Symptoms, Progression & Warning Signs

Leber Hereditary Optic Neuropathy (LHON) is a condition that primarily affects the central vision. While the experience is different for everyone, the disease typically follows a predictable pattern of progression from an initial “acute” phase to a long-term “chronic” phase. Understanding these stages and the warning signs of related symptoms can help you and your care team manage the condition effectively.

The Timeline of Vision Loss

For most people, LHON begins as a painless blurriness or a “cloud” in the center of the vision in one eye ^[1]. This is not a total loss of sight but rather a scotoma (a blind spot) that makes it difficult to recognize faces, read, or drive. Importantly, LHON rarely causes total, pitch-black blindness. It damages the cells responsible for central vision, typically sparing your peripheral (side) vision ^[1].

The most characteristic feature of LHON is sequential involvement, meaning the second eye usually becomes affected after the first ^[2].

• The Gap: In many cases, the second eye begins to lose vision within weeks or a few months of the first ^[1].
• Variability: While the gap is typically short, it can be highly unpredictable. Some patients have reported the second eye being affected years or even decades later—in one documented case, the interval was 18 years ^[3][2].
• Simultaneous Onset: In about 25% of cases, both eyes are affected at the same time ^[1].

Acute vs. Chronic Phases

Doctors categorize LHON into two main stages based on the timing and the physical changes in the eye.

The Acute Phase (First 6–12 Months)

This stage begins the moment vision loss starts. During this time, the mitochondria (the power plants of your cells) in the optic nerve are struggling to function, leading to cell swelling ^[4].

• Clinical Signs: A doctor using OCT (Optical Coherence Tomography, a non-invasive imaging test) may see thickening of the retinal nerve fiber layer ^[4].
• Warning Signs: You may notice the central blind spot expanding or becoming more dense during these months.

The Chronic Phase (After 1 Year)

After the initial period of swelling, the disease enters the chronic phase. At this point, the initial swelling has faded, and the optic nerve begins to thin or atrophy ^[5].

• Vision Stability: Vision loss usually stabilizes during this phase, though it remains severe for most.
• Recovery: While rare, some patients experience “spontaneous recovery” where vision improves slightly even months or years after the chronic phase begins ^[6].

Understanding ‘LHON Plus’

While LHON primarily affects the eyes, some individuals have a version called LHON Plus. This term is used when the mitochondrial mutation affects other parts of the nervous system in addition to the optic nerve ^[7]. Symptoms that distinguish LHON Plus from the classic form include:

• Movement Disorders: Such as dystonia (uncontrollable muscle contractions) or tremors ^[8][9].
• Coordination Issues: Including ataxia (clumsiness or loss of balance) and dysarthria (slurred speech) ^[7][9].
• Neurological Conditions: Some patients develop symptoms similar to Multiple Sclerosis (MS), such as weakness or numbness in the limbs ^[8].

Environmental Triggers: Protecting Your Vision

Research has shown that your environment plays a massive role in whether—and how quickly—LHON progresses. Certain toxins put extra stress on the mitochondria, which are already vulnerable in people with the LHON mutation.

• Smoking: Tobacco use is the single most significant environmental risk factor for triggering vision loss in LHON carriers ^[10][11]. Quitting smoking is the single most critical step you must take to prevent further irreversible vision loss ^[11].
• Alcohol: Excessive alcohol consumption is also linked to an increased risk of vision loss ^[12]. Current guidelines suggest limiting alcohol intake strictly ^[13].
• Chemical Sensitivities: Patients are often advised to avoid certain chemicals, such as benzalkonium chloride (a common preservative in some eye drops), which can be toxic to already-weakened mitochondria ^[14]. Always check with your ophthalmologist before using new eye drops.

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