Micro-afferent pupillary defect, but of course.
Please rule out glioblastoma, meningioma, pheochromocytoma, glaucoma, multiple sclerosis, epilepsy, senile dementia, orbital mass, blue light damage, and anything else.
So are you saying that a RAPD is not specific to glaucoma? So is it an indication of MRI, MRA, cerebral angiogram, etc. Does it have any useful indications for other disciplines besides optometry?
What is a reasonable workup for the patient with RAPD?
Conditions Leading to a RAPD
- Optic nerve disorders: Unilateral optic neuropathies are common causes of RAPD.
- Demyelination Optic neuritis: Even very mild optic neuritis with a minimal loss of vision can lead to a very strong RAPD.
- Ischemic optic neuropathies: These include arteritic (Giant Cell Arteritis) and non-arteritic causes. Usually there will be a loss of vision or a horizontal cut in the visual field.
- Glaucoma: While glaucoma normally is a bilateral disease, if one optic nerve has particularly severe damage, an RAPD can be seen.
- Traumatic optic neuropathy: This includes direct ocular trauma, orbital trauma, and even more remote head injuries which can damage the optic nerve as it passes through the optic canal into the cranial vault.
- Optic nerve tumor: This is a rare cause and includes primary tumors of the optic nerve (glioma, meningioma) or tumors compressing the optic nerve (sphenoid wing meningioma, pituitary lesions, etc.).
- Compressive optic neuropathy with or without orbital disease: This could include compressive damage to the optic nerve from thyroid related orbitopathy (compression from enlarged extraocular muscles in the orbit), orbital tumors, or vascular malformations.
- Radiation optic nerve damage
- Hereditary optic neuropathies, such as Leber's optic neuropathy (usually eventually bilateral) and other inheritable optic neuropathies.
- Other optic nerve infections or inflammations: Cryptococcus can cause a severe optic nerve infection in the immunocompromised. Sarcoidosis can cause inflammation of the optic nerve. Lyme disease can affect the optic nerve.
- Optic atrophy status: post papilledema - This is usually bilateral.
- Post Surgical damage to the optic nerve: This could include damage following retrobulbar anesthesia; damage following orbital hemorrhage related to eye, orbital, sinus, or plastic surgery; damage following neurosurgical procedures such as pituitary tumor resection; and damage related to migration of an orbital plate after surgery to correct a blow-out fracture.
Retinal Causes of a Relative Afferent Pupillary Defect
Again, symmetrically bilateral retinal disease will not show a RAPD. Usually, retinal disease has to be quite severe for an RAPD to be clinically evident.
- Ischemic retinal disease: Causes include ischemic central retinal vein occlusion, central retinal artery occlusion, severe ischemic branch retinal or arterial occlusions, severe ischemic diabetic or sickle-cell retinopathy.
- Ischemic ocular disease (Ocular ischemic syndrome): This usually arises from obstruction of the ophthalmic or carotid artery on one side.
- Retinal detachment: A RAPD can often be seen if the macula is detached, or if at least two quadrants of retina are detached.
- Severe macular degeneration: If unilateral and severe, a RAPD can be seen. Usually the visual acuity would be less than 20/400.
- Intraocular tumor: Retinal and choroidal tumors including melanoma, retinoblastoma, and metastatic lesion could lead to a RAPD if severe.
- Retinal infection: Cytomegalovirus, herpes simplex, and other causes of retinitis can lead to a RAPD if there is extensive disease.
Other Causes of a Relative Afferent Pupillary Defect
- Amblyopia: If severe, can lead to a relative afferent pupillary defect. Usually the visual acuity would be 20/400, or worse.
- Cerebral vascular disease: Usually, it is an optic nerve disorder that leads to a RAPD, rather than an optic tract or visual cortex disorder. However, there tends to be a higher percentage of crossed vs. uncrossed nerve fibers at the optic chiasm. Thus, in a patient with a homonymous hemianopia from an optic tract disorder, an RAPD could be seen in the eye with the temporal visual field defect. The nasal retina serves the temporal visual field, and these are the fibers that would cross at the chiasm [3].
https://eyewiki.org/Relative_Afferent_Pupillary_Defect
Possible Diagnoses
Some articles suggest that an RAPD can occur as a result of the light scatter caused by a very dense asymmetric cataract. Clinically, however, a dense cataract should never be used to explain the presence of an RAPD.7
The presence of an RAPD most often indicates relative optic nerve disease.8 An amblyopic eye may present with a mild RAPD, but you must first rule out optic nerve pathology.
Also, an RAPD can be caused by significant retinal pathology. For instance, a large macular scar, a significant retinal detachment and a central retinal artery or ischemic central retinal vein occlusion can result in an afferent pupillary defect.1-3
I suggest taking a stepwise approach when a patient presents with an RAPD. Specifically:
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, auto-immune 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 patients history and retinal examination do not offer an obvious explanation for the APD, 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 neuro-imaging 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.
In the absence of vascular risk factors, or in patients younger than 40, infectious, inflammatory, infiltrative or medication-induced optic neuropathy must always be ruled out. For instance, optic neuropathy induced by Viagra (sildenafil, Pfizer) is well documented.14 Additionally, amiodarone, a medication used to manage cardiac arrhythmia, has also been implicated.15,16
You must rule out GCA in patients older than 56. This requires emergent sedimentation rate and C-reactive protein tests. Optic neuritis, which is also an acute event, is usually retrobulbar, and more commonly occurs in patients younger than 50; patients mostly present with pain on eye movements. So, any patients who presents with optic nerve disease that cannot be attributable to typical NAION must be worked up and imaged urgently.
When a patient presents with a relative afferent pupillary defect, a correct differential diagnosis of your clinical signs and symptoms can help steer you toward a timely and appropriate referral. The key is not to panic. Let a case history, examination and ancillary testing help you determine how to handle a patient who presents with an APD.
Dr. Canellos practices with the New York Harbor VA Health Care System at the Brooklyn and St. Albans facilities. He is an adjunct assistant clinical professor at the State University of New York State College of Optometry.
https://www.reviewofoptometry.com/article/back-to-the-basics-part-5-my-patient-has-an-rapd-now-what
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