The incidence of glaucoma and cataract increases during the natural ageing process of the human eye. The need for surgery depends upon the dominancy of visual deterioration and the extent to which glaucoma has progressed. If both conditions apply, then surgeries can be combined. Combining cataract and glaucoma surgeries affords several benefits over separate operations, including reduced morbidity, lower costs, and faster recovery. Performing combined procedures also reduces the risk of postoperative IOP spikes and the need for ocular hypotensive. Cataract surgery in an eye with a filter in place poses a risk of a filtering flap; however, performing both operations at the same time can result in significant inflammation. Filtering procedures alone are prone to complications such as inflammation, hypotony, and hyphaemia. Beyond that, a filtering bleb can fail at any time in the postoperative period, from minutes to decades after surgery.[6]
The demographic characteristics of groups in our study were statistically similar. The effects of age on wound healing are evident in filtering surgeries. Because wound healing decreases with aging, advanced age can be regarded as a positive factor in trabeculectomy surgery.[7] GATT surgery is conjunctiva-sparing surgery; it is not affected by wound healing or ocular surface disorder due to topical drugs. However, the success of GATT surgery decreases in patients with advanced glaucoma due to reasons such as possible collector duct atrophy.[8] Therefore, the age and gender distributions of the groups needed to be matched in our study to ensure their comparability.
In our study, preoperative IOP was significantly higher in the PTRAB group, largely because trabeculectomy surgery, a conventional filtrating surgery, is a more effective method of lowering target IOP. Likewise, preoperative IOP values were lower in the other group because GATT is preferred in patients with lower IOP, for it causes less vision-threatening complications in early- and middle-stage glaucoma. GATT also seems to be more successful when the target pressure is in the mid-teens, because GATT provides an IOP directly proportional to the episcleral venous pressure. Early IOP was significantly lower in the trabeculectomy group, although its long-term success decreased due to wound healing, as commonly seen in filtrating surgeries over time. That situation increases considerably due to intense inflammatory mediator release, especially during combined phacoemulsification surgery. We also compared combined trabeculectomy with combined GATT and noticed that the long-term effect was more pronounced in the trabeculectomy group, most likely due to the increased inflammatory mediator release after peripheral iridectomy in trabeculectomy surgery and the fact that wound healing in the conjunctiva and scleral flap is more affected by inflammation. However, Siriwardena et al. found that anterior chamber inflammation and the breakdown of the blood–aqueous barrier are far more prolonged after uncomplicated small-incision cataract surgery than after glaucoma filtration surgery with peripheral iridectomy.[9] We thought that, inflammation might be a obstructing factor that affect surgical outcomes, especially after traditional filtration surgeries.
At present, glaucoma surgery comes in different types for different indications. The top reason for the surgery is to reduce complication rates, specifically bleb-related complications. In particular, Schlemm’s canal surgeries have the advantage of using the natural outflow route.[10] Although glaucoma surgery’s effectiveness notoriously decreases in combination with cataract surgery, combined surgery sometimes needs to be performed due to the difficulty of following up with the patient and the intensity of the cataract. The factors that cause PTRAB to be less successful than trabeculectomy include the disruption of the blood–aqueous barrier, the release of inflammatory mediators, the acceleration of wound healing, and secondary bleb failure.[11] In that light, minimally invasive surgery confers the benefits of less inflammatory reaction. Even so, combined surgery should generally be avoided in interventions for glaucoma.
Epithelial cells of the human lens are released after uneventful cataract surgery, which is the principal reason for long-term inflammation and the source of inflammatory mediators. Because postoperative inflammation involves fibrogenesis, all filtration procedures are affected by the wound-healing effect. Despite the lack of proof that natural IOP-reducing procedures such as GATT are affected by postoperative inflammation, we recently found that combined surgery causes shorter-term success. Our findings herein are additional proof that the higher the inflammation following combined trabeculectomy operations other than GATT, the less the long-term complete success. However, additional preclinical studies are needed to clarify the effect of type of glaucoma surgery and inflammation on long-term IOP-reducing potency.[12] One of the best explanations for the inflammatory effect on glaucoma surgery surveillance is uveitic glaucoma surgery. Ample literature on that topic commonly acknowledges that inflammation causes the failure of interventions for glaucoma, especially if they are combined.[13] When we applied glaucoma surgery only in the case of uveitic glaucoma, as a type of surgery that is gaining ground, the effect on the failure could be better understood.[14] Bettis et al[14] found that implanting an Ahmed glaucoma valve (AGV) outperformed the trabeculectomy procedure for uveitic glaucoma, particularly in the first year, possibly because peripheral iridectomy was applied only in the classical trabeculectomy operation. Implanting an AGV can be applied without iridectomy, and the bleb will be more posterior than the trabeculectomy, such that the inflammatory effect is less than the effect of trabeculectomy. Our study shows that amid inflammatory conditions that may affect surgery, type of surgery becomes important for long-term success.
Among our study’s limitations, the long-term results of both groups were not analysed. Because trabeculectomy surgery is an older method, postoperative follow-up times were longer, and we observed that its success decreased over time. Another limitation was that the early and end-stage IOP values were approximate in the PGATT group based on their average scores at 18-month follow-up. That situation decreased efficiency, because combined surgery was significantly less successful in the PGATT group than in the PTRAB group.
In conclusion, we found the PGATT combined procedure to be a well-tolerated, effective procedure that can lower IOP both early and late in the postoperative period with different rates of IOP success compared with the combined PTRAB procedure.