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The Visual Field - For Doctors
- 1. Dwight Thibodeaux, OD THE VISUAL FIELD
- 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. 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. 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 Ocotopus Oculus and others
- 7. GOLDMANN KINETIC FIELD TESTER
- 10. ZEISS/HUMPHRIES HUMPHRIES FIELD ANALYZER (HFA) FDT and MATRIX
- 11. SUPRATHRESHOLD • Targets set at moderate brightness with wide field • Either seen or not seen • Useful for lid/ptosis evaluation • Two field tests, taped and untaped
- 12. THRESHOLDING • First stimuli 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
- 13. SITA / SITA FAST (HFA) Swedish Interactive Thresholding Algorithm SITA 50% faster than standard, but 90% accuracy SITA FAST 70% faster, 80% as accurate
- 15. FDT/FDP • Frequency Doubling Technology (Perimetry) • Grating target flickered quickly creates and illusion of a doubled grating, stimulating a different neuro pathway • For early detection of glaucoma • Resistant to blur (Rx) and pupil size effects
- 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. 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. 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. HFA 10-2 • Central field testing • Most commonly used for patients with risk for macular toxicity • Plaquenil – hydroxychloroquine used chiefly for rheumatoid arthritis • OCT of macula also part of new protocol
- 20. MICROPERIMETRY • Amsler Grid • Automated
- 21. WHEN TO USE WHAT • Glaucoma suspect or pre-perimetric pt. • Established glaucoma patient with field loss • Neuro patient • Ptosis patient • High risk meds patient
- 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. ESTABLISHED GLAUCOMA • SITA Standard 30-2 • Difficult / older patient SITA Fast 24-2
- 24. NEURO FIELDS • SITA Fast 30-2 • Matrix oversensitive
- 25. PTOSIS OR BLEPHAROCHALASIS • Suprathreshold automated or kinetic fields • Wider field to catch more peripheral defects • Don’t need thresholding
- 26. HIGH RISK MEDS • SITA 10-2 • For subtle central defects from retinal toxicity • Used in conjunction with SD-OCT for Plaquenil (hydroxychloroquine) screening
- 27. QUALITY MEASURES • Fixation losses – targets blind spot, need <15%, use gaze tracker for confirmation, ? misaligned • False positives – notes positive response when no target is shown < 20% or not a reliable study • False negatives – notes lack of response in area previously seen at lower illumination <33% • Gaze tracker - camera notes eye
- 28. DATA ANALYSIS
- 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
- 31. DATA ANALYSIS • Grey scale • Threshold values in Db • Variance from normal threshold in Db • Mean Deviation (MD) • Positive Standard Deviation (PSD) • Glaucoma Hemifield Test (GHT)
- 33. GREY SCALE / THRESHOLD VALUES • Quickly identifies overall depressions • Good for patient education • Shows thresholds for each spot tested in Db • No comparison for age related normals • No adjustment for media opacities • Under represents shallow gen. depression and overemphasizes midperipheral non- significant defects
- 34. TOTAL DEVIATION PLOT • Graph and numeric representation • Compared to age-matched normals
- 35. PATTERN DEVIATION PLOT • Probably the most important data • Takes total deviation and filters out overall depression • Looks for focal damaged areas pertinent to glaucoma
- 36. GLAUCOMA HEMIFIELD TEST - GHT • Compares top and bottom half of field • General reduction in sensitivity • Abnormally high sensitivity • Outside Normal Limits – difference not found in 99% of patients without glaucoma • Borderline – difference not found in 97% of normals
- 37. GLOBAL INDICES • Single number representations of the visual field • Overall guidelines to help assess the field • Probability values when numbers reach significant levels
- 38. 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
- 39. 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
- 40. PATTERN STANDARD DEVIATION (PSD) • Sensitive measurement of localized loss • Especially useful in glaucoma evaluation/progression • The higher the number, the greater the loss
- 41. COMMON GLAUCOMA DEFECTS (SCOTOMAS) • Arcuate • Nasal step • Temporal wedge • Localized paracentral • Generalized depression • Compare to clinical picture – know what to expect
- 42. ARCUATE OR NERVE FIBER BUNDLE DEFECT
- 43. NASAL STEP
- 45. SECTOR OR WEDGE DEFECTS
- 47. 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
- 48. HOMONYMOUS • Hemianopsia – right homonymous, congruous, points to cortical lesion such as stroke • Quadranopsia or sectoranopsia– cerebral (congruous) or lateral geniculate nucleus
- 49. HETERONOMOUS Hemianopsia- bitemporal, congruous— points to chaismal lesion such as a pituitary tumor Quadranopsia- very rare, also points to area of chaism
- 50. ALTITUDINAL • Almost always unilateral • Associated with AION – stroke at the optic disc
- 51. CENTRAL SCOTOMA • More commonly unilateral as in: optic neuritis macular degeneration early AION retinal dystrophy Bilateral – toxic, nutritional, heriditary optic neuropathy and maculopathy