Test 1: Vision Rehab History and Exam Flashcards
low vision exam
different from PC exam
goal driven optical consultation
focus on rehab
low vision exam scheduling
initial consultation first visit 1.5-2 hours loan devices 2-6 weeks follow up 30-60 min separate or combined rehab or O/M eval
equipment
standard lane magnifying devices optical/non-optical equipment VF instrument color vision contrast sensitivity scotoma test maybe SLO or MP-1, slit lamp camera, retinal camera
fee structure
exam fees - many ways to bill
material fees - conventional glasses, magnifying devices
home visits
telescopic driving instruction
history
first impressions, psychosocial, all doctors seen: PCP, ret specialists, medical/visual, mobility/falls, activities of daily living, pt impression of vision at different distances, illumination use, devices or owned
purpose of low vision history
emotional status task analysis functional review goals communication needs with providers
distance VA
projection charts - snellen most common
light box charts - bailey lovie, ETDRS gold standard in research, high and low contrast chart versions
flip charts/handheld charts - feinbloom common clinically, ETDRS, bailey lovie
bailey-lovie chart
6m/20ft distance typical
advantages - five letters in each row task is equivalent for each row, equal contour, more letters for patients with poorer acuity
letter spacing on each row is equal to one letter width
row spacing is equal to height of letters below
contour interaction is scaled in relation to letter size
test distance can be varied with simple proportional acuity conversion
letter size follow log
increasing in 0.1 logMAR steps
20/20 = 0.0 logMar, 20/25 = 0.1 logMAR
each letter on each line is assigned a score of 0.02
ETDRS
early treatment of diabetic retinopathy sloan letters log progression NIH studies similar to bailey-lovie log letter size complicates legal blindness
feinbloom chart
designs fro vision 5 or 20 feet test distance most common test distance can be varied proportionally letter size 10-700 has 20/120 and 20/160 high contrast single optotypes better figure ground easily use eccentric viewing more realistic test conditions
office projection chart
snellen chart/letters most common acuities taken at 20 feet letter size 10-400 acuities 20/400 or better 20/200 then 20/150, some to 20/100 contrast? single optotypes? figure ground? easy to use eccentric viewing? not logMAR standard - cannot vary test distance
M notation
introduced by sloan to prevent confusion with non-metric snellen
metric system
M units specify the size of print by indicating the distance in meters at which the height of the letters of the printed material subtends 5 min of arc
2M subtends 5 min at 2 meters, 3M subtends 5 min at 3 meters
1M - 20/50 @ 40 cm
pt reads 1M at 1m = 1m/1M = 6/6 (in m), or 20/20 in ft
advantages of M notation
test distance can be varied very large effective letter size large range of possible acuities same system works for dist and near standardizes VAs across providers enhances inter-provider communication
near acuity assessment
single letter
continuous text - better simulation of real world, very different result than single letter, words or paragraphs with or without meaning, don’t be afraid to use magazine, book or newspaper as target, MN read common chart used
lighthouse near visual acuity chart
lighthouse near acuity test letter size .3M to 8M metric system - linear scale, recorded at any distance lists M notation and snellen high contrast good figure ground logMar standards - uses sloan letters eccentric viewing possible
hi/low contrast near charts
reduced contrast versions available
ex. colenbrander mixed contrast chart by precision vision
difference of 2 lines or more between high and low contrast lines - CS problem
MN read
white on black or black on white
continuous text
same number of letters in each paragraph
can calculate reading speeds words/min, allows finding of size print pt reads most quickly, allows investigation of effect of mag on reading speed
VF
confront may be adequate - apart from legal blindness determination
may need multiple assessment methods
kinetic may differ from static - kinetic may impact driving and mobility more
VF type selected depends on disease, what you need it to tell you, office availability
common VF instruments
goldmann
humphrey - 24-2 threshold, 30-2 threshold, 120 pt screener, 81 pt screener, ester man
octopus
VF testing
test used to understand function and or monitor disease
often confrontation VF is adequate
generally 5 degree or less VF may limit use of magnification, 10 degrees or more usually mag is not limited, 40 degrees or less magnification not limited, also consider scotomas, mobility instruction should be considered
amsler grid testing
may use to understand location of scotomas
right of fixation - difficult to find the next word in a sentence
left of fixation - difficult to return to next line in left column
central - can’t see anything just black
paracentral - island effect, loses text, careful with mag, won’t eccentrically view
fletcher california central test
manual way to quickly map scotomas
uses concentric grid and central fixation pt
must be able to see fixation pot - variable fixation pt sizes options
flash red laser light from behind grid along each tangential meridian - mark when light is not seen and reappears along meridian, repeat for each meridian, connect your marks to map scotoma, alternate method move light along meridian as kinetic test
hints about CA central test
3 intensities of laser available to map relative vs complete scotomas
binocular provides more realistic functional conditions
binocular results usually differ from monocular
size of fixation pt you choose will depend on VA loss
this test underestimates the number and size of scotomas
preferred retinal locus
a preferred retinal area to fixate targets
may be eccentric
may or may not be optimal location for maximizing VA
