High-Frequency Ultrasound Biomicroscopy Measurement of Anterior Chamber Angle Structures in Patients with Primary Congenital Glaucoma

Abstract

Purpose : To provide in vivo values of anterior chamber angle structure dimensions and their relations to age as evaluated by high-frequency ultrasound biomicroscopy (UBM) in primary congenital glaucoma (PCG).

Methods : Cross-section study that include 51 PCG eyes of 40 patients (aged from 3 to 96 months) (Group 1) and 11 unaffected contralateral eyes (Group 2). High-frequency UBM examination was done for all participants for measurement of the largest cross-sectional area (CSA) of Schlemm’s canal (SC), SC meridional diameter, trabecular-iris angle (TIA), trabecular meshwork (TM) thickness, distance between Schwalbe’s line (SL) and the anterior point of SC (SL-SC distance), distance between SL and scleral spur (SL-SS distance), iris thickness, ciliary process length, corneal limbus thickness, and distance between SL and the anterior point of iris root (SL-iris distance).

Results : The largest CSA of SC, the SC meridional diameter, the SL-SS distance, the iris thickness, the corneal limbus thickness and the SL-iris distance in Group 1 were 3363.91±1082.98 μm², 257.70±66.70 μm, 418.57±93.42 μm, 188.10±40.62 μm, 702.73±100.37 μm and 405.09±186.81 μm respectively, and they were all significantly smaller than those in Group 2 (5130.66±1231.90 μm², 335.09±104.76 μm, 541.21±96.05 μm, 235.25±65.34 μm, 771.62±78.59 μm and 595.45±131.74 μm respectively, all P<0.05). TIA and ciliary process length in Group 2 were both smaller than that in Group 1 (48.02±15.62 vs 64.52±15.28 degree and 1278.37±130.28 μm vs 1498.88±300.02 μm, both P<0.05). There were no statistical differences among groups in TM thickness and SL-SC distance (all P>0.05). Among all those anterior chamber angle parameters, that the largest CSA of SC (P=0.001) and iris thickness (P=0.021) were factors contributing to the PCG diagnosis. The largest CSA of SC (r²=0.111 P=0.011), TM thickness (r²=0.116, P=0.010), SL-SC distance (r²=0.122, P=0.048), iris thickness (r²=0.114, P=0.011), ciliary process length (r²=0.395, P<0.001) and SL-iris distance (r²=0.279, P<0.001) were significantly correlated to age in 51 PCG eyes.

Conclusions : The anatomical information gleaned in this study by using high- Frequency UBM might be useful providing the glaucoma specialist with a useful tool to aid in the diagnosis and understanding the development of anterior chamber angle in childhood glaucoma and normal eyes.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.