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Relative Afferent Pupillary Defect – Symptoms, Causes, ICD 9 Code

Definition of Relative Afferent Pupillary Defect


Relative afferent pupillary defect (RAPD), also known as Marcus Gunn pupil, is a condition wherein the pupils react minimally to bright light. RAPD was named after Scottish ophthalmologist Robert Marcus Gunn.

The mechanism involved in RAPD may be an unequal optic nerve transmission between the two eyes, thereby resulting in an unequal pupillary response to light. When light is shone into the normal or unaffected eye, the pupil normally contracts to control the amount of light that goes in, but when light is shone in the affected eye, the pupil dilates due to the inability to detect bright light, or when it does constrict, it may be less than the unaffected eye, revealing a reduced pupillary sphincter constriction.

RAPD is different from anisocoria, which is characterized by the unequal size of the pupils at the same time. Anisocoria is more an efferent defect rather than an afferent one.

Relative Afferent Pupillary Defect Symptoms

Symptoms of RAPD are usually seen following diagnostic tests. It is not apparent in the eyes unless light is shone into the eyes. The symptoms of RAPD are identified using a swinging light test.

Swinging light test is done in a dimly lit room to adequately observe for the pupillary changes. Light is shined on the eye and constriction is observed. The light is then shone on the other eye, and the action should produce similar effects. When light is shined on one eye, both pupils must constrict. The swinging light test may be repeated until a specific category is found. There are four categories of degrees of RAPD. These include:

  • No relative afferent pupillary defect: This is a normal finding, and the pupils constrict equally to light with absence of re-dilation.
  • Mild relative afferent pupillary defect: There is a presence of weak pupillary constriction followed by pupillary dilation when light is directed in the affected eye .
  • Moderate relative afferent pupillary defectThere is an absence of initial constriction followed by dilation when light is shone into the affected eye.
  • Severe relative afferent pupillary defect– There is an immediate dilation when light is shone into the affected eye.


There are a lot of possible causes of RAPD, including:

  • Optic nerve disorders: Optic nerve problems may cause inability of pupils to react in same way. Optic nerve disorders may include:
    • Optic neuritis
    • Glaucoma
    • Ischemic optic neuropathies
    • Optic nerve tumor
    • Traumatic optic nerve neuropathy
    • Orbital disease
    • Optic nerve infection
    • Optic nerve inflammation
    • Radiation optic nerve damage
    • Papilledema induced optic nerve atrophy
    • Optic nerve damage due to surgery (plastic surgery, eye surgery, orbital surgery, pituitary tumor, and resection)
  • Retina disorders: Severe cases of retinal diseases may result in RAPD. These include:
    • Ischemic ocular disease
    • Ischemic retinal disease
    • Retinal detachment
    • Retinal infection
    • Severe macular degeneration
  • Cerebrovascular disease: Stroke may also cause RAPD as a result of homonymous hemianopsia.
  • Amblyopia: Severe cases of amblyopia may lead to RAPD.
  • Multiple sclerosis: Multiple sclerosis may also cause RAPD due to optic nerve damage.

Differential diagnosis

The main diagnosis of RAPD is the use of the swinging light test as described earlier. The specific degree of pupillary defect is needed to detect mild, moderate, and severe defects. Other tests which may also be performed to detect the specific cause of the condition include:

  • MRI

MRI may be able to detect problems related to the presence of inflammation or tumor in the optic nerve or retina. It may also detect the presence of cerebrovascular diseases.

  • Ophthalmology exams

Ophthalmologists may also perform other tests to detect the presence of glaucoma, retinal detachment, macular degeneration, and other related conditions.

The correct diagnosis should be employed in order to have a clearer picture of the condition, and proper treatments will be employed according to the cause. Ophthalmologists identify whether RAPD is caused by:

  • Optic nerve problems
  • Retinal problems
  • Stroke
  • Multiple sclerosis

The following conditions usually do not result in RAPD, so other diagnosis should be considered:

  • Refractive error
  • Strabismus
  • Cataract
  • Hyphema
  • Corneal scar
  • Vitreous hemorrhage
  • Third cranial nerve palsy
  • Diabetic retinopathy
  • Non-ischemic vein occlusions
  • Retinitis pigmentosa
  • Cerebral infarction

Relative Afferent Pupillary Defect Treatments

Treatments for RAPD depend on the cause. These include:

Steroid therapy

Cases of optic neuritis may require the use of corticosteroids to reduce swelling in the optic nerve. Steroids may be in the form of prednisone or methylprednisolone. The presence of papilledema my also require steroid therapy.

Antibiotic therapy

Presence of infections in the optic nerve may also require antibiotic therapy to kill the causative microorganisms.


Miotic eye drops are also employed in the case of glaucoma to reduce the pressure in the eye and optic nerve.


Interferons may be instituted for patients with multiple sclerosis-induced RAPD in order to promote myelination of the nerves.


Surgery is applied to those who who do need it and those who do not respond to conventional therapies. Patients with glaucoma may need iridectomy, and retinal detachment may require repair of the damaged retina. Other surgeries may be deemed necessary by physicians.

ICD 9 code

RAPD has an icd 9 code of 379.49 under the category of other anomalies of pupillary function.

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