Randomized controlled multi-center trial of multi-periscopic prism glasses for hemianopia: early results

Abstract

Purpose : Multi-periscopic peripheral prisms (MPP) are a novel, high-power field expansion reflective device for homonymous hemianopia (HH). We are conducting a multi-center trial to evaluate the MPPs for general mobility with a virtual reality pedestrian collision detection test - a randomized crossover design in which (100Δ, ~42°) MPP glasses are being compared to commercially available (65Δ, ~32°) Fresnel peripheral prism (FPP) glasses, both in the oblique design. We hypothesize that detection of colliding overtaken pedestrians at 40° bearing angles will be higher with MPPs.

Methods : Patients (with HH and neither neglect nor cognitive decline) are being recruited at 7 sites. Eligible patients are randomly allocated to receive either 1) MPP first and FPP second, or 2) FPP first and MPP second. There are 4 visits: V1 screening; V2 fitting 1^st pair of prism glasses; V3 evaluation of 1^st pair (after 4 weeks of home wear) and fitting 2^nd pair; V4 evaluation of 2^nd pair (after 4 weeks) and clinical decision whether to continue with one pair for the longer term. A collision detection test, presented on a large screen (104° H by 74° V), simulates walking through a busy shopping mall with multiple pedestrians walking in various directions; in each trial one pedestrian might be on a collision course. Patients whose detection without devices on the blindside was > 70% were excluded. Questionnaires documented patients’ experience with the devices.

Results : To date, 25 patients have been screened, 9 were ineligible, 2 withdrew and 14 enrolled (48±22 years, 10 Male), 6 have completed and kept one device (3 chose MPPs, 3 FPPs). Median detection rates for these 6 patients for pedestrians at 40° and 20° bearing angles, with and with NO prisms on the same visits are shown in the table (image).
All 6 reported benefits with MPP and FPP for mobility/obstacle avoidance, 3/6 had difficulty interpreting prism image with FPPs/MPPs, 5/6 rated MPPs much better in terms of image clarity and how far to the blind side they could see, but worse than FPP for appearance. Early data suggests some learning effects in performing the task without prisms.

Conclusions : Recruitment and enrolment are progressing well. A large proportion were excluded at screening because with detection rates > 70% on the blind side there was no possibility for a significant improvement with prisms. Updated data will be presented at the meeting.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.