Automated perimetry

Automated perimetry

1. Automated Perimetry Dr.Vikram.S.Nakhate Dr.Vijay.Shetty

2. Automated way of mapping the visual field Important diagnostic test in glaucoma Diagnosing and monitoring progression of other disease

3. Traquair described it as a field of vision in a sea of darkness It has a shape of a hill Peak representing fovea 2 slopes representing nasal and temporal field of vision

4. Kinetic perimetry Stimuli is moved from a non seeeing area to a seeing area along a set meridian Aim is to find points in the visual field of equal retinal sensitivity Lister perimetry Campimetry Goldman perimetry

5. Static perimetry Intensity of the stimuli at the same pre determined spot is varied Find out threshold at those locations More accurate than kinetic perimetry Gives a 3D picture of the hill of vision Picks up field defects more accurately

6. Apostlib is an absolute measure of luminance and is equal to 0.3183 candela m2 or 0.1 mililambert Decibel is a measure of sensitivity of retina Inversely proportional It is a relative measure varies from machine to machine

7. Testing strategy Full threshold Threshold Suprathreshold

8. Full threshold strategy Staircase method (4-2 bracketing strategy) Used to detect threshold

9. 4-2 bracketing Intensity of stimulus is decreased in 4-db step till stimulus is no longer seen Increasing the stimulus in 2-db step till stimulus is seen again

10. Threshold perimetry Threshold found at predetermined points Time consuming process

11. Suprathreshold perimetry Intensity of stimulus shown at a spot much higher than threshold at that spot Mainly for screening Picks up gross visual defects

12. Newer threshold strategy Fastpac : Decreases the test time by 40% 3-db increment instead of 4-db Threshold crossed only once

13. Sita standard: Takes half time than full threshold method Sita fast: Takes half time than fast pac threshold method

14. 30-2 Number of test points:76 Density :6 degree Only 3 degree bare area is left surrounding the fixation spot

15. 24-2 Number of test points:54 Density: 6 degree Only 3 degree bare area is left surrounding the fixation spot

16. 10-2 central threshold test Number of test points: 68 Density: 2 degree Only 1 degree bare area is left surrounding the fixation spot

17. Macular programme Number of test points: 16 Density: 2 degree Only 1 degree bare area is left surrounding the fixation spot

18. Reliabilty indices Fixation losses: Indicates steadiness of gaze Presenting stimuli at blind spot loss.>20% is unreliable

19. False positives Trigger happy patients Responds to an audible stimuli when no target is presented >33% is unrelible

20. False negative: Fails to respond to a suprathreshold stimuli Indicates fatigue,inattentiveness >33% is unreliable

21. Zone 1 Colour of the stimulus Background illumination: 31.5 asb Stimulus size: III Testing strategy

22. Zone 3

23. Zone 4 total deviation Depicts difference between patients threshold fom that of age matched normals Reveals generalised depression Cannot confirm scotoma

24. Zone 5 pattern deviation Reveals focal defects after adjusting for overall depression Confirms scotoma

25. Global indices Mean deviation: Indicates overall deviation of the visual field from normal Positive number indicates an elevated field Negative number indicates a depressed field Cannot confirm scotoma

26. Psd Derived from total deviation Indicates the degree to which the numbers differ from each other Highlights pot-holes in hill of vision Calls attention for scotoma

27. Short term fluctuation Measure of intra-test variability Threshold at 10 pre selected points is tested Difference between 1 & 2 measurement noted

28. Cpsd is psd corrected for sf If sf is due to unreliability Then cpsd is better If sf is due to pathology Then psd is better

29. GHT 5 set of points above horizontal meridian Compared to mirror image below horizontal meridian

30. Zone 8 Numerical display: Gives the threshold for all points checked Value in () indicates that the point has been tested twice

31. Never rely on first report Always correlate clinically Correct any significant refractive error before proceeding

32. Sources of error Miosis : decreases the threshold sensitivity in peripheral field Increases the variability in central field Uncorrected refractive errors: Threshold sensitivity appears less Hyperopic patient with contact lens: Defect gets magnified & vice versa

33. Spectacles can cause rim scotomas Ptosis : Suppression of superior visual field

34. Principle Is there a field defect ? Is it due to glaucoma ? Is the defect progressing ? Compare to selected baseline Discard learning fields from baseline Recognise false progression

35. False progression Learning curve Long term fluctuation Pupil size

36. Pupil: 1 mm

37. Pupil: 2.5 mm

38. Andersons criteria 1. pattern deviation plot: 3 non-edge points with p<5% One point with p<1% Cluster in arcuate area 2.cpsd Abnormal with p<5% on 2 consecutive occasion 3.abnormal GHT

39. CATARACT

40. GLAUCOMA

41. CATARACT & GLAUCOMA

42. Detecting progression Overview printout Glaucoma change probability analysis

43. Overview print out Sequential series of field of same patient over a period of time Displays gray scales,total &pattern deviation Statistical analysis is however not provided

44. This patient developed cataract,which was extracted later Pattern deviation plot remained clear

45. Glaucoma progression

46. Glaucoma change probability analysis Compares rate of change in patients visual field,with that of stable glaucoma patient Clear triangle represents improvements Solid ones shows points of deterioration Progression represented by a cluster of black triangles in same area increasing in size with time

47. 2 or more points deteriorate on 2 consecutive test

48. 3 or more points deteriorate on 3 consecutive test

49. Advanced field defects Why pattern deviation plot not showing defect

50. Not enough points with sensitivity to produce pattern deviation plot

51. Follow up with 10-2 Enough sensitive points to produce pattern deviation

52. Advanced defect f/u with a size V target(64mm 2 )

53. Macular programme in advanced defects

54. Size V target:macular split Macular split (0 db) next to fovea may indicate wipe out

55. Thank you