Multi-periscopic prism device for field expansion

Review: Binocular double vision in the presence of visual field loss

Binocular double vision in strabismus is marked by diplopia (seeing the same object in two different directions) and visual confusion (seeing two different objects in the same direction). In strabismus with full visual field, the diplopia coexists with visual confusion across most of the binocular field. With visual field loss, or with use of partial prism segments for field expansion, the two phenomena may be separable. This separability is the focus of this review and offers new insights into binocular function. We show that confusion is necessary but is not sufficient for field expansion. Diplopia plays no role in field expansion but is necessary for clinical testing of strabismus, making such testing difficult in field loss conditions with confusion without diplopia. The roles of the three-dimensional structure of the real world and the dynamic of eye movements within that structure are considered as well. Suppression of one eye's partial view under binocular vision that develops in early-onset (childhood) strabismus is assumed to be a sensory adaption to diplopia. This assumption can be tested using the separation of diplopia and confusion.

Efficacy of a wearable night-vision aid in patients with concentric peripheral visual field loss: a randomized, crossover trial

PURPOSE

To investigate the efficacy of our wearable night-vision aid in patients with concentric peripheral visual field loss.

STUDY DESIGN

Prospective, single blind, three-group, and three-period crossover clinical study.

METHODS

The study included patients with concentric peripheral visual field loss, a best-corrected visual acuity (decimal visual acuity) of 0.1 or higher in the better eye, and the presence of a central visual field. HOYA MW10 HiKARI® (HOYA Corporation), our original wearable night-vision aid, was used as the test device with three types of camera lenses (standard-, middle-, and wide-angle lenses). Under both bright and dark conditions, the angle of the horizontal visual field was measured using each of the three lens types for each group. The baseline angle was measured when each participant wore the night-vision aid (powered off).

RESULTS

The study included 21 participants. Under bright condition, the perceived horizontal visual field was significantly wider than the baseline setup when using the standard-angle lens ("the standard lens"); the middle-angle lens ("the middle lens") was significantly wider than both the baseline setup and the standard lens; and the wide-angle lens ("the wide lens") was significantly wider than the other lenses. Under dark condition, the perceived horizontal visual field was again significantly wider when using the middle lens than the baseline setup and the standard lens, and when using the wide lens, the perceived horizontal visual field was again wider than when using the other lenses. The control in the bright condition was significantly wider (p < 0.001) than when used in the dark condition, while the standard-angle lens in the dark condition was significantly wider (p = 0.05) than when used in the bright condition. In regards to the middle and wide lenses, there was no statistically significant result emerging from either of the illumination conditions.

CONCLUSION

Our wearable night-vision aid with a middle-angle or wide-angle lens appears to provide wider visual field images in patients with concentric peripheral visual field loss, regardless of whether the illumination conditions are bright or dark.

The effect of visual rivalry in peripheral head-mounted displays on mobility

Recent head-mounted displays and smart glasses use vision multiplexing, an optical approach where two or more views are superimposed on each other. In vision multiplexing, augmented information is presented over an observer's natural field of view, providing field expansion and critical information during mobility situations like walking and driving. Yet despite its utility, vision multiplexing may produce visual rivalry, a phenomenon where perception alternates between the augmented information and the background scene for seconds at a time. To investigate, we compared the effect of different peripheral vision multiplexing configurations (unilateral opaque, unilateral see-through and bilateral see-through) on the detection of augmented information, incorporating at the same time real-world characteristics (target eccentricity, depth condition, and gaze movement) for a more realistic assessment. Results showed a persistently lower target detection rate in unilateral configurations than the bilateral configuration, suggesting a larger effect of binocular rivalry on target visibility. Nevertheless, this effect does become attenuated when more naturalistic elements are incorporated, and we discuss recommendations for vision multiplexing design and possible avenues for further research.

Oblique multi-periscopic prism for field expansion of homonymous hemianopia

Oblique Fresnel peripheral prisms have been used for field expansion in homonymous hemianopia mobility such as walking and driving. However, limited field expansion, low image quality, and small eye scanning range limit their effectiveness. We developed a new oblique multi-periscopic prism using a cascade of rotated half-penta prisms, which provides 42° horizontal field expansion along with 18° vertical shift, high image quality, and wider eye scanning range. Feasibility and performance of a prototype using 3D-printed module are demonstrated by raytracing, photographic depiction, and Goldmann perimetry with patients with homonymous hemianopia.

3D Printing in Eye Care

Three-dimensional printing enables precise modeling of anatomical structures and has been employed in a broad range of applications across medicine. Its earliest use in eye care included orbital models for training and surgical planning, which have subsequently enabled the design of custom-fit prostheses in oculoplastic surgery. It has evolved to include the production of surgical instruments, diagnostic tools, spectacles, and devices for delivery of drug and radiation therapy. During the COVID-19 pandemic, increased demand for personal protective equipment and supply chain shortages inspired many institutions to 3D-print their own eye protection. Cataract surgery, the most common procedure performed worldwide, may someday make use of custom-printed intraocular lenses. Perhaps its most alluring potential resides in the possibility of printing tissues at a cellular level to address unmet needs in the world of corneal and retinal diseases. Early models toward this end have shown promise for engineering tissues which, while not quite ready for transplantation, can serve as a useful model for in vitro disease and therapeutic research. As more institutions incorporate in-house or outsourced 3D printing for research models and clinical care, ethical and regulatory concerns will become a greater consideration. This report highlights the uses of 3D printing in eye care by subspecialty and clinical modality, with an aim to provide a useful entry point for anyone seeking to engage with the technology in their area of interest.

Photographic Depiction of the Field of View with Spectacles-mounted Low Vision Aids

SIGNIFICANCE

Photographic depiction helps to illustrate the primary and secondary field of view effects of low vision devices along with their utility to clinicians, patients, and caretakers. This technique may also be helpful for designers and researchers in improving the design and fitting of low vision devices.

PURPOSE

The field of view through spectacles-mounted low vision devices has typically been evaluated using perimetry. However, the perimetric field diagram is different from the retinal image and often fails to represent the important aspects of the field of view and visual parameters. We developed a photographic depiction method to record and veridically show the field of view effects of these devices.

METHODS

We used a 3D-printed holder to place spectacles-mounted devices at the same distance from the empirically determined reference point of the field of view in a camera lens (f = 16 mm) as they would be from an eye, when in use. The field of view effects of a bioptic telescope, a minifier (reverse telescope), and peripheral prisms were captured using a conventional camera, representing retinal images. The human eye pupil size (adjusting the F number: f/2.8 to f/8 and f/22 in the camera lens) and fitting parameters (pantoscopic tilt and back vertex distance) varied.

RESULTS

Real-world indoor and outdoor walking and driving scenarios were depicted as retinal images illustrating the field of view through low vision devices, distinguishing optical and obscuration scotomas, and demonstrating secondary effects (spatial distortions, viewpoint changes, diplopia, spurious reflection, and multiplexing effects) not illustrated by perimetric field diagrams.

CONCLUSIONS

Photographic depiction illustrates the primary and secondary field of view effects of the low vision devices. These images highlight the benefit and possible trade-offs of the low vision devices and may be beneficial in education and training.