Neuro-Ophtho

Question 1

The three components of a neuro-ophthalmologic examination

Answer 1

1. Afferent vision pathways: visual acuity, visual fields, color, stereovision, and optic fundus exam
2. Efferent pathways of ocular motility: saccade, pursuit, vestibulo-ocular and opticokinetic test- ing, cover–uncover testing, and use of “red glass”
3. Afferent and efferent pupillary tests: response to light, near stimulus, and sometimes response to eyedrops

Question 2

The best eyedrops for pupil dilation

Answer 2

1% tropicamide (brand Mydriacil)

Muscarinic antagonist

Question 3

Testing visual acuity (afferent sensory)

Answer 3

Snellen vision test is the main component.

Peripheral acuity may be tested by having the patient fix their eyes on a target (often your nose) and respond to peripheral stimuli.

Question 4

Testing color vision

Answer 4

Performed one eye at a time

The Ishihara color test is one of the best for this assessment (photo attached). Of note, The first number in the Ishihara book is a 12 and is not pseudo-isochromatic. This is your control.

Question 5

Stereo visual acuity test

Answer 5

Titmus Stereoacuity Chart is most commonly used

There are nine little diamonds, each of which consists of four circles, one circle at each corner of the diamond. One of the four circles is three-dimensional and the other three are not. The task is a forced-choice test that asks the patient to identify which of the four circles appears elevated or three-dimensional. These stereo images range from 800 to 40 seconds of arc. The smaller the number in seconds of arc perceived, the better the stereoacuity.

Question 6

The blocks listed in “Zen and the art of viewing the optic fundus”

Answer 6

Not knowing your own refraction (also if the pt wears glasses, you may need to look through their glasses to see properly)

Not dilating the patient

Not realizing where you are focused (Start at 0 and go a bit into the red numbers (minus lenses or myopia) or the green numbers (plus-lenses—less commonly a problem—hyperopia)

Not being close enough with the ophthalmoscope (you should be 1-1.5 inches from the patient’s cornea)

Not being confident of your abilities

Not knowing what you are looking for

Question 7

Riddoch phenomenon

Answer 7

The ability to detect movement in the periphery even when objects, colors, and finger counting in the periphery cannot be identified.

Question 8

Convention for presenting visual fields

Answer 8

Record your diagram of the visual field as the patient would see it through their own eyes

Question 9

A full test of visual mobility requires testing of:

Answer 9

1. Smooth pursuit through all occulomotor regions
2. Saccadic refixations, horizontal and vertical.

Question 10

Assessing refixation saccades

Answer 10

You are primarily looking for hypermetric overshoot or hypometric undershoot and an accompanying corrective saccade.

Internuclear ophthalmoplegia can also come out on this part of the exam.

Ocular lateropulsion (preference towards or away from the side of a CNS lesion) may be observed.

Question 11

Assessing smooth pursuit

Answer 11

Pursuit must be performed with a SLOW moving stimulus.

Here you are looking for inability to maintain smooth pursuit and the need for corrective saccades, or complete replacement of smooth pursuit by a series of saccades.

Question 12

Near-light dissociation

Answer 12

Poor light retraction, good near retraction

Indicates one of the three following:
1. Neurosyphilis (Argyll Robertson pupil)
2. Adie’s tonic pupil (parasympathetic denervation of the afflicted pupil)
3. Dorsal midbrain syndrome

Question 13

Argyll Robertson pupil is ___ while Adie’s pupil is ___.

Answer 13

Argyll Robertson pupil is bilateral while Adie’s pupil is unilateral.

Question 14

How to definitively diagnose Adie’s pupil

Answer 14

Compare light response to 0.1% pilocarpine response.

Adie’s pupil does not respond to light, but does respond to pilocarpine.

Question 15

1% pilocarpine

Answer 15

Should constrict any “normal” pupil that is dilated due to CN3 damage, but will NOT overcome a pharmacologic blockade.

Some accidental cases may be due to atropinics in perfumes or deodorants, or be due to accidental contamination by a medical professional.

Question 16

5% Cocaine test

Answer 16

For Horner’s syndrome. A positive test confirms the presence of Horner’s syndrome.

Using this test, a pupil with sympathetic damage and Horner’s syndrome, no matter at what anatomic level, will produce a pupil that dilates poorly to cocaine, whereas the normal pupil dilates quickly.

Of note: You should only give 2 drops. More than that per eye may result in corneal erosions.

Question 17

Paredrine test

Answer 17

Differentiates a 1st/2nd order nerve injury from a 3rd order nerve injury in Horner’s syndrome

If the first or second neurons of the oculosympathetic system have been damaged and the final common pathway is intact, the third-order (ganglion cell) neurons are able to produce, transport, and store norepinephrine.

When Paredrine is installed, the pupils normally dilate because norepinephrine is released. But, if the 3rd order neuron is damaged, the eye will not respond.

As a reminder, the nuclei of the 3rd order sympathetic neurons here are in the superior cervical ganglion.