NystagmusNystagmus is a condition of involuntary (or voluntary, in some cases) eye movement. People can be born with it but more commonly acquire it in infancy or later in life. In many cases it may result in reduced or limited vision. In normal eyesight, while the head rotates about an axis, distant visual images are sustained by rotating eyes in the opposite direction of the respective axis. The semicircular canals in the vestibule of the ear sense angular acceleration, and send signals to the nuclei for eye movement in the brain.
Anxiety disorderAnxiety disorders are a cluster of mental disorders characterized by significant and uncontrollable feelings of anxiety and fear such that a person's social, occupational, and personal function are significantly impaired. Anxiety may cause physical and cognitive symptoms, such as restlessness, irritability, easy fatiguability, difficulty concentrating, increased heart rate, chest pain, abdominal pain, and a variety of other symptoms that may vary based on the individual.
NyctalopiaNyctalopia (ˌnɪktəˈloʊpiə; ), also called night-blindness, is a condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases. Night blindness may exist from birth, or be caused by injury or malnutrition (for example, vitamin A deficiency). It can be described as insufficient adaptation to darkness. The most common cause of nyctalopia is retinitis pigmentosa, a disorder in which the rod cells in the retina gradually lose their ability to respond to the light.
Melancholic depressionMelancholic depression, or depression with melancholic features, is a DSM-IV and DSM-5 specifier of depressive disorders. This type of depression has specific symptoms that make it different from the standard clinical depression list of symptoms. Furthermore, melancholic depression has a specific subset of causes and can respond differently to treatment than other clinical depression types. Depression with melancholic features is classified under the fourth and fifth versions Diagnostic and Statistic Manual of Mental Disorders (DSM-IV and DSM-5) as a specifier of depressive disorders.
Psychological painPsychological pain, mental pain, or emotional pain is an unpleasant feeling (a suffering) of a psychological, non-physical origin. A pioneer in the field of suicidology, Edwin S. Shneidman, described it as "how much you hurt as a human being. It is mental suffering; mental torment." There is no shortage in the many ways psychological pain is referred to, and using a different word usually reflects an emphasis on a particular aspect of mind life.
