Correlation of macular thickness metrics between 200 kHz and 100 kHz SS-OCT scans

Abstract

Purpose : As swept-source optical coherence tomography (SS-OCT) evolves, so do the laser acquisition components. Faster laser speeds allow for shorter scan acquisition times, but one trade-off is a reduction of signal that may influence image quality. The purpose of this study was to evaluate images from both the 100 kHz and 200 kHz scanning speeds of a dual-laser SS-OCT system to verify if there were any significant differences in macular thickness measurements.

Methods : Subjects were scanned multiple times with the PLEX^® Elite 9000 (ZEISS, Dublin, CA) SS-OCT device at both 100 kHz and 200 kHz speeds. A sample of patients from two retinal clinics, predominantly representing eyes with macular degeneration or diabetic retinopathy, were imaged using the Angio 6 x 6 mm scan pattern. Macula thickness measurements were made utilizing the internal limiting membrane (ILM) and retinal pigment epithelium (RPE) as the upper and lower thickness limits respectively. Mean thickness and SDs were determined for the regions of the standard ETDRS target centered at the fovea. Linear regression and Bland-Altman plots were used to evaluate the macular thickness values for the two speeds on the first scan taken and paired t-tests were used to determine p-values.

Results :
Macular thicknesses of 37 diseased eyes from 24 subjects were measured. The mean differences between the macular thickness measurements for the 100 kHz and 200 kHz scanning speeds were less than one micron in most ETDRS regions. No statistical difference was found in any of the regions as shown in Table 1. An example of the regression and Bland-Altman plots for the Central region can be seen in Figure 1.

Conclusions : This study demonstrated that capturing SS-OCT images with the faster scanning speed did not create any significant differences for the measurement of macular thickness in diseased retinas. The faster 200 kHz scan speed should be appreciated by both technicians and patients with shorter scan times and will not make a difference in clinical decision making.

This is a 2021 ARVO Annual Meeting abstract.

 

Table 1: Mean differences, confidence intervals and p-values for the nine ETDRS regions used to evaluate the macular thickness. No sector showed a significant difference between scan speeds.

 

Figure 1: Linear regression and Bland-Altman plots displaying results of the Central region measurements for the two scan speeds