Relative afferent pupillary defect
Relative afferent pupillary defect
Description, Causes and Risk Factors:
A relative-afferent-pupillary defect, commonly referred to as the Marcus Gunn pupil, points to asymmetric function of the retina or optic nerve. The anterior midbrain, controlling pupillary size, receives a message from the affected eye that illumination is reduced as compared with the fellow eye, or relative to the fellow eye. The pupillary hallmarks are, therefore, either: (1) pupillary dilatation following a constrictive reaction to a light stimulus applied to the affected side, or (2) the dilation of both pupils when a light stimulus is moved from the non-affected eye to the affected eye.
RAPD is a medical sign observed during the swinging-flashlight test whereupon the patient's pupils constrict less (therefore appearing to dilate) when a bright light is swung from the unaffected eye to the affected eye. The affected eye still senses the light and produces pupillary sphincter constriction to some degree, albeit reduced.
An RAPD generally occurs with significant optic nerve or retinal disease, when there is a difference in the disease process between the two eyes. Each eye has severe but equal disease, there will be no RAPD. Thus, a "bilateral" RAPD does not exist.
Severe disease in one eye leading to an RAPD will not lead to anisocoria. The diseased eye's pupil will appear to be of equal size to the other eye due to the consensual light reaction (unless the iris itself is diseased or unreactive).
Because of the consensual light reaction, only one functioning pupil is needed to determine the presence of an RAPD.
The visual acuity does not necessarily correlate with an RAPD. Some conditions will lead to a marked reduction of visual acuity with an RAPD, while others spare the central vision. Often an extensive loss of peripheral vision correlates with an RAPD.
In an afferent pupillary defect, there is a relative decrease in the direct response. This is most clearly demonstrated by the “swinging flashlight test. Even the flashlight is shined first in the abnormal eye, then in the healthy eye, and then again in the eye with the pupillary defect, the affected pupil becomes larger rather than
An relative afferent pupillary defect is identified by examining the eyes with a bright light. In normal circumstances, when a light is shone in one eye, both pupils constrict. However, when a light is shone in the abnormal eye of a patient with an RAPD, the pupil of the affected eye paradoxically dilates rather than constricts. This abnormal response signifies the brain is not receiving the message properly.
A mild RAPD (slight constriction of the affected pupil), may be a sign of underlying amblyopia, vitreous hemorrhage, retinal scars, severe age related macular degeneration, branch retinal vein or artery occlusion, or retinal detachment. If an RAPD is severe (dilation of the affected pupil), it generally indicates optic nerve disease such as ischemic optic neuropathy, optic neuritis, severe glaucoma, central retinal artery or vein occlusion, or in rare cases, a lesion of the optic chiasm or tract due to a pituitary tumor or stroke.
We suggest taking a stepwise approach when a patient presents with an RAPD.
Ask if the patient is aware of changes in vision. If so, are these changes acute or gradual? An acute optic neuropathy or retinal detachment would be associated with sudden vision loss, while gradual vision loss might support the existence of a compressive lesion.
Elicit significant ocular and medical history. Does the patient have a history of vascular disease, cancer, autoimmune disease, recent infections or trauma?
Carefully examine the patient, and pay special attention to the retina and optic nerve. Optic nerve findings can be subtle or non-existent. For instance, a relatively normal appearing nerve might be present in a retrobulbar optic neuritis. That is why color vision testing and perimetry are so important to the evaluation.
The need to refer for further testing depends on the case. If the patient's history and retinal examination do not offer an obvious explanation for the RAPD, one must assume that a condition affecting the optic nerve or optic tract is causing it. An immediate visual field and color vision test should be performed.
Depending on the condition, the patient may need to be referred for emergent neuroimaging and laboratory testing. For example, an individual who presents with an RAPD as a result of swollen optic nerve and a history of leukemia, would require emergent imaging and radiation treatment if the swollen nerve represented a leukemic infiltrative optic neuropathy.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
A new research from the University of Edinburgh, UK, suggests that cheap cilostazol tablets may reduce damage to arteries, which lead to blood clots, resulting in strokes and cognitive decline. The researchers plan to assess the medications’ ability to cut the risk of...
A new study from the US discovers that flavonoids, natural compounds found in fruits and vegetables, may help preserve the lung function, which tends to decline with age. For the study, a team of researchers looked at data from 463 adults from Norway and England whose...
Quiz about this article
0 of 2 questions completed
Please answer on few questions to make our service more useful
You have already completed the quiz before. Hence you can not start it again.
Quiz is loading...
You must sign in or sign up to start the quiz.
You have to finish following quiz, to start this quiz:
0 of 2 questions answered correctly
Time has elapsed
You have reached 0 of 0 points, (0)
Question 1 of 2
Was this article useful for you?Correct
Thanks for your feedback!Incorrect
Thanks for your feedback!
Question 2 of 2
What else information about this disease you want to know ?Correct
Thanks for feedback!Incorrect
Thanks for feedback!
Good weather is the best reason to do outdoor sports, which will help not only lose weight, but also will strengthen health. Bicycle The sun dries out the local paths, so you can safely sit on your favorite bike and confidently twist the pedals, where the eyes look....read more
First aid for injuries consists of simple rules that need to be clearly implemented. If this is a closed injury, you need to immobilize the injured limb, otherwise the person may lose consciousness from a painful shock. If you need to get to the emergency room...read more
Many people spontaneously decide starting to do sport, while others weigh all the pros and cons for a log time. But almost all of them make the same mistakes, listening to the advice of non experts. There are 10 anti-tips for those who want to do plan to do some sport...read more