Reproducibility of pixel-by-pixel analysis of Heidelberg retinal flowmetry images: the Thessaloniki Eye Study.
Τίτλος | Reproducibility of pixel-by-pixel analysis of Heidelberg retinal flowmetry images: the Thessaloniki Eye Study. |
Publication Type | Journal Article |
Year of Publication | 2008 |
Authors | Mavroudis, L., Harris A., Topouzis F., M Wilson R., Yu F., Anastasopoulos E., Koskosas A., Siesky B., Pappas T., Founti P., & Coleman A. L. |
Journal | Acta Ophthalmol |
Volume | 86 |
Issue | 1 |
Pagination | 81-6 |
Date Published | 2008 Feb |
ISSN | 1755-3768 |
Λέξεις κλειδιά | Aged, Aged, 80 and over, Female, Humans, Laser-Doppler Flowmetry, Linear Models, Male, Observer Variation, Regional Blood Flow, Reproducibility of Results, Retinal Vessels |
Abstract | PURPOSE: To identify the investigator effect in the analysis results of Heidelberg retinal flowmetry (HRF) images when pixel-by-pixel analysis is performed.METHODS: Thirty-two of 732 HRF images were randomly selected from a population-based study. Pixel-by-pixel analysis was performed by two trained masked graders in the following way: a square window of 40 x 40 pixels or two windows of 30 x 30 pixels or four windows of 20 x 20 pixels free from blood vessels at the peripapillary retina were identified. Using a 1 x 1-pixel window, the grader performed pointwise analysis according to a specific protocol. The analysis process was performed by each observer three times (A, B, C) at 1-week intervals. The percentage of pixels with < 1 arbitrary unit of flow (zero flow), the 10th, 25th, 50th, 75th and 90th percentiles and mean flow values were calculated. The difference between the results of analyses B-A and C-A for all HRF parameters was estimated using the Wilcoxon signed rank test. Mixed-effect regression models were also used after controlling for grader effect and correlation within subjects.RESULTS: There was no statistically significant difference between the results of analyses B-A and C-A or for any parameter in the mixed-effect regression models. Intraclass correlation was 0.9665 for the percentage of zero flow pixels.CONCLUSIONS: Pixel-by-pixel analysis of HRF images by trained graders remains a highly reproducible method. No grader effect was found. If a precise protocol is followed, the results are independent of the exact placement of the analysis windows and the pointwise analysis of the identified and mapped retinal tissue. |
DOI | 10.1111/j.1600-0420.2007.01003.x |
Alternate Journal | Acta Ophthalmol |
PubMed ID | 17850404 |