Visual field defects Flashcards
what is static perimetry?
location of the stimulus is constant
Intensity increases/decreases
what is kinetic perimetry?
Intensity contant
Location of target moved from non-seeing to seeing
what are the 2 types of static perimetry?
- Threshold
- Suprathreshold
What is an example of a threshold test?
ZATA
how does a threshold strategy work?
each location is thresholded using a staircase procedure
Advantages of threshold strategy?
- sensitive to shallow field loss
- VF progression
- allows statistical analysis
- provides info about reliability
Disadvantages of threshold strategy?
- time consuming: newer methods offer a comparable time
Advantages of supra threshold strategy?
- speeds up investigation
- good screening test
- no need for specialist training
disadvantage of supra threshold strategy?
- insensitivity to shallow field defects
- can miss defects if threshold is measured incorrectly
which condition do you get shallow field defects?
POAG
what is an example of static perimetry machines?
- Humphrey field analyser
- modern Henson models
Which VF test can be carried out routinely as part of a screening process?
gross perimetry/confrontation
if unable to use glasses, how do you correct the patient on the machine?
use closest BVS to the reading rx
when do you correct for cyls when doing VFs?
if = or > 1DC
use full correction
if rx 8D or higher, od you use glasses or CLs?
use CLs if possible
When do you use an Amsler chart?
- suspicious macula
- unable to see macula
- CSR
- neovas
- CMO
- ERM
what distance do you use the Amsler?
28-32 cm
do you use correction when doing Amsler?
yes - use near rx
Limitations of Amsler?
only detects 50% of patients with macular disease
how many different types of Amsler charts are there?
7
Which Amsler chart is this and when is it used?
Chart 1 - Standard chart which must be used in every case and in many cases is sufficient
Which Amsler chart is this and when is it used?
Chart 2 - used when central point is not seen as the diagnoal lines help to fixate the centre of the square in spite of central scotoma
Which Amsler chart is this and when is it used?
Chart 3 - used in cases of colour scotoma
Which Amsler chart is this and when is it used?
Chart 4 - reveals only the scotoma - nothing is distorted
Which Amsler chart is this and when is it used?
Chart 5 - looked at horizontally and vertically. It will show metamorphopsia
Which Amsler chart is this and when is it used?
Chart 6 - used for metamorphopsia again but thinner lines allow for more minute examination of distortion
Which Amsler chart is this and when is it used?
Chart 7 - used for more minute examination of the central area where the rectangle with subdivided squares indicates the limits of the fovea.
GOOD FOR HIGH MYOPES WHEN HELD AT THE PUNCTUM REMOTUM OF THE UNCORRECTED EYE
