A Prospective Ultrasound Biomicroscopy Evaluation Of Changes In Anterior Segment Morphology Of Primary Angle Closure After Laser Therapy

Objective:To discover primary angle closure (PAC) in eyes of natomic narrow angle (ANA), evaluate quantify changes of the PAC in anterior segment morphology after laser therapy using ultrasound biomicroscopy (UBM) and explore primary angle closure mechanism and therapy.Methods:Prospective interventive observational case series. Fifty-one eyes of patients presented ANA in the Department Ophthalmology at Zunyi Medical College Hospital.UBM examination was carried out respectively under both standard light and dark conditions for the ANA eyes. PAC was presented on iris contacting with trabecular meshwork temporally in the UBM image. The PAC eyes was examined by UBM in the same lighting conditions and parameters at two weeks after laser peripheral iridotomy(LPI).UBM images were analyzed using UBM SW-3200 software,UBM parameters before LPI were compared with those after LPI.UBM parameters including anterior chamber distance(ACD),angle open distance(AOD500),trabecular iris angle(TIA),iris thicness(IT1),iris ciliary process distance(ICPD),trabecular ciliary process distance(TCPD),iris lens angle(ILA),iris lens contact distance(ILCD).The all parameters were processed and analysised by SPSS 16.0.Results:First, fifty-One ANA patients were examined by UBM, the rate of PAC was 78.43%(40/51) in dark contion, and 50.98%(26/51) in light condition (χ2=23.588, P=0.000). Second, twenty-eight PAC eyes were cared by LPI, the rate of PAC was significantly decreased after LPI in the same condition. The AOD500, TIA and ILCD significantly increased after LPI, and the ILA decreased after LPI (P< 0.05). IT1 was thiner in super quadrant in dark condition after LPI, but was thiner in inferior quadrant in light condition (P<0.05). There were no significant changes of the ACD, ICPD and TCPD (P>0.05). Third, after LPI, ten eyes still presented on iris contacting with trabecular meshwork, the thick iris and preposition ciliary body was the major contributing factors to angle cloure after LPI. We cared the ten PAC eyes by combining with laser peripheral iridoplasty, after the operation, the iris of the ten eyes was out of touch with trabecular meshwork. The AOD500 and TIA significantly increased in some review points after laser peripheral iridoplasty (P< 0.05).Conclusions:We can diagnose PAC earlier by UBM, especially in dark condtion.The primary angle closure mechanism of PAC is pupillary block and multiple mechanism. LPI produces a significant widening of the anterior chamber angle without deepening the anterior chamber centrally for major PAC eyes. Laser peripheral iridoplasty can open the anterior chamber angle of the PAC those cared after LPI.