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Variation associated with measurement of retinal vessel diameters at different points in the pulse cycle
M D Knudtson1, B E K Klein, R Klein
1UW-Madison Department of Ophthalmology and Visual Sciences, University of Wisconsin, 610 N. Walnut Street, 4th floor WARF, Madison, WI 53726, USA. knudtson@epi.ophth.wisc.edu
Insights
Retinal vessel measurements show significant variability across images, not specific pulse points. Understanding this variability is crucial for epidemiological studies using these techniques.
Area of Science:
- Ophthalmology
- Medical Imaging
- Biometry
Background:
- Retinal vessel diameter measurement is a key biometric in ophthalmology.
- Variability in these measurements can impact the reliability of diagnostic and research findings.
Purpose of the Study:
- To quantify the variability in retinal vessel diameter measurements.
- To assess how pulse cycle timing influences measurement variability.
Main Methods:
- 30 digital retinal images were acquired from a healthy subject at three pulse cycle points.
- Retinal vessel diameters (arterioles and venules, large and small) were measured by two graders.
- Pulse-synchronised imaging was employed to capture images at specific points in the cardiac cycle.
Main Results:
- Variability within an image was consistent across graders, pulse points, and vessel types.
- Across images, retinal arterioles showed 6-17% change and venules 2-11% change from min to max measurement.
- The primary source of variability (over 50%) was across images, irrespective of pulse point or grader, with small vessels exhibiting greater changes than large ones.
Conclusions:
- Large retinal venule measurements exhibit lower variability compared to other retinal vessels.
- Measurement variability across images is the dominant factor, even after controlling for pulse timing and grader.
- Accurate characterization of variability components is essential for applying retinal vessel measurement techniques in large-scale epidemiological research.
Background/Aims:
To assess the variability in retinal vessel measurements at different points in the pulse cycle.
Methods:
A healthy white male aged 19 years had 30 digitised images taken at three distinct points in the pulse cycle over a one hour period. A pulse synchronised ear clip trigger device was used to capture images at the desired point in the pulse cycle. Two trained graders measured the retinal vessel diameter of one large arteriole, one large venule, one small arteriole, and one small venule 10 times in each of these 30 images.
Results:
Within an image, variability was similar between graders, pulse point, and vessel type. Across images taken at the same point in the pulse period, the change from the minimum to maximum measurement was between 6% and 17% for arterioles and between 2% and 11% for venules. In addition, measurements of small vessels had greater changes than large vessels and no point in the pulse period was more variable than another. Ignoring pulse cycle increased variability across images in the large venule, but not in the other vessel types. Mixed effect models were fit for each of the vessel types to determine the greatest source of variability. Controlling for pulse point and grader, the largest source of variability for all four vessels measured was across images, accounting for more than 50% of the total variability.
Conclusion:
Measurements of large retinal venules is generally less variable than measurements of other retinal vessels. After controlling for pulse point and grader, the largest source of variation is across images. Understanding the components of variability in measuring retinal vessels is important as these techniques are applied in epidemiological studies.
