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 highresolution swept-source optical coherence tomography(SS-OCT)and to compare those values with horizontal white-to-white(WTW)distance.Methods:Sixty-eight 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 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.