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- Brusini, Irene, et al.
(author)
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Fully automatic estimation of the waist of the nerve fiber layer at the optic nerve head angularly resolved
- 2021
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In: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE-Intl Soc Optical Eng. ; , s. 1D1-1D8
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Conference paper (peer-reviewed)abstract
- The present project aims at developing a fully automatic software for estimation of the waist of the nerve fiber layer in the Optic Nerve Head (ONH) angularly resolved in the frontal plane as a tool for morphometric monitoring of glaucoma. The waist of the nerve fiber layer is here defined as Pigment epithelium central limit –Inner limit of the retina – Minimal Distance, (PIMD). 3D representations of the ONH were collected with high resolution OCT in young not glaucomatous eyes and glaucomatous eyes. An improved tool for manual annotation was developed in Python. This tool was found user friendly and to provide sufficiently precise manual annotation. PIMD was automatically estimated with a software consisting of one AI model for detection of the inner limit of the retina and another AI model for localization of the Optic nerve head Pigment epithelium Central limit (OPCL). In the current project, the AI model for OPCL localization was retrained with new data manually annotated with the improved tool for manual annotation both in not glaucomatous eyes and in glaucomatous eyes. Finally, automatic annotations were compared to 3 annotations made by 3 independent annotators in an independent subset of both the not glaucomatous and the glaucomatous eyes. It was found that the fully automatic estimation of PIMD-angle overlapped the 3 manual annotators with small variation among the manual annotators. Considering interobserver variation, the improved tool for manual annotation provided less variation than our original annotation tool in not glaucomatous eyes suggesting that variation in glaucomatous eyes is due to variable pathological anatomy, difficult to annotate without error. The small relative variation in relation to the substantial overall loss of PIMD in the glaucomatous eyes compared to the not glaucomatous eyes suggests that our software for fully automatic estimation of PIMD-angle can now be implemented clinically for monitoring of glaucoma progression.
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- Sandberg Melin, Camilla, et al.
(author)
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A strategy for OCT estimation of the optic nerve head pigment epithelium central limit-inner limit of the retina minimal distance, PIMD-2π
- 2019
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In: Acta Ophthalmologica. - : Wiley. - 1755-375X .- 1755-3768. ; 97:2, s. 208-213
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Journal article (peer-reviewed)abstract
- Purpose To develop a semi-automatic algorithm for estimation of pigment epithelium central limit-inner limit of the retina minimal distance averaged over 2 pi radians (PIMD-2 pi) and to estimate the precision of the algorithm. Further, the variances in estimates of PIMD-2 pi were to be estimated in a pilot sample of glaucomatous eyes. Methods Three-dimensional cubes of the optic nerve head (ONH) were captured with a commercial SD-OCT device. Raw cube data were exported for semi-automatic segmentation. The inner limit of the retina was automatically detected. Custom software aided the delineation of the ONH pigment epithelium central limit resolved in 500 evenly distributed radii. Sources of variation in PIMD estimates were analysed with an analysis of variance. Results The estimated variance for segmentations and angles was 130 mu m(2) and 1280 mu m(2), respectively. Considering averaging eight segmentations, a 95 % confidence interval for mean PIMD-2 pi was estimated to 212 +/- 10 mu m (df = 7). The coefficient of variation for segmentation was estimated at 0.05. In the glaucomatous eyes, the within-subject variance for captured volumes and for segmentations within volumes was 10 mu m(2) and 50 mu m(2), respectively. Conclusion The developed semi-automatic algorithm enables estimation of PIMD-2 pi in glaucomatous eyes with relevant precision using few segmentations of each captured volume.
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- Sandberg Melin, Camilla
(author)
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Morphometry of the Optic Nerve Head as a Diagnostic Tool for Glaucoma
- 2019
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Doctoral thesis (other academic/artistic)abstract
- Glaucoma is a chronic optic nerve head (ONH) disease. Gradual retinal ganglion cell and nerve fiber loss lead to morphological ONH change and visual field defects. Initial loss is often focal. Rate of progression and life expectancy guide treatment. Currently, confocal scanning laser tomoghraphy (HRT) and optic coherence tomography (OCT) are available for ONH imaging. However, there is no consensus for which morphometric measurement of ONH nerve fiber content to use for glaucoma follow-up.Purpose: To measure ONH nerve fiber content as neuroretinal rim area (NRA) with HRT, estimate NRA measurement variation and its impact on designing a follow-up strategy. To develop a custom algorithm, Pigment epithelium central limit-Inner limit of the retina Minimal Distance (PIMD), for measuring ONH nerve fiber content in OCT data cubes. To measure PIMD in glaucomatous eyes, estimate the variance sources for PIMD and their impact on designing strategies for glaucoma follow-up.Methods: NRA was measured with HRT in non-glaucomatous and glaucomatous eyes. Sources of variance for NRA were estimated. An OCT data cube of a non-glaucomatous eye was used in developing the PIMD algorithm. PIMD was measured in 500 radii along the ONH circumference. PIMD averaged over the circumference is PIMD-2π. Sources of variance for PIMD-2π were estimated for glaucomatous eyes. Strategies for following PIMD-2π and segments of PIMD-2π within subject over time were proposed.Results: Variation among subjects was substantial for NRA and PIMD-2π. Contrarily, within subject variation was small for NRA and PIMD-2π. When within subject variation, a previously reported loss rate for progressing glaucoma, and measuring NRA 3 times every 4 months were applied, a significant loss was detected after 54 months. When within subject variation and a PIMD-2π loss rate resulting in blindness after 20 years were applied, a significant PIMD-2π loss was detected in 16 months with visits every 4 months. Within subject segmental PIMD-2π loss can be detected from the 3rd visit. Loss rate of each PIMD can be estimated with linear regression from the 4th visit. Change in segmental PIMD-2π loss rate can be detected at a later visit.Conclusions: Small within subject variation allows for within subject NRA and PIMD follow-up over time. Segmental PIMD-2π has potential to detect focal glaucomatous defects and worsening of existing defects. There is potential to detect a change in segmental PIMD-2π loss rate. Segmental PIMD-2π has potential as a tool for within subject follow-up of glaucoma.
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| 9. |
- Sandberg Melin, Camilla, et al.
(author)
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Variance components for PIMD‐2π estimation of the optic nerve head and consequences in clinical measurements of glaucoma
- 2020
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In: Acta Ophthalmologica. - : John Wiley & Sons. - 1755-375X .- 1755-3768. ; 98:2, s. 190-194
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Journal article (peer-reviewed)abstract
- Purpose To estimate the sources of variation for Pigment epithelium central limit-Inner limit of the retina Minimal Distance averaged over 2 pi (PIMD-2 pi), 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-2 pi. The magnitude of the sources of variation for PIMD-2 pi measurements was estimated with an analysis of variance. Results A 95% confidence interval for mean PIMD-2 pi was estimated to 215 +/- 12 mu m (df = 38). The estimated variance for subjects was 1280 mu m(2). The within-subject estimated variance for occasions, volumes and segmentations was 10 mu m(2), 30 mu m(2) and 40 mu m(2), respectively. The within-subject variances were used to model follow-up of PIMD-2 pi over time. A linear loss rate of 0.05 of baseline PIMD-2 pi/year was assumed. A significant PIMD-2 pi 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-2 pi change from baseline can be detected in approximately 18 months. Detection of significant PIMD-2 pi loss in a subject requires knowledge of normal age loss and measurement variability.
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- Sandberg Melin, Camilla, et al.
(author)
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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
- 2016
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In: Acta Ophthalmologica. - : Wiley. - 1755-375X .- 1755-3768. ; 94:7, s. 705-711
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Journal article (peer-reviewed)abstract
- PurposeTo estimate the variation in measurements of neuro-retinal rim area (NRA) determined by confocal scanning laser tomography and consequences for clinical follow-up. MethodsAltogether, 24 healthy subjects were randomized on -320m, Moorfields and Standard NRA plane strategies. Additionally, NRA was measured in 32 glaucoma subjects. Variance components for subjects, visits and measurements were estimated with analysis of variance. Sample sizes required to detect a 6.0x10(-2)mm(2) NRA change were estimated assuming a significance level of 0.05 and a power of 0.8. Consequences for independent group, and paired comparison design, respectively, were analysed. Further, precision in estimates within subjects over time was investigated. ResultsThe variation of NRA among subjects was considerably larger than the variation among visits and measurements. For glaucoma subjects, the variation among visits and measurements were of the same order but larger than in healthy subjects. It was found that independent group comparisons require inconveniently large sample sizes. Within-subject paired comparisons over time require sample sizes of below 15 subjects. The estimated variations for glaucoma subjects imply that 54months of follow-up is required for detection of change from baseline. ConclusionsThe variance for subjects is substantial in relation to those for visits and measurements. Cross-sectional independent group comparisons of levels of NRA are unsuitable, due to considerable subject variation. Levels of NRA differences within subjects between visits can be estimated with acceptable precision. Neuro-retinal rim area (NRA) measurement can be used for long-term follow-up of glaucoma progression.
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