Special Testing Flashcards
Reasons for testing VF in low vision
Determine functional impairment
Determine legal blindness
Correlate with pathology
Automated VF
- advantage of standardization and is easier to use
- can be used to determine legal blindness (MD greater than 22DB)
- has both static and kinetic automated programs
Arc perimetry
- the VF can also be tested using a hand perimeter
- came with various target sizes, generally uses 3mm first and increases the target to 5mm if the patient struggles
Arc perimetry instruction
- Cover OS, habe the patient hold instrument horizaontal and place against the patients nose
- Position the OD a few inches above the center dot and tell the patient to fixate on the central target
- The wand is held just temporal to the fixation point, the patient is asked if he or she can hold fixation o the central target whilst seeing th peripheral target. Can also ask if patient is able to see two dots, including the one you are moving and the one on the disc
- The wand is moved outward gradually and the patient is instructed to report when the moving target disappears. If it disappears within appx 15 degrees, the patient is reassured that this area is the normal physiological blind spot. If the examiner suspects malingering, occasionally turn the wand around during testing so that the target disappears. If the patient still claims to see the target while it is turned, the malingering is confirmed
- continue to test in clockwise pattern in order to maintain a systematic order
- If the patient has poor response to the smaller target increase
- Switch eyes and repeat until all 8 meridian ends rate eval
Arc perimetry norms
For a 3mm target at 13 inches (the typical target at the distance of the radius of the perimeter), the normal findings are as follows
- 90 degrees or more temporally
- 55 degree superiority
- 60 degrees nasally
- 70 degrees downward
Norms are demonstrated on the official recording form by the shaded areas
Arc perimetry recordings
- the limits of the field can change based on the level of illumination in the room-make sure tour room is adequately lit
- for patients that have difficult with speaking, you may have to move your target mroe slowly or use shorter phrases)
- make sure that the disc remains at the meridian you are testing and that you do not accidentally turn your target away from your patient during testing
Conventional perimetry
- allows quantification of the visual field
- accuracy is based on two assumptions
Accuracy of conventional perimetry is based on these two assumptions
Fixation is stable
Fixation is located at he fovea
What is conventional perimetry not good for
Precise evaluation of macular disorders
Microperimetry
- minomer: night stimulus size nor test grid are “micro”
- refers to perimetry when there is real time visualization of the fundus
- first used by Timberlake over 20 years ago
Microperimetry and scotomas
Determination of scotomas
- size
- location
- relative vs absolute
What can microperimety determine
Scotomas and fixation
How can microperimetry determine fixation
Location
Stability
Development of preferred retinal locus (PRL)
Preferred retinal focus
Retinal area that behaves as a pseudofovea and is adopted by the patient to see chosen object
NIDEK MP1
- is NOT and SLO
- infrared fundus camera 45 degree FOV
- automated eye tracking
- automated static threshold or customized using liquid display
Spectral OCT/SLO
A tool used with microperimetry that can show retinal damage in certain diseases
Macualr integrity assessment (MAIA)
- linear SLO system and fundus controlled perimetric exam
- limited ability to adjust parameters
- can adjust stimuli locations
MAIA useful for
Rehabilitation recommendations
Patient and family education
Making sense out of patient complaints
Location of PRL and reading speeds (fletcher)
Not strongly associated with reading speeds
PRL and reading speeds today
- PRL training using a microperimeter like the MAIA can be very successful and improve reading time
- groups trained in two different methods to adopt a more efficient retinal locus improved the median reading speed by 20-21 wpm
- when reading a 2000 word newspaper page, a reading speed of 83 wpm would require 24 minutes. When increased by 21 wpm to 104 wpm, it would require 19m, which saves 5 minutes
Amsler grid testing
- patients may report normal even in the present of large macular scars
- nearly half of scotomas are missed by the amsler grid
- AG underestimates extent of scotomas
- 65% of patients placed their PRL on the center of the grid, giving the illusion of a paracentral scotoma when in fact it was central
Facial amsler
- have patient view your face looking right at your nose. Which part of your face is the most clear?
- sunless found facial fields to be accurate to microperimetry results in 74% of cases. In clinics with not access to a microperimeter, facial amsler is quick and recommended
- you can hold your hand at different places around your face and ask the patient to look at your hand. At which place is your face the most clear in their peripheral vision?
Home exercises for training locus
- place an object near their TV in the appropriate location that they should look at when watching TV
- use large print playing cards
- with hand held steady, patient presents the playing cards directly in front of themselves. They turn only their eyes to the appropriate EV point to identify the card. Go through the deck 3x daily. Once able to do this easily, move on to pre-reading exercises.
Pre-reading and reading exercises
- often trained by occupational therapists
- more about this later in the course
