Dwight Thibodeaux, OD

THE VISUAL FIELD

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.

NORMAL FIELDS

• Visual Field - Roughly 140 degrees monocularly and just over 180 degrees binocularly

• Field of Gaze – Over 200 deg

• Field of View – Over 300 deg

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

HISTORICAL FIELD TESTS

CONFRONTATION FIELD TESTING

Technique

Targets

GOLDMANN KINETIC FIELD TESTER

GOLDMANN KINETIC PERIMETRY

OCTOPUS AND OCULUS

ZEISS/HUMPHRIES

HUMPHRIES

FIELD ANALYZER (HFA)

FDT and MATRIX

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

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

SITA / SITA FAST (HFA)

Swedish Interactive Thresholding Algorithm

SITA 50% faster than standard, but 90% accuracy

SITA FAST 70% faster, 80% as accurate

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

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

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

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

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

MICROPERIMETRY

• Amsler Grid

• Automated

WHEN TO USE WHAT

• Glaucoma suspect or pre-perimetric pt.• Established glaucoma patient with field loss• Neuro patient• Ptosis patient• High risk meds patient

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

ESTABLISHED GLAUCOMA

• SITA Standard 30-2

• Difficult / older patient

SITA Fast 24-2

NEURO FIELDS

• SITA Fast 30-2

• Matrix oversensitive

PTOSIS OR BLEPHAROCHALASIS

• Suprathreshold automated or kinetic fields

• Wider field to catch more peripheral defects

• Don’t need thresholding

HIGH RISK MEDS

• SITA 10-2

• For subtle central defects from retinal toxicity

• Used in conjunction with SD-OCT for Plaquenil (hydroxychloroquine) screening

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 movement

DATA ANALYSIS

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

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)

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

TOTAL DEVIATION PLOT

• Graph and numeric representation

• Compared to age-matched normals

PATTERN DEVIATION PLOT

• Probably the most important data

• Takes total deviation and filters out overall depression

• Looks for focal damaged areas pertinent to glaucoma

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

GLOBAL INDICES

• Single number representations of the visual field

• Overall guidelines to help assess the field

• Probability values when numbers reach significant levels

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

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

PATTERN STANDARD DEVIATION (PSD)

• Sensitive measurement of localized loss

• Especially useful in glaucoma evaluation/progression

• The higher the number, the greater the loss

COMMON GLAUCOMA DEFECTS (SCOTOMAS)

• Arcuate

• Nasal step

• Temporal wedge

• Localized paracentral

• Generalized depression

• Compare to clinical picture – know what to expect

ARCUATE OR NERVE FIBER BUNDLE DEFECT

NASAL STEP

LOCALIZED PARACENTRAL SCOTOMAS

SECTOR OR WEDGE DEFECTS

GENERALIZED DEPRESSION

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

HOMONYMOUS

• Hemianopsia – right homonymous, congruous, points to cortical lesion such as stroke

• Quadranopsia or sectoranopsia– cerebral (congruous) or lateral geniculate nucleus

HETERONOMOUS

Hemianopsia- bitemporal, congruous—points to chaismal lesion such as a pituitary tumor

Quadranopsia- very rare, also points to area of chaism

ALTITUDINAL

• Almost always unilateral

• Associated with AION – stroke at the optic disc

CENTRAL SCOTOMA

• More commonly unilateral

as in:

optic neuritis

macular degeneration

early AION

retinal dystrophy

Bilateral – toxic, nutritional, heriditary optic neuropathy and

maculopathy

QUESTIONS? DRTHIB@MSN.COM