ORIGINAL RESEARCH


https://doi.org/10.5005/jp-journals-10078-1414
Journal of Current Glaucoma Practice
Volume 17 | Issue 3 | Year 2023

Outcomes of Trainee-performed MIGS at Parkland Memorial Hospital: A Retrospective Cohort Study


Joseph Da1https://orcid.org/0000-0003-0122-1334, Matthew Gillings2, Shivani Kamat3, Niraj Nathan4

1-4Department of Ophthalmology, UT Southwestern Medical Center (UTSW), University of Texas, Dallas, Texas, United States of America

Corresponding Author: Niraj Nathan, Department of Ophthalmology, UT Southwestern Medical Center (UTSW), University of Texas, Dallas, Texas, United States of America, Phone: (678) 381-2020, e-mail: nnathan@milaneyecenter.com

Received on: 23 May 2023; Accepted on: 31 August 2023; Published on: 11 October 2023

ABSTRACT

Aims and background: As the use of minimally invasive or microinvasive glaucoma surgery (MIGS) continues to expand, it is important to look at its outcomes in the hands of trainees. This study aims to examine the efficacy and safety of Kahook Dual Blade (KDB) goniotomy and endocyclophotocoagulation (ECP) with cataract extraction (CE) done by residents and fellows.

Methods: All cases of KDB or ECP performed with CE between 2012 and 2020 at Parkland were reviewed, excluding cases with multiple MIGS procedures or other procedures.

Results: A total of 153 eyes of 136 patients who underwent KDB and 125 eyes of 124 patients who underwent ECP were included. Mean intraocular pressure (IOP) decreased from 17.2 ± 5.2 at baseline to 15.4 ± 5.5 mm Hg at postoperative (post-op) month (POM) 12 in the KDB group (p = 0.02) and from 18.6 ± 6.3 at baseline to 15.1 ± 4.9 mm Hg at POM12 in the ECP group (p < 0.001), with wide variation in IOP change among subjects for both. The mean change in IOP across all time points was statistically significant for both groups. Medication counts were reduced from baseline at POMs 1, 3, and 6, but not 12, in both the KDB and ECP groups (p = 0.43 and p = 0.35, respectively). The rate of serious complications was very low; the most common complication was cystoid macular edema (CME) (six cases) and active inflammation beyond POM1 (15 cases) for KDB and ECP, respectively.

Conclusion: Combined CE/MIGS procedures performed by trainees were safe but less efficacious in lowering IOP and medications compared to literature reporting outcomes of attending surgeons, apart from ECP/MIGS with regards to IOP lowering, which was found to be similarly efficacious.

Clinical significance: Cataract extraction (CE) combined with KDB or ECP in the hands of trainees decreased mean IOP from baseline and was safe. IOP and medication reduction of MIGS/CE in the hands of trainees were overall lesser than reported values by attending surgeons.

How to cite this article: Da J, Gillings M, Kamat S, et al. Outcomes of Trainee-performed MIGS at Parkland Memorial Hospital: A Retrospective Cohort Study. J Curr Glaucoma Pract 2023;17(3):134–140.

Source of support: Nil

Conflict of interest: None

Keywords: Cataract surgery, Minimally invasive glaucoma surgery, Retrospective cohort study, Trainee outcomes

INTRODUCTION

Minimally invasive or microinvasive glaucoma surgery (MIGS) refers to the emerging class of glaucoma procedures that lower intraocular pressure (IOP) with minimal disruption to the sclera or conjunctiva. Compared to conventional glaucoma surgeries (e.g., trabeculectomy and tube shunts), MIGS demonstrates greater safety profiles by decreasing adverse events such as hypotony and other bleb-related complications,1 but also tends to be less effective on average in lowering IOP.2 The use of MIGS increased fivefold in the United States from 2013 to 2018,3 allowing for expanded surgical options for glaucoma patients earlier in the disease course.1 MIGS may be performed standalone or in combination with cataract extraction (CE) and intraocular lens placement (IOL) to reduce IOP and medication burden.2

Certain MIGS procedures are now accepted by the Accreditation Council for Graduate Medical Education (ACGME) to count toward ophthalmology resident minimums for glaucoma surgeries.4 MIGS already make up a considerable proportion of glaucoma surgeries performed by residents; Qiu et al. reported an average of nine traditional glaucoma surgeries vs 5.2 MIGS per resident in the graduating class of 2018,5 and it has been shown that the involvement of residents with MIGS is underestimated in case logs.6 As residents increasingly perform MIGS procedures as part of their training, it is important to study the safety and efficacy of resident-performed MIGS. There is also a paucity of research on the outcomes of MIGS performed by glaucoma fellows. While previous studies reported outcomes of cataract surgeries7,8 and trabeculectomy performed by trainees,9,10 few studies have examined trainee outcomes with MIGS procedures.

In this study, the MIGS procedures most commonly performed by trainees during the study period were endocyclophotocoagulation (ECP) and Kahook Dual Blade (KDB) goniotomy, though this has continued to change over time. ECP uses a microprobe laser (Iridex Oculight, Mountain View, California, United States of America) and endoscopy system (Endo Optiks, Little Silver, New Jersey, United States of America) to directly visualize and ablate the ciliary body to decrease aqueous humor production.11 At the 2-year follow-up, ECP combined with CE/IOL has been shown to decrease IOP by 2.1–4.9 mm Hg and decrease glaucoma medications by 0.2–1.1.12-14 In KDB goniotomy, the dual blade (New World Medical, Rancho Cucamonga, California, United States of America) is used to excise a strip of trabecular meshwork (TM), allowing for increased aqueous outflow through the conventional outflow pathway.15 At a 2-year follow-up, KDB combined with CE/IOL has been shown to decrease IOP by 4.3–7.2 mm Hg and decrease glaucoma medications by 0.7.16,17 Only a few studies have examined outcomes of trainee-performed KDB,18,19 and to our knowledge, none have characterized trainee outcomes with ECP. No studies have directly compared KDB and ECP on a large scale. This study examines the safety and efficacy of KDB and ECP performed by ophthalmology residents and glaucoma fellows in the public hospital setting.

METHODS

The study was conducted in compliance with the tenets of the Declaration of Helsinki and the standards set forth by the United States Health Insurance Portability and Accountability Act. Approval was obtained from the institutional review board of the University of Texas Southwestern Medical Center. Individual consent for the study was waived. A computerized search of the Parkland billing database was performed to extract all patient charts with procedure codes 65820 (trabeculotomy ab interno/goniotomy) and 66711 (ciliary body destruction; cyclophotocoagulation; endoscopic) from 1st January 2011 to 2nd March 2021. All eligible subjects were adults with glaucoma and visually significant cataracts who were undergoing elective cataract surgery in combination with KDB or ECP. Standalone KDB or ECP and cases involving multiple MIGS or other procedures were excluded. Which MIGS to perform, whether to perform MIGS before or after CE and immediate postoperative (post-op) management were all at the discretion of the supervising surgeon for each case. Primary surgeons were all trainees, residents, and glaucoma fellows.

The surgeon performed each MIGS procedure according to the manufacturer’s recommendations, usually after standard phacoemulsification and lens placement. KDB goniotomy was performed through a temporal clear corneal wound. Under visualization with a gonioscopy lens, the KDB blade was used to excise approximately 90° of TM and the inner wall of Schlemm’s canal. ECP was also performed through the temporal corneal wound. After the ciliary processes were visualized, the ECP laser was treated at approximately 90–270° using 0.1–0.35 W of power. Post-op medication management was not standardized and was at the discretion of each provider at each post-op visit.

A total of 153 eyes of 136 patients who underwent KDB and 125 eyes of 124 patients who underwent ECP were analyzed. IOP was measured by Goldmann applanation tonometry (Haag-Streit AG, Köniz, Switzerland) or Tono-Pen AVIA (TPA; Reichert Inc., Depew, New York, United States of America) when applanation was not available. Baseline IOP was defined as the average IOP from the two visits prior to the surgery. The baseline number of topical glaucoma medications was recorded at the preoperative visit closest to the surgery. Eyes were assigned glaucoma staging as per the International Classification of Diseases, 9th revision, and eyes with indeterminate staging were excluded from the total number of eyes in staging calculations. Preoperative angle assignments were taken from the most recent gonioscopy measurement to the surgery, where the open angle was defined as grade 3 or greater in two or more quadrants, and narrow-angle was defined as three or four quadrants with grade 2 or less according to the Schaffer grading system.20 Intraoperative complications, degrees of TM and ciliary body treatment, and laser power (Watts) for ECP were collected. Complications were monitored throughout the 12-month post-op follow-up period and included cystoid macular edema (CME), hyphema, a ≥10 mm Hg increase in IOP compared to baseline IOP, need for subsequent glaucoma surgery, and rebound inflammation. Rebound inflammation was defined as the worsening of anterior chamber cells on a routine post-op topical steroid regimen requiring increased dosages or a prolonged course of topical steroids or recurrent anterior chamber cells after routine discontinuation of topical steroids. Data were gathered at baseline, post-op month 1 (POM1, including visits post-op weeks 3–5), POM3 (including visits post-op weeks 10–14), POM6 (including visits POMs 5–7), and POM12 (including visits POMs 11–13). Patients who did not have an office visit for a given time point were censored from the data pool for that specific time point.

Primary outcomes were IOP reduction, glaucoma medication reduction, and success. Success was defined as ≥1 medication reduction or ≥20% IOP reduction, provided that the post-op IOP was not greater than the baseline IOP. Reductions in IOP and number of medications from baseline at POMs 1, 3, 6, and 12 were assessed using paired t-tests. Multiple linear regression was performed for baseline characteristics (age, race, glaucoma classification and severity, gonioscopy angle, preoperative mean medication count, and preoperative mean IOP) to evaluate possible associations between reduction in IOP at POM12. Holm–Bonferroni method was applied to control for multiple hypothesis testing. No prespecified hypothesis was tested, so a priori power and sample size calculations were not undertaken, and the sample size was set by the number of cases that were pulled from the computerized search that met inclusion/exclusion criteria. Any value of p < 0.05 was considered statistically significant.

RESULTS

Baseline demographics and glaucoma classification for both groups are summarized in Table 1. Participants were 69.7 ± 9.7 years old (range 33–90 years), predominantly African American (126/260, 48.5%) or Hispanic (102/260, 39.2%), and predominantly female (61.2%, 159/260). Most eyes were characterized as having primary open-angle glaucoma (74.8%, 208/278), primarily moderate or severe stage (124/278, 44.6% and 100/278, 36%, respectively). Baseline characteristics between KDB and ECP groups were similar, except that the ECP group had a higher preoperative IOP (18.6 ± 6.3 vs 17.2 ± 5.2 mm Hg, p = 0.004), a higher preoperative medication count (3.3 ± 1.1 vs 2.6 ± 1.3, p < 0.001) (Table 1).

Table 1: Demographic and baseline glaucoma data
KDB (n = 138 pts, 153 eyes) ECP (n = 125 pts, 126 eyes) p-valuea
Subject-level parameters
Age (years), mean ± SD 69.4 ± 9.5 70.0 ± 9.9 0.60
Sex, n (%) 0.58
Female 81 (59.6) 78 (62.9)
Male 55 (40.4) 46 (37.1)
Race, n (%) 0.15
White 7 (5.1) 13 (10.5)
Black 72 (52.9) 54 (43.5)
Hispanic 53 (39.0) 49 (39.5)
Asian 4 (2.9) 8 (6.5)
Eye-level parameters
Glaucoma type 0.90
Primary open-angle 118 (77.1) 90 (73.2)
Narrow-angle 18 (11.8) 19 (15.4)
Combined mechanisms 10 (6.5) 7 (5.7)
Pseudoexfoliation 3 (2.0) 3 (2.4)
Other (pigmentary, neovascular, ocular hypertension, other secondary) 4 (2.6) 4 (3.3)
Glaucoma severity 0.10
Mild 9 (5.9) 8 (6.4)
Moderate 78 (51.0) 46 (36.8)
Severe 50 (32.7) 50 (40.0)
Indeterminate 16 (10.5) 21 (16.8)
Preoperation angle 0.10
Open 133 (86.9) 93 (74.4)
Narrow 11 (7.2) 19 (15.2)
No gonioscopy recorded 9 (5.9) 13 (10.4)

ECP, endocyclophotocoagulation; KDB, Kahook Dual Blade goniotomy; pts, patients; SD, standard deviation; acalculated using student’s t-test, Chi-squared test, or Fisher’s exact test

For the KDB group, surgeons stripped an average of 94 ± 17° of TM (range 30–180°). For the ECP group, surgeons treated an average of 201 ± 57° of the ciliary body (range 90–270°). The average power used for cyclophotocoagulation was 0.22 ± 0.05 W (range 0.10–0.35 W). The ECP group had a greater average length of follow-up compared to the KDB group (9.8 ± 3.9 vs 8.5 ± 4.3 months, p = 0.01).

Mean IOP reduction compared to baseline was statistically significant at all post-op time points for both the KDB group and the ECP group (Table 2). At POM12, the mean IOP reduction from baseline was 1.7 mm Hg (10.0%) in the KDB group and 2.7 mm Hg (15.2%) in the ECP group. There was not a statistically significant difference in mean IOP reduction at any post-op time point between the KDB and ECP groups.

Table 2: Mean IOP values over time for each MIGS group
KDB ECP
N Mean IOP ± SD (mm Hg) Mean IOP difference from baseline (mm Hg) (%) p-value (from baseline)b N Mean IOP ± SD (mm Hg) Mean IOP difference from baseline (mm Hg) (%) p-value (from baseline)b p-value (comparing KDB and ECP differences compared to baseline)b
Timepoint
Baseline 153 17.2 ± 5.2 125 18.6 ± 6.3
POM1 138 15.3 ± 4.7 −1.7 (−9.8) <0.001a 120 16.7 ± 6.3 −1.9 (−10.2) 0.002a 0.76
POM3 102 14.5 ± 4.1 −2.5 (−14.7) <0.001a 104 16.6 ± 5.8 −2.0 (−10.6) <0.001a 0.50
POM6 107 15.3 ± 4.8 −1.4 (−8.6) 0.01a 107 16.6 ± 7.2 −1.9 (−10.1) 0.006a 0.63
POM12 85 15.4 ± 5.5 −1.7 (−10.0) 0.02a 92 15.1 ± 4.9 −2.7 (−15.2) <0.001a 0.26

ECP, endocyclophotocoagulation; KDB, Kahook Dual Blade goniotomy; POM, post-op month; SD, standard deviation; astatistically significant; bcalculated using student’s t-test

Mean medication reduction compared to baseline was significant at all post-op time points aside from POM12 for both the KDB group and the ECP group (Table 3). At POM12, the mean medication change from baseline was a medication addition of 0.1 in the KDB group and a medication reduction of 0.1 in the ECP group, which was not statistically significant in either group (p = 0.43 and p = 0.35, respectively). There was not a statistically significant difference in medication reduction from baseline between the KBD and ECP groups at any post-op time point.

Table 3: Mean medication counts over time for each MIGS
KDB ECP
N Mean medication count ± SD Mean difference in medication count from baseline p-value (from baseline)b N Mean medication count ± SD Mean difference in medication count from baseline p-value (from baseline)b p-value (comparing KDB and ECP differences compared to baseline)b
Timepoint
Baseline 153 2.6 ± 1.3 125 3.3 ± 1.1
POM1 139 2.0 ± 1.5 −0.6 <0.001a 120 2.8 ± 1.3 −0.5 <0.001a 0.48
POM3 102 2.2 ± 1.4 −0.3 <0.001a 104 3.1 ± 1.1 −0.3 0.01a 0.64
POM6 108 2.3 ± 1.4 −0.2 0.03a 101 3.0 ± 1.2 −0.3 0.02a 0.52
POM12 85 2.7 ± 1.4 +0.1 0.43 92 3.1 ± 1.2 −0.1 0.35 0.23

ECP, endocyclophotocoagulation; KDB, Kahook Dual Blade goniotomy; POM, post-op month; SD, standard deviation; astatistically significant; bcalculated using student’s t-test

Success rates were primarily driven by achieving a ≥20% reduction in IOP compared to the preoperative baseline rather than a decrease in medication count (Fig. 1). No difference was found between the KDB and ECP groups at any post-op time point.

Fig. 1: Trainee success rates for KDB and ECP combined with cataract extraction up to POM12, broken down into meeting success criteria by IOP response, medication response, or both; ECP, endocyclophotocoagulation; KDB, Kahook Dual Blade goniotomy; IOP, intraocular pressure

There was a wide range in individual IOP responses in both the KDB and ECP groups (Fig. 2). Preoperative IOP was found to be associated with post-op IOP reduction for both KDB and ECP (p < 0.001, p = 0.003, respectively; Fig. 3). All other measured variables (age, race, glaucoma type and severity, preoperative angle by gonioscopy, and preoperative medication count) were not found to be associated with post-op IOP reduction in either KDB or ECP groups among IOP response subgroups.

Fig. 2: Postoperative (post-op) IOP spread for KDB and ECP groups; ECP, endocyclophotocoagulation; IOP, intraocular pressure; KDB, Kahook Dual Blade goniotomy; POM, post-op month

Fig. 3: Multiple linear regression displaying correlation of baseline IOP as a significant variable in predicting IOP response, adjusted with the Holm–Bonferroni method; IOP, intraocular pressure

The KDB group had two cases (1.2%) of intraoperative complications: one case of a one-clock-hour iridodialysis and one case of vitreous loss. The ECP group had no cases of intraoperative complications. Post-op complications are reported in Table 4. By POM12, 26 (17.0%) of eyes in the KDB group and 30 (23.8%) of eyes in the ECP group experienced post-op complications; this difference was not statistically significant. The most common complications included IOP spike, CME, and persistent anterior chamber inflammation. In the KDB group, three cases with hyphema ≤1 mm in size resolved spontaneously by post-op week 2, and one case with hyphema 2 mm in size resolved spontaneously by POM1.

Table 4: Adverse events in each treatment group that affected >1% of eyes, N (%)
Adverse events, n (%) KDB ECP p-valueb
IOP elevation (≥10 spikes) 5 (3.3) 12 (9.6) 0.03a
CME 6 (3.9) 0 (0) 0.03a
Hyphema 4 (2.6) 0 (0) 0.13
Active inflammation beyond POM1 6 (3.9) 15 (11.9) 0.01a
Post-op hypotony 2 (1.3) 0 (0) 0.50
Other 3 (2.0) 2 (1.6) 1
Total 26 (17.0) 30 (23.8) 0.18

ECP, endocyclophotocoagulation; IOP, intraocular pressure; KDB, Kahook Dual Blade goniotomy; POM, post-op month; astatistically significant; bcalculated using Fisher’s exact test

DISCUSSION

Our study demonstrated that trainee-performed KDB and ECP surgeries combined with CE/IOL were both safe and efficacious in lowering IOP over a 12-month follow-up period. IOP lowering at POM12 in the ECP group was comparable to other studies looking at ECP outcomes of attending-level surgeons or including attending-level surgeons, where other studies have ranged in POM12 reduction from 2.1–5.4 mm Hg.12-14 IOP lowering at POM12 in the KDB group was lower than those of other studies, which had POM12 reductions ranging from 2.4–6.5 mm Hg.17,21-23

One of the striking results of this study is the high variability in individual IOP response (Fig. 2), including sustained IOP increases and decreases of large magnitude. It is unclear whether surgeon experience and/or the characteristics of the study population contributed to this result. Previous studies have shown higher rates of POD1 IOP spikes after cataract surgeries performed by residents compared to those performed by attending physicians, but not particularly sustained differences.24,25 Our regression analysis suggested higher preoperative IOP in both MIGS groups as a predictor of IOP response, as also found by Meer et al. in a study reviewing Hydrus, iStent, and KDB outcomes when performed by residents.18 This warrants further study as improved patient stratification and selection may help improve the consistency of efficacy of these procedures in specific patient subsets.

Our study did not show a statistically significant POM12 medication reduction in either group, whereas, in most of the comparison studies, significant reductions were found by POM12, with 1.1 medication reduction for ECP and 0.7–2.2 medication reduction for KDB.12,14,17,21,22 However, in one ECP study, no significant reduction was found by POM12, and the authors cite a reason that it was part of their practice to not stop glaucoma medications after phacoemulsification-ECP. In our study, there may be a similar factor in trainee hesitancy to discontinue glaucoma medications, as well as less patient reliability and more severe glaucoma in our patient population.

It is important to mention the demographics of this county’s hospital-based patient population, which may include a higher percentage of poorly controlled and severe-stage glaucoma. Around 51.7% of eyes in this study qualified as moderate glaucoma and 41.3% had severe glaucoma—higher respective rates than in comparative studies, including data on preoperative severity.12,14,17,22 One previous study of a county hospital population found patients with severe glaucoma to be less likely to adhere to treatment plans and recommended follow-up than patients with mild or moderate disease.26 Salinas et al. reported that KDB in severe refractory glaucoma can still have favorable IOP reduction.27 Also, medication compliance has been shown to be significantly more difficult for patient populations with more socioeconomic difficulty and language barriers—a demographic reflected in a substantial proportion of our county hospital population.28 Although compliance was not specifically measured in our study, there were 5/5 KDB patients and 7/12 ECP patients with 10+ mm Hg spikes in IOP who had been reported to have some degree of noncompliance with their prescribed glaucoma medication regimen. Our study suggests that MIGS did not often confer medication independence in this study population with increased disease severity or prior noncompliance, which may be a consideration when considering MIGS vs traditional glaucoma surgery in this population.

Compared to previous studies addressing trainee-performed MIGS, our study demonstrated similar post-op complication rates.19 The nature of complications in both MIGS groups was similar to that of other studies as complications were minimal in severity and self-limiting.29,30 The most striking observation was the high rate of active inflammation beyond POM1 in the ECP group compared to the KDB group. A previous study reported that up to 24% of ECP cases could be complicated by protracted post-op inflammation.31 In our study, each case of inflammation was resolved with steroid therapy with proper patient compliance. This finding suggests the need for a more aggressive steroid regimen with a slower taper in the first month after ECP, aligning with the opinion set forth by Tassel et al.32 Our study confirms a potential IOP elevation effect of ECP, possibly induced by inflammation. Interestingly, with regards to the difference in the incidence of CME in the KDB group, previous studies have shown a greater incidence with ECP instead.13,17,33,34 The reason for this disparity in our study is unclear.

This study is limited by multiple factors. The absence of a standalone CE/IOL control group prevents an estimate of the effect of the MIGS procedures specifically, as cataract surgery itself has been shown to lower IOP.35 This study did not record the individual trainee surgeon’s relative skill or experience (number of cases previously performed). The study’s retrospective nature and absence of randomization could have led to selection bias, resulting in unmeasured baseline differences between the KBD and ECP groups. Last, the lack of standardization in post-op medication management may have affected medication reduction and complication rates, particularly prolonged post-op inflammation.

CONCLUSION

In conclusion, trainee-performed KDB and ECP were similarly efficacious in lowering IOP, while medications were not significantly reduced at 1 year. IOP reduction was lower on average compared to previous trials looking at KDB/ECP outcomes that involved attending-level surgeons, although these results may have been affected by our study population having more poorly controlled glaucoma and being based in a county hospital. These procedures in the hands of trainees did, however, demonstrate comparable safety profiles to studies looking at attending-level physicians’ MIGS outcomes.

Clinical Significance

Cataract extraction (CE) combined with KDB or ECP in the hands of trainees decreased mean IOP from baseline to was safe. Glaucoma medications were reduced from baseline, although this effect did not last at 1-year follow-up. IOP and medication reduction of MIGS/CE in the hands of trainees were lesser than reported values with attending surgeons, apart from ECP/MIGS with regards to IOP lowering, which was found to be similarly efficacious.

ORCID

Joseph Da https://orcid.org/0000-0003-0122-1334

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