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N. Hutchings, N. Jung, L. Dowling, L. Lillakas, E.L. Irving; Eye and Head Movements inAdaptation to Progressive Addition Lens Wear . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2766.
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Purpose: To determine whether eye and head movements conducted by presbyopic subjects naïve to progressive addition lens (PAL) wear can be used to characterize the adaptation process to the spectacles. Methods: Horizontal and vertical eye and head movements were recorded using the EL–MAR 2020 binocular CCD video eye tracker for 10 presbyopic participants (age: 41–50; 8 females; distance visual acuity: 20/20 or better). The study was a double–blind crossover design, with each participant receiving two different PAL designs over a two month period. Each PAL design was worn for 3–4 weeks and recordings were obtained at the beginning and end of each period (four visits in total). Five participants wore the first PAL design (PAL1) followed by PAL2, and in the other five the order was reversed. The participants carried out the following tasks at each visit: (a) Flash letter identification (∼6/20) on a screen at 2m, 1m and 40cm; (b) Reading text (Single sheet; 10 point Times NR) and (c) Visual search. On completion of the study visits, each participant was asked to select their preferred PAL pair. Repeated measures ANOVA was used to evaluate differences between visits for the recorded parameters and to examine for the presence or absence of carry–over effects inherent to the study design. Results: Two parameters, the number of vertical head movements when carrying out letter identification at 2m and the number of horizontal saccade corrections for letter identification at 40cm, showed a statistically significant reduction between visits for both PAL designs. However, five parameters showed significant carry–over effects. The magnitude of these effects changed between the first and second visits, irrespective of lens design, and reversed between the third and fourth visits returning to baseline levels of the measure. Seven of the ten participants selected the second PAL design worn as their preferred lens. Conclusions: No specific parameter could be identified that characterized the adaptation process. However, the study suggests that the process of adaptation to PAL wear occurs over a period that is longer than 3–4 weeks and when adapted the PAL wearer returns to their habitual eye and head movement characteristics.
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