A considerable shift from traditional glaucoma surgeries to MIGS procedures has occurred in recent years [26, 27]. A study from the American Academy of Ophthalmology Intelligent Research in Sight (IRIS®) Registry data found that, from 2013 to 2018, MIGS surgeries rose to comprise nearly half of all glaucoma surgeries in the US. The most common concurrent procedures were ECP and iStent/iStent inject implantation, which accounted for 55.4% of all concurrent glaucoma procedures [26]. These trends underscore the relevance and value of the current study.
The present report provides safety and effectiveness outcomes of phacoemulsification plus ECP or plus ECP + iStent inject implantation in a group of patients from Brazil with cataract and glaucoma. Substantial IOP lowering and reductions in ocular hypotensive medication use were observed for both treatment groups and were sustained for up to 1 year. Both procedures were generally well tolerated with few procedure-related adverse events.
The combination of micro-bypass stent, cataract surgery, and ECP leverages different mechanisms of action in glaucoma management [28]. Not unexpectedly, the eyes receiving the iStent inject in combination with phacoemulsification + ECP demonstrated significantly greater reductions in IOP throughout the 1 year of follow-up (P < 0.01). At Year 1, the difference in percent IOP reductions from preoperative were nearly twice as large for Group 2 than Group 1 (P < 0.001). Overall, the reductions in IOP for eyes with the combined ECP + iStent inject procedure appeared to be maintained with less upward drift over time than for those undergoing the single ECP procedure.
Both treatment groups achieved clinically significant categorical reductions in IOP, with more marked reductions in the group undergoing iStent inject implantation (Group 2). In Group 1, 97.0% and 33.3% of eyes attained IOP ≤ 18 mmHg and ≤ 15 mmHg at Year 1, respectively. In Group 2, from 3 months onward, 100% of eyes achieved both IOP ≤ 18 mmHg and ≤ 15 mmHg through Year 1.
These findings are consistent with the literature on ECP and trabecular micro-bypass. A retrospective consecutive case series by Ferguson et al.[28] demonstrated significantly greater IOP reductions in eyes with mild to severe OAG that received ECP + iStent than those that underwent iStent implantation alone (P < 0.01). Twelve months after surgery the mean IOP reductions were 7.14 mmHg and 4.48 mmHg in the two groups, respectively. Similarly, a longitudinal retrospective 12-month study by Pantalon and colleagues [29] in eyes with early-to-moderate OAG reported significantly larger IOP reductions from baseline of 35% versus 21% for eyes undergoing phacoemulsification + ECP + 2 iStents versus phacoemulsification + 2 iStents (P = 0.03). These results support those of the current study in which the combined procedure provided greater IOP-lowering efficacy than cataract surgery with ECP alone.
Favorable trends also were observed in terms of the reduction in topical ocular hypotensive medications in the current study. The vast majority of eyes in both groups achieved reductions in the number of medications from Month 1 to Year 1. At Year 1, both procedures resulted in substantial mean reductions in medication use (50.2% for Group 1 and 71.5% for Group 2). As with IOP, the medication reductions were significantly greater in the group undergoing iStent inject implantation (Group 2) (P < 0.001). At Year 1, about 73% of eyes were still using 2 medications in Group 1 compared to only 20% in Group 2. Similarly, 24.2% versus 77.1% of eyes in Group 1 and Group 2, respectively, were using 0–1 medication at Year 1. For both groups, at the end of the study, only about 3% of eyes required 3 medications and none required 4 medications. These results represented significant benefits at the level of each patient, given the well-known personal, physical, social, and financial consequences of chronic medication exposure. The benefits were particularly apparent in eyes that underwent iStent inject implantation.
The medication outcomes observed in the present study are aligned with those of Pantalon and colleagues, who reported significantly greater 1-year medication reductions after phacoemulsification + ECP + iStent inject than after phacoemulsification + iStent inject [29]. In contrast, Ferguson et al [28] reported 1-year medication reductions that were less marked in eyes undergoing phacoemulsification + ECP + iStent (38%) than in eyes undergoing phacoemulsification + iStent (63%). This difference may be attributed to differences in baseline characteristics, or to the fact that the Ferguson study involved eyes with 1 stent (iStent) compared to eyes with 2 stents (iStent inject) in the Pantalon study [29] and in our present study. It is also possible that the treatment groups in the Ferguson study were not as well-matched at baseline, since that study was retrospective and non-randomized. Such between-group differences would not be expected in the current dataset, in which patients were prospectively enrolled, randomized, and treated. at 1 year with ECP + iStent compared with iStent and phacoemulsification alone (P = 0.01) [29].
Long-term topical ocular medication use can be associated with substantial downsides. The cost of chronic medication can be a financial burden for patients; not surprisingly, numerous studies have shown the cost effectiveness of the iStent device compared with the use of chronic topical medications [30–36]. Topical ocular hypotensive medications often contain preservatives, such as benzalkonium chloride, which are known to cause adverse effects on the ocular surface [4, 11]. In addition, patient adherence to topical ocular hypotensive drops is typically less than ideal [7, 9, 10, 37, 38]. Barriers to patient adherence also may include complex medication regimens, difficulty with drop instillation, and other factors (patient, provider, social, or environmental) [9]. Poor adherence to glaucoma medication therapy can put a patient at risk for irreversible optic nerve damage and vision loss. Thus the implantation of micro-bypass stents provides a treatment alternative for the surgeon that can reduce preservative load to the ocular surface [18, 39–45] and lessen reliance on patient adherence, thereby helping to preserve visual function.
Both ECP and iStent inject implantation were associated with few intraoperative complications or postoperative adverse events in our study. The majority of events occurred in the initial days following surgery and resolved soon thereafter. Cup:Disc ratios, visual fields, and retinal nerve fiber layer thickness remained stable over the course of the 1-year study in both groups. Best-corrected visual acuity improved dramatically at Year 1 versus preoperative, consistent with what would be expected after cataract surgery alone; there was no indication that the addition of iStent inject or ECP detracted from patients’ overall visual potential.
These visual acuity findings are consistent with prior evaluations of phacoemulsification + ECP and/or iStent implantation [22, 29, 46–51]. For example, a previous study from our group demonstrated improvements in the logMAR visual acuity (P = 0.01) for up to 2 years in eyes receiving phacoemulsification + ECP [22]. Morales and colleagues [50] found improvements in corrected distance visual acuity of 2 Snellen lines or more at 1 year in 73% of patients undergoing ECP and phacoemulsification. In another study of eyes undergoing ECP with phacoemulsification, Clement et al. [47] reported 94% of eyes achieved stable or improved vision after 1 year. Kang et al. [48] demonstrated maintenance or improvement in visual acuity for 95% of their ECP + phacoemulsification group with a mean follow-up of 21 months. Several studies have shown improvements in visual acuity 1 year or more following iStent implantation, either as a stand-alone procedure,51 or when combined with cataract surgery [46, 49]. Finally, Pantalon et al. [29] reported similar 1-year BCVA results in eyes undergoing phacoemulsification plus either iStent inject + ECP or iStent inject. All of these studies, as well as the current one, demonstrate favorable outcomes with ECP, iStent inject implantation, or the combination of the two procedures in combination with phacoemulsification in terms of preserving the visual improvements expected after cataract surgery alone.
This study is limited by its modest sample size, 1-year follow-up duration, and inclusion of data from 2 surgeons at 2 sites. Patients with other forms of glaucoma than OAG were excluded, as well as those who had undergone previous glaucoma filtration surgery. Not all data were available for all parameters at all time points. A future study could include a greater number of patients, longer duration of follow-up, data from more sites, or a broader range of glaucoma subtypes.