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Chloé Pagot, Karine Becker, ARIEL ZENOUDA, Emilie Bochin, Huchet Delphine, Coen Cécilia, Saddek Mohand-Said, Jose Alain Sahel; Locomotion and visual search of objects with patients affected by retinitis pigmentosa in twilight conditions. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3284.
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© ARVO (1962-2015); The Authors (2016-present)
Retinitis pigmentosa (RP) causes significant difficulties for patients in their daily life, especially for visual search of objects and locomotion, which are increased in twilight conditions. The objectives of this study are to analyze the behavior of patients affected by RP in twilight conditions and also provide knowledge about the threshold of comfort and discomfort for performing tasks in dark conditions.
10 fully-sighted people (CO) and 17 RP subjects were recruited. RP people had a visual acuity > 0.5 and two groups were formed: visual field ≤ 20° (RP1) and 20° < visual field ≤ 40° (RP2). Tests took place in the Streetlab platform, a controlled environment integrating objective measurement tools. Two tasks were realized in five lighting conditions: adapted (235, 2 and 1 lux) and in transition (235 to 2 or 1 lux). For the locomotion task, the subjects had to avoid obstacles. To analyze the behavior with precision (preferred walking speed (PWS), percentage of PWS (PPWS), movement strategies, etc.) they were equipped with biometric sensors. The visual search task consisted of finding target objects on a desk among “distracters”. The data collected included scanning strategies, errors and time taken.
During the locomotion task, PWS of RP1 was lower than the RP2 group (p<0.001). All RP PWS were reduced in twilight (p<0.01). PWS of all groups was lower in transition than in adapted conditions (p<0.05). Similar results were found for PPWS except there was no difference between RP1 and RP2. Initiation time to walk was longer in RP1 group than in RP2’s, and increased in twilight for all groups. A significant difference was observed between RP groups and controls for all the walking parameters. RP patients also made more curves than controls (p<0.001). In the visual search task, RP1 were slower (p<0.001) and committed more recognition errors than RP2 (p<0.05). Bigger objects were better identified (p<0.05) by all, but contrast and object localization had no influence on finding objects. In RP1 group, 14% of target objects were not found in the time allotted, against 3% in RP2 group.
We provide quantitative measurements on the impact of twilight in RP patients, who are indeed more perturbed and anticipate less than the CO. In the future, it would be interesting to investigate other illumination values in twilight or glare conditions.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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