Abstract
Purpose :
Recent studies have suggested that swept-source optical coherence tomography (SS-OCT) may be superior to spectral-domain OCT (SD-OCT) in imaging eyes with pathological myopia. Here, we compare SD-OCT and SS-OCT optic nerve head (ONH) scans in highly myopic (HM) eyes, to determine if one modality is superior to the other in terms of the percentage of usable scans produced (perUSABLE), and if this difference in perUSABLE is correlated with axial length (AL) and the presence of myopic defects, such as staphyloma, peripapillary atrophy and myopic macular degeneration.
Methods :
413 eyes from 212 patients with HM in at least 1 eye (AL 29.1 ± 2.5 mm, range 22.8 to 35.8 mm) were scanned with SD-OCT (Cirrus) and SS-OCT (Triton). Metrics for the quality of each scan were acquired, namely signal strength (SS), centration and motion artifact. Usable scans were defined as having adequate SS (Cirrus: SS≥7; Triton: SS≥30), adequate centration and lack of motion artifact. Paired t-tests and linear regression analysis were performed to compare SD-OCT vs. SS-OCT and evaluate the association between perUSABLE and potential baseline predictor variables (AL, age, gender, lens status, glaucoma diagnosis, myopic macular degeneration presence, peripapillary atrophy presence, disc tilt presence and presence of intrachoroidal cavitations).
Results :
On average, ONH RNFL scans resulted in significantly greater likelihood of useable scans in Triton (41.8%p) vs. Cirrus scans (15.0%p, p<0.001, paired t-test). Specifically, it was the SS metric that drove this difference. Insufficient SS was found in 1.3%p of Triton scans, but 83.9%p of Cirrus scans (p<0.001). After accounting for potential confounders in multivariate analysis in Cirrus scans, every 1 mm of longer AL was associated with a 1.7%p greater likelihood of insufficient SS (p=0.005), and presence of MMD with +11.8%p (p=0.001). In contrast, in Triton scans, only logMAR VA (worse vision) increased the likelihood of insufficient SS (+1.3%p/ 1.0 LogMAR, p=0.019).
Conclusions :
SS-OCT appears to be more successful than SD-OCT in providing useable ONH RNFL scans, mainly based on SS differences. In particular, Cirrus SS was affected by longer AL and presence of MMD. Our findings suggest SS-OCT may be more likely to avoid the need for repeated scans to achieve useable ONH RNFL data in HM eyes with MMD.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.