In optometry school, our professors often stress how important close observation of a patient’s pupils can be in assessing his or her ocular and systemic health.
ANISOCORIA: unequal pupil sizes
1. Horner’s syndrome
- Interruption in the sympathetic nervous system pathway which controls mydriasis in normal circumstances
- Can be first, second, or third order depending upon which area of the pathway is affected
- First order refers to the part of the pathway from the hypothalamus to C8-T1
- Possible etiology: stroke
- Second order refers to C8-T1 to the superior cervical ganglion
- Possible etiology: Pancoast tumor
- Third order is anything beyond the superior cervical ganglion to the pupil dilators and lid
- Possible etiology: problem at the internal carotid; cavernous sinus problem
- First order refers to the part of the pathway from the hypothalamus to C8-T1
- Typically presents with anisocoria (worse in dim lighting) and mild ptosis; the smaller or miotic pupil is the affected pupil
- Pharmacologic testing can be used to confirm Horner’s and indicate which part of the pathway has been affected
- Confirming Horner’s
- 4-10% cocaine drops
- A Horner’s pupil WILL NOT dilate after instillation (normal pupil will)
- 1% or 0.5% apraclonidine
- A Horner’s pupil WILL dilate MORE than the normal pupil, reversing the anisocoria
- 4-10% cocaine drops
- Determining which order is affected
- Hydroxyamphetamine
- To be used only after confirmation testing has been performed
- Will dilate the Horner’s pupil as long as the third order pathway is intact
- Hydroxyamphetamine
- Confirming Horner’s
Remember the phrase: FAIL SAFE
If hydroxyamphetamine fails to dilate your patient, they are likely safe from 1st and 2nd order problems, such as a Pancoast tumor or stroke. However, clinicians should remember that an internal carotid problem (aneurysm/dissection) can cause a third order Horner’s Syndrome.
2. Pharmacologic
- Most commonly, the patient has been exposed to pilocarpine
- Opioids/opiates can cause miosis, typically bilaterally
- Pupil will not dilate normally with instillation of any medication
- Thorough history is key
1. Third Nerve Palsy
- Full presentation includes mydriasis, ptosis, and restricted EOM’s often resulting in a “down and out” appearance of the affected eye
- Can present with mild signs, and pupil involvement may not be seen in early or ischemic cases
- Pupil involvement suggests possible aneurysm or compressive lesion
- Patients who present with ptosis and EOM restriction, but no pupil involvement, are likely suffering from ischemia affecting the 3rd cranial nerve (most commonly due to diabetes)
- All patients presenting with a CN3 palsy should be imaged to evaluate for impending aneurysm regardless of pupil involvement, and clinicians should re-evaluate a patient’s pupils often during the early presentation of the condition to determine if the pupil is becoming mydriatic
- Ischemic cases typically resolve in 3-6 mo; compressive cases do not resolve until the underlying systemic cause is addressed
2. Adie’s Tonic Pupil
- Mydriatic pupil will not constrict with light, will constrict when in near gaze (light-near dissociation)
- Will take longer than a normal pupil to release the miosis reached in near gaze after looking away from the near target
- Pupil will constrict with instillation of weak (0.1%) pilocarpine, which will minimally or not affect a normal pupil
- Caused by damage to the postganglionic parasympathetic pupil pathway
- More common in females than males and usually unilateral
- Main cause is unknown; Herpes-zoster, varicella, giant cell arteritis, and orbital trauma can cause Adie’s in rare cases
3. Pharmacologic
- As with miotic pupils, thorough history is key
- Will present with one or both pupils fixed and dilated in early stages, may be slightly reactive to light as agent wears off
- Beyond a patient’s abuse of dilation drops, common causative drugs that can result in mydriasis include scopolamine patches for motion sickness (may present with dilation only on the side to which the patch was applied), cold medications/decongestants, marijuana, and stimulants (cocaine, meth, etc)
REMEMBER: Physiologic anisocoria is not uncommon. However, unlike anisocoria caused by an underlying condition, there will be minimal difference in amount of anisocoria in both light and dim conditions.
Reactivity
The most important abnormal reactivity finding is the afferent pupillary defect (APD).