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Flashcards in Visual Field 2 Deck (23)
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1

what are the advantages of automated perimetry

1. test conditions are reproducible
2. accurate
3. numerical results
4. most testing can be done by technicians
5. insurance carries reimburse

2

what are the disadvantages of automated perimeters

1. interpretation of results can be difficult
2. variability btwn diff manufacturers
3. length of time for threshold testing
4. initial cost of instrument

3

what are the different types of stimulus presentations

1. projection (humphrey)
2. movable LED (octopus 1-2-3)

4

what is apostilb (asb.)
what are the units

the unit of light intensity
candela/pi m2 = lumens/m2

5

what is the background of all automated perimeters

chosen to be in the mesopic range of illuminance
-resopic range is btwn 1 and 100 asb
-it is the range that both rods and cones are stiumulated

6

what is the background to hymphrey?
regular octopus?
octopus 1, 2, 3?

humphrey: 31.5 asb
regular octopus: 4asb
octopus 1, 2, 3: 31.5

7

on instruments with brigher backgrounds what is the stimulus brightness?
on instruments with dim backgrounds what is the stimulus brightness?

brighter: from .08 asb to 10,000 asb
dim: .01 asb to 1,000 asb

8

the definition of a decibel does not take into consideration the...

size of the target or the background illumination

9

what does 0dB correspond to

the brightest stimulus on a given machine

ex. humphrey 10,000 asb, <0 on a printout means they cannot see the brightest stimuli

10

in the humphrey system, what is the RX needed for ages
30-40
40-45
45-50
50-55
55-60
over 60

30-40: +1.00
40-45: +1.50
45-50: +2.00
50-55: +2.50
55-60: +3.00
over 60: +3.25

11

what is the add needed if the pt is dilated w/ an anticholingeric secondary to cycloplegia

+3.25 add

12

when is the spherical equivalent used in humphries

rxs with 0.75 cyl or under

13

on the gray scale, what does the darker the shade mean

the greater the reduction in sensitivity

14

what is the gray scale an excellent tool for

pt education

15

if greater than _____ it is usually considered invalid or unreliable

0.20-0.25

16

what is gaze tracking

humphrey system projects infra red light onto the cornea enabling the perimeter to calculate the eye rotation from the dist the corneal reflex moves from a baseline measurement taken before the vf begins

17

what do upspikes represent? what do down spikes rep?

upspikes: eye movements
down spikes: blinks

18

is an rx needed for peripheral field? central field?

peripheral field: no rx, the ring of the lens or lens holder will interfere w/ the test
central field (central 30 degrees): rx is needed

19

how deep is humphrey the bowl

30 cm deep

20

when should the pupil be dilated in a humphrey

if the pupil diameter is less than 2-3mm

21

what is a false positive error

when the projector moves as if to present a stimlus but no stimuls is presented

22

what is a SITA false positive

recorded by measuring the response time of the pt if the pt presses it outside the allowable response time that a false positive is recorded

23

what is a false negative

after a point in threshold a stimulus 9db brighter is presented at the same point
-if pt does not see this point it is a false neg
-indicates pt is tired or no longer attentive