Types of Visual Symptoms
1. Light Sensitivity
Light sensitivity, or photophobia is an intolerance of light. This is fairly common after a minor head injury. (Bright) light will cause discomfort, along with a need to squint or close your eyes. Sometimes this is accompanied by headache.
2. Visual Blurring
Typically, people complain that their vision intermittently goes “blurry” and they have to screw up their eyes to make things come back to normal. Sometimes the vision may even be double. This symptom is often due to “convergence spasm”. This is when one of the eyes is too actively ‘turning in’ towards the nose. Convergence is a normal eye movement but sometimes it becomes hyperactive.
3. Visual Snow
Sometimes people become aware of a snowlike effect in their vision. This could be due to an eye or brain disorder but it can also be a normal phenomenon. If anyone looks at a bright background they may become aware of a fuzzy, ‘static’ with a sense that things are moving around. In some people this persists probably because of attention paid to it. Normally the brain blocks out this additional visual information. It often helps to understand what it is and that it will improve the less you pay attention to it.
4. Visual Persistence Phenomena
People also can become aware of persistence of visual images, especially after they have been looking at something for a while or if they are trying to follow a rapidly moving object. Like visual snow its really important to exclude a neurological or ophthlamological cause for this but it can occur, like visual snow, as a symptom arising without neurological disease. Its due to the same problem of the normal ‘filtering’ mechanism in the brain which blocks out the excess visual information going wrong.