Gaze Scanning at Street Crossings by Pedestrians With Homonymous Hemianopia With and Without Hemispatial Neglect.

Purpose: To investigate compensatory gaze-scanning behaviors during street crossings by pedestrians with homonymous hemianopia (HH) and hemispatial neglect (HSN). Methods: Pedestrians with right homonymous hemianopia (RHH) and left homonymous hemianopia without (LHH) and with left spatial-neglect (LHSN) walked on city streets wearing a gaze-tracking system that also captured scene videos. Street-crossing instances were manually annotated, and horizontal gaze scan of magnitude ≥20° and scanning rates were compared within-subject, between the side of the hemifield loss (BlindSide) and the other side (SeeingSide). Proportion of instances with scans to both the left and the right side at nonsignalized crossings (indicative of safe scanning behavior) were compared among the three subject groups. Results: Data from 19 participants (6 LHH, 7 RHH, and 6 with mild [4] or moderate [2] LHSN), consisting of 521 street-crossing instances of a total duration of 201 minutes and 5375 gaze scans, were analyzed. The overall gaze magnitude (mean [95% confidence interval (CI)]) was significantly larger toward the BlindSide (40.4° [39.1°-41.9°]) than the SeeingSide (36° [34.8°-37.3°]; P < 0.001). The scanning rate (mean [95% CI] scans/min) toward the BlindSide (14 [12.5-15.6]) was significantly higher than the SeeingSide (11.5 [10.3°-12.9°]; P < 0.001). The scanning rate in the LHSN group (10.7 [8.9-12.8]) was significantly lower than the LHH group (14 [11.6-17.0]; P = 0.045). The proportion of nonsignalized crossings with scans to both sides was significantly lower in LHSN (58%; P = 0.039) and RHH (51%; P = 0.003) than LHH (75%) participants. Conclusions: All groups demonstrated compensatory scanning, making more gaze scans with larger magnitudes to the blind side. Mild to moderate LHSN adversely impacted the scanning rate.

Validation of a Semiautomatic Optical Coherence Tomography Digital Image Processing Algorithm for Estimating the Tear Meniscus Height.

Purpose: To design and validate a high-sensitivity semiautomated algorithm, based on adaptive contrast image, able to identify and quantify tear meniscus height (TMH) from optical coherence tomography (OCT) images by using digital image processing (DIP) techniques. Methods: OCT images of the lacrimal meniscus of healthy patients and with dry eye are analyzed by our algorithm, which is composed of two stages: (1) the region of interest and (2) TMH detection and measurement. The algorithm performs an adaptive contrast sequence based on morphologic operations and derivative image intensities. Trueness, repeatability, and reproducibility for TMH measurements are computed and the algorithm performance is statistically compared against the corresponding negative obtained manually by using a commercial software. Results: The algorithm showed excellent repeatability supported by an intraclass correlation coefficient equal to 0.993, a within-subject standard deviation equal to 9.88, and a coefficient of variation equal to 2.96%, and for the reproducibility test, the results did not show a significant difference as the mean value was 244.4 ± 114.9 µm for an expert observer versus 242.4 ± 111.2 µm for the inexperienced observer (P = 0.999). The method strongly suggests the algorithm can predict measurements that are manually performed with commercial software. Conclusions: The presented algorithm possess high potential to identify and measure TMH from OCT images in a reproducible and repeatable way with minimal dependency on user. Translational Relevance: The presented work shows a methodology on how, by using DIP, it is possible to process OCT images to calculate TMH and aid ophthalmologists in the diagnosis of dry eye disease.

Measuring Virtual Reality Headset Resolution and Field of View: Implications for Vision Care Applications.

SIGNIFICANCE: To judge the feasibility of virtual reality (VR) headsets for vision testing and treatment of binocular vision disorders and low vision, angular resolution (logMAR) and field of view must be known and may not be reliably provided. This is the first study to measure the limitations of VR systems for eye care applications. PURPOSE: This study aimed to measure, in a sample of VR headsets, eye-to-screen distance and other physical and optical characteristics needed to calculate minimum angular resolution in logMAR and field of view in determining feasibility for vision applications. METHODS: Eye-to-screen distance was measured, and logMAR, field of view, and maximum convergence demand were calculated for two standalone VR devices, Oculus Rift DK2 and HTC Vive, and, for four smartphone VR headsets, Zeiss VR1, Samsung Gear VR, VR Box, and SunnyPeak, each paired with four high-resolution smartphones, Samsung Galaxy S7/S8, iPhone X, and LG VR30. RESULTS: On average, the smallest letter that could be displayed in VR was 0.41 ± 0.09 (20/51), ranging from 0.59 (20/78) in the DK2 to 0.28 (20/39) in VR Box with S7. Mean field of view was 50.2 ± 4.8°, ranging from 39.6° in the VR Box with S7 to 55° in the HTC Vive. The mean field of view when used as a low vision aid was 23.0° and 12.7° for 2.2× and 4×, respectively. The mean maximum near convergence demand produced for a 60-mm interpupillary distance was 38.6 ± 10.1Δ. CONCLUSIONS: The minimum angular resolution in logMAR of current VR technology is insufficient for visual acuity testing and may be insufficient for standalone treatment of amblyopia. Field of view during movie watching or gaming is about half that reported by manufacturers but adequate for some types of visual field testing. Use for vergence testing and training is a concern for headsets with long eye-to-screen distance or interpupillary distances <60 mm.

Using an Automated Hirschberg Test App to Evaluate Ocular Alignment.

A smartphone app has been developed to perform the automated photographic Hirschberg test for objective measurement of ocular misalignment. By computing the difference in corneal reflection generated by the phone camera flash relative to the iris center based on high resolution images, the app can measure misalignment with a much higher precision than the naked eye performing the Hirschberg test. It has been validated in a previous clinical evaluation study by comparing to the clinical gold standard-prism and alternate cover test. The goal of this article is to describe the testing techniques regarding how to use the app to measure ocular alignment for different fixation distances, without or with cover to break fusion, as well as angle kappa, so that users can use the app to perform equivalent tests typically done in clinic using prisms.

Development and Preliminary Evaluation of a Smartphone App for Measuring Eye Alignment.

PURPOSE: We evaluate a smartphone application (app) performing an automated photographic Hirschberg test for measurement of eye deviations. METHODS: Three evaluation studies were conducted to measure eye deviations in the horizontal direction. First, gaze angles were measured with respect to the ground truth in nonstrabismic subjects (n = 25) as they fixated monocularly on targets of known eccentricity covering an angular range of approximately ±13°. Second, phoria measurements with the app at near fixation (distance = 40 cm) were compared with the modified Thorington (MT) test in normally-sighted subjects (n = 14). Third, eye deviations using the app were compared to a cover test with prism neutralization (CTPN; n = 66) and Synoptophore (n = 34) in strabismic subjects. Regression analyses were used to compare the app and clinical measurements of the magnitude and direction of eye deviations (prism diopters, Δ). RESULTS: The gaze angles measured by the app closely followed the ground truth (slope = 1.007, R 2 = 0.97, P < 0.001), with a root mean squared error (RMSE) of 2.4Δ. Phoria measurements with the app were consistent with MT (slope = 0.94, R 2 = 0.97, P < 0.001, RMSE = 1.7Δ). Overall, the strabismus measurements with the app were higher than with Synoptophore (slope = 1.15, R 2 = 0.91, P < 0.001), but consistent with CTPN (slope = 0.95, R 2 = 0.95, P < 0.001). After correction of CTPN values for near fixation, the consistency of the app measurements with CTPN was improved further (slope = 1.01). CONCLUSIONS: The app measurements of manifest and latent eye deviations were consistent with the comparator clinical methods. TRANSLATIONAL RELEVANCE: A smartphone app for measurement of eye alignment can be a convenient clinical tool and has potential to be beneficial in telemedicine.

Preliminary Evaluation of a Wearable Camera-based Collision Warning Device for Blind Individuals.

SIGNIFICANCE: This work describes a preliminary evaluation of a wearable collision warning device for blind individuals. The device was found to provide mobility benefit in subjects without (or deprived of) vision. This preliminary evaluation will facilitate further testing of this developmental stage device in more naturalistic conditions. PURPOSE: We developed a wearable video camera-based device that provided tridirectional collision warnings (right, center, and left) via differential feedback of two vibrotactile wristbands. We evaluated its mobility benefit in blind and normally sighted (NS) blindfolded individuals in indoor mobility courses. METHODS: Three evaluation experiments were conducted. First, the ability of the device to provide warnings for hanging objects not detected by a long cane was evaluated in eight NS and four blind subjects in an obstacle course with and without the device. Second, the accuracy of collision warning direction assignment was evaluated in 10 NS subjects as they walked toward a hanging object at random offsets and verbally reported the obstacle offset position with respect to their walking path based on the wristbands' vibrotactile feedback. Third, the mobility benefit of collision warning direction information was evaluated by 10 NS and 4 blind subjects when walking with and without differential wristband feedback. RESULTS: In experiment 1, collisions reduced significantly from a median of 11.5 without to 4 with the device (P < .001). Percent preferred walking speed reduced only slightly from 41% without to 36% with the device (P = .04). In experiment 2, the most likely reported relative obstacle positions were consistent with the actual positions. In experiment 3, subjects made more correct navigational decisions with than without the collision warning direction information (91% vs. 69%, P < .001). CONCLUSIONS: Substantial mobility benefit of the device was seen in detection of aboveground collision threats missed by a long cane and in enabling better navigational decision making based on the tridirectional collision warning information.

The Magnetic Levator Prosthesis for Temporary Management of Severe Blepharoptosis: Initial Safety and Efficacy.

PURPOSE: We further optimized and evaluated the safety of the magnetic levator prosthesis (MLP) for temporary management of severe blepharoptosis, and compared efficacy and comfort against the ptosis crutch. METHODS: The interpalpebral fissure (IPF) of participants (n = 12) with ptosis was measured during attempted eyelid opening, volitional closing, and spontaneous closing with no device, ptosis crutch, or the MLP. A 10-point scale documented comfort. Additionally, a 20 minute and then 1 week trial of the MLP was offered. Safety measures were skin erythema rating, change in visual acuity, and change in corneal staining. RESULTS: The MLP and crutch opened the eye (IPF 11.2 and 9.3 mm), but the MLP allowed better volitional closure (IPF 1.0 vs. 4.9 mm, P = 0.009), but was no better in allowing spontaneous blink (IPF 7.5 vs. 7.7 mm, P = 0.722). Both devices were equally comfortable (both median 8/10 comfort, P = 0.46). With extended use, opening with the MLP showed IPF 9.24 mm at 20 minutes and 9.46 mm at 1 week, and volitional closure was IPF 0.95 and 0.52 mm, respectively. Closure on spontaneous blink improved with extended wear to IPF 5.14 and 5.18 mm, respectively (P = 0.002). Two participants exhibited moderate skin erythema and one had increased corneal staining without change in acuity. CONCLUSIONS: The MLP is safe and feasible for temporary correction of severe ptosis. TRANSLATIONAL RELEVANCE: First group data in patients showing successful reanimation of the eyelid with magnetic force.

Mobile gaze tracking system for outdoor walking behavioral studies.

Most gaze tracking techniques estimate gaze points on screens, on scene images, or in confined spaces. Tracking of gaze in open-world coordinates, especially in walking situations, has rarely been addressed. We use a head-mounted eye tracker combined with two inertial measurement units (IMU) to track gaze orientation relative to the heading direction in outdoor walking. Head movements relative to the body are measured by the difference in output between the IMUs on the head and body trunk. The use of the IMU pair reduces the impact of environmental interference on each sensor. The system was tested in busy urban areas and allowed drift compensation for long (up to 18 min) gaze recording. Comparison with ground truth revealed an average error of 3.3° while walking straight segments. The range of gaze scanning in walking is frequently larger than the estimation error by about one order of magnitude. Our proposed method was also tested with real cases of natural walking and it was found to be suitable for the evaluation of gaze behaviors in outdoor environments.

Evaluation of a Portable Collision Warning Device for Patients With Peripheral Vision Loss in an Obstacle Course.

PURPOSE: A pocket-sized collision warning device equipped with a video camera was developed to predict impending collisions based on time to collision rather than proximity. A study was conducted in a high-density obstacle course to evaluate the effect of the device on collision avoidance in people with peripheral field loss (PFL). METHODS: The 41-meter-long loop-shaped obstacle course consisted of 46 stationary obstacles from floor to head level and oncoming pedestrians. Twenty-five patients with tunnel vision (n = 13) or hemianopia (n = 12) completed four consecutive loops with and without the device, while not using any other habitual mobility aid. Walking direction and device usage order were counterbalanced. Number of collisions and preferred percentage of walking speed (PPWS) were compared within subjects. RESULTS: Collisions were reduced significantly by approximately 37% (P < 0.001) with the device (floor-level obstacles were excluded because the device was not designed for them). No patient had more collisions when using the device. Although the PPWS were also reduced with the device from 52% to 49% (P = 0.053), this did not account for the lower number of collisions, as the changes in collisions and PPWS were not correlated (P = 0.516). CONCLUSIONS: The device may help patients with a wide range of PFL avoid collisions with high-level obstacles while barely affecting their walking speed.

A Prototype External Magnetic Eyelid Device for Blepharoptosis.

PURPOSE: To test a prototype magnet system (magnetic levator prosthesis) for the ability to comfortably and non-invasively provide eye opening with maintenance of the blink in people with paralytic ptosis and determine preliminary efficacy for short-term clinical application. METHODS: The prototype device consisted of a magnet on a spectacle frame and a micro-magnet array mounted externally on the eyelid. Participants with unilateral CN III palsy (n=3) trialed the predicate (ptosis crutch) and magnet device. Video analysis was used to quantify changes in eyelid opening and subjective responses were documented with a rating scale. A 20-minute and then a 1-week trial were offered. RESULTS: The magnetic levator prosthesis device was effective to provide eye opening while allowing, at minimum, a volitional blink without ill effects on the eyelid skin or ocular surface. Comfort scores ranged from 6 to 9 out of 10 over 3 evaluations. All patients chose an extended trial of the magnet device and reported continued 8-9/10 comfort and efficacy after the extended 1-week trial. CONCLUSIONS: Comfortable and effective restoration of eye opening with maintenance of the blink is feasible using external static magnets and warrants further study. TRANSLATIONAL RELEVANCE: This is the first careful documentation of the successful use of an externally mounted static magnet system to treat paralytic ptosis.