From the Guidelines
The workup for anisocoria should begin with a comprehensive eye examination, including a sensorimotor exam, evaluation of ptosis and anisocoria, and pupillary responses in bright and dim illumination, as recommended by the most recent guidelines 1. The examination should include a detailed medical and ocular history, with specific questions about patient symptoms, speed of onset of the strabismus, and possible associated unilateral or bilateral ptosis or other neurologic symptoms 1. Key elements of the examination include:
- A careful review of the current optical correction and the presence of any ground-in or overlay prism 1
- Dry manifest and cycloplegic refraction to reveal anisometropia or high hyperopia 1
- Complete motility examination, including cover-uncover, alternate-cover testing, and prism and alternate cover measurements 1
- Testing for binocular fusion and stereopsis, as well as assessment of alignment by light reflex testing 1
- Evaluation for possible duction deficits suggesting a possible slipped muscle or stretched scar 1 Pharmacologic testing with topical agents such as 0.5-1% apraclonidine and 1% pilocarpine may be necessary to confirm the diagnosis of Horner syndrome or tonic pupil 1. Additional testing depends on the suspected etiology, and urgent neuroimaging is indicated if anisocoria accompanies headache, altered mental status, or other neurologic deficits, as this could indicate serious conditions like third nerve palsy from aneurysm or increased intracranial pressure 1. The evaluation of the third nerve palsy depends on the presumed location of the lesion and is based on other accompanying neurologic findings, with a classic pupil-sparing third nerve palsy having normal pupillary function, complete ptosis, and complete motility dysfunction 1. In cases of pupil-involving third nerve palsy, a compressive lesion must be ruled out, urgently, especially an aneurysm involving the posterior communicating artery, and neuroimaging, including MRA or CTA, is recommended 1.
From the Research
Workup for Anisocoria
The workup for anisocoria, which describes asymmetric pupillary diameter, involves a thorough understanding of normal ocular neuroanatomy and common causes of pathologic anisocoria 2. The following steps can be taken:
- Determine if the anisocoria is physiologic or pathologic
- Check for associated symptoms such as ptosis, blurry vision, or anhydrosis
- Perform a thorough ocular examination, including assessment of pupil reactivity and extraocular muscle function
- Consider pharmacological testing, such as with cocaine, apraclonidine, or hydroxyamphetamine, to diagnose and localize Horner's syndrome 3
- Obtain imaging studies, such as MRI or CT scans, to rule out underlying structural abnormalities or compressive lesions 4, 5
Diagnostic Considerations
When evaluating a patient with anisocoria, it is essential to consider the degree of anisocoria and the presence of associated signs and symptoms. In pediatric patients, anisocoria greater than 1.3 mm is unlikely to be physiologic and should prompt further evaluation for underlying conditions such as Horner's syndrome 6. The workup should also include a review of the patient's medical history and a thorough physical examination to identify any potential causes of the anisocoria.
Common Causes of Anisocoria
Some common causes of anisocoria include:
- Horner's syndrome, which results from an interruption of the oculosympathetic pathway 4
- Third cranial nerve palsy, which can be caused by compressive lesions or other underlying conditions 5
- Medication-induced anisocoria, which can occur with certain medications such as those used to treat glaucoma or uveitis 2
- Traumatic or inflammatory conditions, which can affect the eye or surrounding structures and cause anisocoria 2