Test 3 Flashcards
The ON causes a physiologic blind spot where
15 degrees temporal
Along horizontal meridian 40% above, 60% below. Vertically oval.
7 degrees high, 5 degrees wide.
Absolute scotoma
Limit of foveal vision
Normal peripheral sensitivity range
Typical range of abnormal vision
40 dB
20-40dB
0-30 dB
As dB increases, brightness decreases.
Brightest stimulus in dB and abs
Brightest = 0 dB, 10,000 abs
Dimmest= 50dB, 0.1 Abs
How is the size of the stimulus defined
Defined as the target size and distance from eye.
1mm target at 33 cm distance
Traditional unit of light for perimetry- standard background luminance
31.5abs
Most common stimulus size
0.43 degrees (Goldman size III)
temporal summation ensures linear relationship between
Stimulus duration and threshold.
Stimulus duration doubles = threshold doubles.
Max duration - 500msec
Most frequent used duration - 200msec (prevents tendency for re-fixation and gives pt time to respond)
Kinetic perimetry speed
3 to 5 degrees per second. (4)
too slow- encourages refixation
too fast- Isopter becomes artificially small.
When is contrast sensitivity used for the stimulus?
Sine wave gratings to increase the sensitivity of peripheral defects.
Temporal contrast. Flickering.
About __% of normal first time testers have abnormal results
15%
Pupil size that is too small and reduces retinal luminance
2.5mm. May need to dilate. Large pupils may reduce sensitivity in central target locations.
Lack of correction reduces sensitivity by ___dB per diopter of blur using goldman size 3 target
1 dB per 1 D
Astigmatism should be corrected when it is more than
1.50DC
Age reduces visual acuity __dB per decade
1dB per 1 decade
Relative scotoma
Big target/easy to see =
Small target/hard to see =
Big target= small defect
small target= big defect
Manual perimetry tests and if they can do static or kinetic testing or both
- Tangent screen- kinetic, static
- Arc perimeter, kinetic only
- Goldman Perimeter- kinetic, standard
Advantages and disadvantages to tangent screen
Low cost, simple to operate
Hard to reproduce results, room lighting is variable, does not assess peripheral field.
Tangent screen Tests ___ central degrees in the visual field
What two techniques can be performed?
30
Kinetic and supratrheshold
results with a hysterical patient (conversion disorder)
Tubular field
Psychological, not pathological.
Move patient back from 1m to 2m, VF results stay the same.
Arc perimeter measures what how far in the periphery? Target sizes (2) how many meridians tested? Testing distance?
Both central and peripheral fields. Out to 90 degrees from fixation. Far periph Target sizes either 3mm or 10mm 8-12 meridians tested Testing distance is 33cm
Goldman perimetry working distance
extends how far into the periphery?
how to document the size, intensity, and finer adjsustments.
How many meridians tested
30cm working distance 90 degree field Size is 0-V Intensity/brightness is 1-4 Light transmission/fine adjustment is a-e 8 meridians tested
Standard goldman stimulus
III 4 e
0.43 degrees, max brightness, max fine adjustment
Advantages and disadvantages to automated perimetry
Uniform, reproducible, stat analysis, random presentation, screening and threshold, central and peripheral
Expensive, long test time.
How does Automated perimetry Humphrey monitor pt fixation
Video monitoring
-Restests blind spot and monitors K light reflex.
Eye movement increases false negatives