Angle-to-angle and spur-to-spur distance analysis with high-resolution optical coherence tomography

To measure angle-to-angle (ATA) and spur-to-spur (STS) distances along six meridians using high-resolution swept-source optical coherence tomography (SS-OCT) and to compare those values with horizontal white-to-white (WTW) distance.

68 eyes from 68 patients were quantitatively assessed with the Anterion SS-OCT (Heidelberg Engineering, Heidelberg, Germany). ATA and STS distances were measured with the SS-OCT's B-Scan in six cross-sectional images corresponding to the vertical (6-12 o'clock), 1-7 o'clock, 2-8 o'clock, horizontal (3-9 o'clock), 4-10 o'clock and 5-11 o'clock meridians. WTW was measured horizontally with the device's infrared camera. A Pearson correlation analysis was carried out to compare ATA and STS distances with WTW.

The largest values were found for the vertical meridian and the shortest for the 2-8 o'clock meridian, both for ATA and STS distances. No statistically significant differences were found between WTW, ATA and STS along the horizontal meridian (p > 0.1). However, ATA and STS showed statistically significant differences elsewhere, except for the horizontal and the 2-8 o'clock meridians (p > 0.05). Moreover, we found that ATA and STS varied significantly depending on the meridian being assessed, except for ATA at 4-10 versus 3-9 o'clock and for STS at 4-10 versus 3-9 o'clock and at 3-9 versus 2-8 o'clock (p > 0.1). R² values ranged from 0.49 to 0.75 for ATA and STS at the different meridians, showing the best correlation at 3-9 o'clock meridian (0.64 and 0.75, respectively) and the worst at 6-12 o'clock meridian (R² = 0.49 for both ATA and STS).

ATA and STS distances vary radially, thus showing that the anterior chamber is vertically oval. Therefore, it is advisable to measure these two distances along the meridian to be used.