The term “optical seizure” describes two different neurological events. The first is a seizure triggered by a visual stimulus, like flashing lights. The second refers to a seizure originating in the brain’s vision center, the occipital lobe, causing visual symptoms. Both involve abnormal electrical discharges in the brain but differ in cause and effect.
Visual Triggers of Seizures
Certain types of epilepsy are photosensitive, meaning seizures are provoked by specific visual inputs. In these individuals, hyperexcitable neurons in the brain are prompted to fire abnormally by certain patterns and frequencies of light. This electrical response occurs when the visual cortex cannot properly process high-contrast or rapidly changing light signals.
Common triggers include strobe lights at concerts or on emergency vehicles, which often flash at frequencies between 15 and 25 Hz. Flickering screens from televisions and video games are also well-documented triggers. In 1997, a Pokémon anime episode with a rapid sequence of red and blue flashes reportedly caused seizures in hundreds of viewers in Japan. Even natural light, like sunlight flickering through blinds, can induce a seizure.
Symptoms Originating in the Visual Cortex
Some seizures begin in the occipital lobe, the brain’s visual processing center. For these seizures, the visual disturbance is the primary manifestation of the event, not the trigger. These episodes can occur spontaneously and may be caused by an injury or lesion in the occipital lobe.
Many people report experiencing elementary visual hallucinations, which are simple, unformed images. These can include seeing brief flashes of light (photopsia) or perceiving bright, multicolored spots or rings. These visual phenomena develop rapidly over a few seconds and are typically brief.
Other symptoms involve a temporary disruption of normal sight. A person might experience a partial or complete loss of vision (amaurosis) or severely blurred vision. Involuntary eye movements are also characteristic, such as rapid blinking or a deviation of the eyes and head to one side. These visual symptoms can be followed by other sensations or progress to a more widespread seizure.
The Medical Diagnosis Process
Diagnosis begins with a detailed patient history, documenting the person’s description of the events. This history helps differentiate between causes like an occipital seizure or a migraine with aura, which can present with similar visual disturbances.
The primary diagnostic tool is an electroencephalogram (EEG), which records the brain’s electrical activity via scalp electrodes. To test for photosensitivity, intermittent photic stimulation is used during the EEG. A strobe light is flashed at varying frequencies to determine if it provokes abnormal brainwave discharges.
A doctor may also order a magnetic resonance imaging (MRI) scan. While an EEG shows brain function, an MRI provides a detailed image of the brain’s structure. This can help identify underlying abnormalities in the occipital lobe, such as a tumor or lesion, that could be causing the seizures.
Managing Visually Induced Seizures
Managing visually triggered seizures involves medical treatment and lifestyle adjustments. For recurrent seizures, neurologists often prescribe anti-seizure medications. These drugs work by stabilizing the brain’s electrical activity, making neurons less likely to fire abnormally and reducing seizure frequency.
A significant part of management focuses on avoiding or mitigating known triggers. Common strategies include:
- Wearing polarized sunglasses outdoors to reduce glare and flickering light.
- Using a screen filter on monitors and televisions and adjusting brightness and contrast.
- Choosing modern screens with higher refresh rates (100 Hz or more) as they are less provocative.
- Taking frequent breaks from prolonged screen time on televisions or video games.
When encountering an unavoidable trigger, like an ambulance’s flashing lights, a simple technique is to cover one eye with the palm of a hand. This action can significantly reduce the impact of the photic stimulation on the brain.
Informing friends, family, and colleagues about the condition is also helpful. Explaining the triggers and what to do during a seizure ensures that others can provide appropriate assistance. This support network can help manage the condition and reduce anxiety about potential triggers.