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Marion Swital, Guillaume Le Gall, Caroline Chauvire, Arnaud Koustanai, Johan Le Brun, Thierry Villette, Philippe Chaumet-Riffaud, Saddek Mohand-Said, Jose A. Sahel, Avinoam B. Safran; Improved reading with a Novel Enhanced Reality Non-Immersive Head-Mounted Display using a Snapshot Function in Patients with Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4389.
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Age-related Macular Degeneration (AMD) results in macular scotomas. Fixation is then performed using spared peripheral retinal locations, a condition associated with increased fixation instability. In AMD, Head Mounted Displays (HMD) improve vision by providing the wearer with a processed virtual real-time image, which however is deteriorated during head movements associated to fixation instability. To suppress image deterioration induced by such head movements, a snapshot function was implemented into a novel non-immersive HMD. Its use in affected patients was evaluated.
We included five patients with atrophic AMD (62 to 81 years old, mean 71.4; binocular visual acuity +0.9 to +0.6 logMAR, mean +0.78). We used a novel non-immersive HMD (Lumus, Rehovot, Israel; Essilor Int., and Institut de la Vision, Paris, France), which provides an augmented reality image, displayed through transparent lenses. The wearer saw the scene both in virtual and processed mode in the HMD and in natural mode through each lens. We presented 2 meter-distant, 21x29.7 cm posters, showing four lines of numbers and common city names, characters being 0.2° in viewing angular dimension. Poster content was read randomly using either a snapshot (i.e., a freeze frame) or without snapshot (video mode), at the same magnification. The trial was repeated 10 times, each with different poster content. We recorded and analyzed the time needed to read the content with and without the snapshot function, using two magnification levels (for either comfortable reading or minimum acceptable character size).
Patients showed shorter reading time when using a frozen image, in both magnification conditions (F(1,8)=9.5; p<.02). Benefits of snapshot function was greater when minimal magnification was used (F(1,8)=12; p<.009) compared to comfort magnification (F(1,8)=1.57; p=.25).
Snapshot function of the HMD markedly improves distant reading in the conditions tested. The benefits of the snapshot are more important when deciphering smaller characters, a condition associated with larger visual span. Moreover, reading comfort is also increased using a snapshot, as frozen image can be viewed against a darker background, thus improving luminance contrast of the augmented reality image.
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