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

Background: 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.

Methods: 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.

Results: 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).

Conclusions: 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.