spotsociety.blogg.se - Fixed dilated pupil differential diagnosis

In summary, clinicians should be aware that the RAPD can be tested in any patient who has two eyes and at least one working pupil. In this instance, the left pupil should be watched the whole time the examination is conducted to identify if there is an RAPD. įigure 2 shows the swinging flashlight test in a patient with a right RAPD and a non reactive right pupil. Some clinicians may neglect to check for a RAPD by reverse testing because they are misled by to believe that the fixed and dilated pupil precludes assessment of that pupil’s afferent response. However, if this same patient with a CN III palsy also has an RAPD (by reverse testing) then the localization of the lesion moves from the posterior communicating artery to the orbital apex. In this setting, a CN III palsy is potentially life threatening and urgent vascular imaging (e.g., computed tomography (CT) and CT angiogram of the brain) may be necessary. For example, in a patient with a cranial nerve (CN) III palsy with a dilated pupil, one of the main diagnostic considerations is possible aneurysm of the posterior communicating artery (PComm). In fact however BOTH pupils dilate in every RAPD but in the reverse RAPD the clinician will be observing the dilation of the unaffected rather than the affected pupil (in the setting of a patient with both an afferent and efferent pupillary defect).Ī reverse RAPD should be evaluated in every patient with an efferent pupillary defect. This finding is present in every RAPD but most examiners are used to only observing the affected pupil during the swinging flashlight test. Reverse RAPD, or reverse testing for RAPD, utilizes the swinging flashlight test while evaluating the normal, unaffected pupil for dilation. Where one eye has an efferent pupillary defect (e.g., iris posterior synechiae, trauma, third nerve palsy, or pharmacological mydriasis), a ‘reverse RAPD’ test can be employed. Testing for a RAPD requires two eyes, but only one functioning pupil.

Dense macular lesions (chorioretinal scar).

Ischemia (e.g., ischemic central retinal vein occlusion or central retinal artery occlusion).

Lesions of the optic nerve regardless of the cause of optic neuropathy (e.g., optic neuritis, glaucoma, compression, infection etc.).

Occur in lesions affection the visual pathway in front of the lateral geniculate body The RAPD is a critically important sign in patients with unexplained visual loss because it is an objective findings of afferent pupillary dysfunction. The pathologic response that characterizes the RAPD includes the following: 1) the light reaction causes pupil constriction in both eyes when the light shines in the normal eye, and (2) dilatation of the pupils in both eyes when the light stimulus is rapidly transferred from the normal eye to the pathologic eye. The normal pupillary response is characterized by equal constriction of the pupils in both eyes when the light stimulus is applied to each eye individually and no dilation or pupillary escape when the light swings from the one eye to the fellow eye. In the case of an afferent pupillary pathway lesion, the light response is tested individually in each eye and then the light swings between the two eyes in order to detect an RAPD. In a normal patient without afferent pupillary disease, shining a light in either eye will produce constriction of both eyes equally. No anisocoria.Ī RAPD is seen in unilateral or bilateral but asymmetric lesions of the prechiasmal optic nerve starting from the retina but can occur anywhere in the afferent pupillary pathway including the optic tract and the pretectal afferent fibers in the dorsal midbrain. The test requires two eyes but only one working pupil. The RAPD manifests as a difference in pupillary light reaction between the two eyes. An RAPD is relative to the fellow eye and occurs because of the bilateral and equal innervation of the pupils in normal individuals.

2.2 Lesions of the Retina/Posterior SegmentĪ relative afferent pupillary defect (RAPD) also known as a Marcus Gunn pupil, is a critically important ophthalmological examination finding that defines a defect ( pathology) in the pupil pathway on the afferent side.2.1 Lesions of the Anterior Optic Pathway.