Lecture 3: Visual fields-revision of clinical procedures with patients

Question 1

Why should you test visual fields?

Answer 1

*Incidence of VF loss in general population is 3-5% and increases with age
*VF loss can be sight threatening and life-threatening (can tell you if px has tumour)
*Normal VF can help your diagnosis
*VF defect can be evidence of disease

Question 2

What is kinetic perimetry?

Answer 2

*Considered outdated
*A stimulus of constant intensity is bought from a non-seeing point to a seeing point

Bjerrum screen/Goldmans perimetry

Question 3

What is static perimetry?

Answer 3

*Location of stimulus is constant. Intensity increases/decreases.
*Best technique for detection and the investigation of early field loss

Question 4

What is full threshold testing?

Answer 4

*Intensity at which px can see stimulus at each location is checked
*This is done by staircase procedure (varying stimulus intensity)
*SITA/ZATA- faster.

Question 5

What are the advantages of full threshold testing?

Answer 5

-sensitive to shallow VF loss and early fluctuations in gluacomatous VF loss
-visual field progression (glaucoma)
-allows statistical analysis
-diagnostic information
-provides information about the reliability of the data by comparing the measured vf with normal vf
-highly skilled perimetrist not needed
-reproducible

Question 6

What is the disadvantage of full threshold testing?

Answer 6

time consuming

Question 7

What is suprathreshold testing?

Answer 7

*Stimuli are presented at the intensity that is calculated above the pc threshold. If stimuli is seen, it assumed no significant defect exits
*A stimulus falling in scotoma are not seen

*Single stimulus or multiple stimulus

Question 8

What are the advantages of suprathreshold testing?

What are the disadvantages?

Answer 8

-speeds up investigation. Able to do it every visit
-good screening test
-dont need highly trained periemtrist
-rapid examination of vf

-insensitvity to shallow field defects
-shallow defects are the earliest in POAG
-can miss defects if threshold is incorrectly estimated

Question 9

What visual field equipment can be used to test kinetic perimetry?

Answer 9

-gross perimetry/confrontation
-arc perimeters
-certain bowl perimeters

Question 10

What is the typical bowl radius of HVFA 2?

What distance correction should be used based on age?

Answer 10

30 cm

40-44: +1.50
45-49: +2.00
50-54: +2.50
55-59: +3.00
60-64: +3.50
>64: +4.00

Question 11

When should astigmatism be corrected for visual field testing?
can tints be worn?
What can be used for very high rx?

Answer 11

equal to or greater than 1D

no-reduced brightness of stimulus

Contact lenses

Question 12

What suprathreshold statergies are used to measure threshold on the HFA?

Answer 12

1.threshold-related
-expected hill of vision is calculated
-stimulus intensity set to 6dB brighter than expected at each location

2. three-zone
   -expected hill of vision is calculated as in 1
   defects callsifed as relative to absolute
3. Quantify defect
   -locations missed twice at screening level are thresholded
   -C-76 quantify defect is standard for screening
4. Age reference
   -expected hill of vison is estimated from the px birth date