Your Date with Mr. Humphrey

Automated Visual Field Testing is critically important. It assesses the functioning of the entire visual system including the brain, optic nerves and retinas. Obtaining a reliable, quality test is the job of the visual field technician.  This article discusses the two keys to obtaining a quality test.

Key # 1: Instructions

How can you expect to get a quality test if you don't tell the patient what you want them to do? Patient Instruction is critical.

Following are bullet pointed instructions. I recommend you post them to the left side of your visual field screen so you can easily glance at them while instructing the patient.

 


 Patient Instructions

  • Test of side vision
  • Makes a map of vision
  • Chin in chin rest, forehead against bar
  • Look straight ahead at yellow light. Do not look away from the yellow light
  • You’ll see flashing lights. Some will be very bright, some very dim
  • Sometimes you won’t see a light for a short time - that’s normal
  • Push button whenever you see any light other than the yellow light
  • Keep chin in chin rest, forehead against bar
  • Do not move your head
  • Blink whenever you want
  • Remember to only look at the yellow light and push the button whenever you see any light other than the yellow light

Instructions for the Visual Field Technician

This test requires a partnership between the patient and the technician therefore, it's equally important the technician also knows what to do. Following are bullet pointed instructions for the technician: 

  • Place lens(es) in lens holder
  • If possible, align handle of lens supero-temporally
  • Patch eye not being tested
  • Confirm patient cannot see around patch
  • Give patient response button
  • Position patient
  • Height of table ok for pt?
  • Chin on chin rest
  • Teeth together
  • Forehead against bar
  • No head tilt or turn
  • “Can you see the yellow light in the center?”
  • If no, change fixation target small or large diamond target. Pt should fixate in middle of diamond
  • Align pupil in cross hairs on monitor screen
  • KEEP CROSS HAIRS CENTERED IN PUPIL THROUGHOUT TEST

During the Test

 “Push the button whenever you see any light other than the yellow light”

Encourage patient but don't distract from test

  • You’re doing great
  • You’re almost done

For Fixation Losses

  • Remind patient to look only at yellow light
  • Is fellow eye fully patched?
  • Click ‘Retry to find blind spot”
  • Recheck patient's head and eye position
  • Goal: < 20% fixation losses

 Key # 2: Patient Positioning

If you're not sure how to fix a positioning problem, ask the patient to sit back, pull the patient's chair back and start from scratch with positioning the patient. Here are the important points:

  • Chin down, teeth together

  • Forehead against bar

  • Lens as close to eye as possible without eyelashes touching lens

  • Head straight (no tilt or turn)

  • The patient's chair should be aligned straight with the chin rest/VF machine

  • Pupil aligned in cross hairs

 

Yes, Visual Field Testing can be boring and arduous for the technician and for the patient, but if you carefully instruct your patient and closely observe the patient's positioning, you will be much more likely to obtain an accurate, quality test.  Your patient AND doctor will appreciate your efforts.