Abstract
Purpose :
Although the clinical features of Usher Syndrome 1B (USH1B) have been adequately characterized, the actual effect of this syndrome implying impaired hearing, vision and balance on daily living has not been objectively evaluated. This is a prospective clinical study to assess this impact of reduced visual function in USH1B patients compared to non-syndromic retinitis pigmentosa (RP) patients.
Methods :
The subjects are 12 USH1B and 20 non-syndromic RP patients, and 10 fully-sighted controls (CO). All were asked to perform three tasks. The locomotion task consisted of moving around avoiding obstacles. The spatial localization task involved picking out one mannequin amongst four in differing locations. Both took place at 500 and 7.5 lux (in transition from 500 lux and adapted) in an artificial street (Streetlab platform). The visual search task took place in an experimental apartment (Homelab platform) and aimed to look for target objects among 48 placed in a kitchen and grasp them. Errors and time parameters were some of the main objective measures analysed for each task.
Results :
During locomotion, RP and USH1B showed reduced Pourcentage of Preferred Walking Speed (PPWS) (p<0.0001) and greater number of collisions than the CO (p<0.001). These differences between RP/USH1B and CO were also observed at 7.5 lux compared to 500 lux. USH1B hit more obstacles than RP when their visual field was ≤ 20°. Number of intentional touches was increased in RP than in USH1B (p<0.05). PPWS was correlated with age, and collisions were correlated with visual acuity and contrast sensitivity. PPWS and collisions were also correlated with dark adaptation at 7.5 lux only. In spatial localization task, RP and USH1B took more time to identify the mannequins than CO (p<0.001). Visual search task showed that RP and USH1B were slower than CO to identify objects (p<0.0001), and that bigger objects were found faster in all groups (p<0.001). USH1B made more identification errors than CO (p<0.05).
Conclusions :
People with RP and USH1B have worse performances than CO, especially under low illumination. In general, few differences appear between RP and USH1B but we observed that USH1B encounter more difficulties in locomotion and visual search tasks.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.