Amblyopia/Strabismus Flashcards
Moderate Amblyopia
20/40 - 20/80
Severe Amblyopia
20/100 - 20/400
Amblyopia Treatment
- correction of RE
- occlusion therapy (patching/atropine)
- vision therapy
How many hours a day to patch:
a) moderate amblyopia
b) severe amblyopia
a) 2 hours/day + 1 hour of near activitiy
b) 6 hours/day + 1 hour of near activitiy
How much atropine to use?
Moderate: 2 days/week (weekend)
Severe: 2 days/week may be effective
Atropine SE
- increased blood pressure
- mental confusion
- increased pulse
- dryness of mouth and throat
- loss of neuromuscular coordination
^ very rare
Hot as a hare, mad as a hatter, dry as a bone.
Angle of anomaly
Difference between the objective and subjective tropia
Harmonious ARC
- most common type
- angle of anomaly = angle of deviation
- no diplopia
Unharmonious ARC
angle of anomaly < angle of deviation
Diplopia present, but not large
Paradoxical ARC
Movement of fovea is in the wrong direction, makes diplopia worse because angle of deviation is larger than it initially was
After Image Test
Two lines are shifted horizontally, they have ARC
Horror fusions
Heterotropic patients that cannot fuse even with prisms
Visual confusion
Two maculas view two different images and they are super imposed
Infantile/congenital Exotropia
- 30-80 prism diopters
- occurs <6 months
- may be neuorological problem, especially if constant
- typically not amblyogenic because it is alternating
- decreased stereopsis
Isometropia
equal refractive error
Amblyogenic refractive error for hyperopia
> 1 D aniso, >5D OU
Amblyogenic refractive error for myopia
> 3D aniso, >8D OU
Amblyogenic refractive error for astigmatism
> 1.5D aniso, >2.5D OU
Hirschberg Test
- tested at 50cm
- difference in angle is termed lambda
Normal angle lambda: slight nasal displacement by ~0.5mm
Nasal displacement from normal represents exotropia.
Temporal - esotropia
Superior - hypotropia
1mm = 22 prism diopter
Krimsky Test
Essentially Hirschberg test, but a prism is used to assess/quantify deviation.
Stereopsis: contour testing
Laterally displaced targets which allows for monocular cues.
- Titmus fly, animals and Wirt circles
- better for detection for peripheral stereopsis (>60s of arc)
Stereopsis: global testing
Random dot targets which have NO monocular cues.
Normal stereopsis
~20 seconds of arc with contour testing and appreciation for gross random dot tests
Mallet box
- used for fixation disparity testing
- binocular cues for motor fusion
Other examples:
Vectographic slides, Bernell lantern, Wesson fixation card, Sheedy disparometer
Saccadic suppression
Suppression occurs during a saccade to suppress vision eliminating possibility of oscillopsia.
Form deprivation amblyopia
Obstruction of a clear image to the retina before the age of 6-8 years of age.
Examples: congenital cataracts, ptosis, corneal opacity.
Refractive amblyopia
Large amount of anisometropia between the two eyes, anisometropic amblyopia, or large amount of refractive error in both eyes (isometropic amblyopia)
