XT Flashcards
posterior embryotoxin
anteriorly displaced schwalbes line
-increased risk for glaucoma
how much does having a posterior embryotoxon increase someones risk for glaucoma
50%
axenfeld syndrome
posterior embryotoxin + glaucoma
Reiger’s anomaly
embryotoxin + glaucoma + iris atrophy
Axenfeld syndrome + iris atrophy
Rieger’s Syndrome
embryotoxin + glaucoma + iris atrophy + systemic problems
embryotoxin + glaucoma + iris atrophy + systemic
types of XT
infant
acquired
secondary
micro
acquired XT
acute
mechanical
secondary XT
sensory
mechanical
intermittent acquired XT
after age 6m
deviation present more when tired
50% have basic XT and the other 50% will have either convergence insufficiency or divergence excess
types of acquired XT
basic XT (equal D and N)
divergence excess
convergence insufficiency
infantile/congenital XT
large deviation of 30-80 that occurs prior to 6m of age. Because it is usually alternating, infantile usually does NOT lead to amblyopia, but it can result in a reduction iin stereopsis. Patient’s may have associated neurological problems, esp in cases of a constant infantile XT
acute acquired XT
occurs after 6m of age.
acute acquired XT
characterized by sudden onset, constant exodus deviation. potential etiologies include neurological issues, trauma, or a decompensated phoria
mechanical acquired XT
due to physical restriction of an EOM (type 2 Duanes, graves, etc). Patients will NOT have full versions due to the EOM restrictions
sensory XT
after age of 5; it is more common in adults with acquired vision loss in one eye, resulting in a loss of a stimulus to fuse. Treatment involves correcting the vision loss, if possible
consecutive XT
iatrogenic, secondary to over correction of an ET during strabismus surgery
micro XT
exo deviation of less than 10 PD that is usually undetectable with CT. Similar to micro ET, it is associated with small suppression scotoma that may be confirmed with a 4BO test. Very uncommon
treatment for intermittent, acquired XT
VT, BI, over-minusing the distance RX
prism for XT
BI
lenses for XT
more minus, increased accommodation, eyes turn in. Over minus best for XT
-be sure to look at AC/A
fusion and BV
3 bad in strabismus
- 2 clear images
- same size
- fall on corresponding retinal points
counteracting diplopia and confusion
the brain may suppress an image in the strabismic eye, or may develop ARC
ARC
a sensory adaptation that must develop before age 5. Only occurs under binocular viewing conditions. Under monocular viewing conditions, the deviated eye will use the fovea to fixate the target
the non foveal point in the deviated eye that is viewing the object becomes “linked” to the fovea of the fellow (non deviated) eye. The new ARC ensures that the object will be perceived in the same visual direction in each eye, thus eliminating diplopia and confusion
NRC
present when the fovea of each eye corresponds to the same visual direction in space. if a patient develops strabismus, the fovea of one eye will be deviated compared to the fellow eye, resulting in diplopia and condition
ARC and ET
nasal non foveal point
ARC and XT
temporal non foveal point
angle of anomaly
distance between the “new fovea” and the actual fovea
difference between the objective angle of deviation (the deviation measured by CT) and the subjective angle of deviation (the patient’s perception of the magnitude of the deviation)
harmonious ARC
present when the angle of anomaly equals the objective angle of deviation. In other words, the new foveal point of the deviated eye corresponds with the fovea of the fellow eye so that the subjective angle of deviation is zero. The patient WILL NOT have symptoms of diplopia or confusion. This is the most common type of ARC
-the Fn of the deviated eye is constantly changing, depending on where the patient is looking., At any point in time, the point on the retina that is hit by the object in the deviated eye will become the Fn and will be linked to the f of the fellow eye under binocular conditions
UHARC
present when the angle of anomaly is less than the objective angle of deviation. in other words, a point in between f and fn (where the object hits the retina) in the deviated eye becomes linked to f in the fellow eye. the subjective angle DOES NOT equal zero, and the patient WILL have diplopia and confusion (although less than with NRC) because there is not perfect correspondence between the two eyes
CT=10BI
Maddox=5BI
type 1 paradoxical ARC
occurs when the point used to fixate the object in the deviated eye is further away from the fovea than fn (whereto object hits the retina). In other words, the subjective angle of deviation is greater than the objective angle of deviation. Both the subjective and objective angles of deviation are in the same direction (both esophaguses or both exo)
CT=10BO
Maddox=5BO
type 2 paradoxical ARC
occurs when fn moves in the direction OPPOSITE to the deviation, causing the subjective and objective angles of deviation to be in opposite directions. Patients will have worse diplopia and confusion than if they had NRC
paradoxical ARC in ET
when fn is TEMPORAL to f in the deviated eye
paradoxical ARC in XT
when fn is NASAL to f in the deviated eye
harmonious ARC
angle of anomaly=objective angle and deviation-no diplopia
unharmonious ARC
angle of anomaly < objective angle of deviation-diplopia is present but less than with NRC
type 1 paradoxical ARC
angle of anomaly objective angle-greater diplopia than with NRC
type 2 paradoxical ARC
angle of anomaly>objective angle of deviation-greater diplopia than with NRC
after image test
detects ARC. A line light image is flashed before each eye separately, with one eye receiving a horizontal image and the fellow eye receiving a vertical image. If the patient has NRC, the patient will see a plus sign (regardless of whether there is a deviation present). If the two lines are shifted horizontally, the patient has ARC
horror fusionis
patients who have a tropia and cannot obtain fusion with prism correction. The patient will report the images become closer together with the addition of prism, but the images will eventually jump over each other without fusion
what tests can detect suppression
W4D, 4BO, and Bagolini lenses
bagolini lenses
good for ARC and suppression. they are Plano, clear, striated lenses that produce a line image 90 degrees from the orientation of the striations when the patient views a light source (similar to Maddox rod). The lenses are oriented so the right eye sees a line oriented as / (striations at 45 degrees) and the left eye sees a \ (striations at 135 degrees)
most sensitive test for retinal correspondence
bagolini lenses
bagolini: /
OS suppression
bagolini: \
OD suppression
Bagolini: X
NRC if cover test shows no tropia
HARC if cover test shows tropia
bagolini: V
ET with NRC or UHARC
bagolini: ^
XT with NRC or UHARC
4BO test
detects a small suppression scotoma in a patient with a microstrabismus (less than 10) that cannot be detected on CT (the patient will likely have a mildly reduced VA without an apparent ocular etiology). As the patient views a distant target, a loose 4BO prism is introduced in front of one eye and the clinician observes the movement of both eyes.
normal 4BO test
OS makes an outward moment and then re-fixates on the target
4BO OS suppression
OD moves in and OS moves out due to Herings law. However, OS will not move back in
4BO OD suppression
left eye never moves
zero degree fusion
no fusion, monocular/supression
first degree fusion
superimposition targets. testing uses two very different targets, patients will have diplopia as the targets are difficult to suppress used in anti-suppression therapy
second degree fusion
flat fusion
testing uses identical targets with suppression checks. patients do NOT have diplopia. The image is single but is NOT in stereo. Requires motor fusion
Third Degree fusion
ultimate sensory fusion characterized by stereopsis. Requires motor and sensory fusion
visuoscopy
detects EF, which occurs when a patient uses a non-foveal point to fixate on object in the deviated eye under monocular conditions. The patient is asked to look in the center of a grid target in the direct ophthalmoscope under monocular conditions. The examiner views the location if the foveal light reflex in relation to the center of the grid
visuoscopy: FLR centered
no EF
visuoscopy: grid superior to FLR
superior EF
visuoscopy: grid inferior to FLR
inferior EF
visuoscopy: grid temporal to FLR
T EF
visuoscopy: grid nasal to FLR
F EF
tests for EF
VHS
- visuoscopy
- haidengers brushes
- MAxwells spot
- Monocular Hirschberg
Bruckner
used to detect strabismus, anisometropia, and/ormedia opacities in infants. The examiner uses a direct Oscope 80-100cm away from the patient on the midline to view the red reflexes of the two eyes as the patient views the lights, the Brightness of the red reflexes are compared to each other
deviated eye on bruckner
brighter
darker eye on Bruckner
SOS
- smaller refractive error eye
- opacity
- straight eye
when should infantile ET be treated
should be corrected with surgery prior to 2 years of age in order to increase the likelihood of BV and stereopsis following correction of the deviation
treatment guidelines for strabismus
optical correction plus or minus lenses VT prism patching or atropine EOM surgery