VF Flashcards
relative unit of sensitivity in perimetry
Db
Unit of luminance/light density
Apostilb
*max luminance varies with VF
Hill of vision
- What is it
- Varies with what
- Max sensitivity at
3D profile of pt’s retinal sensitivity
- Varies with age, response of patient and light adaptation.
- Fovea
Isopter
Line of equal retinal sensitivity plotted on a VF
Horizontal slice of HOV
Two types of scotoma
Absolute or relative
Two types of depression
Localized or general (real or artifact)
Causes of general depression
Could be due to media opacities, refractive error, ON disease, small pupil, poor pt attention, age
Contraction/constriction
Peripheral boundaries are moved inward
5 types of test paradigms
- Kinetic field. Goldman and tangent screen.
- Static field.
- Threshold. Stimulus that has 50% probability of being detected.
- Superthreshold. Screening. Presenting stimuli above expected threshold. Points noted as seen or not seen.
- Threshold related. 4 threshold test points. Remaining points tested at 6dB above threshold. More sensitive than 4
Visual field projection
VF on paper represents field as seen by the patient
Increasing or decreasing test distance.
What stays the same, what changes
Angular dimension does not change.
Lateral dimension will change proportionally with distance. Tangent screen utilizes this to check for hysterical amblyopia/tubular fields.
Damage to papillomacular fibers
Enter ON on the temporal side. Centrocecal defect.
Involves macula and blind spot.
Damage to temporal fibers
Arcuate defect
Damage to nasal fibers
Wedge defect
Superior and inferior fiber defects
Defects do not cross midline
Macular fibers initially run along which portion of ON
Outer
Altitudinal defect
Anterior ON damage close to retina
ON tract. The more posterior the damage
More likely it is to be congruous
Optic radiation is located after the
LGN
Pie in the sky defect
Damage to temporal/inferior/myers loop in optic radiation
Pie on the floor defect
Damage to the parietal/superior loop in optic radiation
Occipital cortex damage
Lesions here are highly congruous
Could exhibit macular sparring
Frequency of seeing curve
Plots the percentage of time a stimulus is seen at a given intensity.
The gradient of the curve is a measure of the patient reliability. Steep is better.
Reliability increases with patient attention, previous test experience, additional auditory cues, multiple stimulus presentations.
Sensitivity profile
Plots the change in retinal sensitivity with eccentricity. Varies with dark/light adaptation.
Photopic- steep
Mesoptic- flat
Scotopic- central depression
Affected by level of background illumination.
Pre adapted state of patient
Stimulus size
Background illumination
Controls sensitivity profile and length of adaption of the patient.
Adaptation time depends on
Background illumination
Prior state of adaption
Length of pre adaption period
Retinal eccentricity (greater sensitivity potential take longer)
-Local effect (ex bright fixation light will result in local area of reduction)
Stimulus size
- Due to ____ summation
- Inverse relationship between size and ___
- Based on what law
- Spatial summation increases with
- Spatial summation.
- Between size and threshold. Small stimulus, complete inverse relationship. (Riccos law) with large stimuli, partial.
- Riccos is luminance x area = constant
- Spatial summation increases with eccentricity and dark adaption. (bigger fields in periphery)
Blur can affect sensitivity due to increased spatial summation
True
Goldman stimulus size ___ is normally used
III
Stimulus duration
- Due to ___ summation
- Inverse relationship between duration and
- Critical duration varies with
- Saccadic reaction time
- Temporal.
- Threshold up to critical duration according to Bloch.
- Bloch: luminance x duration = constant
- Size, background illumination and retinal eccentricity.
- Saccadic reaction time is 250 ms
Keep stimulus duration between __ and __ msec
100 and 250
5 types of perimetry
Confrontation - Static or kinetic
Ampler
Tangent - Kinetic or static. Tubular field.
Goldman- gold standard. Manual. Kinetic and static. Longer in duration than other forms.
automated
4 types of automated perimetry
Humphrey - projects stimuli in bowl. Must correct for test distance for presbyopes. Static.
Octopus- Projects stimuli onto retina. Tests 30 degrees only. Only correct distance Rx. Static.
Dicon- Kinetic/dynamic only. Has sounds.
Frequency doubling tech (FDT)- Static.
3 components of automated perimetry
- LED vs projection stimuli.
- LED cannot alter size or color. Silent.
- Projection can alter size and color. Makes noise. - Fixation target
- Humphrey, octopus and FDT all use static.
- Dicon uses dynamic/kinetic - Fixation monitor using Heijl Krakau method.
- K purkinje image alignment used for humphrey gaze tracking.
Quantify defects test strategy
Missed points are ran at threshold level. All others are super
Humphrey analyzer algorithms
- Fast Pac. 40% less time than full threshold.
- SITA standard. 50% less than full threshold.
- SITA Fast. 50% faster than Fast pac
- SWAP. Blue stimulus on yellow background. Early detection of glaucoma since glaucoma damages short wavelength fibers first.
SWAP test
- What is it for
- Significant dB values
- Requires what type of patient
Blue stimulus on yellow background. Early detection of glaucoma since glaucoma damages short wavelength fibers first.
HOV drops more rapidly. 9db Centrally or greater than 9Db peripherally is significant.
Requires young attentive patient with no lens opacities.
Greater than what percentage indicates low patient reliability for
Fixation loss
False Positive
False negative
more than 20
more than 33
more than 33
High FN rate could indicate
Disease
Short term fluctuation (SF)
- Greater than what is considered high
- What does it indicate if high
- Could be early detection of
- Greater than 0.3 is high
- Indicates variability of patient response.
- Could be early indication of pathology
4 types of reliability indicies
Fixation loss
False Positive
False negative
Short term fluctuation (SF)
Types of statistical analysis
Raw data
Grey scale
Probability plots
Central reference level
Defect depth plot
Total deviation plot - Shows local and overall defects
Pattern deviation plot- only shows local defects
Types of global indicies
Mean deviation - elevation of depression of overall sensitivity. Normal is +/- 2
Pattern standard deviation: 0 to 2. High value indicates patient variability in responses.
Short term fluctuation- Normal is less than 3. Response consistency.
Corrected pattern standard deviation- Corrects for SF. Abnormal is p < 5%. Indicates field abnormalities. Can be fooled by advanced glaucoma !
