Randomised trial of sequential pretreatment for Nd:YAG laser iridotomy in dark irides.

AIMS: To compare iridotomy outcomes in dark irides by 1064 nm pulsed Nd:YAG laser with and without 532 nm continuous-wave Nd:YAG (frequency-doubled) green laser pretreatment.

METHODS: 30 patients with occludable anterior chamber angles underwent bilateral standard pulsed 1064 nm Nd:YAG laser iridotomy with one eye randomly assigned to sequential pretreatment with 532 nm continuous-wave Nd:YAG laser. Outcome measures were iridotomy patency and complications including haemorrhage and elevated intraocular pressure (IOP).

RESULTS: Median pulsed YAG power in the standard treatment group was 37.5 mJ (IQR 25-77) and 22.5 mJ (IQR 14-32) in the sequential treatment group (p=0.0079). Iris haemorrhage occurred in 43% of the standard treatment group and 13% of the sequential treatment group (p=0.0126). All iridotomies were patent at the end of the procedure in the sequential treatment group, while 2/30 in the standard treatment group were abandoned due to significant haemorrhage. Mean IOP at 1 h was significantly lower than pre-laser values in both groups (with magnitude of reduction significantly more in the sequential treatment group). There was no significant change in IOP at 1 week. All iridotomies were patent at last follow-up of median 38.5 months (IQR 32.0-42.3).

CONCLUSIONS: This study provides evidence that iridotomy with pretreatment using a continuous-wave Nd:YAG laser is safer and more effective than pulsed Nd:YAG-only laser iridotomy for dark irides and should be considered as the preferred technique.