Retinal micropsia is characterized by an increase in the distance between retinal photoreceptors and is associated with decreased visual acuity. Cerebral micropsia is a rare form of micropsia that can arise in children with chronic migraines. Hemimicropsia is a type of cerebral micropsia that occurs within one half of the visual field. Differential diagnosis
Of all of the visual distortions, micropsia has the largest variety of causes. Migraines
Micropsia can occur during the aura phase of a migraine attack, a phase that often precedes the onset of a headache and is commonly characterized by visual disturbances. Micropsia, along with hemianopsia, quadrantopsia, scotoma, phosphene, teicopsia, metamorphopsia, macropsia, teleopsia, diplopia, dischromatopsia, and hallucination disturbances, is a type of aura that occurs immediately before or during the onset of a migraine headache. The symptom usually occurs less than thirty minutes before the migraine headache begins and lasts for five to twenty minutes. Only 10-20% of children with migraine headaches experience auras. Visual auras such as micropsia are most common in children with migraines. Seizures
The most frequent neurological origin of micropsia is a result of temporal lobe seizures. These seizures affect the entire visual field of the patient. More rarely, micropsia can be part of purely visual seizures. This in turn only affects one half of the visual field and is accompanied by other cerebral visual disturbances. The most common cause of seizures which produce perceptual disturbances such as micropsia and macropsia is medial temporal lobe epilepsy in which the seizures originate in the amygdala-hippocampus complex.
Japanese encephalitis vaccine is a vaccine that protects against Japanese encephalitis. The vaccines are more than 90% effective. The duration of protection with the vaccine is not clear but its effectiveness appears to decrease over time. Doses are given either by injection into a muscle or just under the skin.It is recommended as part of routine immunizations in countries where the disease is a problem. One or two doses are given depending on the version of the vaccine. Extra doses are not typically needed in areas where the disease is common. In those with HIV/AIDS or those who are pregnant an inactivated vaccine should be used. Immunization of travellers who plan to spend time outdoors in areas where the disease is common is recommended.The vaccines are relatively safe. Pain and redness may occur at the site of injection. As of 2015, 15 different vaccines are available: some are based on recombinant DNA techniques, others weakened virus, and others inactivated virus.The Japanese encephalitis vaccines first became available in the 1930s. It is on the World Health Organizations List of Essential Medicines. Efficacy
Randomized control trials on JE-VAX have shown that a two-dose schedule provides protection for one year. History
Japanese encephalitis vaccines first became available in the 1930s. One of them was an inactivated mouse brain-derived vaccine (the Nakayama and/or Beijing-1 strain), made by BIKEN and marketed by Sanofi Pasteur as JE-VAX, until production ceased in 2005. The other was an inactivated vaccine cultivated on primary hamster kidney cells (the Beijing-3 strain).