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
preferred retinal locus detected by
amsler grid scanning laser ophthalmoscope nidek-MP1 face with feinbloom method california central test
nidek MP-1
scotoma detection
retinal photography
feedback examination - to train eccentric fixation
scanning laser ophthalmoscope
larger and more comprehensive version of MP-1
been around much longer - 1979
very large and expensive
high contrast images
retinal slicing
projects reading and fixation stimuli directly on retina
pupils
particularly important to evaluate neuro conditions
evaluating may inhibit pt ability to try devices
can go back and perform after devices is needed - do at end of exam
a lot of pts have APDs
EOMs
evaluate under or over actions
assessment of neurological function
pick large target o flight
binocularity patient types
binocular - uses both eyes typically equal VA between eyes
monocular - prefers the VA of one eye
biocular - one eye used at distance, other used at near, or can use either eye independently
retinal rivalry patients - monocular vision of better eye worsens binocularly
cover test/binocularity
very important to function and treatment
dominant eye
suppression?
may encourage suppression or patch if helps function
stereopsis and effect on mobility, driving
mono vs binocular devices
methods for measuring binocularity
cover test - large fixation point, complicated by EV and nystagmus
worth 4 dot - if they can perceive lights
10 BD tests - see 2 targets
other tests of suppression
inference from eye posture
inference from VA difference longstanding
contrast sensitivity
two patients
same corrected distance VA
visually impaired/legally blind
function differently - ADLs, mobility, use of optical devices
due to personality differences?
differences in contrast sensitivity - predicts function better than VA does
when to measure CS
assessment of VS should be performed when the patients performance does not match the expected results
may require experience
perform on EVERY vision rehab patient
wonderful communication tool with pt, family and referring doc
vistech contrast sensitivity chart
diagnostic chart
vistech or newer version functional acuity contrast test (FACT) from stereo optical
perform at 1 meter with low vision patients
perform at 3 meters with normal vision patients
diagnoses - high frequency, mid frequency and low frequency losses
may have losses in none, one, two, or all frequencies
bailey hi-low contrast acuity chart
screening chart
visual acuity taken on high contrast side
VA taken on low contrast side
contrast problem indicated when low contrast side two lines or more worse
doesn’t identify high middle or low
peli robson contrast chart
same letter size
contrast varies in groups of 3 letters
MARS contrast sensitivity chart
similar to peli robson but smaller
50 cm test distance
3 letters of same contrast
stop when miss two in a row at a contrast level
record contrast of last corrected letter
subtract letters missed prior to last correct
use shaded grid to find result of: normal, mild CS loss, moderate loss, severe loss, profound loss
weber contrast
common measure of contrast calculated difference between luminance of an object and its background divided by the brighter of the two contrast varies from 0-100% greater the percentage = higher contrast
weber contrast of common reading materials
71-75 daily newspaper 55-60 US currency 76-80 paperback books 81-85 large print newspaper 86-90 large print magazines 88-93 glossy periodicals
weber contrast of common objects
5 maroon chair maroon carpet 74 maroon chair gray carpet 64 wood door light wall 80 red illuminated sign 82 black car sunny day 32 gray car shady day
contrast threshold
defined as an object with the lowest contrast that a patient can recognize
CT is expressed as a percentage
CS is the complement (reciprocal of CT)
100%=1, 50%=2, 25%=4
as vision improves, CT decreases and CS increases
as vision worsens, CT increases and CS decreases
if reduced VA with reduction in low spatial frequencies is more difficult to see larger objects….
can’t change their spatial frequency so change contrast
higher object contrast threshold allows this patient to see better
reflector tape on stairs
red plates when eating
toilet seat brightly colored
felt tipped pen
wide lined writing paper
management plan for high frequency CS loss
lighting - directional
increased contrast of materials
increase magnification - magnifiers at near
use of closed circuit television CCTV
management plan for mid and/or low frequency CS loss
vary contrast (environmental modifications)
increase magnification (telescopes)
filters (enhancing)
mobility training
binocular CS
binocular CS is higher than monocular CS usually
binocular summation
if a low vision patient demonstrates binocular summation, then binocular devices should be encouraged at distance and near
low vision patients without binocular summation should use the eye with the better CS assuming other factors such as VA and VF don’t contraindicated the use of the other eye
clinical relevancy - blurred vision
mag you need may need to be increased if CS is an issue
materials are a factor
use the newspaper when determining reading magnification - then able to read higher contrast materials also
clinical relevancy - mobility
can’t prepare for all environments
dusk, night, low contrast materials
justifies need for white cane or guide dog
color testing
why/when functional test - maculopathies result in a desaturation of color vision vocations avocations school
types of color tests
large chip D-15 dichotomous test
color vision made easy
ishihara
low vision refraction
trial frame vs phoropter
central scotoma - trial frame!
determine if phakic or pseudophakic
if phakic a refraction may be more helpful - cataracts a consideration
pseudophakes usually have minimal change
refraction often helps near normally sighted 20/25 to 20/60
may help visually impaired 20/70 to 20/160
seldom helps legally blind
refractive procedure
place habit Rx in phoropter or trial frame
ret spherical and cylinder meridians or more commonly use lensometry as starting point
subjective distance trial frame refraction using just noticeable difference or JND
just noticeable difference
smallest amount of power change necessary to differentiate variation in blur
JND = denominator of snellen/100
subjective refraction
determine spherical sensitivity - JND choices, attempt to bracket
cylinder - allow patient to rotate JCC with best single letter to find axis, bracket power using JND, cylinder power and axis equals keratometry in pseudophakes
recheck sphere
sphere check, refine cylinder axis, find axis power, sphere check
JND hints
don’t forget that your JND formula result must be divided by two for the +/- choices
may change sphere lens to keep spherical equivalent or wait and recheck sphere again at end
correct sphere and cylinder for room length if trial frame refraction performed at 10 or 5 feet
skill evaluation
may ask patient to perform a task
allows better understanding of struggles - appropriate devices, appropriate referrals
may use home environment room
device demonstration
reassure pts that change is frustrating and you’re here to help
act as coach through process of device demo
start simple and increase in complexity
start with achievable goal
usually start with near devices
start with lower powers
explain basic principles of magnification
ocular health testing in pts referred for vision rehab
depends on pt history, VA consistent with report
if patient has recently been examined elsewhere
if patient is in care of one or more other eye care providers and sees them regularly
if some red flags contact the referring doctor
education and information
patient must be involved in decision process when deciding what devices to take home
pt needs to understand it takes time and practice to improve at using devices
pt needs to understand importance of their own motivation
explain disease process and functional implications
explain Rx/s and what they will and won’t do for the pt
additional resources should be provided to take home
referrals
guest speakers will introduce available services
pt ed on where to go from there
letters
letter writing - templates in EHR
critical to referrals and successes
release of pt care
release of Sex
referral for additional services
letter after every visit - comprehensive letter after first eval, highlight goals, functional problems, VA, VF, CS, scotomas, maybe color deficits, explain plan and propose solutions, explain additional referrals
brief letter after f/u visit - what is working for pt, plan from this point, release of care
