes = 5 db • a, b, c, d and e settings represent 0.1 log unit changes = 1db
  27. 27. Target Range in Goldmann • More than 100 combinations of size and intensity of test targets are Possible – but only a few isopter are needed to define the visual field. • Size “0” generally is omitted – because results of the plots are inconsistent. • The fine-intensity filter is usually set to the letter “e” – which eliminates the small-increment light filters. – Test target : Denoted by – Size + (Std. + fine) Luminance • Eg: V4e, I4e, II3e
  28. 28. Some interesting facts • A change of one number of intensity – is roughly equivalent to a change of one Roman numeral of size i.e. III4e = IV3e • Isopter plotted with Targets of equal Sum of – Roman Numerals (size) & Number (Intensity) • are considered equivalent. – For example, • the I4e isopter is roughly equivalent to the II3e isopter. • I + 4 = 5, II + 3 = 5
  29. 29. Standard VF plot of RE
  30. 30. Required Equipment for VF mapping • Goldmann bowl perimeter • Lens holder • Recording paper • Colored markers • Patch for monocular testing
  31. 31. Goldmann Perimeter Pantoscopic handle Horizontal cut Patient Side (Bowl)
  32. 32. Goldmann Perimeter Patient Side (Bowl) Fixation target Chin rest Head rest Len Holder
  33. 33. Guideline to Plot • First demonstrate the procedure to patient – by statically presenting large test General rules for plotting “Isopters” – An isopter is mapped for the particular stimulus size and intensity • move from NON-SEEING TO SEEING while presenting stimulus • move at a rate of 5 degrees per second inside • present kinetically every 15 degrees interval
  34. 34. Guidelines for plotting • Begin in the far periphery and kinetic plot isopter in all meridians –Use a V4e, I-3e , I-2e or target (depending upon age –Plot the Blindspot • only 4 meridians are required( more if irregular or Large) – Use the I-4e for the blind spot • within isopter of I-2e or I-3e
  35. 35. Guidelines • Central static test with I-2e – Explore for any scotomas • Kinetic plot with I-3e stimulus only in suspected defect area • Static test between I-3e and I-2e isopters with the I-3e stimulus (scotoma search)
  36. 36. Guidelines • Special case plots – Glaucoma suspects – Plot more points along the nasal edge of the isopter – Plot approximately • every 3-5 degrees, • 15 degrees above and below the horizontal raphe Repeat for central, intermediate and peripheral plots • Suspected neurological lesions – Plot more points on either side of the vertical meridian – Repeat for central, intermediate and peripheral plots
  37. 37. Recording • All recording should be done on the Goldmann recording paper – Patient name, – Date, – Rx used, – Pupil size, – Eye tested and – Patient cooperation / Fixation – Indicate the target sizes used in the bottom right hand block (color marker)
  38. 38. Color coding of Isopters • I-2e Blue • I-3e Orange • I-4e Red • II-4e Green • III-4e Purple • IV-4e Brown • V-4e Black
  39. 39. Expected findings for normal Isopters • Patients under 50 years of age i. Peripheral I-4e (size=same, brighter luminance) ii. Intermediate I-3e iii. Central I-2e (size=same, dimmer luminance)
  40. 40. Expected findings for normal Isopters • Patients 50 years or older i. Peripheral II-4e (size=larger, brighter luminance) ii. Intermediate I-4e iii. Central I-2e or I-3e (size=smaller, dimmer luminance)
  41. 41. Interpretation • The visual field is considered abnormal if: – the threshold values are significantly brighter (0.5 log units or more) than the expected values AND / OR – Scotomas or depressions are present
  42. 42. Some Visual field defects
  43. 43. Some Visual field defects
  44. 44. Bitemporal hemianopia Right eye Left eye
  45. 45. Automated Perimetry ( Static) • Machine constructed along the basic lines of a Goldman perimeter + sophisticated software programs. • Key reason for increased interest in automated perimetry has been due to the standardization automated perimetry allows.
  46. 46. Automated Perimetry • Visual threshold is measured at a series of fixed points in the visual field. • The brightness of the test spot is varied, but not its location. • Threshold is usually plotted relative to normal fields, to reveal defects
  47. 47. Automated Perimetry
  48. 48. Automated Perimetry • Humphrey: • Octopus:
  49. 49. Threshold determination Frequency of seeing curve
  50. 50. Threshold determination 28dB 24 dB 32 dB 30 dB 29 dB 0 dB brightest stimulus
  51. 51. Threshold determination • Age matched normal data are used to compare patient’s data • Normal range determined by – Sensitivity of each retinal points 10,000 individuals – Upper 95% as normal – Lower 5% as abnormal
  52. 52. Testing strategies • Octopus – Normal – Dynamic – TOP ( Tendency oriented perimetry) • Humphrey – SITA (Swedish Interactive threshold algorithm) – SITA fast – Full threshold
  53. 53. Difference between Octopus and Humphrey (test parameters)
  54. 54. Factors affecting Automated Perimetry • Background luminance • Stimulus size • Fixation control • Refractive errors • Cataracts and other media opacities • Miosis • Facial structure • Fatigue • Experience of a perimeter
  55. 55. Validity of the test • False positive response – > 20% unreliable • False negative – >20% unreliable • Short term fluctuation – 1-3 dB normal fluctuation • Fixation loss – >33% unreliable
  56. 56. Choosing an appropriate program Examination procedure Test program(G1, G2, 32, M2) + Test strategy (Normal, dynamic, top) + Perimetry method( W/W, flicker, B/Y, kinetic)
  57. 57. Programs G1/G2 • Central 30 degree • Glaucoma screening • 59 points • Locations more closely with topography of retina (in areas of concern of glaucoma) • 2.8 deg spacing
  58. 58. Programs 32 ( general examination)= 30-2 in Humphrey • introduced with early automated perimetry • 76 test locations • Wide spacing (6 degrees) ( not appropriate for glaucoma)
  59. 59. Programs Macula program(M2) • Central and paracentral visual defects in neurological and macular problems • Central 10 deg • 56 test locations • spacing 2 degrees • 0.7deg spacing in the macula
  60. 60. Programs LVC (central low vision) • To test how much sensitivity is remained in the central foveal area. • 77 locations • 30 degrees • End stage glaucoma
  61. 61. Strategies • Normal strategy – Standard – 4-2-1 bracketing procedure – 10-15 min – Early and shallow defects – Younger patients ( good condition in answering the question till the end of a long program)
  62. 62. Strategies • Dynamic strategy – One threshold crossing – Small steps in regions with Normal sensitivity and large towards depressed field – Test duration reduced by two – Especially when focal defects are expected
  63. 63. Strategies • TOP ( tendency oriented perimetry) – Light sensitivity of the retinal is interrelated rather than having an individual value – 2 minutes – For patients with depressed fields, for children, elderly ones who are not capable of finishing a longer examination
  64. 64. Interpretation of results
  65. 65. Different zones
  66. 66. Greyscale
  67. 67. Value table
  68. 68. Comparison /corrected comparison(Total and pattern deviation)
  69. 69. Probability plots
  70. 70. Cumulative defect curve
  71. 71. Glaucoma Hemifield test • 5 sectors in the upper field are compared to five mirror images in the lower • If value in two sectors differ to an extent that found in – <0.5% of the normal population ( highly sensitive) – <1% of normal population (outside normal limit) – <3% of the normal population (Boderline) – <5% of the normal population ( can be a normal plot)
  72. 72. Global indices Octopus • Mean sensitivity (MS) • Mean deviation (MD) (– 2dB to +2dB) • Loss variance (LV) (0- 6dB) • CLV(0-4dB) • SF (1.5dB- 2.5dB) • RF < 15% Humphrey • GHT • Mean deviation • PSD • CPSD • SF
  73. 73. Octopus criteria for visual field defect§
  74. 74. HFA criteria for VF loss • Pattern deviation plot
  75. 75. Recent advances in automated perimetry • Goldman kinetic module • High-pass resolution perimetry - Uses thin rings instead of spots • Short wavelength sensitive perimetry - Blue on Yellow for S cones • Flicker Perimetry - Flickering targets instead of static flashes • Aulhorn's Snow field campimetry - Uses TV “snow” and pointing • Motion perimetry - Detect moving targets instead of flashed ones • Rarebit perimetry- uses very small, bright spots • Pupil Perimetry - measures pupil responses instead of subject reports • Multifocal VEP - measures cortical evoked potentials instead of subject reports
  76. 76. Summary • Principle of kinetic and automated perimetry • Appropriate selection of visual field testing for a particular patient • Accurate interpretation of VF reports

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