Perimetry & Humprey visual field assay (HVFA)

Perimetry & Humprey visual field assay (HVFA)
HVFA is the most common tool diagnoses & follow up of field defect due to glaucoma & neurological damage.

1. PERIMETRY & HUMPHREY VISUAL FIELD ASSAY Lt Col A.K.M. Rashed-Ul-Hasan Long Term Fellow Trainee(Glaucoma) CMH Dhaka

2. VISUAL FIELD Visual field is an island hill of vision surrounded by a sea of blindness – Traquair Visual field is all the space that one eye can see at any given instant ---Tate & Lynn

3. 60  50  50  90  90  70  70  Fixation X X = Physiological Blind spot X NORMAL VISUAL FIELD LIMITS

4. Visual Field Testing Methods Central Field Amslar Grid- 20° Tangent (Bjerrum) Screen- 30° Goldmann Automated (Octopus/Humphrey)- 30° Peripheral Field Confrontation Goldmann Automated 90° programm

5. Location of Visual Field Defects Peripheral > 30º Central 5 º or less from the point of fixation Paracentral > 5º – 30º Ceacal Paraceacal Periceacal Centroceacal

6. Perimetry is defined simply as the study of the visual field . PERIMETRY & PERIMETER Perimeter is an instrument designed for perimetry.

7. Kinetic Stimulus moves Confrontation Lister Tangent screen Goldman Type of Perimetry Static Stimulus does not moves HVFA OCTOPUS

8. Static Kinetic VFD detect earlier with 20% defect Area fixed but stimulus varies in intensity 3D Computarized Threshold type Less error Both glaucoma and neurological VFD detect earlier with 40% defect Intensity fixed but stimulus moves from non-seeing to seeing area 2D Not Computarized Non Threshold type More error Good for neurological, periphery of field & adv glaucoma

9. Role of Perimetry To diagnose clinical conditions. Ocular- Glaucoma, Optic nerve disorders. B) CNS conditions- Optic nerve pathway disorders. CNS Tumors. Occipital lobe disorders. 2. To manage glaucoma. To set target IOP Follow up.

10. Different types of Automated Perimetry

11. THRESHOLD If a particular intensity of light is shown 100 times and if it is appreciated 50 times then that particular intensity of light is termed as threshold.

12. Determination of threshold

13. APOSTILB ( Asb ) Absolute units of light intensity / brightness Humphrey : 1 - 10,000 asb Goldman & Octopus : 1 - 1000 asb

14. DECIBEL (dB) Tenth of logarithm unit ( 1 dB = 0.1 log unit ) Relative units of light intensity Higher the dB lower intensity of light stimulus high retinal sensitivity.

15. 0 dB = 10,000 asb 10 dB = 1,000 asb 20 dB = 100 asb 30 dB = 10 asb 40 dB = 1 asb 0 dB = Brightest light = low retinal sensitivity. 40 dB = Dimmest light = high retinal sensitivity.

16. NB: Central 30º : 66% of ganglion cell & 83% visual cortex

17. Interpretation

18. Zone 1 Patient data & test data Zone 2 Foveal Threshold & Reliable indices Zone 3 Gray Scale Zone 4 Total Deviation Zone 5 Pattern Deviation Zone 6 Global Indices Zone 7 Glaucoma Hemi-field Test Zone 8 Raw Data

19. 0.2 second duration The effect of size of pupil: Pupil should be 3-4 mm Constricted pupil Diffuse visual field depression Edge scotoma Very important in follow up test

20. RELIABILITY INDICES

21. Central : Yellow light at centre of bowl. Small diamond : Below the central target M acular degeneration Large diamond : When central fixation lost Central scotoma Bottom LED: Superior field test Fixation of target

22. Fixation loss Indicates steadiness of gaze during the test >20% is unreliable 5% Stimulus is presented over blind spot

23. False positive >15% is unreliable (SITA Standard) >33% is unreliable (Full threshold) Trigger Happy Abnormally pale

24. False Negative >15% is unreliable (SITA Standard) >33% is unreliable (Full threshold) Fatigue, inattention, malingering Clover leaf patern

25. Gaze Tracker Upward spikes: indicating eye movements Downward spikes: indicating blinking during stimulus presentation.

26. Total Deviation plots Numeric value in upper plot Diff. in dB between the patients test results and the age corrected normal values at each tested point in the visual Field. Value is abnormal : if >5 dB less than normal . Gray scale symbols in lower plot translates values of upper plot, Darker the symbols, more the depth of defect Generalized depression: Media opacities Refractive error Miosis

27. Pattern Deviation It is derived from total deviation values and adjusted to demonstrates the localized defect.

28. P Value

29. Global Indices It’s the summary values that represent distilled statistical information. Used to monitor progression of glaucomatous damage Consist : VFI: Patient’s overall VF function. 2. MD: Overall sensitivity of the field. 3. PSD: Focal loss within the field.

30. Glaucoma Hemifield Test Compare 5 zone of upper field with mirror image of lower field to see asymmetric field loss in glaucoma. 5 comments 1. Outside normal limit 2. Borderline 3. General reduction of sensitivity 4. Abnormal high sensitivity 5. With in normal limit

31. Localized Field defect The TDPP and PDPP looks similar. Causes- Early glaucomatous ON damage AION ON pathway defect Occipital lobe infarcts

32. Generalized field defect in TDPP. Localized defect in PDPP. Found in advance stage of glaucoma. Cataract associated with glaucoma Irregular Generalized Field defect

33. Generalized defect in TDPP. Normal PDPP. Cause Media opacities. Advanced and end stage glaucoma. Optic neuritis. Uniform Generalized Field defect

34. PRACTICE

35. Nasal Step Pattern

36. Arcuate pattern

37. Advanced case of glaucoma

38. Enlargement of blind spot

39. Left Sided Homonymous Haemianopia

40. Bi-nasal hemianopia

41. Bi-temporal hemianopia

42. AION

43. Upper Haemiretinal Vein Occlusion

44. Tubular field defect due to RP

45. Toxoplasma choroidoretinitis

46. Glaucomatous Field Defect

47. Progression of field defects in POAG Initially observed in Bjerrum’s area ( 10 ˚ -25 ˚ from fixation) Generalised contraction of field Baring of blind spot : exclusion of the blind spot from the central field due to inward curve of the outer boundary of 30° central field (Fig A) Small wing-shaped paracentral scotoma (Fig B) Seidel’s scotoma : paracental scotoma joins the blind spot (Fig C) Arcuate or Bjerrum’s scotoma : by the extension of Seidel’s scotoma in an area either above or below the fixation point to reach the horizontal line (Fig D) Ring or double arcuate scotoma & Roenne's central nasal step : when the two arcuate scotomas join (Fig E) Advanced glaucomatous field defects : Tubulur vision