Accuracy of the Heidelberg Spectralis in the Alignment Between Near-Infrared Image and Tomographic Scan in a Model Eye: A Multicenter Study

Abstract

Purpose To evaluate temporal changes and predictors of accuracy in the alignment between simultaneous near-infrared image and optical coherence tomography (OCT) scan on the Heidelberg Spectralis using a model eye. Design Laboratory investigation. Methods After calibrating the device, six sites performed weekly testing of the alignment for 12 weeks using a model eye. The maximum error was compared to multiple variables to evaluate predictors of inaccurate alignment. Variables included the number of weekly scanned patients, total number of OCT scans and B-scans performed, room temperature and its variation, and working time of the scanning laser. A 4-week extension study was subsequently performed to analyze short-term changes in the alignment. Results The average maximum error in the alignment was 15±6 µm; the greatest error was 35 µm. The error increased significantly at week 1 (p=0.01), specifically after the second imaging study (p<0.05), reached a maximum after the eighth patient (p<0.001), and then it varied randomly overtime. Predictors for inaccurate alignment were temperature variation and scans per patient (p<0.001). For each 1 unit of increase in temperature variation, the estimated increase in maximum error was 1.26 µm. For the average number of scans per patient, each increase of 1 unit increased the error of 0.34 µm. Conclusion Overall, the accuracy of the Heidelberg Spectralis was excellent. The greatest error happened in the first week after calibration, and specifically after the second imaging study. To improve the accuracy, room temperature should be kept stable and unnecessary scans should be avoided. The alignment of the device does not need to be checked on a regular basis in the clinical setting, but should be checked after every other patient for more precise research purposes.

Longitudinal Analysis of Reticular Drusen Associated with Age-Related Macular Degeneration Using Combined Confocal Scanning Laser Ophthalmoscopy and Spectral-Domain Optical Coherence Tomography Imaging

“…While presumably negligible for most pathological alterations and in routine clinical imaging examinations, it is assumed that the predefined tolerance for the registration between the en face cSLO image and the corresponding SD-OCT B scan as well as between examinations at different time points would result in a small but still relevant inaccuracy when it comes to the visualization of lesions with very small dimensions such as RDR. This assumption is underscored by a recent publication of Barteselli et al [19], who investigated the accuracy of the alignment of the cSLO + SD-OCT device with a model eye and found an error of 15 ± 6 µm (maximum up to 35 µm).…”

Photoreceptor Damage and Reduction of Retinal Sensitivity Surrounding Geographic Atrophy in Age-Related Macular Degeneration

“…Photoreceptor damage surrounding geographic atrophy Page 4 SD-OCT in a pixel-by-pixel manner, 9 thus enabling the determination of the exact sites of the disrupted EZ band regions. An area of interest (i.e., the area exhibiting EZ disruption) was defined by manually drawing a line in each B-scan image and projecting it onto the IR image (Fig 1).…”

Reticular Pseudodrusen on Infrared Imaging Are Topographically Distinct From Subretinal Drusenoid Deposits on en Face Optical Coherence Tomography

“…Regarding the potential for mismatches between OCT and corresponding IR images, point-to-point colocalization errors of large magnitude have been reported especially in Spectralis, and were shown to be directly proportional to the length of time taken to scan. 31 Hence, in the Spaide 30 study, where dense rasters and averaging were performed to obtain these scans, these errors are more likely. In contrast, in the present study, as well as previously published studies, 17 manual registration and overlay was performed between IR and OCT cube from the same machine without the need for averaging or software registration, which minimized potential mismatch-error (Figure 1 and 2).…”