Change in refractive anisometropia in presbyopic adults wearing monovisioncontact lens correction

Background. Researchers studying the refractive development of infant monke ys suggest that monocular refractive error changes in response to induced a metropia; specifically, slightly blurring one eye may cause a difference to develop between each eye's correction (anisometropia) when none existed be fore wearing the correction, The important question of whether similar chan ges occur in humans has not been addressed. Methods. We compared premonovis ion correction and the correction after at least 12 months of monovision so ft contact lens wear (artificially induced anisometropia prescribed to focu s one eye for near and the other for distance so that bifocal glasses are n ot needed) for 62 healthy predominantly female soft contact lens wearers an d (a) 62 age- and sex-matched spectacle wearers and (b) 62 age- and general ly sex-matched contact lens wearers. Control patients wore corrections of l ike power and had similar follow-up periods. Results. Development of anisom etropia occurred significantly more frequently among monovision wearers tha n among spectacle (p = 0.043) or contact lens wearing controls (p = 0.025). Changes in anisometropia greater than or equal to 0.50 D, with amounts up to 1.25 D, occurred in 29% of monovision wearers. Conclusions. Changes in r efractive correction occur for adults who have monocular blur intentionally induced with monovision contact lenses. Similar changes may also occur aft er refractive surgery if one eye is corrected for a different distance than the other. Care should be taken when counseling presbyopic patients so tha t they are aware of the possibility of inducing refractive changes after mo novision correction.