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Simulation of thalamic prosthetic vision: reading accuracy, speed, and acuity in sighted humans.

Vurro M, Crowell AM, Pezaris JS - Front Hum Neurosci (2014)

Bottom Line: Reading accuracy, reading speed, and reading acuity of 20 subjects were measured as a function of letter size, using a task based on the MNREAD chart.Results here were consistent with previous results from our laboratory.Results were also consistent with those from the literature, despite using naive subjects who were not trained on the simulator, in contrast to other reports.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurosurgery, Massachusetts General Hospital/Harvard Medical School Boston, MA, USA.

ABSTRACT
The psychophysics of reading with artificial sight has received increasing attention as visual prostheses are becoming a real possibility to restore useful function to the blind through the coarse, pseudo-pixelized vision they generate. Studies to date have focused on simulating retinal and cortical prostheses; here we extend that work to report on thalamic designs. This study examined the reading performance of normally sighted human subjects using a simulation of three thalamic visual prostheses that varied in phosphene count, to help understand the level of functional ability afforded by thalamic designs in a task of daily living. Reading accuracy, reading speed, and reading acuity of 20 subjects were measured as a function of letter size, using a task based on the MNREAD chart. Results showed that fluid reading was feasible with appropriate combinations of letter size and phosphene count, and performance degraded smoothly as font size was decreased, with an approximate doubling of phosphene count resulting in an increase of 0.2 logMAR in acuity. Results here were consistent with previous results from our laboratory. Results were also consistent with those from the literature, despite using naive subjects who were not trained on the simulator, in contrast to other reports.

No MeSH data available.


Related in: MedlinePlus

System architecture. The system consists of the Tobii TX300 gaze tracker operating in normal, streaming mode. Gaze position information relative to the TX300's built-in display screen is streamed over a low-latency dedicated connection to an intermediary interface computer that runs a small gaze-position server program. The server code accepts streaming data and, upon request from the behavioral control system, computes an instantaneous gaze position value (with non-linear noise reduction), that is returned over a second, low-latency dedicated connection. The behavioral computer runs the experiment and performs data logging. Whenever the behavioral task requires instantaneous gaze information (such as during the Reading Phase of the task; see main text), a request is sent to the gaze-position server that typically replies in under 2 ms. Total system latency from gaze measurement to video frame update is typically under 16 ms, with an additional 4 ms of LCD lag to an updated image on the subject retina. The intermediary gaze-position server eliminates the need for the behavioral control system to deal with streaming data, and thus simplifies the overall design, at the cost of a modest increase in total system latency.
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Figure 1: System architecture. The system consists of the Tobii TX300 gaze tracker operating in normal, streaming mode. Gaze position information relative to the TX300's built-in display screen is streamed over a low-latency dedicated connection to an intermediary interface computer that runs a small gaze-position server program. The server code accepts streaming data and, upon request from the behavioral control system, computes an instantaneous gaze position value (with non-linear noise reduction), that is returned over a second, low-latency dedicated connection. The behavioral computer runs the experiment and performs data logging. Whenever the behavioral task requires instantaneous gaze information (such as during the Reading Phase of the task; see main text), a request is sent to the gaze-position server that typically replies in under 2 ms. Total system latency from gaze measurement to video frame update is typically under 16 ms, with an additional 4 ms of LCD lag to an updated image on the subject retina. The intermediary gaze-position server eliminates the need for the behavioral control system to deal with streaming data, and thus simplifies the overall design, at the cost of a modest increase in total system latency.

Mentions: The experimental apparatus consisted of a heads-free binocular gaze tracker with integrated display (TX300, Tobii, Inc.), and two additional computers (M92p, Lenovo, Inc.) running custom-written software for interfacing, behavioral control, and data collection (Figure 1). The gaze tracker provided streaming gaze information at 300 Hz (0.4° accuracy and 0.14° precision) that was received and processed on the interface computer to be made available upon periodic request from the behavioral control computer running the experiment. The behavioral control computer coordinated experimental activities, including computing stimuli and presenting them on the TX300 integrated display, and logged experimental data. A small consumer-grade computer microphone was used to record audio during the experiment for post-hoc blind verification of subject performance. The stimulus display was operated at the native 1920 × 1080 resolution with 60 Hz vertical refresh rate. With the standard viewing distance of 65 cm, the display subtended 43° × 25° of visual angle.


Simulation of thalamic prosthetic vision: reading accuracy, speed, and acuity in sighted humans.

Vurro M, Crowell AM, Pezaris JS - Front Hum Neurosci (2014)

System architecture. The system consists of the Tobii TX300 gaze tracker operating in normal, streaming mode. Gaze position information relative to the TX300's built-in display screen is streamed over a low-latency dedicated connection to an intermediary interface computer that runs a small gaze-position server program. The server code accepts streaming data and, upon request from the behavioral control system, computes an instantaneous gaze position value (with non-linear noise reduction), that is returned over a second, low-latency dedicated connection. The behavioral computer runs the experiment and performs data logging. Whenever the behavioral task requires instantaneous gaze information (such as during the Reading Phase of the task; see main text), a request is sent to the gaze-position server that typically replies in under 2 ms. Total system latency from gaze measurement to video frame update is typically under 16 ms, with an additional 4 ms of LCD lag to an updated image on the subject retina. The intermediary gaze-position server eliminates the need for the behavioral control system to deal with streaming data, and thus simplifies the overall design, at the cost of a modest increase in total system latency.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4219440&req=5

Figure 1: System architecture. The system consists of the Tobii TX300 gaze tracker operating in normal, streaming mode. Gaze position information relative to the TX300's built-in display screen is streamed over a low-latency dedicated connection to an intermediary interface computer that runs a small gaze-position server program. The server code accepts streaming data and, upon request from the behavioral control system, computes an instantaneous gaze position value (with non-linear noise reduction), that is returned over a second, low-latency dedicated connection. The behavioral computer runs the experiment and performs data logging. Whenever the behavioral task requires instantaneous gaze information (such as during the Reading Phase of the task; see main text), a request is sent to the gaze-position server that typically replies in under 2 ms. Total system latency from gaze measurement to video frame update is typically under 16 ms, with an additional 4 ms of LCD lag to an updated image on the subject retina. The intermediary gaze-position server eliminates the need for the behavioral control system to deal with streaming data, and thus simplifies the overall design, at the cost of a modest increase in total system latency.
Mentions: The experimental apparatus consisted of a heads-free binocular gaze tracker with integrated display (TX300, Tobii, Inc.), and two additional computers (M92p, Lenovo, Inc.) running custom-written software for interfacing, behavioral control, and data collection (Figure 1). The gaze tracker provided streaming gaze information at 300 Hz (0.4° accuracy and 0.14° precision) that was received and processed on the interface computer to be made available upon periodic request from the behavioral control computer running the experiment. The behavioral control computer coordinated experimental activities, including computing stimuli and presenting them on the TX300 integrated display, and logged experimental data. A small consumer-grade computer microphone was used to record audio during the experiment for post-hoc blind verification of subject performance. The stimulus display was operated at the native 1920 × 1080 resolution with 60 Hz vertical refresh rate. With the standard viewing distance of 65 cm, the display subtended 43° × 25° of visual angle.

Bottom Line: Reading accuracy, reading speed, and reading acuity of 20 subjects were measured as a function of letter size, using a task based on the MNREAD chart.Results here were consistent with previous results from our laboratory.Results were also consistent with those from the literature, despite using naive subjects who were not trained on the simulator, in contrast to other reports.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurosurgery, Massachusetts General Hospital/Harvard Medical School Boston, MA, USA.

ABSTRACT
The psychophysics of reading with artificial sight has received increasing attention as visual prostheses are becoming a real possibility to restore useful function to the blind through the coarse, pseudo-pixelized vision they generate. Studies to date have focused on simulating retinal and cortical prostheses; here we extend that work to report on thalamic designs. This study examined the reading performance of normally sighted human subjects using a simulation of three thalamic visual prostheses that varied in phosphene count, to help understand the level of functional ability afforded by thalamic designs in a task of daily living. Reading accuracy, reading speed, and reading acuity of 20 subjects were measured as a function of letter size, using a task based on the MNREAD chart. Results showed that fluid reading was feasible with appropriate combinations of letter size and phosphene count, and performance degraded smoothly as font size was decreased, with an approximate doubling of phosphene count resulting in an increase of 0.2 logMAR in acuity. Results here were consistent with previous results from our laboratory. Results were also consistent with those from the literature, despite using naive subjects who were not trained on the simulator, in contrast to other reports.

No MeSH data available.


Related in: MedlinePlus