Axial Length Changes after Trabeculectomy Measured with Contact and Non-contact Biometries

To compare axial length (AL) changes after trabeculectomy with mitomycin C (MMC) measured using two methods, contact and non-contact biometry. Thirty-four eyes of 31 glaucoma patients who were candidates for primary trabeculectomy were enrolled. AL was measured using A scan ultrasound biometry (UD-6000 Ultrasonic A/B scanner biometer, TOMEY) and non-contact optical biometry device (LenStar LS 900,Haag Stereit) preoperatively and 3 and 6 months postoperatively. Postoperative values, measured at 3 and 6 months, were compared with the preoperative values. After trabeculectomy, AL decreased by 0.21±0.16 mm and 0.14±0.13 mm at month 3 and 0.19±0.15 and by 0.14±0.15 mm at month 6 after surgery using A scan and LenStar, respectively (P 0.001 for all comparisons). The mean reduction in AL was significantly lower with LenStar compared with A scan with a mean difference of 0.07±0.15 mm (P=0.011) at month 3 and 0.04±0.09 mm (P=0.02) at month 6. LenStar can provide more accurate AL measurements than A scan which is attributable to the elimination of false AL reduction caused by the effect of contact biometry probe on softened eyes after trabeculectomy.