Stereotests & Heterophorias Flashcards
What are the principles and 2 types of stereotests?
Project 2 similar images to non~RCPs
qualitative or quantitative
Describe the TNO test
random dot, px points out images 40cm away ~ uses screening/graded plates
no monocular cues but difficult for kids
Describe the Lang test
random dot, cylindrical gratings
no glasses needed but only 200” arc
Describe polarised vectograms
2 similar views polarised perpendicular to each other at diff. angles
Describe the Titmus (WirtFly) and Randot stereotests
Both use polarised vectograms/glasses
Titmus: 40cm away, px reports which image sticks out (good stereoacuity for kids but involves monocular cues)
Randot: 40cm away, good stereoacuity range, no monocues but kids need glasses (if kids can’t do TNO do this)
Explain stereoanomalies
No stereopsis in strabismic px producing abnormal BSV or reduced vision
reduced SA due to incorrect rx or amblyopia
What are monocular cues and how do they affect stereotests?
Spatial - linear perspective, contours overlap, retinal image size of known objects
Temporal - motion parallax during movement
these enhance stereoacuity causing false -ves
Define phorias and tropias
Heterophoria: eyes deviate from fixation when dissociated disrupting fusion
Heterotropia: eye deviation is normal without dissociation, present with strong fusional stimuli
Orthophoria (no deviation upon dissociation)
How do heterophoria change with age for distance and near?
distance stable
near exophoria increases (accommodation)
Describe (de)compensated phorias and any symptoms
Compensated (well controlled, no symptoms)
Decompensated (difficult to control, can manifest to tropia/suppression/amblyopia, symptoms due to developed unstable BV system)
headaches, eye strain, excessive blinking, blurred vision, transient diplopia
