The Impact of Field of View on Understanding of a Movie Is Reduced by Magnifying Around the Center of Interest

Radial and Tangential Retinal Magnifications as Functions of Visual Field Angle Across Spherical, Oblate, and Prolate Retinal Profiles

Purpose

To provide a tool for calculating radial and tangential retinal magnifications as functions of field angle and retinal shape and to articulate patterns of magnification across the retina for monocular and binocular combinations of prolate-, oblate-, and spherical-shaped retinas.

Methods

Formulae were derived to calculate radial and tangential retinal magnifications (mm/deg) from field angle (degrees), retinal asphericity (unitless conic constant), retinal vertex radius of curvature (mm), and nodal point position (mm). Monocular retinal magnifications were determined for eyes with prolate, spherical, and oblate retinas as functions of field angle. Bilateral differences in magnifications were examined for combinations of those eyes.

Results

Retinal shape substantially affects magnification profiles even for eyes with the same axial length. Greatest magnification changes across a retina and between eyes, as well as greatest increase in radial-tangential differences (distortion), occur with prolate retinas. Binocular magnification differences were smallest for oblate retinas. Nodal points anterior to the vertex center of curvature and oblate asphericity both cause field-dependent reductions in magnification relative to the fovea (barrel distortion), whereas nodal points posterior to vertex center of curvature and prolate asphericity cause the opposite (pincushion distortion). Retinal magnification differences due to eye shape are much greater than aniseikonia thresholds and chromatic differences in magnification. A spreadsheet tool implements the magnification calculations.

Conclusions

Local retinal magnifications as functions of field angle have substantial effects on objective applications (imaging retinal anatomy) and subjective experiences (aniseikonia) and quantify an ocular property that differs across eye shapes and refractive errors.

Translational Relevance

Methods are provided to customize the calculation of radial and tangential magnifications across the retina for individual eyes, which will bolster the multifactorial study of the effects of foveal and peripheral optics across eye shapes and refractive errors.

The Effect of Zoom Magnification and Large Display on Video Comprehension in Individuals With Central Vision Loss

Purpose

A larger display at the same viewing distance provides relative-size magnification for individuals with central vision loss (CVL). However, the resulting large visible area of the display is expected to result in more head rotation, which may cause discomfort. We created a zoom magnification technique that placed the center of interest (COI) in the center of the display to reduce the need for head rotation.

Methods

In a 2 × 2 within-subject study design, 23 participants with CVL viewed video clips from 1.5 m (4.9 feet) shown with or without zoom magnification, and with a large (208 cm/82" diagonal, 69°) or a typical (84 cm/33", 31°) screen. Head position was tracked and a custom questionnaire was used to measure discomfort.

Results

Video comprehension was better with the large screen (P < 0.001) and slightly worse with zoom magnification (P = 0.03). Oddly, head movements did not vary with screen size (P = 0.63), yet were greater with zoom magnification (P = 0.001). This finding was unexpected, because the COI remains in the center with zoom magnification, but moves widely with a large screen and no magnification.

Conclusions

This initial attempt to implement the zoom magnification method had flaws that may have decreased its effectiveness. In the future, we propose alternative implementations for zoom magnification, such as variable magnification.

Translational Relevance

We present the first explicit demonstration that relative-size magnification improves the video comprehension of people with CVL when viewing video.

An implementation of Bubble Magnification did not improve the video comprehension of individuals with central vision loss

PURPOSE

People with central vision loss (CVL) watch television, videos and movies, but often report difficulty and have reduced video comprehension. An approach to assist viewing videos is electronic magnification of the video itself, such as Bubble Magnification.

METHODS

We created a Bubble Magnification technique that displayed a magnified segment around the centre of interest (COI) as determined by the gaze of participants with normal vision. The 15 participants with CVL viewed video clips shown with 2× and 3× Bubble Magnification, and unedited. We measured video comprehension and gaze coherence.

RESULTS

Video comprehension was significantly worse with both 2× (p = 0.01) and 3× Bubble Magnification (p < 0.001) than the unedited video. There was no difference in gaze coherence across conditions (p ≥ 0.58). This was unexpected because we expected a benefit in both video comprehension and gaze coherence. This initial attempt to implement the Bubble Magnification method had flaws that probably reduced its effectiveness.

CONCLUSIONS

In the future, we propose alternative implementations of Bubble Magnification, such as variable magnification and bubble size. This study is a first step in the development of an intelligent-magnification approach to providing a vision rehabilitation aid to assist people with CVL.

Saccade Landing Point Prediction Based on Fine-Grained Learning Method

The landing point of a saccade defines the new fixation region, the new region of interest. We asked whether it was possible to predict the saccade landing point early in this very fast eye movement. This work proposes a new algorithm based on LSTM networks and a fine-grained loss function for saccade landing point prediction in real-world scenarios. Predicting the landing point is a critical milestone toward reducing the problems caused by display-update latency in gaze-contingent systems that make real-time changes in the display based on eye tracking. Saccadic eye movements are some of the fastest human neuro-motor activities with angular velocities of up to 1,000°/s. We present a comprehensive analysis of the performance of our method using a database with almost 220,000 saccades from 75 participants captured during natural viewing of videos. We include a comparison with state-of-the-art saccade landing point prediction algorithms. The results obtained using our proposed method outperformed existing approaches with improvements of up to 50% error reduction. Finally, we analyzed some factors that affected prediction errors including duration, length, age, and user intrinsic characteristics.