Retinal detachment : an RAPD can often be seen if the macula is detached.Severe ischaemic retinal disease – eg, ischaemic central retinal vein occlusion, central retinal artery occlusion, sickle-cell retinopathy.Sarcoidosis can cause inflammation of the optic nerve. Optic nerve infections or inflammations: cryptococcus can cause severe optic nerve infection in the immunocompromised.Optic atrophy : such as Leber’s optic atrophy.Orbital disease: including compressive damage to the optic nerve from thyroid-related orbitopathy, orbital tumours, or vascular malformations.Optic nerve tumour : this is a rare cause.
Traumatic optic neuropathy: this includes direct ocular trauma, orbital trauma, and head injuries which damage the optic nerve as it passes through the optic canal.Severe glaucoma : while glaucoma normally is a bilateral disease, if one optic nerve has particularly severe damage, an RAPD can be seen.Optic neuritis : even very mild optic neuritis can lead to a very strong RAPD.Usually there will be a loss of vision or of part the visual field. These include arteritic ( giant cell arteritis ) and non-arteritic causes. Unilateral optic neuropathies are common causes of an RAPD.Comparing the direct and consensual reaction to light in both eyes is helpful in locating a lesion, remembering that the retina and optic nerve are needed for the afferent signal and that the oculomotor nerve provides the efferent component of both the direct and consensual reflexes.Īn RAPD is a defect in the direct pupillary response and usually suggests optic nerve disease or severe retinal disease. Normally, pupils react (ie constrict) equally. Pharmacological constriction (constricting drops).Argyll Robertson (AR) pupil (may also be irregular, usually bilateral – see below).This is a pupil showing poor dilatation in low light. Pharmacological dilation (ie dilating drops).Holmes-Adie syndrome: may also be irregular, unusually unilateral – see below.Rubeosis iridis (neovascular eye disease).This is a pupil showing poor constriction in a well-lit room. Compare the pupils in light and dim conditions: It is necessary to ascertain first which pupil is behaving abnormally. Anisocoria of new onset can suggest serious underlying pathology such as trauma, Horner’s syndrome, pharmacological mydriasis/miosis, or third nerve palsy. Anisocoria is physiological (and harmless) in about 20% of people. Disorders of the iris, including application of cholinergic agents, also need to be considered in impaired pupillary light reaction. Disorders of the parasympathetic system impair the light response and they include third nerve palsy and tonic pupil. Anisocoria, where not physiological, indicates a problem of the efferent pupillary pathway, either parasympathetic or sympathetic (Horner’s syndrome). Pupillary disorders may involve the afferent pathways (RAPD) or the efferent pathways. Abnormal pupillary light reflex can be found in optic nerve injury, oculomotor nerve damage, brain stem lesions, such as tumors, and medications like barbiturates. Pupillary light reflex is used to assess the brain stem function.
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