Valonherkkyyttä

Valonherkkyyttä, known medically as photophobia, is an abnormal intolerance to light. It is not a disease in itself, but rather a symptom that can be caused by a wide range of underlying conditions, both ocular and systemic. Individuals experiencing photophobia may feel discomfort or pain when exposed to light, even to normal ambient levels. In severe cases, bright sunlight or even indoor lighting can be unbearable, leading to the person seeking dim environments or wearing protective eyewear.

The exact mechanisms behind photophobia are not fully understood, but it is believed to involve the trigeminal nerve, which transmits sensory information from the face and head, including the eyes, to the brain. When light stimulates certain light-sensitive cells in the eye, it can trigger an overreaction in this nerve pathway, resulting in the sensation of pain or discomfort.

Common causes of photophobia include eye conditions such as migraine headaches, uveitis, keratitis, iritis, conjunctivitis, dry eye syndrome, and certain types of eye surgery. Migraines are particularly well-known for causing photophobia, which can persist even after the headache has subsided. Beyond eye issues, photophobia can also be a symptom of neurological conditions like meningitis, encephalitis, and traumatic brain injury. Certain medications and substance use can also lead to increased light sensitivity. Diagnosing the cause of photophobia typically involves a comprehensive eye examination and a review of the patient's medical history. Treatment focuses on addressing the underlying condition responsible for the light sensitivity.