BCSC Neuro-Op Flashcards
What is the pattern deviation plot of a visual field?
It reports the analysis of sensitivity values based on age-expected values for all points tested after shifting (by the 7th highest point). This helps account for media opacities, although optic neuropathy may also cause total deviation depression without pattern deviation abnormalities.
What is the false-positive rate for a visual field?
frequency of patient signalling light when no light is displayed
What is the false-negative rate for a visual field?
Frequency of patient failing to signal when a target brighter than the previously determined threshold for the same spot is displayed
What are fixation losses on a visual field?
the frequency with which the patient signals seeing a light when it is presented in the physiologic blind spot (e.g., 4 signals out of 21 times presented)
What are the two types of contrast sensitivity tests?
Grating tests (give contrast threshold vs. spatial frequency function) and Letter tests
Can contrast sensitivity be diminished in the absence of visual acuity decrease?
Yes
Is contrast sensitivity testing specific for optic nerve dysfunction?
No
How does photostress recovery testing differentiate between optic neuropathy and other etiologies of decreased vision?
Patients with optic neuropathy demonstrate normal recovery times (30 seconds) from photostress (bright light fixation for 10 seconds), while patients with maculopathy or ischemia show slowed recovery from photostress (90-180 seconds)
What is done in PAM (Potential Acuity Meter) testing?
Optotypes are projected onto the retina through a dilated pupil, providing an estimate of best potential visual acuity
How can true edema and pseudoedema of the optic disc be differentiated?
On FA, a truly swollen disc will leak, while pseudoedema (as in LHON) will not leak
What type of light source does OCT use?
near infrared
What is visual evoked potential recording?
Electrical signals produced in response to a visual stimulus are measured via electrodes placed on the scalp overlying the occipital cortex
In which situations is VEP particularly helpful?
1) Patient unable to communicate, 2) confirmation of intact visual pathways in patient with suspected non-organic disease
What does electroretinogram (ERG) measure?
The electrical activity of the retina in response to various light stimuli under different states of light adaptation.
How is electrical activity measured for an ERG?
With electrodes embedded in a corneal contact lens worn for testing
What are the major components of the electrical waveform generated by ERG?
a-wave (photoreceptors), b-wave (inner retina: Muller and ON-bipolar cells), c-wave (RPE, photoreceptors)
What are the 3 forms of ERG?
Full-field ERG, Pattern ERG, and Multi-focal ERG
Is the multifocal ERG signal usually normal or abnormal in optic nerve disease?
Normal
What are common maculopathies and retinopathies that can present similarly to optic neuropathy?
1) Acute Idiopathic Blind-Spot enlargement, 2) MEWDS, 3) Cone Dystrophy, 4) Vitamin A deficiency, 5) Hydroxychloroquine and chloroquine retinopathy, 6) Cancer-associated retinopathy, 7) Melanoma-associated retinopathy
With what findings do patients with optic neuropathies present?
visual acuity loss, visual field loss, dyschromatopsia, RAPD
What are the 3 major groups of ganglion cell nerve fibers entering the optic nerve?
1) Papillomacular fibers, 2) Arcuate fibers, 3) Nasal radiating fibers
What types of scotomata result from damage to the papillomacular fibers?
1) cecocentral scotoma, 2) paracentral scotoma, 3) central scotoma
What types of scotomata result from damage to the arcuate fibers?
1) altitudinal defect, 2) nasal step defect
What types of scotomata result from damage to the nasal radiating fibers?
1) temporal wedge defect