Assistive peripheral prosthetic vision aids perception and mobility in outdoor environments: A virtual-reality simulation study

Visual fatigue induced by watching virtual reality device and the effect of anisometropia

The effect of small anisometropia on visual fatigue when using virtual reality (VR) devices was investigated. Participants (n = 34) visited three times. In the first visit, VR exposure (10 min) was conducted with the full correction of the refractive error of both eyes. Experimental anisometropia was induced by adding a + 1.0 dioptre spherical lens either on the dominant eyes in the second visit or on the non-dominant eyes in the third visit. At each visit, the participants played a predetermined video game using a head-mounted display VR for 10 min. Visual fatigue was assessed before and after playing VR game using the Virtual Reality Symptom Questionnaire (VRSQ) and high-frequency component of accommodative microfluctuation. Results showed that watching VR induced significant increase of VRSQ score, significant decrease in the maximum accommodation power and objective increase in visual fatigue. Experimental anisometropia induction either on the dominant or non-dominant eyes did not aggravate visual fatigue. Practitioner summary: Mild differences in refractive error (up to 1.0 dioptre) between both eyes do not significantly increase ocular fatigue by viewing virtual reality device (10 min). The impact of small anisometropia may be limited in developing a virtual reality device. Abbreviations: VR: virtual reality; VRSQ: virtual reality symptom questionnaire; HMD: head-mounted display; HFC: high-frequency component.

Assistive peripheral phosphene arrays deliver advantages in obstacle avoidance in simulated end-stage retinitis pigmentosa: a virtual-reality study

OBJECTIVE

The prospective efficacy of peripheral retinal prostheses for guiding orientation and mobility in the absence of residual vision, as compared to an implant for the central visual field (VF), was evaluated using simulated prosthetic vision (SPV).

APPROACH

Sighted volunteers wearing a head-mounted display performed an obstacle circumvention task under SPV. Mobility and orientation performance with three layouts of prosthetic vision were compared: peripheral prosthetic vision of higher visual acuity (VA) but limited VF, of wider VF but limited VA, as well as centrally restricted prosthetic vision. Learning curves using these layouts were compared fitting an exponential model to the mobility and orientation measures.

MAIN RESULTS

Using peripheral layouts, performance was superior to the central layout. Walking speed with both higher-acuity and wider-angle layouts was 5.6% higher, and mobility errors reduced by 46.4% and 48.6%, respectively, as compared to the central layout. The wider-angle layout yielded the least number of collisions, 63% less than the higher-acuity and 73% less than the central layout. Using peripheral layouts, the number of visual-scanning related head movements was 54.3% (higher-acuity) and 60.7% (wider-angle) lower, as compared to the central layout, and the ratio of time standing versus time walking was 51.9% and 61.5% lower, respectively. Learning curves did not differ between layouts, except for time standing versus time walking, where both peripheral layouts achieved significantly lower asymptotic values compared to the central layout.

SIGNIFICANCE

Beyond complementing residual vision for an improved performance, peripheral prosthetic vision can effectively guide mobility in the later stages of retinitis pigmentosa (RP) without residual vision. Further, the temporal dynamics of learning peripheral and central prosthetic vision are similar. Therefore, development of a peripheral retinal prosthesis and early implantation to alleviate VF constriction in RP should be considered to extend the target group and the time of benefit for potential retinal prosthesis implantees.