Diagnosis of Optic Atrophy
Diagnosis involves recognizing the characteristic changes in the optic disc with an ophthalmoscope, and measuring visual acuity, usually with an eye chart. Visual field testing can test peripheral vision. Color vision and contrast sensitivity can also be tested. Family history is important in the diagnosis of inherited conditions. Exposure to poisons, drugs, and even medications should be determined. Suspected poisoning can be confirmed through blood and urine analysis, as can vitamin deficiency.
Brain magnetic resonance imaging (MRI) may show a tumor or other structure putting pressure on the optic nerve, or may show plaques characteristic of multiple sclerosis, which is frequently associated with optic neuritis. However, similar MRI lesions may appear in Leber’s hereditary optic neuropathy. Mitochondrial DNA testing can be done on a blood sample, and can identify the mutation responsible for Leber’s.
Visual evoked potentials (VEP), which measure speed of conduction over the nerve pathways involved in sight, may detect abnormalities in the clinically unaffected eye in early cases of Leber’s. Fluorescein angiography gives more detail about blood vessels in the retina.
ONA in children is diagnosed by a pediatric ophthalmologist in a number of ways, including:
* Visual acuity and color vision may be found to be abnormal (if testable).
* Pupil reactions to light are diminished.
* The optic nerve, when examined with an ophthalmoscope, has a gray-white appearance, which may not be apparent for four to six weeks from time of optic nerve injury.
* Optic atrophy which occurs in both eyes from time of birth (bilateral and congenital) may cause rhythmic, involuntary eye movements (nystagmus).
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