Near-vision lens effects on nearwork-induced transient myopia

Nearwork-induced transient myopia (NITM), a lenticular-based pseudomyopia, is commonly found in myopic teenagers and young adults. It has been speculated that its presence may be a factor in nearwork-related symptoms and in the development of permanent myopia. Thus, the differential effect of various powered near-vision lenses on NITM was investigated. Nine young adults monocularly-viewed a near target (25 cm) for 20 min through either a +4, +2, or 0 diopter (D) near lens, or a 0.5-mm pinhole, over their habitual distance prescription. Monocular distance refraction was objectively assessed immediately before and after the near task. Decreasing the accommodative stimulus reduced the blur-driven adaptive aftereffect. Only with the 0 D accommodative stimulus condition was NITM not produced. These results suggest that the full blur-driven monocular stimulus to accommodation must be negated to prevent the occurrence of NITM. With the pinhole providing blur-free viewing conditions, a substantial proximal accommodative adaptive component was present. Copyright (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.