Entrance test Flashcards
Hirschberg test
- objective estimate and measurement of a deviation/strabimus
- evaluate the visual axes OU under binocular conditions at near
- useful in young/difficult patients
- WITHOUT GLASSES
- penlight held 50cm and patient fixates on it with both eyes
3 possible corneal reflex positions
- center of pupil
- nasal to the pupil
- temporal to the pupil
Positive angle lambda/kappa
- exo posture
- eye naturally sits out, reflex brings it in
- nasal to the pupil reflex
Negative angle lambda/kappa
- eso posture
- eye natually sits it, reflex brings it out
- temporal to the pupil reflex
Absence of strabismus
- if the reflex are in the same relative position compared to when the eyes are occluded
- corneal reflex should be centered in both eyes
Presence of strabismus
- reflexes are not in the same relative position
- totally different angle monocularly and binocularly
deviation and prism diopters
For 1mm of estimated deviation, it is approximately a deviation of 22 prism diopters
-FUR SURE ON BLOCK
Recording of Hirschberg
- indicate you used hirschberg
- no strabismus=ortho/symmetrical
- yes strabismus=record deviated eye, size and direction of the deviation
44pd LET
Krimsky Test
- use prisms to determine the angle of deviation seen on Hirschberg
- prisms are placed in front of the FIXATING eye until the corneal reflexes are symmetrical
- prism reflection test
- not super accurate
Base prism correction
esotropia=BO
exotropia=BI
Near point convergence
- determine the ability to converge and maintain fusion
- both eyes come in to one point
- WITH CORRECTION, good lighting, 40cm
- transilluminator is used for initial screening and if there is receeding, use red glass and then accommodative target
Basic Krimsky method
- patient look at light
- ask if they see double, if yes, more target back
- move target towards patient until they hit break point
- move the target until they hit recovery point
Break point
-patient first reports double vision or one eye loses fixation
Recovery point
-patient first regains single vision or where you notice fixation of both eyes
Normal NPC reading
- measure with ruler at bridge of nose or at glasses
- Break: 2.5cm
- recovery: 5cm(TTN)
Abnormal NPC
- repeat procedure with red/green glasses
- red is always for OD
- differentiate what each eye is doing
- result is more receding
if still abnormal,
-repeat procedure with accomodative target
Convergence and accommodation
VERY CLOSELY RELATED TO EACH OTHER
convergence-focus it
accommodation-keep it clear
Convergence insufficiency
- if a patient has convergence insufficiency and you keep repeating procedures, you’re gonna get a ton of different readings because of fatigue
- fatigue=more receding
Recording NPC
- with or without correction
- the target used
- break distance cm/ recovery distance cm
- deviated eye and direction
- diplopia or suppression
- light, red/green, accommodative
diplopia/ supression
- diplopia:double vision
- suppression: eye move
Receded NPC can cause…
- binocular vision problems
- eyestrain/asthenopia
- reading problems
- difficulty with near point tasks
Amplitude of Accommodation
- measures a patient;s ability to accommodate
- WITH GLASSES
- monocular
- in diopters
Push-up method
- method of amplitude of accommodation
- tell patient to keep letter CLEAR
- slowly move letters closer to the patient until they report blur
Measure amplitude
- measure the distance from the patient’s spectacle plane in cm
- this is near point of accommodation
Convert near point of accommodation
- cm to diopters
- 100/NPA
What size is target?
20/30ish
-too big doesn’t let patient use their full accommodative ability
Pull Away method
- method of amplitude of accommodation
- hold letter painfully close to patient(0.5cm) until they see blur
- slowly move target out until they can TELL YOU the letter
Record amplitude of accommodation
- method used
- amplitude of accommodation in Diopters
Normal amplitude of accommodation
- both eyes should be within 1D of each other
- accommodation decreases with age, can be affected by meds and disease
Hofstetter’s formula
minimum expected amplitude= 15-0.25(age of patient)
Donder’s table
-table for age and amplitude
What affects accommodation?
- decreases with age
- alcohol
- meds(CNS stimulants, cyclo)
- trauma to iris
- iridocyclitis
- diabetes/MS
Binocular vision
- allows us to appreciate many ASPECTS of a target
- minute details
- fuse image
Sensory system and binocular image
- fusion
- constructs single perception from two retinal images
- gives the distance of the target
- brain
Motor system and binocular vision
- vergences and eye movements
- muscles
- coordinates the orientation of the eyes in all distances and on your moving targets
- coordinates with accommodative system to maintain clear image
- depth and focus
Poor binocular vision can lead to…
- fatigue
- eye strain
- headaches
Binocular vision is in jeopardy with…
- eye disease: takes one eye out of commission
- strabismus: no way you can have binocular vision
- trauma: eye can not function due to trauma
When binocular vision works well…
- one image from both retinal images
- high resolution
- little disparity
Disparity
- eyes bounce back and forth because trouble with fusion
- sees double/blur
Binocular vision advantage
- depth
- more precise
- quicker
Stereopsis
- measure fine depth perception by evaluating the ability to fuse stereoscopic targets
- wear corrective lenses over Polaroid glasses
- overhead light
- 40cm
basic steps for stereopsis
- start with middle box(most difficult) and keep going until patient misses 2 in a row
- if they can’t do that row, go to the bottom row
- if can’t see those, go to top row
Record Stereo
- at N and what test used
- indicate with or without correction
- recorded in seconds of arc
Expected stereo
at near:20-30 seconds of arc
if really high, oh no do cover test
Worth 4 Dot
- assess flat fusion at N(40cm) and D
- ability to detect a small central scotoma
- do when stereo is below normal
- WITH CORRECTION
- red lens=OD
3 degrees of fusion
- simultaneous perception and superimposition(NPC break)
- Flat fusion(2 images into 1, but no depth)
- Stereopsis(binocularity is excecllent)
Why is worth 4 dot done with correction?
- you want best possible vision
- do it with habitual and if you think you should do it again after refraction, do it again
What do the dots look like?
- red on top
- white on bottom
- green to the side
What does it mean based on the number of dots the patient sees?
4 dots: normal flat fusion
2 dots: only OD being used, OS suppressed
3 dots: only OS being used, OD suppressed
5 dots: diplopia(ONLY 5 DOTS NO MORE)
Uncrossed diplopia
- eso deviation
- red dots all on right and green dots all on left
Crossed diplopia
- exo deviation
- red dots all on left and green dots all on right
worth 4 dot hyper deviation
- vertical diplopia
- red dots on bottom, green dots on top=right hyper
- red dots on top and green on bottom=left hyper
Testing for scotoma at Near
- make sure there is normal worth 4 dot test at near
- have patient tell you if there is a change in what they see
- move flashlight AWAY
- STOP when patient says there is a change in the number of dots of at 10 feet.
Analyze W4D at near
- if it changes to see 2 dots, OD is working, OS is suppressed, cover OD, if dots come back, scotoma is only there with fusion.
- if the dots do not come back, the scotoma is unilateral
Recording W4D
-record the distance
Fusion at distance and near
fusion at distance, suppression OD at near
diplopia, eso with right hyper at N
