Macular thickness measurements from spectral domain and swept-source OCT devices

Abstract

Purpose : Macular thickness has been extensively measured in spectral domain optical coherence tomography (SD-OCT) devices. However, the differences in retina layer thickness measurements between SD-OCT and swept-source optical coherence tomography (SS-OCT) devices has not been previously characterized. This study compares the macular measurements from SD-OCT and SS-OCT devices in normal and diseased subjects.

Methods : Subjects were scanned with both the Angio 6 x 6 mm and Angio 12 x 12 mm scans on the PLEX^® Elite 9000 (ZEISS, Dublin, CA) swept-source OCT and the Macular Cube 200 x 200 scan with the CIRRUS^TM HD-OCT 5000 (ZEISS, Dublin, CA) spectral domain OCT. Differences of the mean measurements, significance, and confidence intervals were determined and Bland-Altman plots used to illustrate agreement (Figure 1).

Results : Thirteen eyes of 13 normal subjects (mean age: 36.6 years, SD: 11.6, range 25-63) and 28 eyes of 28 patients with macular disease were analyzed with both devices. Macular thickness measurements were higher with the PLEX Elite for all 9 ETDRS grid locations (Table 1). The differences of the mean ranged from 5.0 to 9.8 microns (1.9% to 3.7%) for normal and 0.2 to 12.7 microns (0.1% to 4.4%) for diseased eyes. All differences for normal eyes were statistically significant (P<0.001). Measurements of the same ETDRS areas from the PLEX Elite 12 x12 mm scans showed minimal differences from the 6 x6 mm results; up to 1.3 microns (0.4%) for normal and 3.4 microns (1.1%) for disease.

Conclusions : Macular thickness measurements from the PLEX Elite 9000 SS-OCT are consistently higher than CIRRUS SD-OCT. PLEX Elite SS-OCT has better outer retinal layer contrast due to both deeper scan penetration and higher signal collection compared to Cirrus SD-OCT. The minimal amount of difference between the PLEX Elite 6 x 6 mm and 12 x 12 mm scan measurements means ETDRS grid measurements can be extracted from the wider-field Angio 12 x12 mm scans and will be comparable to the traditional 6 x 6mm ETDRS values.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Table 1: Macular measurements for normal and disease subjects

 

Figure 1: Central macular thickness measurements for PLEX Elite Angio 6 x 6 mm and CIRRUS Macular Cube 200 x 200 (6 x 6 mm) scans for a) normal and b) disease