Mechanism of presbyopia and adaptation changes of near triad with age

Abstract

Presbyopia is the decrease of accommodative power as a part of the structural and functional physiological aging process. Aging has been regarded as an interesting evolutionary negligence resulting in irreversible visual impairment and psychological shock. Despite reviewing the many theories proposed over time, the dispute is still unresolved; however, the mechanism of the lens itself appears to be the most important factor in the determination of presbyopia. The Helmholtz theory of the regulation mechanism is the most widely accepted. Weakening of the accommodative power occurs due to hardening of the lens capsule and leads to a convergence–accommodation (near triad) cross-link. The attenuation of the adjustment increases the exophoria at near. From this, it is conceivable that the fusion convergence becomes stronger. The miosis accompanying the near vision also eliminates blurring by increasing the depth of focus so as to compensate for the decrease in accommodative power. Hence, the adaptation of near triad accompanying presbyopia was discussed.