Visual Field 2

Question 1

what are the advantages of automated perimetry

Answer 1

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

Question 2

what are the disadvantages of automated perimeters

Answer 2

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

Question 3

what are the different types of stimulus presentations

Answer 3

1. projection (humphrey)

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

Question 4

what is apostilb (asb.)

what are the units

Answer 4

the unit of light intensity

candela/pi m2 = lumens/m2

Question 5

what is the background of all automated perimeters

Answer 5

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

Question 6

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

Answer 6

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

Question 7

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

Answer 7

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

Question 8

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

Answer 8

size of the target or the background illumination

Question 9

what does 0dB correspond to

Answer 9

the brightest stimulus on a given machine

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

Question 10

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

Answer 10

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

Question 11

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

Answer 11

+3.25 add

Question 12

when is the spherical equivalent used in humphries

Answer 12

rxs with 0.75 cyl or under

Question 13

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

Answer 13

the greater the reduction in sensitivity

Question 14

what is the gray scale an excellent tool for

Answer 14

pt education

Question 15

if greater than _____ it is usually considered invalid or unreliable

Answer 15

0.20-0.25

Question 16

what is gaze tracking

Answer 16

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

Question 17

what do upspikes represent? what do down spikes rep?

Answer 17

upspikes: eye movements

down spikes: blinks

Question 18

is an rx needed for peripheral field? central field?

Answer 18

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

Question 19

how deep is humphrey the bowl

Answer 19

30 cm deep

Question 20

when should the pupil be dilated in a humphrey

Answer 20

if the pupil diameter is less than 2-3mm

Question 21

what is a false positive error

Answer 21

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

Question 22

what is a SITA false positive

Answer 22

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

Question 23

what is a false negative

Answer 23

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