BASICS

DESCRIPTION

• Different response of one pupil compared with the contralateral pupil when stimulated by a bright light. It is a sign that can be seen in a large variety of disease entities.

• Previously known as the Marcus–Gunn pupillary phenomenon.

Geriatric Considerations

Cataract (commonly seen in geriatric patients) does not cause a relative afferent pupillary defect (RAPD).

Pediatric Considerations

Absolute indication of pathology involving the afferent visual pathway especially in preverbal patients

Pregnancy Considerations

Meningiomas and pituitary tumors occur or increase in size with increased frequency during pregnancy resulting in RAPD

EPIDEMIOLOGY

Incidence

Not applicable

Prevalence

Relates to the prevalence of afferent visual system disease in the particular population

RISK FACTORS

Depends on underlying pathology

Genetics

• Most inherited retinal conditions are less likely to cause an RAPD unless there exists considerable asymmetry of involvement of one eye compared with the other.

• Mitochondrial disease such as Leber’s hereditary optic neuropathy may present asymmetrically or with one eye involved prior to the contralateral eye.

PATHOPHYSIOLOGY

• Decreased amount of light transmitted along one side of the anterior visual pathway

• Pathology resulting in loss of function within the afferent visual pathway, which may include the retina, optic nerve head, optic nerve, chiasm, and the anterior optic tract proximal to the lateral geniculate body

– Media opacity within the eye such as cataract will not cause an RAPD. Dense, extensive anterior chamber or vitreous hemorrhage produce RAPD

ETIOLOGY

• Optic neuropathy of any etiology if unilateral or asymmetric

• Extensive retinal involvement from multiple causes

COMMONLY ASSOCIATED CONDITIONS

• Demyelinating disease (multiple sclerosis)

• Hypertension

• Diabetes

• Giant cell arteritis

• Optic nerve/chiasmal compression

• Nonarteritic anterior ischemic optic neuropathy (NAION)

DIAGNOSIS

HISTORY

• Unilateral vision loss

• Unilateral loss of brightness

• Unilateral loss of color perception or desaturation of color

– Pain associated with eye movement in optic neuritis

– Various visual field defects

PHYSICAL EXAM

• Patient asked to distance fixate preferably in dim ambient light conditions

• A bight light source is directed at the right eye

• The direct ipsilateral pupillary response is observed (pupil should constrict)

• The consensual contralateral pupillary response in the left eye is observed (pupil should also constrict)

• The light is now directed at the left eye (swinging flashlight test), and both the direct and consensual pupillary reflexes are observed.

• When an RAPD is present the pupil on the affected side will dilate more (pupillary escape)

– Subjective grading by the examiner often ranging from “trace” or ±, through +1 to +4

– Objective measurement using a neutral density filter to quantitate

– Subjective impression of brightness differential can be asked of the patient

– Advanced objective measurements with pupillometry devices but less often used clinically

DIAGNOSTIC TESTS & INTERPRETATION

Imaging

Initial approach

• An RAPD infers objective evidence of pathology of the anterior visual pathways. If there is no explanation from the ophthalmic examination, neuroimaging is mandatory.

• MRI with fat suppression and gadolinium of the orbits and brain is considered the minimum work-up.

Follow-up & special considerations

• Exclude other associated intracranial abnormalities such as demyelinating plaques

– Adequate consultation with neuroradiology is highly recommended.

Diagnostic Procedures/Other

• Automated visual field analysis of both eyes looking for topographical patterns of vision loss

• Complete ophthalmic examination including measurement of intraocular pressure and dilated retinal examination

– CBC count with ESR and CRP in patients older than 60 years or if other symptoms or signs of giant cell arteritis (GCA)

Pathological Findings

Depends on underlying pathology

DIFFERENTIAL DIAGNOSIS

• Retinal disorders

• Optic neuropathy

• Chiasmal disease

• Optic tract lesions

TREATMENT

MEDICATION

Depends on the underlying pathology

ADDITIONAL TREATMENT

Issues for Referral

Refer to neuroophthalmology if the cause or treatment of the cause is in doubt

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

Depends on underlying pathology

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