Visual Field Examination

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Visual Field Examination

  1. 1. VISUAL FIELD EXAMINATION AND INTERPRETATION OF AUTOMATED PERIMETRY IN GLAUCOMA DR PAAVAN KALRA DEPARTMENT OF OPHTHALMOLOGY S P MEDICAL COLLEGE BIKANER
  2. 2. VISUAL FIELD • That part of environment wherein a steadily fixating eye can detect visual stimulus. • BASIS - presence of Photoreceptors and corresponding visual pathways upto the periphery of retina away from point of fixation i e fovea. • IMPORTANCE – Reflects topographic sensitivity of various foci on retina and corresponding visual apparatus. Resolution – Acuity differential light sensitivity and contrast colour flicker motion
  3. 3. PHYSIOLOGICAL BASIS
  4. 4. VISUAL ACUITY
  5. 5. DIFFERENTIAL LIGHT SENSITIVITY Basis of most modern visual field examination methods TRAQUAIR – “HILL OF VISION IN THE SEA OF DARKNESS”
  6. 6. FACTORS Apparent size of spot – real size -- distance from eye Duration of stimulus Background illumination Stimulus intensity Contrast Colour Patient factors Light / dark adaptation Vision Refractive status Education , attentiveness, cooperation
  7. 7. Stereoscopic field
  8. 8. PHYSIOLOGICAL BLIND SPOT Corresponding to optic nerve head 15 deg temporal to point of fixation Span – 5 deg horizontal -- 7 deg vertical Two thirds below the horizontal meridian
  9. 9. COLOUR FIELD • Point at which passing from periphery to centre, the colour first becomes evident • Peripheral to the limit, the object is perceptible but appears grey • First red and green are used followed by blue and yellow • Extent of field for objects of same size and intensity white > yellow > blue > red > green
  10. 10. VISUAL FIELD DEFECTS
  11. 11. • SCOTOMA : focal region of abnormally decreased sensitivity surrounded by an area of normal sensitivity ABSOLUTE RELATIVE POSITIVE NEGATIVE • DEPRESSION : is an area of reduced sensitivity without a surrounding area of normal sensitivity appears as denting of isopters
  12. 12. • Generalized depression (both peripheral and central contraction) e g cataract • Peripheral Contraction – retinitis pigmentosa • Temporal contraction - age
  13. 13. • Hemifield defect : B/L - Hemianopias homonymous heteronymous • Altitudinal defect
  14. 14. • Central scotoma • Pericentral • Centrocaecal scotoma • Arcuate scotomas Seidel scotoma paracentral scotoma Bjerrum scotoma • Nasal step • Ring – double arcuate • Split fixation • Barring of blind spot
  15. 15. EXAMINATION METHODOLOGY
  16. 16. KINETIC • Test object of particular size and intensity is passed from non seeing area to seeing area along a particular meridian at the rate of 3 – 5 deg per sec • Repeated every 15 – 30 deg • To find points in the visual field of equal sensitivities – ISOPTER (Groenouw) marking • Intensity and size of stimulus is varied to mark various isopters • Thus 2 D Contour map of the hill of vision is made • Extent of scotomas and blind spot marked from inside out
  17. 17. STATIC • The location, size and duration of stimulus is kept constant and the luminance is gradually increased until seen • Actual estimation of sensitivity ( THRESHOLD ) of each point is made out • SUPRA THRESHOLD stimulus used for screening ------------------------------------------------------------------------------- IMPORTANT : one eye is tested at a time, other is occluded fixation of the patient has to be steady and is monitored throughout the test ---------------------------------------------------------------------------------
  18. 18. CLINICAL METHODS GROSS DEFECTS
  19. 19. PROJECTION OF LIGHT In patients with very poor vision –> HM + to PL + e g dense cataracts -dark room, other eye occluded -patients are constantly instructed to look straight to avoid tendency to deviate eye towards light source -light shown onto 4 quadrants from 30-50 cm and switched on and off -Patient tells about the direction of light source Accurate in all quad Inaccurate in some quad Inaccurate in all quad
  20. 20. HAND IDENTIFICATION Other eye is occluded Patient fixates on the nose of examiner Examiner keeps both hands on either side of eye 50 cm away One hand absent or indistinct – hemianopic defect Either palms or fingers of both hands missing / faint – altitudinal defect
  21. 21. FINGER COUNTING Varying no of fingers are held in each quadrant, 1 m and 45 deg from fixation If unable to count, fingers are brought closer to fixation, until patient sees (kinetic)
  22. 22. RED DESATURATION Can be confirmed kinetically Patient has to indicate when color appears to change Can also be used to compare the two eyes in case of optic neuropathy
  23. 23. CONFRONTATION (kinetic) Patient‟s and examiner at same level Compares the visual field of eye of patient with opposite eye of the examiner in a plane perpendicular to line of gaze Red pin is particularly useful for neurological cases GROSS PERIMETRY (kinetic) Follows facial contour
  24. 24. AMSLER GRID For Central 10 deg ( static ) Other eye occluded Near correction given Chart at held 28-30 cm – each small square subtends angle of 1 deg Patient fixates at central dot – tells whether all corners are seen simultaneously and about lines- parallel, distorted, missing Can be used for mapping blind spot – patient fixates at edge of grid
  25. 25. EQUIPMENTS
  26. 26. PERIMETRY Examination and quantification of visual field by using stimulus of various sizes, intensities and colours
  27. 27. ARC PERIMETERS eg LISTER‟s PERIMETER • Only kinetic • Peripheral charting
  28. 28. BJERRUM’s SCREEN ( CAMPIMETRY) • Patient sits at 1 or 2 m from flat screen • Kinetic and static • For central 30 deg only • Done under subdued lighting
  29. 29. GOLDMANN’s PERIMETER • Bowl type • Standardization • Both kinetic and static • Peripheral as well as central
  30. 30. AUTOMATED PERIMETRY standard automated perimetry HUMPHREY FIELD ANALYZER OCTOPUS • STATIC perimetry • Measurement of threshold values • STATPAC (HFA)- Comparison to normative data • Inbuilt program for analysis – diagnosis and progression
  31. 31. ADVANTAGES • Removal of examiner variability • More sensitive to subtle field defects • Reproducibility • Retests abnormal points automatically • Gives reliability parameters like fixation monitoring – HEIJL KRAKAU method Gaze tracking False positive False negative
  32. 32. SHORT COMINGS • EXPENSIVE • Learning curves • Difficult to follow by older debilitated patients especially neurological problems • Not infallible – only 1 % of field is actually examined • Diagnosis and management decisions based on correlation with other clinical findings A well performed tangent screen examination is better than poorly carried out automated perimetry In neurological patients, clinical methods may be the only possible assessment techniques
  33. 33. • WHITE ON WHITE • BACKGROUND ILLUMINATION - 31.5 asb • STIMULUS SIZE – GOLDMANN - III • DURATION OF SPOT EXPOSURE 0.2s
  34. 34. PROGRAMS / PATTERNS 30-2 – gold standard 24-2 10-2 MACULAR Nasal step program – additional 12 locations upto 50 deg nasal peripheral 60 and 60-4 prog Estermann test – for binocular 120 deg field
  35. 35. MACULA PROGRAM :16 locations within the central 5° with 2° spacing. Each location is tested three times
  36. 36. STRATEGIES SUPRATHRESHOLD – screening Fixed suprathreshold contour suprathreshold 3 zone suprathreshold
  37. 37. FULL THRESHOLD BRACKETING STRATEGY( staircase) – GOLD STANDARD FASTPAC Estimation of SHORT TERM FLUCTATIONS at 10 prefixed points
  38. 38. SWEDISH INTERACTIVE TESTING ALGORITHM (SITA) SITA STANDARD ( Bracketing strategy based) SITA FAST ( FASTPAC based) Analyzes patients response and responds accordingly Decreases overall no of stimuli presented, hence test duration Paces the test according to patients speed Doesn‟t estimate Short term Fluctuations
  39. 39. • Selection of adequate test • Proper environment • Comfortable sitting position • Adequate size of pupil >3mm • Adequate Near correction • Proper explanation – running of demonstration • Reassurance – not all points will be seen - test can be paused by keeping the response button pressed
  40. 40. Patient data • Name, DOB, eye • Vision, refraction, • Pupil diameter Test data • Date and time • Program and strategy • Background illumination • Test size, color, duration, i nterval ZONE 1 : REPRODUCIBILITY
  41. 41. ZONE 2 : RELIABILITY • Fixation monitor • Fixation target – central, small diamond, large diamond, bottom LED • Test duration • Reliability indices Fixation losses ( Heijl Krakau) <20 % Gaze tracking False positives < 33% (trigger happy) False negatives < 33 % Foveal threshold
  42. 42. ZONE 3 : GREY SCALE • Based on actual threshold values at each location • General identification • Patient information
  43. 43. ZONE 4 :TOTAL DEVIATION PLOT • Numerical plot – indicates by how much decibels is each point depressed compared to mean value in normal population of similar age • Probability plot- grey scale indicates the probability of occurrence of the deviation in normal population Generalized depression due to media opacities, refractive error, miosis may hamper appearance of a pattern
  44. 44. ZONE 5 : PATTERN DEVIATION PLOT • Numerical - calculated by adjustment for generalized depression or elevation of visual field • Thus brings out pattern • Probability plot • Significance - ANDERSON‟S CRITERIA
  45. 45. ZONE 6 : GLOBAL INDICES single numbers to denote whole field • MEAN DEVIATION : average loss of sensitivity from normal age matched population along with probability calculated from total deviation plot • PATTERN STANDARD DEVIATION : range over which change of sensitivity at all the points has occurred, along with probability compensates for effect of generalized depression or elevation of field on mean deviation value local defects affect PSD > MD • SHORT TERM FLUCTUATIONS • CORRECTED PATTERN STANDARD DEVIATION
  46. 46. ZONE 7 : GLAUCOMA HEMIFIELD TEST • PLAIN ENGLISH LANGUAGE MESSAGE • Comparison of 5 clusters of points in superior hemifield with mirror images in inferior hemifield
  47. 47. OUTSIDE NORMAL LIMITS all cluster pairs differ @ p < 1% OR 1 cluster pair differs @ p < 0.5% BORDERLINE hemifields differ @ p < 3% GENERAL REDUCTION OF SENSITIVITY overall field depressed @ p < 0.5% ABNORMAL HIGH SENSITIVITY overall field elevated( best 15 % points) @ p < 0.5 % WITHIN NORMAL LIMITS
  48. 48. ANDERSON and PATELLA CRITERIA • 3 or more congrous „non edge points‟ in typical arcuate area on 30-2 program depressed @ p< 5 % with at least one point @ p<1 % •PSD / CPSD @ p< 5% •GHT – outside normal limits  Must be demonstrated on 2 field tests
  49. 49. CLINICAL CORRELATION : MUST DISC and NERVE FIBRE LAYER
  50. 50. OVERVIEW
  51. 51. CHANGE ANALYSIS
  52. 52. GLAUCOMA PROGRESSION ANALYSIS
  53. 53. ARTEFACTS • OBSTRUCTION RIM ARTEFACTS PTOSIS MEDIA OPACITIES ANGIOSCOTOMA • MIOSIS • REFRACTION ARTEFACTS • High power plus and minus lenses
  54. 54. NEWER METHODS
  55. 55. SHORT WAVELENGTH AUTOMATED PERIMETERY “BLUE ON YELLOW” detects glaucomatous defects 3-5 years earlier than SAP high fluctuation rates
  56. 56. FREQUENCY DOUBLING PERIMETRY Based on frequency doubling illusion Test stimulus – series of white and black bands flickering at 25 Hz ( low spatial frequency & high temporal frequncy) Detects damage to Magnocellular Ganglion cells C – 20  17 points – screening N – 30  19 points – diagnosis n management
  57. 57. RANDOM DOT MOTION PERIMETRY Patient has to tell direction in which dots are moving HIGH PASS RESOLUTION PERIMETRY Test resolution and not mere threshold detection
  58. 58. THANK YOU

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