Lecture 3 Flashcards
VEP
Objective test to determine if the patient can see. Does not tell you how well they can see, but lets us know that they have the pathway intact from the central retina to the primary visual cortex.
3 types of VEP
- Pattern reversed. Black and white alternating stripes or checkerboard squares. Most preferred.
- Sweet VEPs. Quicker, but similar to pattern VEP. Same stimulus as pattern VEP. Pattern sizes/contrast changes rapidly. Clinician can see where good response drops off to determine VA. Only few seconds of attention needed.
- Flash VEP. looks at central 20 degrees. Less than 5ms. Least preferred method.
VEP
- Test distance
- Monocular vs binocular
- 50-150 cm. Depends on size of pattern.
2. Can do both mono and bind. Bino should be at least 10% more than OD or OS alone
How to analyze the VEP readout
There are peaks (P) and trophs (N) that show amplitude.
Numbers associated with peaks and trophs are the time in ms.
Y: Amplitude
X: Time in ms.
Time from stimulus to largest amplitude wave= implicit time (latency) avg is 85-120ms
Implicit time (VEP)
AKA latency. Time from stimulus to largest amplitude wave. Usually 85-120ms.
Cardiff Cards.
- What age kids?
- What is it?
- Test distance
- Technique
- Mono or bino
- Range of VA
Kids age 1-3 years
Vanishing optotype of different pictures in a vertical presentation.
1 meter or 50 cm
See if child looks at picture or gray background. Same technique as preferential looking. Have child name the picture to make sure they actually see it!
Mono preferred, otherwise bind.
20/160 to 20/12.5 (can get better than 20/20. Acuities improve with age
When should child be able to ID letters?
End of kindergarten
How to occlude for pre school and beyond
Pirate patch, sticky patch.
Do not use childs hand or let them hold occluder. If you use occluder, you hold it. Otherwise, they will peak.
Pay close attention to posture/squinting.
What are allen pictures?
Technique
Downsides
Pictures of phone car bird cake and hand.
Recognition acuity.
Child names pictures.
Downsides: Dated, pictures do not blur equally, may over estimate VA. Does not go to 20/20
Why you shouldn’t do tumbling E test before age 8
Directional confusion. Not consistent with L and R until age 8. Up and down is easier.
Good for non-verbal adults.
Or let child hold cut out letter E and rotate it to match.
Lea symbols/HOTV
Child can use matching cards for 4 lea symbols (apple, house, circle, square) or HOTV instead of speaking.
Pre school expected acuity Early 3 years 3.5-4 years 4-4.5 years 5 year
20/60
20/50
20/40
20/30
Preferred to use letter tests such as HOTV
Acuity tests from Snellen to FPL (forced preference looking)
Snellen Whole line of Lea/HOTV Blocked lea/HOTV Cardiff FPL
After VAs, check
binocular vision
3 techniques for ocular alignment
CT, hirschberg, Bruckner, Krimsky
Binocular vision tests
Alignment Motilities NPC Vergences Stereo
Do children have binocular vision problems at birth?
Children may look eso at birth due to lid anatomy and they do have poor control of convergence in first couple weeks of life.
Is exo or eso more common in kids from birth to 10 months?
Exo
At what age should alignment, convergence, and stereo improve?
3 months AKA 12 weeks.
Normal CT values at distance and near
Distance: Ortho to 3XP
Near: Ortho to 6XP’
Eso and strab are not normal.
Angle Kappa
Angle between line of sight (fixation to fovea) and pupillary axis (center of pupil)
Is angle kappa done mono or bino
MONO
Angle kappa technique
Hold penlight 50cm in front of pt along midline while one eye is occluded.
Angle kappa results
+ Kappa: temporal displaced fovea
- Kappa: Nasal displaced fovea
Most patients have mildly positive kappa (fovea is 5 degrees temporal to center of posterior pole)
