Comparing performance on the MNREAD iPad application with the MNREAD acuity chart

Abstract

Our purpose was to compare reading performance measured with the MNREAD Acuity Chart and an iPad application (app) version of the same test for both normally sighted and low-vision participants. Our methods included 165 participants with normal vision and 43 participants with low vision tested on the standard printed MNREAD and on the iPad app version of the test. Maximum Reading Speed, Critical Print Size, Reading Acuity, and Reading Accessibility Index were compared using linear mixed-effects models to identify any potential differences in test performance between the printed chart and the iPad app. Our results showed the following: For normal vision, chart and iPad yield similar estimates of Critical Print Size and Reading Acuity. The iPad provides significantly slower estimates of Maximum Reading Speed than the chart, with a greater difference for faster readers. The difference was on average 3% at 100 words per minute (wpm), 6% at 150 wpm, 9% at 200 wpm, and 12% at 250 wpm. For low vision, Maximum Reading Speed, Reading Accessibility Index, and Critical Print Size are equivalent on the iPad and chart. Only the Reading Acuity is significantly smaller (I. E., better) when measured on the digital version of the test, but by only 0.03 logMAR (p = 0.013). Our conclusions were that, overall, MNREAD parameters measured with the printed chart and the iPad app are very similar. The difference found in Maximum Reading Speed for the normally sighted participants can be explained by differences in the method for timing the reading trials.

Figures

Figure 1

Printed MNREAD chart. (A) Front and back of the MNREAD acuity chart printed in black-on-white (regular polarity); (B) Example MNREAD curve showing the four MNREAD parameters—Maximum Reading Speed (MRS—red star) is 225 words/min, with Critical Print Size (CPS—green diamond), and Reading Acuity (RA—blue triangle) of 0.0 and −0.2 logMAR, respectively. The Reading Accessibility Index (ACC) is 1.12.

Figure 2

MNREAD testing sequence using the iPad app. (A) Preparation screen displayed before each sentence; (B) After the experimenter clicks the “GO” button, the first sentence is displayed in the center of the screen, launching the time recording; (C) Once the participant is done reading, a simple click will stop the trial and record the reading time. A score screen appears, allowing the experimenter to enter the number of errors and launch the next trial; (D) When reading becomes impossible, the test is stopped and the app displays the MNREAD data plot and parameter estimates.

Figure 3

Experimental protocol for Experiments 1 and 2.

Figure 4

Agreement between the Maximum Reading Speed (MRS) measured with the chart and the iPad app. (A) shows data from Experiment 1 (normally sighted participants). (B) shows data from Experiment 2 (low-vision participants). Bland-Altman plots show the difference between measured MRS (iPad-Chart) plotted against the mean MRS. The red dashed lines represent the average difference. The blue dashed lines represent the agreement limits (±1.96 SD). The dotted lines show the 95% CI limits. Top and right histograms show the data distribution along the x and y axis respectively. Tables summarize the chart and iPad average values as well as their difference (as given by the LME models).

Figure 5

Percentage difference in MRS between chart and iPad as a function of MRS as measured on the chart. As shown by the regression lines, the percentage difference between the two measures increases when the MRS (as measured on the chart) increases.

Figure 6

Agreement between the Reading Accessibility Index (ACC) measured with the chart and the iPad app. (A) shows data from Experiment 1 (normally sighted participants). (B) shows data from Experiment 2 (low-vision participants). Bland-Altman plots show the difference between measured ACC (iPad-Chart) plotted against the mean ACC. The red dashed lines represent the average difference. The blue dashed lines represent the agreement limits (±1.96 SD). The dotted lines show the 95% CI limits. Top and right histograms show the data distribution along the x and y axis respectively. Tables summarize the chart and iPad average values as well as their difference (as given by the LME models).

Figure 7

Agreement between the Critical Print Size (CPS) measured with the chart and the iPad app. (A) shows data from Experiment 1 (normally sighted participants). (B) shows data from Experiment 2 (low-vision participants). Bland-Altman plots show the difference between measured CPS (iPad – Chart) plotted against the mean CPS. To avoid overlapping data points, similar CPS values are grouped and shown with a size code in (A). The red dashed lines represent the average difference. The blue dashed lines represent the agreement limits (±1.96 SD). The dotted lines show the 95% CI limits. Top and right histograms show the data distribution along the x and y axis respectively. Tables summarize the chart and iPad average values as well as their difference (as given by the LME models).

Figure 8

Agreement between the Reading Acuity (RA) measured with the chart and the iPad app. (A) shows data from Experiment 1 (normally sighted participants). (B) shows data from Experiment 2 (low-vision participants). Bland-Altman plots show the difference between measured RA (iPad – Chart) plotted against the mean RA. The red dashed lines represent the average difference. The blue dashed lines represent the agreement limits (±1.96 SD). The dotted lines show the 95% confidence interval limits. Top and right histograms show the data distribution along the x and y axis respectively. Tables summarize the chart and iPad average values as well as their difference (as given by the LME models).