LHON Defined
Leber Hereditary Optic Neuropathy (LHON) is a rare genetic disorder. LHON symptoms usually begin as sudden, painless, profound loss of central vision, which causes reading standard-sized text, driving, and recognizing faces to be impossible. The classic pattern is for one eye to suddenly become affected and lose central vision, then the other eye to become affected within weeks to months. Each eye quickly gets worse than 20/200 (the threshold for legal blindness) as the central scotoma (blurry blind spot) rapidly expands over about 6-8 months. Severe vision loss in both eyes is the usual outcome. In rare cases, the interval between eyes can be years, and in some cases, both eyes onset at the same time.
The affected person retains some amount of peripheral vision, varying significantly by individual. This allows the person to walk around independently, though in many cases a white cane or guide dog is required for safe mobility. Since the LHON affected individual does not “look blind,” those around them don’t realize how profound their vision loss is. Color vision usually becomes impaired also, with red lost first. Bright royal blue is the color that typically remains most visible.
With LHON, the eyes are working fine. The problem is with the 1.2 million optic nerve fibers that transmit information between each eye and the brain. The retinal ganglion cells (RGCs) and their axons that form the optic nerves become unhealthy, swell, and then atrophy.
The following video, The Science of LHON from the Patient Perspective, was recorded at the 2015 LHON Conference and addresses the most commonly-asked medical questions about LHON with three of the world’s LHON leaders [Dr. Patrick Yu-Wai-Man (UK), Dr. Valerio Carelli (Italy), and Dr. Alfredo Sadun (USA)].
The following video, LHON Overview, is from the 2017 LHON Conference with Dr. Nancy Newman, another global LHON expert.
Additional LHON overviews can be found here:
