Unit 5 Flashcards
types of deviation?
-eso
-exo
-hypo
-hyper
3 binocular tests in free space
-cover test
-EOM
-ROM (range of motion)
-stereopsis
binocular vision testing w. a phoropter?
von graefe
why is binocular vision important?
- single vision
- steropsis
- enlargement of the field of vision
- compensation of the blind spot
- prevents diplopia
eso deviation
-inward misalignment
-BASE OUT PRISM
-can be refractive or nonrefractive
accomodative esotropia
-most common type of childhood esotropia
-high hyperopid refractive errors
-treated by prescribing plus lenses, which may or may not fully correct the deviation
Exo deviation
-outward misalignment
-Base IN prism
-Small exophoria (<10Δ), usually greater at near, is common in the normal population
-Also common for newborns to have a transient exotropia in the first few months
convergence insufficiency (CI)
exo is larger at near
-may be treated using excercies or prisms
hyper deviations
-upward misalignment
-Base DOWN prism
hypo deviation
-downward misalignment
-Base UP prism
Ocular motility /EOM testing
-Determine if the eyes acheive each position together.
~smoothly, accurate, fast and equal (SAFE)
-normal results will show equivalent movement of the eyes into each position
~documented as FULL
-if the eye do not move equally together, further EOM testing is needed
stereopsis testing assesses??
-the ability to use both eyes
-the brains ability to fuse the slightly difference image from each eye into one three-dimensional image
when is steropsis often done?
-during the pediatric screening
-adults who present with history of strabismus, new complaints of diplopia, or self-reported problems with depth perception should be tested
how many positions do we analyze during EOM
9 positions of gaze
von graefe method ; Lateral phoria
-Ensure prism adaptation has a minimal effect, the letters should only be made visible for brief 1 second flashes.
-Occlude the right eye with the handheld occluder, then remove and ask if the top letter is to the right or left of the bottom letter.
-Reduce the base in prism (in front of the right eye) accordingly until the letters line up ‘like buttons on a shirt
von graefe method ; Vertical phoria
-usually measured after the distance lateral phoria
-reduce the base up prism in front of the left eye until the px reports that the two letters line up like headlights on a car
3 systemic conditions with ocular involvement that can impact the prescription
-thyroid eye disease
-myasthenia gravis
-multiple sclerosis
thyroid eye disease (TED)
-graves eye disease, graves orbitopathy
-autoimmune inflammatory disorder that can cause immune cells to infiltrate the EOMs
-there is swelling of the fat behind the eyeball cause the eye to buldge forward (EXOPHTHALMOS)
-may cause double vision
(prisms or patching may be used to relief diplopia)
how much prism for von graefe
12 base in OD
6 base up OS
Myashenia gravis
-an autoimmune disease that affects the transmission of impulses between nerves and muscles and results in muscle weakness
-about 90% of ppl with MG have ocular involvement (ptosis and diplopia are first signs)
-prisms or occlusion therapy may be needed
multuple sclerosis
-chronic immune-mediated disease that attacks the central nervous system (MS damages myelin)
-interripts nerve impulses traveling to and from the brain, spinal cord and eye
-effects on the eye may include ; optic neuritis, nystagmus, diplopia
what condition does an ice cube help with ?
Myasthenia Gravis
what condition does optic neuritis relate to
Multiple Sclerosis
Amblyopia
-early detection and treatment is so important
-if left untreated it can result in permanent visual defect or loss of depth perception
-if vision in the “good” eye is lost down the road, one might suddenly be unable to work or drive
Spectacle correction in children
-primarily done by objective means until the age of 6
-limited cooperation
-questionable reliability
-must consider:
the pxs VA needs according to age
-accomodative elements
-risk of amblyopia
many young children with strabismus are hyperopic or mnyopia
hyperopia and require glasses
can gls fix children with fully accommodative esotropia
glasses fully correct the deviation
-GIVEN the full amount of plus and px wears FT
can gls fix children with partially accomodative esotropia?
-gls lessen the deviation
-sx may be required
do all children with starbismus have a refractive error?
no, some children may be emmetropic or have minimal refractive error.
-there would be little or no improvement in the strabismus or VA
spectacle correction with prism
-adults are often prescribed prism to help control diplopia
-sometimes given a trial of fresnel prism
-range 1 to 40Prism
-can be orientated BD, BU, BI, BO
convergence insufficiency
-most commonly prescribed eye exercises are used to treat convergence insufficiency
-Aim: to increase convergence ability
-taught in office and carried out at home
-BI prism may be used to help manage CI in severe cases
CI exercise = Pencil push ups
-A pencil is held at arm’s length and brought toward the nose until the patient reports seeing double
-Goal is to keep the target clear and single
-Patient tries to get the target closer and closer each day
Alternative CI excersises - Stereogram Cards
-a card consists of two similar images
-Patient holds the card at 40 cm and a pen in front of it at 20 cm
-Patient focuses on the pen, converging the eyes to elicit physiological diplopia
-Once the exercise is done easily the patient is asked to practice it without the pen
-used to fuse the two images into one
excercise follow up visit
-specific data is used to evaluate the effectiveness of the treatment
~deviation
~near point convergence
~fusional convergence amplitudes
allow comparions for pxs when a change in rx like..
-dial in the old and new values and have the px compare
-put the new rx in a trial frame and let them compare
-use flippers to illustrate a change in sphere over the current specs. This is useful when discussing an increase in ADD powers and verifying working distance
is it normal to have large changes in astig?
these are no common and may suggest a refraction error/cortical cat/ lid lesions creating corneal distortions
-cyl changes are hard to adapt to especially if they are not oblique
can myopia decrease?
yes, particulary in pxs in their 20-30s but be extremely careful especially if no symptoms
things to know if they are refracting in a smaller room
-remember you may be only refracting at 20ft not infinity so the final result may be a little over plussed (ex; +0.17 with a 20ft correction)
-some practitioners may add an extra -0.25 to compensate for the shorter room
