How Soon Does LHON Affect the Second Eye? Typical Timeline

If you have just experienced sudden vision loss in one eye and suspect it might be Leber hereditary optic neuropathy (LHON), please seek immediate medical attention. Sudden vision loss can have many causes—including vascular or neurological emergencies—that require same-day evaluation. Do not wait for a routine appointment to confirm the underlying cause.

If your diagnosis of LHON is already confirmed or strongly suspected by a specialist, it is completely normal to feel terrified about what will happen to your other eye. In most cases of LHON, the second eye is affected within weeks to a few months after symptoms begin in the first eye ^[1][2].

The typical time between the first eye losing vision and the second eye showing symptoms is often reported as a median (the middle value of all patient timelines) of 6 to 8 weeks ^[3]. However, every person’s timeline is different. It is critical to contact your neuro-ophthalmologist or care team promptly to discuss your specific situation, monitor your vision, and explore potential treatment options ^[4].

What Are the Typical Timelines?

LHON usually follows one of two patterns when it comes to eye involvement:

• Sequential Onset (One after the other): This is the most common pattern. After the first eye is affected, the second eye typically follows within a few weeks to a few months. Studies often cite a median timeframe of 6 to 8 weeks (about 1.5 to 2 months), though some clinical subgroups show medians ranging from 2 to 4 months ^[2][3].
• Simultaneous Onset (Both at once): In approximately 25% to 50% of cases, both eyes are affected at the same time, or so close together that the vision changes are noticed simultaneously ^[1].

In extremely rare cases, the second eye might remain unaffected for much longer—sometimes years—though this is the exception rather than the rule ^[5]. It is important to remember that these statistics are averages from large groups of patients, and no doctor can predict your exact individual timeline.

Can Treatment Protect the Second Eye?

Because the window between the first and second eye’s involvement is usually short, many patients wonder if starting a treatment immediately can save the second eye.

The primary medication discussed for LHON is Idebenone (often known by the brand name Raxone). Its approval, availability, and prescribing rules vary significantly by country, so you will need to discuss local options with your specialist. Where authorized, expert consensus often suggests starting Idebenone early (within the first months of symptom onset) and continuing it for at least 24 months, though the exact duration is individualized based on patient response ^[4][6].

While doctors recommend evaluating treatment promptly, it is vital to understand what the medication actually does. Research indicates that Idebenone is used to help limit further vision loss and maximize the chances of visual recovery or stabilization over time ^[7][8]. It has not been proven to act as a preventative shield that completely stops the second eye from becoming affected ^[7].

In clinical studies, the focus has been on improving or stabilizing visual acuity (the sharpness of your vision) rather than successfully delaying the onset of symptoms in the second eye ^[7][8]. Pooled analyses of patient data suggest that prompt treatment offers a persistent benefit for visual recovery compared to the natural course of the condition, which is why early intervention is often encouraged ^[9][10]. However, if your second eye does become affected despite early treatment, it does not mean that you or the medication failed.

Your Period of Monitoring

The time between the first and second eye becoming affected is a highly stressful period of monitoring. During this time, consider the following practical steps to manage your care and well-being:

• Know What to Watch For: Monitor your “good” eye for subtle changes. Early warning signs include colors looking washed out, a new blur or blind spot in the center of your vision, or difficulty reading and recognizing faces. If your clinician recommends it, check each eye separately by covering one at a time. Contact your medical team immediately if you notice these changes.
• Discuss Treatment and Monitoring: Ask your doctor about the availability of Idebenone or clinical trials in your area ^[6]. Discuss how frequently your visual acuity, color vision, and optic nerve health should be checked.
• Reduce Environmental Risks: Limit your exposure to metabolic stressors—environmental factors that make it harder for your cells to produce energy. Experts highly recommend stopping smoking and avoiding heavy alcohol use, as these can further stress the optic nerve. While avoiding these will not guarantee the second eye remains unaffected, it is a sensible, evidence-based risk-reduction measure for your overall eye health.
• Seek Broad Support: Ask your care team about low-vision rehabilitation, assistive technology, and genetic counseling. Connecting with mental health professionals or LHON peer-support groups can also help you navigate the emotional weight of this uncertainty and prepare for practical changes in your daily life.