Starting With The Basics:
Evaluating a patients pupils starts when you first meet the patient. You are being trained to be a very astute observer. Therefore, the patient's pupil size and equality are something you should mentally note and observe in the waiting room. Furthermore, you should note the way the patient walks, carries their head, their speech pattern, facial features, e.g., scars, lip soars, redness of their eyes, anatomical location of their eyes, etc. These observations could help guide the direction of your case history and ultimately other testing.

The pupillary light reflex is a four neuron arc. The first neuron connects the retina to the pretectal nucleus in the midbrain at the level of the superior colliculus. The second neuron (internuncial neurons) connects each pretectal nucleus to both Edinger-Westphal nuclei, thus explaining why a unilateral light stimulus evokes a bilateral pupil constriction. The third neuron connects the Edinger-Westphal nucleus to the ciliary ganglion. The fourth neuron leaves the ciliary ganglion and innervates the sphincter muscle.
OCULOSYMPATHETIC NERVE PATHWAY TO THE EYE
The sympathetic nerve supply to the eye is a three neuron arc. The first neuron (Preganglionic) starts in the posterior hypothalamus and terminates in the ciliospinal center of Budge. The second neuron (Preganglionic) passes to the superior cervical ganglion. The third neuron (Postganglionic) joins the ophthalmic division of the trigeminal nerve to reach the ciliary body and the pupil dilator muscle via the nasociliary and long ciliary nerves.
Anisocoria: The two pupils are not of equal size.
Light-near dissociation, refers to a condition where the light reflex is absent or abnormal but the near response is intact. There is no clinical condition in which the light reflex is present and the near response is absent.

What follows are only several ways of recording your pupillary findings there are of course others.
Recording Your Observations And Findings

Iris Color	Pupil Size	Direct And Consensual Pupil Reflex	Accommodation Pupillary Reflex	Pupil Shape	Afferent Pupil Defect
Green/Green Gn / Gn	4mm/4 mm	3 / 3__3 / 3	++ / ++	Round/Round R/R	- APD / OU

The speed of the pupil reaction can be broken down in the following way:

Brisk: = 4 To 3

Sluggish: = 2 To 1

None: = 0

Accommodation:

Brisk: = ++

Sluggish:= +

None: = 0

Abbreviations:

Color:

Grey=Gy

Green=Gn

Brown=Bn

Blue=Bu

Size = S
Direct = D
Consensual = C
Accommodation = Acc

Shape = Sh

R = Round

O = Oval

S = Sector

IRR = Irregular

Afferent Pupil Defect=APD:

(-APD) = Neg

(R)APD = Right

(L)APD = Left

Example:

Color	S	D	C	Acc	Sh	APD
Gy/Gy	4/4	3+/3+	3+/3+	++/++	R/R	- APD

The abbreviation "PERRLA" stands for Pupils Equal Round Respond to Light and Accommodation. Which tells a doctor very little to nothing about the patient's pupillary status the day they had their examination. Therefore, you may see it used, but it is not clinical protocol and no longer generally used.
Depending on the author, approximately 25% of the population have unequal pupils of some degree with no known etiology or pathological consequences. This should not be misconstrued that unequal pupils are normal and benign findings.
Detection and Diagnosis of Pupillary Defects:
Examination of the pupillary reactions should be performed in a semidarkened room. The patient should be viewing a distant object when testing the pupillary reactions. This prevents both accommodative and convergence from coming into play. Accordingly, if a patient has anisocoria the pupils should be reassessed in varying illumination. Generally speaking, patients who have anisocoria that varies with illumination levels are more suspect of having a pathological etiology.

Light Reflex:
Have the patient view a distant target then a near target. Be sure to observe both eyes to confirm the responses are equal and symmetrical.

• 1. ) It is important that both direct and consensual reflexes be assessed.
• 2. ) If the afferent arc is intact the direct response should be equal to the consensual reflex.
• 3. ) It is also important that the light source NOT be shined directly into the patient's eye. The light source should be directed from slightly inferior and upward toward the patient's pupil.

Near Reflex Triad:
1) Accommodation
2) Convergence
3) Pupillary Constriction
Near Reflex: Have the patient view a distant target then a near target. Be sure to observe both eyes to confirm the responses are equal and symmetrical.
It is important you take a systematic approach to evaluation your patient's pupils. Even if the pupils are unequal you really do not know which is the faulty eye.

A.) Are the patents visual acuities equal, corrected or with pinholes?

B.) Are the patients pupils unequal in size?

1.) If not, is there a change in the size in different illuminations?
a.) Is there a larger increase in anisocoria in the dark than in the light? (Very diagnostic)
See flow chart!
b.) Is there a larger increase in anisocoria in the light than in the dark? (Very diagnostic)
See flow chart!

C.) Are the pupils equal in size? If they are then:

1.) Is the direct light reflex equally strong in both eyes or more sluggish in one eye than the other?
2.) Is the consensual light reflex equally strong in both eyes and equal to the direct light reflex? Or is one more sluggish.
3.) Is the near accommodative reflex present and equal in both eyes?

D.) Are the accommodative amplitudes equal in both eyes?

Abnormal Pupils:
Amaurotic, "blind eye," with no light perception as a result of an optic nerve lesion.

A.) Pupils are of equal size.

B.) Neither pupil reacts when the defective eye is stimulated.

1.) There is no direct light response.
2.) There is no consensual light response to the contralateral eye.

C.) Both pupils react when the contralateral eye is stimulated.

1.) Direct light response is present.
2.) Consensual light response is present.

D.) Near reflex is normal.

Argyll Robertson Pupil (ARP):

A.) Hallmark of neurosyphilis.

B.) Light-near dissociation (no reaction to light but brisk response to near).

C.) Both pupils usually involved, but the degree may be asymmetrical.

D.) Virtually no response to light, but brisk response to near.

E.) Pupils are small and frequently irregular in shape.

F.) Pupils dilate poorly after instillation of mydriatics.

G.) To make a diagnosis of ARP vision in the affected eye must be normal.

Adie's (Tonic) Pupil:
The lesion is in the ciliary ganglion. This lesion is thought to be caused by denervation of the postganglionic nerve supply to the sphincter and ciliary muscle (pupils and accommodation are affected).

A.) Common cause of anisocoria, typically in women in their third to fourth decade of life.

B.) Unilateral in 80% of cases; women greater than men by 3:1 ratio.

C.) Unilateral there is no response to either direct or consensual light reflex.

D.) Internal ophthalmoplegia with loss of sphincter and accommodation; with the accommodation being very sluggish. Usually both the pupillary response and accommodation are impaired.

E.) Affected pupil relatively dilated in bright light and relatively constricted in dim.

F.) 2.5% mecholyl (which is no longer available) or 0.125% pilocarpine 1 gtt placed in both eyes will cause the Adie's pupil to constrict, because of denervation and hypersensitivity, whereas the normal pupil will not be affected by such a low concentration.

G.) There is a reduction in the knee jerk reflex in a number of these patients.

H.) It is a benign condition; with time the accommodative response improves while the tonicity of the light response gets worse. There is no treatment and patient reassurance is important.

Horner's Syndrome:
Differential diagnosis between central or preganglionic located lesions and postganglionic is of extreme importance in patient management. See management flow sheet. Miosis (small pupil), ptosis (lid droop), anhydrosis (lack of sweat), and apparent enophthalmos (affected eye appears to be sunken) make up a total Horner's Syndrome. Hydroxyamphetamine 1% has proved clinically useful for differentiating between pre- and postganglionic sympathetic denervation. Since the drug stimulates release of endogenous norepinephrine from its stores in adrenergic nerve terminals, it will, depending on the extent of damage, fail to dilate a pupil with postganglionic sympathetic denervation. However, if the lesion causing a Horner's syndrome is central or preganglionic, hydroxyamphetamine should cause normal mydriasis (dilation) since the nerve endings of the postganglionic fibers should contain normal amounts of norepinephrine and thus respond normally.

A.) There is a total or partial interruption of the sympathetic pathway.

B.) Miosis, which is always present in this syndrome; other components may not be; the anisocoria is more marked in dim illumination.

C.) Moderate Ptosis - paralysis of Müller's muscle

D.) Pupillary responses to light and near are unimpaired.

E.) Decreased sweating (anhydrosis) on the ipsilateral side of the face.

F.) Increased accommodation secondary to unopposed action of the parasympathetic.

G.) If the lesion occurred during early infancy or congenitally, heterochromia of the iris may be present.

H.) The prognosis is much better if the causative lesion is postganglionic than if preganglionic. (See flow chart)

I.) Diagnosis is made by using 2%-4% cocaine which dilates the normal pupil but not Horner's pupil. Cocaine solution is not always clinically available and not diagnostic of the lesions location.

J.) Therefore, 1% hydroxyamphetamine (Paradrine®) instilled in both eyes will cause a preganglionic lesion pupil to dilate; a postganglionically located lesion will not dilate. Lesions located in the central (brainstem or spinal cord) or preganglionic (chest or neck) will cause the pupil to dilate. The most common cause being malignant tumors of the lung usually of the upper lobes (Pancoast's tumor), which place pressure on the cervical sympathetic trunks. Remember Horner's pupil is miotic (small). This drug can be relied on to dilate the Horner's (preganglionic lesions) pupil and a normal pupil with the sympathetic pathway to the eye intact. The dilation will be reduced or absent in patients with postganglionic lesions.

Hydroxyamphetamine (Paradrine®) test in a Horner's patient. With 1 gtt of 1% OU there is dilation of the normal right eye and none in Horner's syndrome.

Afferent Pupillary Defect (APD): "Marcus Gunn"
The condition is sometimes referred to as a "Marcus Gunn" pupil. A more descriptive name is Afferent Pupillary Defect (APD) since it's the afferent fibers that are defective, hence, causing this diagnostic phenomenon of "pupillary escape". This is when an optic nerve conduction defect is present and both pupils dilate somewhat when the abnormal eye is stimulated.

In patients with normal intact afferent fibers, both pupils constrict equally and re-dilate slightly when either eye is stimulated. A patient with an APD the affected eye response as though the light is dimmer, hence, the affected eye constricts less and re-dilates more than a normal eye or (fellow eye). The normal eye will have a greater direct response than consensual; the affected eye has a greater consensual response coming from the normal eye than direct. This occurs because the light seems dimmer to the affected eye and because the consensual response from the normal eye is brisk causing the defective eyes pupil to be smaller when you swing the light over to the affected eye and less light is allowed to enter.

There is another way to explain or think about why you get the pupillary escape. The abnormal eyes pupillary reaction is more sluggish than the normal eye, therefore, when the light stimulus is brought from the normal eye to the abnormal eye the affected pupil dilates instead of constrict. This occurs because withdrawing of the light from the normal eye outweighs the constriction produced by the abnormal eye.

A.) APD can have a number of causes but none severe enough to result in total loss of light perception.

1.) Central Retinal Artery occlusion (CRAO)
2.) Central Retinal Vein occlusion (CRVO)
3.) Optic Atrophy
4.) Marked retinal detachment
5.) Anterior Ischemic Optic Neuropathy (AION)
6.) Branch Retinal Vein Occlusion (BRVO)
7.) Asymmetric Primary Open Angle Glaucoma (POAG)

B.) Diagnosed using the "swinging flashlight" test.

C.) Can also be seen in eyes with extensive retinal pathology.

Swinging Flashlight Test:
Grading an APD: Testing is done in a darkened room with the patient fixating a distance object.
1.) Using only a penlight and allowing the light to remain in each eye for one second; with five complete cycles (10 seconds total) would be a grade (4) four, severe defect.

2.) Using a binocular indirect ophthalmoscope (BIO) and allowing the light to remain in each eye for one second; with five complete cycles (10 seconds total) would be a grade (3) three, next most severe defect.

3.) Using a BIO and allowing the light to remain in each eye for three seconds; with five complete cycles (30 seconds total) would be a grade (2) two.

4.) A grade one (1) APD is usually best detected using the slit lamp and the aid of an assistant.

It is strongly suggested if an APD pupil is suspected the pupils be examined with a BIO light source the brighter the light the more sensitive the test becomes and you will not miss an APD very often. A grade (4) APD is worse than a grade (1), hence, the grade (4) has more damage to the afferent fibers leaving the eye.