Aurélie Calabrèse

Wet versus Dry Age-Related Macular Degeneration in Patients with Central Field Loss: Different Effects on Maximum Reading Speed

PURPOSE To describe new, efficient predictors of maximum reading speed (MRS) in age-related macular degeneration (AMD) patients with central field loss. Type of AMD (wet versus dry) was scrutinized, because this factor seems to offer a promising model of differential visual adaptation induced by different temporal courses of disease progression. METHODS Linear mixed-effects (LME) analyses were performed on a dataset initially collected to assess the effect of interline spacing on MRS. MRS was measured with MNread-like French sentences in 89 eyes (64 dry and 25 wet) of 61 patients with AMD. Microperimetry examination was performed on each eye. The eyes were included only if they had a dense macular scotoma including the fovea, to ensure that patients used eccentric viewing. RESULTS Analyses show the unique contributions--after adjustment for the effects of other factors--of three new factors: (1) MRS was higher for wet than for dry AMD eyes; (2) an advantage of similar amplitude was found for phakic eyes compared with pseudophakic eyes; and (3) MRS decreased when distance between fixation preferred retinal locus (PRL) and fovea increased. In addition, the instantaneous slope of the relationship between scotoma area and MRS was much shallower than reported in two other studies. CONCLUSIONS The four effects improve the ability to predict MRS reliably for AMD patients. The wet/dry difference is a major finding that may result from the different time courses of the two types of disease, thus involving different types of visuomotor and attentional adaptation processes.

Small Effect of Interline Spacing on Maximal Reading Speed in Low-Vision Patients with Central Field Loss Irrespective of Scotoma Size

PURPOSE It has been suggested that crowding, the adverse low-level effect due to the proximity of adjacent stimuli, explains slow reading in low-vision patients with absolute macular scotomas. According to this hypothesis, crowding in the vertical dimension should be released by increasing the vertical spacing between lines of text. However, studies with different experimental paradigms and only a few observers have given discrepant results on this question. The purpose of this study was to investigate this issue with a large number of patients whose macular function was carefully assessed. METHODS MP1 microperimetry examination was performed for each low-vision patient. Only eyes with an absolute macular scotoma and no foveal sparing (61 patients with AMD, 90 eyes; four patients with Stargardt disease, eight eyes) were included. Maximal reading speed was assessed for each eye with French sentences designed on the MNREAD test principles. RESULTS The effect of interline spacing on maximal reading speed (MRS) was significant although small; average MRS increased by 7.1 words/min from standard to double interline spacing. The effect was weak irrespective of PRL distance from the fovea and scotoma area and regardless of whether an eccentric island of functional vision was present within the scotoma. CONCLUSIONS Increasing interline spacing is advisable only for very slow readers (<20 words/min) who want to read a few words (spot reading). Vertical crowding does not seem to be a major determinant of maximal reading speed for patients with central scotomas.

Page mode reading with simulated scotomas: Oculo-motor patterns

This study investigated the relationship between reading speed and oculo-motor parameters when normally sighted observers had to read single sentences with an artificial macular scotoma. Using multiple regression analysis, our main result shows that two significant predictors, number of saccades per sentence followed by average fixation duration, account for 94% of reading speed variance: reading speed decreases when number of saccades and fixation duration increase. The number of letters per forward saccade (L/FS), which was measured directly in contrast to previous studies, is not a significant predictor. The results suggest that, independently of the size of saccades, some or all portions of a sentence are temporally integrated across an increasing number of fixations as reading speed is reduced.

Eye Movements and Reading Speed in Macular Disease: The Shrinking Perceptual Span Hypothesis Requires and Is Supported by a Mediation Analysis

PURPOSE Reading speed of patients with central field loss (CFL) correlates with the size of saccades (measured in letters per forward saccade [L/FS]). We assessed whether this effect is mediated by the total number of fixations, by the average fixation duration, or by a mixture of both. METHODS We measured eye movements (with a video eye tracker) of 35 AMD and 4 Stargardt patients (better eye decimal acuity from 0.08-0.3) while they monocularly read single-line French sentences continuously displayed on a screen. All patients had a dense scotoma covering the fovea, as assessed with MP1 microperimetry, and therefore used eccentric viewing. Results were analyzed with regression-based mediation analysis, a modeling framework that informs on the underlying factors by which an independent variable affects a dependent variable. RESULTS Reading speed and average fixation duration are negatively correlated, a result that was not observed in prior studies with CFL patients. This effect of fixation duration on reading speed is still significant when partialling out the effect of the total number of fixations (slope: -0.75, P < 0.001). Despite this large effect of fixation duration, mediation analysis shows that the effect of L/FS on reading speed is fully mediated by the total number of fixations (effect size: 0.96; CI [0.82, 1.12]) and not by fixation duration (effect size: 0.02; CI [-0.11, 0.14]). CONCLUSIONS Results are consistent with the shrinking perceptual span hypothesis: reading speed decreases with the average number of letters traversed on each forward saccade, an effect fully mediated by the total number of fixations.

Baseline MNREAD Measures for Normally Sighted Subjects From Childhood to Old Age

Purpose The continuous-text reading-acuity test MNREAD is designed to measure the reading performance of people with normal and low vision. This test is used to estimate maximum reading speed (MRS), critical print size (CPS), reading acuity (RA), and the reading accessibility index (ACC). Here we report the age dependence of these measures for normally sighted individuals, providing baseline data for MNREAD testing. Methods We analyzed MNREAD data from 645 normally sighted participants ranging in age from 8 to 81 years. The data were collected in several studies conducted by different testers and at different sites in our research program, enabling evaluation of robustness of the test. Results Maximum reading speed and reading accessibility index showed a trilinear dependence on age: first increasing from 8 to 16 years (MRS: 140–200 words per minute [wpm]; ACC: 0.7–1.0); then stabilizing in the range of 16 to 40 years (MRS: 200 ± 25 wpm; ACC: 1.0 ± 0.14); and decreasing to 175 wpm and 0.88 by 81 years. Critical print size was constant from 8 to 23 years (0.08 logMAR), increased slowly until 68 years (0.21 logMAR), and then more rapidly until 81 years (0.34 logMAR). logMAR reading acuity improved from −0.1 at 8 years to −0.18 at 16 years, then gradually worsened to −0.05 at 81 years. Conclusions We found a weak dependence of the MNREAD parameters on age in normal vision. In broad terms, MNREAD performance exhibits differences between three age groups: children 8 to 16 years, young adults 16 to 40 years, and middle-aged to older adults >40 years.

Development of a Reading Accessibility Index Using the MNREAD Acuity Chart

IMPORTANCE We define a Reading Accessibility Index for evaluating reading in individuals with normal and low vision. OBJECTIVE To compare the Reading Accessibility Index with data from the Impact of Cataracts on Mobility (ICOM) study. DESIGN, SETTING, AND PARTICIPANTS This investigation was a secondary data analysis from the ICOM study performed between July 1, 2014, and September 20, 2015, at 12 eye clinics in Alabama from October 1, 1994, through March 31, 1996. Participants were 321 adults with cataract (n = 92), pseudophakia (n = 131), or natural crystalline lenses without cataract (n = 98). MAIN OUTCOMES AND MEASURES The Reading Accessibility Index (hereafter referred to using the abbreviation ACC for the first 3 letters of Accessibility) is defined as an individuals mean reading speed measured across the 10 largest print sizes on the MNREAD Acuity Chart (Precision Vision) (0.4-1.3 logarithm of the minimum angle of resolution at 40 cm), normalized by 200 words per minute, which was the mean value for a group of 365 normally sighted young adults. The ACC is a single-value measure that captures an individuals range of accessible print sizes and reading fluency within this range. RESULTS The study cohort comprised 321 participants. Their age range was 55 to 85 years, and 157 (48.9%) were female. The ACCs for the ICOM study participants ranged from 0.19 to 1.33, where 1.00 is the mean value for normally sighted young adults. The ACC for the cataract group (mean [SD], 0.65 [0.18]) was significantly lower than that for the pseudophakia group (mean [SD], 0.77 [0.16]) and the control group (mean [SD], 0.76 [0.19]) (P < .001 for both). The correlation between the ACC and Early Treatment Diabetic Retinopathy Study visual acuity (r = -0.22) and Pelli-Robson contrast sensitivity (r = 0.20) was weaker than that with a reading-related measure of instrumental activities of daily living (r = -0.60) (P < .001 for both). CONCLUSIONS AND RELEVANCE The ACC represents an individuals access to text across the range of print sizes found in everyday life. Its calculation does not rely on curve fitting and provides a direct comparison with the performance of normally sighted individuals. Changes in an individuals ACC might be used to evaluate the effect of ophthalmic treatment, rehabilitation programs, or assistive technology on reading accessibility. Data from the ICOM study show that the ACC reflects characteristics of reading performance in everyday life and is sensitive to improved reading accessibility for pseudophakic eyes.

Clustering of Eye Fixations: A New Oculomotor Determinant of Reading Speed in Maculopathy.

PURPOSE To describe and quantify a largely unnoticed oculomotor pattern that often occurs when patients with central field loss (CFL) read continuous text: Horizontal distribution of eye fixations dramatically varies across sentences and often reveals clusters. Also to statistically analyze the effect of this new factor on reading speed while controlling for the effect of saccadic amplitude (measured in letters per forward saccade, L/FS), an established oculomotor effect. METHODS Quantification of nonuniformity of eye fixations (NUF factor) was based on statistical analysis of the curvature of fixation distributions. Linear mixed-effects analyses were performed to predict reading speed from oculomotor factors based on eye movements of 34 AMD and 4 Stargardt patients (better eye decimal acuity from 0.08 to 0.3). Single-line French sentences were read aloud by these patients, who all had a dense scotoma covering the fovea as assessed with MP1 microperimetry. RESULTS Nonuniformity of fixations is a strong determinant of reading speed (-0.76 log units; 95% confidence interval [CI] [-0.86, -0.66]). This effect is not confounded with the effect of L/FS. The per sentence proportion of trials with clustering is predicted by the frequency of occurrence of the lowest-frequency word in each sentence. CONCLUSIONS The NUF factor is a new oculomotor predictor of reading speed. This effect is independent of the effect of L/FS. Reading performance, as well as motivation to read, might be enhanced if new visual aids or automatic text simplification were used to reduce the occurrence of fixation clustering.

Does Vertical Reading Help People with Macular Degeneration: An Exploratory Study.

Individuals with macular degeneration often develop a Preferred Retinal Locus (PRL) used in place of the impaired fovea. It is known that many people adopt a PRL left of the scotoma, which is likely to affect reading by occluding text to the right of fixation. For such individuals, we examined the possibility that reading vertical text, in which words are rotated 90° with respect to the normal horizontal orientation, would be beneficial for reading. Vertically oriented words would be tangential to the scotoma instead of being partially occluded by it. Here we report the results of an exploratory study that aimed at investigating this hypothesis. We trained individuals with macular degeneration who had PRLs left of their scotoma to read text rotated 90° clockwise and presented using rapid serial visual presentation (RSVP). Although training resulted in improved reading of vertical text, the training did not result in reading speeds that appreciably exceeded reading speeds following training with horizontal text. These results do not support the hypothesis that people with left PRLs read faster with vertical text.

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

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.

Beneficial Effects of Spatial Remapping for Reading With Simulated Central Field Loss

Purpose People with central field loss (CFL) lose information in the scotomatous region. Remapping is a method to modify images to present the missing information outside the scotoma. This study tested the hypothesis that remapping improves reading performance for subjects with simulated CFL. Methods Circular central scotomas, with diameters ranging from 4° to 16°, were simulated in normally sighted subjects using an eye tracker on either a head-mounted display (HMD) (experiments 1, 2) or a traditional monitor (experiment 3). In the three experiments, reading speed was measured for groups of 7, 11, and 13 subjects with and without remapping of text. Results Remapping increased reading speed in all three experiments. On the traditional monitor, it increased reading speed by 34% (8°), 38% (12°), and 35% (16°). In the two HMD experiments, remapping increased reading speed only for the largest scotoma size, possibly due to latency of updating of the simulated scotoma. Conclusions Remapping significantly increased reading speed in simulated CFL subjects. Additional testing should examine the efficacy of remapping for reading and other visual tasks for patients with advanced CFL.