Diagnosis
Those who are not aware of any family members with LHON are taken by surprise when they suddenly lose central vision and usually struggle to identify the cause. Since LHON is so rare, the medical community usually suspects, tests for, and treats other causes of sudden vision loss. An MRI may be conducted to rule out a brain tumor and to view any optic nerve swelling or thinning. Since there is no visible damage to the eye or brain, there may be a diagnosis of Functional or Non-Organic Vision Loss which suggests a psychological component, an upsetting misdiagnosis since the vision loss is quite real. It’s helpful to see a neuro-ophthalmologist as they are trained and equipped to assess the optic nerves in ways that an optometrist, ophthalmologist or retinal specialist may not.
Since vision loss usually begins in just one eye, a tentative diagnosis of Optic Neuritis is often made and steroid treatment may be prescribed. Optic Neuritis involves eye pain about 90% of the time while LHON onset is painless, which can help in differentiating LHON from Optic Neuritis. Optic Neuritis usually involves just one eye while LHON usually affects both eyes, so when loss of vision in the second eye begins, it may cause the Optic Neuritis diagnosis to be questioned. Testing for Neuromyelitis Optica (NMO) and other possible causes of sudden, bilateral, painless loss of central vision, as well as genetic testing for LHON, may be initiated.
When LHON vision loss begins in childhood, the onset may be different from the typical pattern of sudden onset in both eyes, making it particularly difficult to diagnose. Vision loss may be gradual, and perhaps in just one eye. In very young children it may be diagnosed as amblyopia or strabismus, rather than as LHON.
