Pupils & Pupillary Distance

Comprehensive flashcards covering clinical examination of pupils, pupillary pathways, pupillary defects, and pupillary distance (PD) measurements.

What pupil testing procedures are included in a standard pupil evaluation?

Pupil size in light and dark, color and shape assessment, direct and consensual responses, APD testing, and accommodative response testing.

What aspects are evaluated during pupil testing?

Size/anisocoria, reactions in light and dark, direct and consensual responses, near reaction, and APD/reverse APD.

How does aging affect pupil size?

Aging causes a smaller pupil diameter.

How does aging affect the pupil's reaction to light?

The reaction to light is reduced in amplitude and less rapid.

Why are aging pupils more susceptible to abnormalities?

Due to ischemia and structural abnormalities.

What is hippus?

A normal pulsating movement of the pupil.

What are the characteristics of hippus?

Rhythmic over seconds, $1\text{--}2\,\text{mm}$ in amplitude, bilateral, caused by balance between parasympathetic and sympathetic systems, and of unknown significance.

What is anisocoria?

Unequal pupil sizes between the two eyes.

What are the three major causes of anisocoria?

A normal variant, disturbance in parasympathetic or sympathetic pathways, and structural disorders of the iris itself.

What amount of anisocoria is considered physiologic?

A difference of $\le 1\,\text{mm}$ between pupils.

What does new-onset or larger anisocoria usually suggest?

A neurological, ocular, or pharmacological cause.

What does anisocoria that is worse in bright light indicate?

The larger pupil is abnormal, suggesting a parasympathetic problem.

What does anisocoria that is worse in dim light indicate?

The smaller pupil is abnormal, suggesting a sympathetic problem.

How common is physiologic anisocoria?

It occurs in approximately $50\%$ of the normal population.

What is the typical pupil size difference in physiologic anisocoria?

Approximately $0.3\text{--}0.4\,\text{mm}$.

How does physiologic anisocoria behave under different lighting conditions?

The degree of anisocoria remains the same under all conditions.

Can physiologic anisocoria switch sides or be transient?

Yes, it may occasionally switch sides or be transient.

When is no further workup needed for anisocoria?

When pupils are structurally normal, react normally to light and near, and maintain the same degree of anisocoria in light and dark conditions.

What part of the autonomic nervous system causes pupil constriction?

The parasympathetic nervous system.

What state is associated with parasympathetic activity?

Restoration, calm, or "rest and digest."

What part of the autonomic nervous system causes pupil dilation?

The sympathetic nervous system.

What state is associated with sympathetic activity?

Stress response or "fight or flight."

Do humans have voluntary control of their pupils?

No, pupil function is autonomic and involuntary.

Why is pupil assessment a powerful clinical tool?

Because it evaluates autonomic neurological pathways.

What is the result of the pupillary light reflex?

Pupil constriction (miosis).

Why do both pupils constrict when light is shined into one eye?

Signals cross within the midbrain, producing direct and consensual responses.

What occurs when shifting fixation from far to near?

The eyes converge, the lens accommodates, and the pupils constrict.

What are the three components of the near reflex triad?

Convergence, accommodation, and miosis.

What is light-near dissociation (LND)?

A condition in which pupils constrict poorly or not at all to light but constrict normally to a near target.

What causes light-near dissociation?

Disruption of afferent fibers in the pretectal region.

How are light and near responses affected in LND?

Light response is diminished while near response is preserved.

What is the approximate near-to-light fiber ratio in LND?

$30:1$.

Can a patient have a normal light reflex with an absent near reflex?

No. There is no circumstance where the light reflex is present but the near reflex is absent.

What conditions may cause light-near dissociation?

Argyll-Robertson pupil, dorsal midbrain syndrome, encephalitis, meningitis, demyelination, pretectal lesions such as pineal tumors, diabetes, aberrant CN III regeneration, and bilateral afferent disease.

What are the characteristics of an Argyll-Robertson pupil?

Bilateral, asymmetrical, miotic, irregular pupils with light-near dissociation.

How do Argyll-Robertson pupils respond to light?

They show virtually no response to light.

How do Argyll-Robertson pupils respond to near fixation?

They show a brisk near response.

What is visual acuity like in Argyll-Robertson pupils?

Visual acuity is typically normal.

What disease is classically associated with Argyll-Robertson pupils?

Tertiary neurosyphilis.

Where is the lesion located in Argyll-Robertson syndrome?

In the pretectal area of the midbrain.

Why is the near response preserved in Argyll-Robertson syndrome?

Near reflex fibers bypass the damaged pretectal area through a different cortical pathway to the Edinger-Westphal nuclei.

What is a fixed pupil?

A pupil that shows no reaction to light or accommodation.

What can cause a fixed pupil?

Pharmacologic blockade, trauma, inflammation, traumatic mydriasis, iris damage or atrophy, sphincter tears, posterior synechiae, acute angle closure glaucoma, structural abnormalities, tumors, IOL-related issues, surgical damage, or Adie's tonic pupil.

Which topical drugs may affect pupil function?

Naphcon and Visine.

Which systemic drugs can cause miosis?

Heroin, morphine, and codeine.

Which systemic drugs can cause mydriasis?

Dramamine, cocaine, levodopa, antihistamines, belladonna, and jimsonweed.

How does 1% pilocarpine help diagnose pupil abnormalities?

It constricts compressive CN III palsy pupils and Adie's tonic pupils but not all pharmacologically dilated pupils such as atropine-induced dilation.

What are examples of afferent pupil defects?

APD, light-near dissociation, and Argyll-Robertson pupil.

What are examples of efferent pupil defects?

Adie's tonic pupil, Horner syndrome, midbrain lesions, and third nerve palsy.

What is the typical appearance of an Adie's tonic pupil?

The affected pupil is initially larger but may become smaller over time.

Is Adie's tonic pupil usually unilateral or bilateral?

Typically unilateral, but it can become bilateral.

What systemic finding is associated with Adie's tonic pupil?

Decreased deep tendon reflexes, especially the Achilles reflex.

How do Adie's pupils react to light?

Poorly, with vermiform movements.

How is Adie's tonic pupil tested?

Using dilute pilocarpine ($0.125\%$ or $0.1\%$).

Why does dilute pilocarpine constrict an Adie's pupil?

Because denervation hypersensitivity causes the affected pupil to respond more strongly than the normal pupil.

Which parasympathetic agonists cause pupillary constriction?

Pilocarpine, methacholine, and physostigmine.

Which parasympathetic antagonists cause dilation?

Atropine, tropicamide, cyclogyl, and botulinum toxin A.

Which sympathetic antagonists are listed in the lecture?

Thymoxamine and dapiprozole.

Which sympathetic agonists are listed in the lecture?

Phenylephrine and hydroxyamphetamine.

What is the purpose of the pupil examination procedure?

To assess the afferent and efferent neurological pathways responsible for pupillary function.

What equipment is needed for pupil testing?

A pupil gauge, transilluminator, and distant fixation target such as a 20/400 letter.

What lighting should be used at the start of pupil testing?

All lights on with the stand light illuminating the face equally from the side.

Should the patient's glasses be on or off during pupil testing?

Off.

How is pupil size in light measured?

The patient fixates on a distance target while the examiner measures pupil size in full light with a pupil gauge, recording to the nearest $0.5\,\text{mm}$.

What additional observations are made during pupil size assessment?

Iris color and pupil shape are noted.

How is pupil size in dark measured?

Reduce room illumination and remeasure pupil size under dim lighting conditions.

What does a light-to-dark pupil difference of only 1 mm or less suggest?

The lighting conditions were likely incorrect and measurements should be repeated.

How can pupil measurements be improved in dark-eyed patients under dim light?

Use a penlight slightly in front of and below the chin aimed upward to illuminate the eye without affecting the pupil.

How is pupil color recorded?

Right eye over left using Bl, Gr, Hz, or Br.

How is pupil shape recorded?

Right eye over left using R, O, or Irg.

How is pupil size recorded?

Either as light and dark values for each eye or as right-over-left values in light and dark conditions.

How is the direct pupillary response tested?

Shine light at one pupil from $5\text{--}6\,\text{cm}$ for $2\,\text{seconds}$ and observe constriction in the illuminated eye.

How is the consensual pupillary response tested?

Observe constriction in the fellow eye while light is directed into the opposite eye.

How are direct and consensual responses graded?

On a $0\text{--}4$ scale where $0$ is no movement and $4$ is very rapid.

What is an APD?

An afferent pupillary defect, also called a Marcus Gunn pupil when present.

What other names are used for APD testing?

The swinging flashlight test and the pupillary escape test.

What lighting is used during APD testing?

Lighting is reduced further than for standard pupil testing.

What should be observed before swinging the flashlight during APD testing?

Hippus and its amplitude.

What is the critical observation during the swinging flashlight test?

Pupil dilation with direct light stimulation.

How many times should the swinging flashlight test be repeated?

At least three times.

What indicates a positive APD?

The pupil dilates when directly illuminated.

How is a positive APD recorded?

Example: APD + OD.

How is a negative APD recorded?

-APD.

What causes an APD?

Impaired function of the sensory retina or optic nerve, or a lesion involving the optic tract causing reduced stimulation of the Edinger-Westphal nucleus.

What optic nerve diseases can cause APD?

Optic neuritis, ischemic optic neuropathy, traumatic optic neuropathy, compressive lesions, and optic nerve drusen.

What retinal disorders can cause APD?

Retinal detachment, macular disease, and central retinal artery occlusion.

Can asymmetric glaucoma cause APD?

Yes, especially when visual field damage is asymmetric.

Which ocular conditions do NOT cause RAPD?

Refractive error, corneal opacities, lenticular opacities, vitreous opacities, and malingering/hysteria.

How can a questionable APD be confirmed?

Using a $0.3\text{-log-unit}$ neutral density filter during the swinging flashlight test.

What effect does a neutral density filter have over a normal eye?

It induces a slight but symmetric APD.

What effect does a neutral density filter have over an eye with a mild APD?

It magnifies the APD.

How is APD quantified with neutral density filters?

Place filters over the normal eye in $0.3\text{-log-unit}$ increments until the defect disappears, then bracket the endpoint.

What happens to the pupils when an object is moved close to the eyes?

The eyes converge and the pupils constrict together.

Why must accommodative pupil response be tested separately from light responses?

Because it is controlled by a different neural center.

When is accommodative pupil testing usually unnecessary?

When all other pupil tests are normal.

With which test is accommodative response commonly combined?

Near point of convergence testing.

What are the testing conditions for accommodative pupil response?

Full light, usually with glasses off, using both distance and near targets.

How is accommodative response tested?

The patient rapidly shifts fixation from a distance chart to a near target approximately $10\,\text{cm}$ from the face and just below the line of sight.

What is the normal accommodative pupil response?

Both pupils constrict equally and quickly.

How is accommodative response recorded?

ACC +/+ or ACC ++/++ for a very rapid response.