Functional evaluation of an iridotomy in primary angle closure eyes.

Abstract

To evaluate the functional efficacy of an iridotomy in primary angle closure (PAC) eyes by measuring IOP responses to provocative tests before and after iridotomy. Prospective cohort study. 50 consecutive adult patients, 40-60years of age, having primary angle closure. Clinical examination, perimetry, biometry and ultrasound biomicroscopy of the angle were done. A darkroom prone provocative test (DRPPT), a mydriatic test and a Valsalva maneuver were performed before and after the iridotomy. IOP change in response to the provocative tests before and after iridotomy, and correlation with baseline parameters. IOP at baseline and after iridotomy was 14.4 ± 2.7mmHg and 14.3 ± 2.6mmHg, respectively (p = 0.)83. There was no significant change on diurnal phasing before and after an iridotomy (p = 0.)11. The mean IOP rise was 5.9 ± 3.7mmHg on the DRPPT, 4.3 ± 3.5mmHg on the Mydriatic test and 9.1 ± 4.9mmHg on the Valsalva maneuver, and was reduced significantly to 3.2 ± 2.1mmHg, 2.3 ± 1.8 and 6.4 ± 3.5, respectively(p < 0.001 for all tests). The decrease in pupillary block component for all 50 eyes was 46.5% for the mydriatic test, 45.8% for the DRPPT and 29.7% for the Valsalva maneuver. PAC eyes positive on the DRPPT and mydriatic test prior to an iridotomy became negative after laser iridotomy in 75.9 and 84.6% eyes, respectively, but on the Valsalva maneuver, only 23.8% became negative. After iridotomy, eyes that continued to be positive on the mydriatic test had a significantly thicker lens (p = 0.02), decreased TCPD (p = 0.014) and narrower trabecular-iris angle (p = 0.048). On the DRPPT, they had a thicker lens (p = 0.03), shorter iris thickness (p = 0.025) and TCPD (p = 0.032), and on the Valsalva maneuver, they had a narrower scleral-ciliary process angle (SCPA; p = 0.019) and shorter TCPD (p = 0.015). This comprehensive functional evaluation of laser iridotomy in early PAC eyes showed a significant reduction in the pupillary block component of IOP response to provocative testing, possibly decreasing IOP fluctuations over time. An iridotomy does not, however, significantly change mean IOP or diurnal phasing of IOP in PAC eyes. Eyes with a very narrow angle or a thick lens may continue to have angle closure due to other pathomechanisms for angle closure.