Purchase this article with an account.
Michael Dorr, Luis A Lesmes, Tobias Elze, Hui Wang, Zhong-Lin Lu, Peter J. Bex; Average Precision as a test-retest reliability measure: a quick CSF study on myopia. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3896.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The Contrast Sensitivity Function (CSF) provides a comprehensive assessment of visual sensitivity, but its routine evaluation in clinical care is hampered by practical challenges. We evaluated test-retest reliability (TRR) of an iPad-based quick CSF implementation (Dorr et al., IOVS 2013) in a cohort of myopes and age-matched controls.
We collected repeated measurements of the full CSF on a handheld device at a viewing distance of 60cm from 101 subjects (63 myopes with 33 uncorrected/30 corrected eyes, 38 controls); in each of 50 trials per measurement, a bandpass-filtered Sloan letter was presented for 500ms. Spatial frequency (SF, 24 levels from .64 to 41cpd) and contrast (48 levels from .2 to 100%) were chosen by the quick CSF algorithm to maximize information gain about the CSF. Subjects then indicated their response (10-AFC) on the touch screen.<br /> We computed cross-correlation coefficients (CC) and Bland-Altman Coefficients of Repeatability (CoR) for contrast sensitivities at 6 individual SF, CSF Acuity (the SF where sensitivity=0), and the Area under the Log CSF (AULCSF). However, both CC and CoR are vulnerable to artefacts due to test score range and quantization. Therefore, we also computed Average Precision, the area under the Precision-Recall curve that more accurately describes test-retest variance in terms of between-subject variability: how easily can a repeat measurement be identified from the whole population-wide set of measurements, given only the initial measurement?
CC ranged from .873 for contrast sensitivity at 1.5cpd to .98 for the AULCSF. CoR were likewise small for AULCSF (.225) and CSF Acuity (.193), and increased for individual contrast sensitivities at higher SF (1.5cpd, CoR=.2; 18cpd, CoR=.308). Precision-Recall scores were worst for low SF (1.5cpd, AveP=.79) and best for AULCSF (AveP=.87). Notably, repeatability as assessed by AveP was better for uncorrected eyes than for corrected eyes, despite much higher Bland-Altman CoR (e.g. uncorrected AULCSF, AveP=.879, CoR=.255; corrected AULCSF, AveP=.829, CoR=.168).
Despite very short testing times (2-3 minutes) and without specialized laboratory equipment, the iPad-based quick CSF test reliably assessed the full CSF in myopes and controls. While Bland-Altman CoR is routinely used to quantify TRR, its absolute scores cannot be compared across different test measures; Average Precision should be used instead.
This PDF is available to Subscribers Only