A randomized crossover clinical trial of multi-periscopic and Fresnel peripheral prism glasses for hemianopia.

Summary

In a single-masked, multicenter randomized crossover trial, both multi-periscopic and Fresnel peripheral prism glasses improved blind-side pedestrian collision detection after 4 weeks of home use, with no significant superiority of one over the other. Participants preferred FPPs for cosmetic appearance and MPPs for image clarity and field expansion; both reduced perceived walking difficulty.

Key Findings

• 63% (24/38) showed improved blind-side detection with at least one prism type after 4 weeks of home use.
• No significant difference in improvement rates between MPPs and FPPs for 40° (31% vs 26%; p=0.75) or 20° (37% vs 42%; p=0.75) bearing angles.
• Preference split: 59% favored FPPs (cosmetic appearance) vs 41% MPPs (image clarity/field expansion) among 32 completing both periods.
• Both prisms reduced perceived walking difficulty in challenging scenarios (p<0.01).

Clinical Implications

Both prism types can be offered, with counseling that FPPs may be cosmetically preferable while MPPs may provide clearer images and broader expansion. Device choice should align with patient priorities (mobility vs. appearance) and be trialed in real-life settings.

Limitations

• Modest sample size with 32 completing both periods
• Short 4-week exposure per device; no long-term safety/effectiveness data

Future Directions

Longer, pragmatic RCTs assessing real-world outcomes (falls, mobility independence), training effects, and head-to-head effectiveness including driving or navigation simulators.