Variance components in confocal scanning laser tomography measurements of neuro‐retinal rim area and the effect of repeated measurements on the power to detect loss over time

Melin, Camilla Sandberg; Nuija, Eva; Alm, Albert; Yu, Zhu Liang; Söderberg, Per G.

doi:10.1111/aos.13079

Cited by 4 publications

(6 citation statements)

References 22 publications

(24 reference statements)

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“…For all 39 subjects, the PIMD‐2 π data were analysed with an analysis of variance according to an hierarchal model (Sandberg Melin et al. , Appendix S2). Variance sources for estimates of PIMD‐2 π were estimated (Sandberg Melin et al.…”

Section: Resultsmentioning

confidence: 99%

“…Variance sources for estimates of PIMD‐2 π were estimated (Sandberg Melin et al. , Appendix S2) (Table )…”

Section: Resultsmentioning

confidence: 99%

“…The sample size required per independent group at one occasion to detect a significant difference between groups was calculated (Sandberg Melin et al. , Appendix S4) applying the estimated variances for subjects, occasions, volumes and segmentations (Table ). The required sample size was estimated to 180 subjects per group if 3 volumes per subject are captured and each volume is segmented three times (Figure ).…”

Section: Resultsmentioning

confidence: 99%

“…The power to detect a significant PIMD‐2 π change from baseline with evenly spaced visits over time was estimated (Sandberg Melin et al. , Appendix S3). (Figure ).…”

Section: Resultsmentioning

confidence: 99%

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Variance components for PIMD‐2π estimation of the optic nerve head and consequences in clinical measurements of glaucoma

Melin

Söderberg

2019

Acta Ophthalmologica

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Purpose To estimate the sources of variation for Pigment epithelium central limit‐Inner limit of the retina Minimal Distance averaged over 2π (PIMD‐2π), and further to analyse their consequences for clinical measurements of glaucoma. Methods Forty subjects with early to moderate stage glaucoma were included. Three SD‐OCT volumes of the optic nerve head (ONH) were captured at two occasions. Each volume was segmented three times for PIMD‐2π. The magnitude of the sources of variation for PIMD‐2π measurements was estimated with an analysis of variance. Results A 95% confidence interval for mean PIMD‐2π was estimated to 215 ± 12 μm (df = 38). The estimated variance for subjects was 1280 μm2. The within‐subject estimated variance for occasions, volumes and segmentations was 10 μm2, 30 μm2 and 40 μm2, respectively. The within‐subject variances were used to model follow‐up of PIMD‐2π over time. A linear loss rate of 0.05 of baseline PIMD‐2π/year was assumed. A significant PIMD‐2π change could be detected in approximately 16–18 months with evenly spaced visits every 4 or 6 months. Conclusions Due to the small within‐subject estimated variances, a clinically undesirable PIMD‐2π change from baseline can be detected in approximately 18 months. Detection of significant PIMD‐2π loss in a subject requires knowledge of normal age loss and measurement variability.

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Section: Resultsmentioning

confidence: 99%

“…Variance sources for estimates of PIMD‐2 π were estimated (Sandberg Melin et al. , Appendix S2) (Table )…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

“…The power to detect a significant PIMD‐2 π change from baseline with evenly spaced visits over time was estimated (Sandberg Melin et al. , Appendix S3). (Figure ).…”

Section: Resultsmentioning

confidence: 99%

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