The test consists of red and green semicircles on a black background with a white round fixation target. The size of the red semicircle is held constant while the green semicircle is varied in size in 1% increments. The patient wears a pair of red/green goggles so that one eye is tested at a time, and the patient attempts to determine when the semicircles are the same size. This is termed the reversal threshold and the size difference between the semicircles is reported as the degree of aniseikonia. A positive value indicates that the object was perceived bigger and thus corresponds to macropsia, and conversely a negative value indicates micropsia. The Aniseikonia Inspector contains an aniseikonia test based on the same principles as the NAT, but the test is run on a computer screen, it is based on a forced choice method, and it can measure the size difference as a function of the size of the objects. The functionality of being able to measure the size difference as function of the size (i.e. field dependent testing) is especially important when the macropsia (or micropsia) has a retinal origin. Treatment
The most common way to treat forms of aniseikonia, including macropsia, is through the use of auxiliary optics to correct for the magnification properties of the eyes. This method includes changing the shape of spectacle lenses, changing the vertex distances with contact lenses, creating a weak telescope system with contact lenses and spectacles, and changing the power of one of the spectacle lenses.
One of these studies was conducted on Japanese adolescents who reported visual episodic illusions with macropsia and showed that illusions are three times more likely to occur in association with migraine. The illusions were most prevalent among girls between the ages of 16 and 18. It is unlikely that macropsia in Japanese adolescents could be due to epileptic seizure since only 0.3% of Japanese adolescents have epilepsy. No evidence of drugs was found, which eliminates the possibility of the macropsia in the adolescents being drug-induced. It is also unlikely for macropsia in adolescent children to be associated with a serious disease. It is usually the macropsia or other visual disturbance which precedes the painful migrainous headaches. The episodes of macropsia can occur as part of the aura in a migraine. These episodes are often brief, lasting only a few minutes. Adolescents who are deemed to have multiple distortions per episode, such as slow motion vision and macropsia, are even more likely to be people with migraine. The macropsia episodes associated with migraine are typically equivalent to the duration of the aura, which can range from moments to 15 minutes. Non-migrainous headaches are not known to be associated with episodic illusions. Even in the absence of a migraine, a fever or a hypnogogic state can provoke visual illusions, which one might claim to be macropsia. A person with macropsia may fail to see the connection between the migraine and the macropsia, since the conditions may not elicit symptoms at the same time.