Abstract
PurposeFirst, to evaluate inter-rater reliability when human raters estimate the reading performance of visually impaired individuals using the MNREAD acuity chart. Second, to evaluate the agreement between computer-based scoring algorithms and compare them with human rating.MethodsReading performance was measured for 101 individuals with low vision, using the Portuguese version of the MNREAD test. Seven raters estimated the maximum reading speed (MRS) and critical print size (CPS) of each individual MNREAD curve. MRS and CPS were also calculated automatically for each curve using two different algorithms: the original standard deviation method (SDev) and a non-linear mixed effects (NLME) modeling. Intra-class correlation coefficients (ICC) were used to estimate absolute agreement between raters and/or algorithms.ResultsAbsolute agreement between raters was ‘excellent’ for MRS (ICC = 0.97; 95%CI [0.96, 0.98]) and ‘moderate’ to ‘good’ for CPS (ICC = 0.77; 95%CI [0.69, 0.83]). For CPS, inter-rater reliability was poorer among less experienced raters (ICC = 0.70; 95%CI [0.57, 0.80]) when compared to experienced ones (ICC = 0.82; 95%CI [0.76, 0.88]). Absolute agreement between the two algorithms was ‘excellent’ for MRS (ICC = 0.96; 95%CI [0.91, 0.98]). For CPS, the best possible agreement was found for CPS defined as the print size sustaining 80% of MRS (ICC = 0.77; 95%CI [0.68, 0.84]). Absolute agreement between raters and automated methods was ‘excellent’ for MRS (ICC = 0.96; 95% CI [0.88, 0.98] for SDev; ICC = 0.97; 95% CI [0.95, 0.98] for NLME). For CPS, absolute agreement between raters and SDev ranged from ‘poor’ to ‘good’ (ICC = 0.66; 95% CI [0.3, 0.80]), while agreement between raters and NLME was ‘good’ (ICC = 0.83; 95% CI [0.76, 0.88]).ConclusionFor MRS, inter-rater reliability is excellent, even considering the possibility of noisy and/or incomplete data collected in low-vision individuals. For CPS, inter-rater reliability is lower. This may be problematic, for instance in the context of multisite investigations or follow-up examinations. The NLME method showed better agreement with the raters than the SDev method for both reading parameters. Setting up consensual guidelines to deal with ambiguous curves may help improve reliability. While the exact definition of CPS should be chosen on a case-by-case basis depending on the clinician or researcher’s motivations, evidence suggests that estimating CPS as the smallest print size sustaining about 80% of MRS would increase inter-rater reliability.
Highlights
Reading difficulty is a major concern for patients referred to low-vision centers [1]
For critical print size (CPS), interrater reliability was poorer among less experienced raters (ICC = 0.70; 95%CI [0.57, 0.80]) when compared to experienced ones (ICC = 0.82; 95%CI [0.76, 0.88])
In the original MNREAD manual provided with the chart, MRS and CPS are defined as follows: “The critical print size is the smallest print size at which patients can read with their maximum reading speed. [. . .] Typically, reading time remains fairly constant for large print sizes
Summary
Reading difficulty is a major concern for patients referred to low-vision centers [1]. Among the standardized tests available, the MNREAD acuity chart can be used to evaluate reading performance for people with normal or low vision in clinical and research environments [7]. The MNREAD test measures four parameters that characterize how reading performance changes when print size decreases: the maximum reading speed (MRS), the critical print size (CPS), the reading acuity (RA) and the reading accessibility index (ACC) [8]. In the original MNREAD manual provided with the chart, MRS and CPS are defined as follows: “The critical print size is the smallest print size at which patients can read with their maximum reading speed. As the acuity limit is approached there comes a print size where reading starts to slow down The maximum reading speed with print larger than the critical print size is the maximum reading speed (MRS).” In short, values for MRS and CPS depend on the location of the flexion point in the curve of reading speed versus print size (Fig 1)
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