Mesoamerica movements of celestial bodies and memorialize public officials. The 260-day cycle was also used for divination, and (like the Catholic calendar of saints) to name newborns. The names given to the days, months, and years in the Mesoamerican calendar came, for the most part, from animals, flowers, heavenly bodies, and cultural concepts that held symbolic significance in Mesoamerican culture. This calendar was used throughout the history of Mesoamerican by nearly every culture. Even today, several Maya groups in Guatemala, including the [[K'iche' people|K'iche']], [[Q'eqchi' people|Q'eqchi']], [[Kaqchikel people|Kaqchikel]], and the [[Mixe]] people of Oaxaca continue using modernized forms of the Mesoamerican
Fixation disparity A patient's associated phoria is the amount of prism needed to reduce their fixation disparity to zero minutes of arc. The Mallett Fixation Disparity Unit Instrument used to measure the associated heterophoria (or compensating prism). It consists of a small central fixation letter X surrounded by two letters O, one on each side of X, the three letters being seen binocularly, and two coloured polarized vertical bars in line with the centre of the X which are seen by each eye separately. The instrument can be swung through 90° to measure any vertical fixation disparity. The associated phoria is indicated