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.
Microspherophakia is a rare congenital autosomal recessive condition where the lens of the eye is smaller than normal and spherically shaped. This condition may be associated with a number of disorders including Peters anomaly, Marfan syndrome, and Weill–Marchesani syndrome. The spherical shape is caused by an underdeveloped zonule of Zinn, which doesnt exert enough force on the lens to make it form the usual oval shape. It is a result of a homozygous mutation to the LTBP2 gene. See also
Ectopia lentis

References
Further reading
Microspherophakia at Online Mendelian Inheritance in Man


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