Abstract
Monovision can be used as a method to correct presbyopia with contact lenses (CL) but its effect on reading behavior is still poorly understood. In this study eye movements (EM) were recorded in fifteen presbyopic participants, naïve to monovision, whilst they read arrays of words, non-words, and text passages to assess whether monovision affected their reading. Three conditions were compared, using daily disposable CLs: baseline (near correction in both eyes), conventional monovision (distance correction in the dominant eye, near correction in the non-dominant eye), and crossed monovision (the reversal of conventional monovision). Behavioral measures (reading speed and accuracy) and EM parameters (single fixation duration, number of fixations, dwell time per item, percentage of regressions, and percentage of skipped items) were analyzed. When reading passages, no differences in behavioral and EM measures were seen in any comparison of the three conditions. The number of fixations and dwell time significantly increased for both monovision and crossed monovision with respect to baseline only with word and non-word arrays. It appears that monovision did not appreciably alter visual processing when reading meaningful texts but some limited stress of the EM pattern was observed only with arrays of unrelated or meaningless items under monovision, which require the reader to have more in-depth controlled visual processing.
Highlights
It has been estimated that presbyopia will affect about 2 billion people by 20501
An initial examination with standard optometric tests was performed to verify the eligibility of participants according to the inclusion criteria, to assess their basic visual and reading performance, to test their general performance in monovision, and to determine the power of the different contact lenses (CL) to be used for the three conditions of the eye movement (EM) recordings
Consistent with previous research[9,10,11,12,13,14], this study showed that monovision in a group of naïve presbyopes produced a complex pattern: on the one hand, monovision determined a drop of stereopsis, an increased level of suppression, a decrease of the visual acuity (VA) at distance in the eye corrected for near and a slight worsening of reading acuity and critical print size (CPS) with respect to the balanced condition of both eyes corrected for near
Summary
It has been estimated that presbyopia will affect about 2 billion people by 20501. Spectacles are the oldest and widespread method of presbyopia correction[2] and contact lenses (CL) and refractive surgery offer alternative solutions. The present study aims to examine the impact of monovision CL correction on reading at near distance through EM recorded while participants read text passages, as well as arrays of unrelated words and non-words (these latter are strings of letters that are used to create a readable item that is not a word and has no meaning).
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