In the current study, we explored the efficacy and safety of trabectome combined with phacoemulsification, IOL implantation, and GSL in PACG patients. The results demonstrate that with the assistance of phacoemulsification and re-establishing the anterior chamber angle, trabectome showed an effective IOP-lowering effect with satisfied reduction of the number of IOP-lowering medications at 2 years.
PACG is a kind of ocular disorder characterized by anterior chamber angle closure, which is the main cause of blindness worldwide as well as in China. The main pathophysiological mechanisms of angle closure are pupillary block and iris plateau configuration. The purpose of treatment is to open the outflow drainage passage and reduce IOP through medical and/or surgical treatment. Traditional surgeries for PACG, including trabeculectomy, glaucoma valve implantation, and phacotrabeculectomy, has traditionally been used to treat a wide range of PAS patients, complications of which include shallow anterior chamber, cataract progression, filtering bleb scar, congenital arthritis, etc. Phacoemulsification with or without GSL and has been shown in many studies to lower IOP in PACG.17,24 Although phacoemulsification with GSL shows great advantages over traditional surgeries from the point of view of complications, IOP-lowering effect was not always satisfied, especially for patients with long duration of angle-closure glaucoma.8,9,25 Tian et al.25 compared the efficacy of phacoemulsification combined with GSL in the treatment of acute and chronic angle closure patients. The success rate in the chronic group (acute vs chronic: 100% vs 64.3%) was lower. Compared the efficacy of phacoemulsification combined with GSL and phacoemulsification alone in patients with well controlled chronic angle closure glaucoma and cataract.Lee et al.8 compare the effect of phacoemulsification combined with GSL and phacoemulsification alone in patients with medically well- controlled chronic angle-closure glaucoma with cataracts. They found there was no significant difference between two groups in lowering IOP and suggested that it is difficult to attain more benefits from additional GSL. Husain et al.9 concluded similar results with Lee et al. through a randomized clinical trial. Furthermore, Wang et al.10 reviewed and analyzed seven randomized controlled trials to determine the effect of phacoemulsification and GSL compared to phacoemulsification alone in ACG patients. A “low to moderate quality evidence” was disclosed that phacoemulsification and GSL surgery lead to an equivalent IOP-lowering effect compared to phacoemulsification alone. This indicates that the temporary re-opening of the angle is insufficient in chronic PACG. Even if the angle is kept open for a longer period of time, the re-exposed TM might fail to function. These findings had led to an ongoing effort to explore new strategies that avoid these pitfalls and offer a longer lasting result.
In our study, with the assistance of phacoemulsification and GSL, trabectome offers an effective IOP-lowering effect with satisfied reduction of the number of IOP-lowering medications for PACG patients at 2 years. The mean glaucoma duration was 53.35 ± 58.61 months and the mean extent of goniosynechia before operation was 319.09 ± 64.94 degrees in our study. Seventeen eyes had been suffering from it for more than 1 year, and 15 of 22 eyes presented the 360 degrees of synechial angle closure. For this group of patients with long term and extensive goniosynechia, we not only performed phacoemulsification and GSL, but trabectome, which creates a cleft that connects the anterior chamber to the SC, allowing aqueous to enter the collector channels more directly without the resistance of the TM. Previous studies26,27 have proved that re-establishing a normal open angle configuration with goniosynechiolysis is not sufficient for successful IOP-lowering. Shihota et al.28 proposed that PAS and angle closure causes pigment accumulation and non-inflammatory degeneration of the TM. For patients with PAS less than 6 months to 1 year, TM function could be preserved and the effect of goniosynechiolysis might be satisfied.29,30 We suggest that the TM function of PACG patients with long term and extensive goniosynechia have undergone irreversible damage. White et al.31, Zhao et al.11 and Husian et al.9 hold the similar opinion with us, which give reasonable explanation that IOP-lowering effect was not always satisfied for patients with long duration of angle-closure glaucoma.
Another potential limitation of goniosynechiolysis combined phacoemulsification or not is that the lowering of the IOP may not be satisfied due to reformation of PAS. Lee et al.8 reported that postoperative PAS reformation was observed in 5 patients (33.3%) after goniosynechiolysis. The recurrence of PAS was more serious than that before operation and the main site was identical before operation. The rate of PAS recurrence was 30%-100% after goniosynechiolysis, and the rate was much higher with long duration of PAS. 8,16,25 However, there was only 2 eyes (9%) experienced PAS recurrence in current study. We speculated that trabecutome combined with goniosynechiolysis makes the anterior chamber angle wider and the space between the peripheral iris and SC larger, which may be another obvious advantage of trabecutome. Even if there is obvious inflammatory reaction after goniosynechiolysis, PAS is hard to reformation.
Relevant factors to the reduction in IOP and the number of medications were determined by regression analysis. As showed by the univariate analysis, we found greater reduction in IOP and the number of medications in PACG patients presented with higher baseline IOP and more IOP-lowering medications respectively. We hypothesized that eyes with higher IOP and more medications may have better results because they will undergo early surgery after diagnosis.
The following study limitations should be considered. First, the sample size was small and the follow-up period was short. Larger-scale, longer-follow up trials would provide stronger evidence to compare the efficacy of this procedure with that of other operations. Second, we only enrolled PACG patients with concurrent cataract who received phacoemulsification, IOL implantation, GSL, and trabectome without control group. Additional studies with two groups who receive phacoemulsification, intraocular IOL and GSL with or without trabectome may be more helpful to elucidate the efficacy and safety of combined trabectome.
In conclusion, the combined procedure of phacoemulsification, IOL implantation, GSL, and trabectome was a possibly effective and safe surgical choice for lowering the IOP and reducing the number of anti-glaucoma medications in PACG patients. It may provide a brand-new method for PACG patients especially those with long term and extensive goniosynechia. Further longitudinal studies with larger sample size, control group, and subgroup analysis are necessary to demonstrate the advantage of this procedure.