Purpose
To determine outcomes of ab interno trabeculotomy for treatment of open-angle glaucoma (OAG).
Design
Retrospective interventional single-surgeon, single-center case series.
Methods
Data were collected from 246 patients undergoing ab interno trabeculotomy between September 1, 2006, and December 1, 2010, with 3 months’ follow-up or longer. Kaplan-Meier analysis was performed using Criteria A (postoperative intraocular pressure [IOP] ≤21 mm Hg or ≥20% reduction from preoperative IOP) and Criteria B (IOP ≤18 mm Hg and ≥20% reduction in IOP). Failure included increased glaucoma medications or subsequent surgery. Failure risk factors were identified using Cox proportional hazards ratio (HR).
Results
Of 88 cases of ab interno trabeculotomy-only and 158 cases of ab interno trabeculotomy with cataract extraction, the retention rate was 70% for 1 year and 62% for 2 years. Preoperative mean IOP was 21.6 ± 8.6 mm Hg; the number of glaucoma medications was 3.1 ± 1.1. At 24 months postoperatively, mean IOP was reduced 29% to 15.3 ± 4.6 mm Hg ( P < 0.001) and the number of glaucoma medications was reduced 38% to 1.9 ± 1.3 ( P < 0.001) with a success rate of 62% (95% CI, 56%–68%) using Criteria A and 22% (95% CI, 16%–29%) using Criteria B. Failure risk factors using Criteria A included primary OAG (HR 3.14, P < 0.01, 95% CI, 1.91–5.17) and past argon laser trabeculoplasty (HR 1.81, P < 0.01, 95% CI, 1.18–2.77). Using Criteria B, the HR for pseudoexfoliative glaucoma was 0.43 ( P < 0.01, 95% CI 0.27–0.67). Of the cases, 66 (26.8%) required subsequent surgery on an average of 10 months (2 days to 3.2 years) after ab interno trabeculotomy.
Conclusions
For criteria involving IOP ≤18 mm Hg, the 24-month survival of ab interno trabeculotomy is low. This surgery is appropriate for patients requiring a target IOP of 21 mm Hg or above.
The Trabectome (NeoMedix, Tustin, California, USA) is a novel surgical device used for ab interno trabeculotomy in open-angle glaucoma (OAG). It reduces intraocular pressure (IOP) by ablating a segment of trabecular meshwork and the inner wall of the Schlemm canal. The inner wall of the Schlemm canal and the juxtacanalicular trabecular meshwork have been identified as the primary sites of abnormal flow resistance in OAG. Partial removal of these tissues results in a significant increase in outflow facility when measured in experimental models. The Trabectome was approved for clinical use by the United States Food and Drug Administration in April 2004, and it was first used in the United States in January 2006.
Initial case series of ab interno trabeculotomy involved patients who had been reported by surgeons at multiple centers as part of a requirement by the instrument’s manufacturer to report their first 20 cases. Inherent limitations of these case series thus included variability in patient selection, surgical technique, and postsurgical patient treatment. Furthermore, patient retention at longer follow-up intervals was low because surgeons were mandated to report only 1 year of follow-up data on their patients, after which reporting of further follow-up data was voluntary. For example, in the largest of the four initial case series there were 1,127 patients preoperatively; by 24 months after surgery, 110 patients had undergone a second glaucoma surgery, and only 50 patients remained in the series.
The purpose of our study was to evaluate the long-term success rate of ab interno trabeculotomy within a large single-surgeon, single-center cohort of patients with a high retention rate.
Methods
Subjects
Patients who had undergone ab interno trabeculotomy by one surgeon (A.J.S.) at the Mayo Clinic in Rochester, Minnesota, between September 1, 2006, and December 1, 2010, were eligible for this study. Patients who underwent ab interno trabeculotomy at our center typically had OAG that was refractory to medical therapy, or they had visually significant cataracts in the setting of OAG on maximal medical therapy. In a small number of cases, patients with potentially occludable angles were included if concurrent cataract extraction was being performed. Patients who had undergone other treatments for OAG prior to ab interno trabeculotomy, such as standard trabeculectomy, tube shunt or laser trabeculoplasty, were also included. Patients were excluded if they had fewer than 3 months of postoperative follow-up at our center unless subsequent glaucoma surgery was performed during this 3-month period. Prior ab interno trabeculotomy surgery was also considered an exclusion factor. The data collected for this study was approved by the Mayo Clinic Institutional Review Board. This study adhered to the Health Insurance Portability and Accountability Act. Only patients who had provided prior consent for their medical records to be used in research were included.
Surgical Procedure
The surgical procedure has been described in detail elsewhere. Briefly, ab interno trabeculotomy was performed through a temporal clear-corneal incision, and the nasal trabecular meshwork was visualized with a modified Swan-Jacob lens. The anterior chamber was filled with viscoelastic to facilitate insertion of the Trabectome hand piece. The Trabectome hand piece was used to ablate the trabecular meshwork and the inner wall of the Schlemm canal over a 120-degree arc nasally. For ab interno trabeculotomy-only cases, viscoelastic was then removed using irrigation and aspiration, and carbachol was injected into the anterior chamber to constrict the pupil. The wound was closed using a single 10-0 nylon suture. For combination cases, cataract extraction and intraocular lens implantation by phacoemulsification was performed after ab interno trabeculotomy.
Definitions of Success
The recommendations of the World Glaucoma Association were used to define treatment success using multiple criteria. The two main criteria used were Criteria A and Criteria B. Success according to Criteria A was postoperative IOP ≤21 mm Hg or ≥20% reduction from baseline. Success according to Criteria B was defined as postoperative IOP ≤18 mm Hg and ≥20% reduction from baseline. Cases were considered as treatment failures if the success criterion was not met at two consecutive visits after the first postoperative month. Treatment failure for these two criteria also included an increase in glaucoma medications from baseline at two consecutive visits, loss of vision to light perception or worse, or a subsequent glaucoma surgery.
Two additional criteria were used to address the potential limitations associated with retrospective data collection. In particular, variable target postoperative pressures based on individual patient profiles and on surgeon preference about when to perform subsequent glaucoma surgery in patients with unsatisfactory postoperative IOPs could result in falsely elevated failure rates. Therefore, Criteria C used a definition of IOP reduction similar to that of Criteria A, and Criteria D used a definition similar to that of Criteria B, except subsequent glaucoma surgery was not included in the definition of failure for these criteria.
Statistical Analysis
Clinical data were collected and managed using REDCap (Research Electronic Data Capture), tools hosted by the Mayo Clinic. REDCap is a secure, web-based application designed to support data capture for research studies; it provides an interface for validated data entry and automated export procedures for data downloads to common statistical packages. Kaplan-Meier survival analysis was conducted for each criterion of success using SAS Statistical Software (SAS Institute, Cary, NC). Kaplan-Meier survival curves were compared between groups using log-rank tests.
The 1-year subject retention rate was calculated as the percentage of cases enrolled prior to December 1, 2009 (1 year prior to the enrollment cutoff date), with at least 1 year of follow-up visits at the Mayo Clinic. Similarly, the 2-year retention rate was calculated as the percentage of cases enrolled prior to December 1, 2008, with at least 2 years of follow-up visits at the Mayo Clinic.
Mean preoperative and postoperative IOP and number of glaucoma medications were compared at several time points up to 4 years after surgery by using generalized estimating equation models to account for the multiple eyes included for some of the patients. For patients who underwent a subsequent glaucoma surgery, all follow-up data after the second surgery were censored from calculations of mean IOP and number of medications for the group. Risk factors for success and failure were identified using the Cox proportional hazards ratio (HR) model with multivariate analysis. To account for multiple eyes in some individuals in the analysis, robust sandwich covariance estimates were used to calculate appropriate tests of significance for the parameters. Variables tested included sex, age, type of open-angle glaucoma, prior glaucoma surgery or laser treatment, preoperative IOP, preoperative refractive error (if phakic), axial length (for combined cases, and pseudophakic patients if known), phakic status, stage of cataract, extent of angle pigment, grade of angle on gonioscopy, number of preoperative glaucoma drops, and prior retina surgery or injections.
Results
During the study period, there were 286 cases (246 patients) of ab interno trabeculotomy in total, of which 40 cases (38 patients) were excluded for the following reasons: lack of consent for medical records to be used for research purposes (9 cases); resident involvement in surgery (7 cases); fewer than 3 months of postoperative follow-up at our center (22 cases); and prior ab interno trabeculotomy (2 cases). A total of 246 cases (208 patients) of ab interno trabeculotomy were included, consisting of 88 ab interno trabeculotomy-only cases and 158 cases of ab interno trabeculotomy combined with cataract extraction. Table 1 shows baseline patient demographics. Patients were followed for a mean of 18.0 ± 13.2 months (median, 14.4 months).
| Parameter | Value |
|---|---|
| Patients, n | 246 |
| Age, years ± SD | 73.0 ± 11.6 |
| Range | 33–97 |
| Sex, n | |
| Female | 176 |
| Male | 70 |
| Race, n (%) | |
| White | 235 (95.5) |
| Asian | 4 (1.6) |
| African American | 2 (0.8) |
| Unknown/not reported | 5 (2.0) |
| Open-angle glaucoma type, n (%) | |
| Primary open-angle glaucoma | 137 (55.6) |
| Pseudoexfoliation | 65 (26.4) |
| Normal tension | 15 (6.1) |
| Mixed mechanism | 15 (6.1) |
| Pigment dispersion | 10 (4.1) |
| Steroid induced | 9 (3.7) |
| Uveitic | 3 (1.2) |
| Juvenile open-angle glaucoma | 2 (0.8) |
| Other | 13 (5.2) |
| Lens status, n (%) | |
| Phakic | 201 (81.7) |
| Pseudophakic | 45 (18.3) |
| Spherical equivalent (phakic patients), D | −1.4 ± 3.2 |
| Axial length (n = 203), mm ± SD | 23.9 ± 1.3 |
| Cup-to-disk ratio | |
| Mean ± SD | 0.82 ± 0.15 |
| Median | 0.90 |
| Central corneal thickness, μm | 549.7 ± 39.3 |
| Schaffer grade, n (%) | |
| I | 5 (2.0) |
| II | 47 (19.1) |
| III | 101 (41.1) |
| IV | 83 (33.7) |
| Degree of angle pigment, n (%) | |
| None | 20 (8.5) |
| 1+ | 79 (33.5) |
| 2+ | 85 (36.0) |
| 3+ | 46 (19.5) |
| 4+ | 6 (2.5) |
| Positive family history of glaucoma, n (%) | 122 (49.6) |
| Prior glaucoma treatments, n (%) | |
| Argon laser trabeculoplasty | 93 (37.8) |
| Selective laser trabeculoplasty | 14 (5.7) |
| Laser peripheral iridotomy | 24 (9.8) |
| Trabeculectomy | 20 (8.1) |
| Tube shunt | 3 (1.2) |
| None | 95 (38.6) |
| Prior non-glaucoma treatments, n (%) | |
| Pars plana vitrectomy | 8 (3.3) |
| Scleral buckle | 8 (3.3) |
| YAG capsulotomy | 7 (2.8) |
| Intravitreal steroid injection | 3 (1.2) |
| Intravitreal anti-VEGF injection | 2 (0.8) |
| Brachytherapy | 1 (0.4) |
More than 1 year prior to the enrollment cutoff date, 194 cases were enrolled. Of these, 135 had at least 1 year of follow-up visits, resulting in a 1-year retention rate of 69.6%. More than 2 years prior to the enrollment cutoff date, 109 cases were enrolled. Of these, 68 had at least 2 years of follow-up visits, resulting in a 2-year retention rate of 62.4%. A total of 186 cases (75.6%) had follow-up visits within 1 year of the enrollment cutoff date.
Preoperatively, the mean IOP (all cases) was 21.6 ± 8.6 mm Hg and the mean number of glaucoma medications was 3.1 ± 1.1. At 24 months postoperatively, there was a 29% reduction in mean IOP to 15.3 ± 4.6 mm Hg ( P < 0.001) and a 38% reduction in the mean number of glaucoma medications to 1.9 ± 1.3 ( P < 0.001). There was a significant reduction in mean IOP up to 36 months after surgery and in mean number of glaucoma medications up to 42 months after surgery, as shown in Table 2 and Table 3 . At each time point in the tables, the number of cases with follow-up data of at least the duration of the specific time point is reported and does not reflect the retention rate. On subgroup analysis, there was a significant mean IOP reduction up to 36 months after ab interno trabeculotomy-only and up to 18 months after ab interno trabeculotomy combined with cataract extraction. The reduction in mean number of medications was significant up to 18 months after ab interno trabeculotomy-only and up to 42 months after ab interno trabeculotomy combined with cataract extraction.
| Mean IOP (mm Hg) ± SD | |||
|---|---|---|---|
| All cases | Trabeculotomy-only cases | Trabeculotomy with CE cases | |
| Baseline | 21.6 ± 8.6 | 25.9 ± 8.9 | 19.3 ± 7.4 |
| n | 246 | 88 | 158 |
| 1 week | 15.7 ± 7.4 | 16.1 ± 7.1 | 15.5 ± 7.6 |
| % reduction, P a | 27.4, <0.001 | 37.8, <0.001 | 19.6, <0.001 |
| n | 242 | 87 | 155 |
| 1 month | 16.2 ± 7.1 | 19.4 ± 8.1 | 14.4 ± 5.8 |
| % reduction, P | 25.2, <0.001 | 25.1, <0.001 | 25.1, <0.001 |
| n | 243 | 86 | 157 |
| 3 months | 15.8 ± 6.0 | 17.5 ± 6.2 | 14.8 ± 5.6 |
| % reduction, P | 27.0, <0.001 | 32.6, <0.001 | 23.0, <0.001 |
| n | 218 | 81 | 137 |
| 6 months | 15.6 ± 5.5 | 17.4 ± 6.4 | 14.8 ± 4.8 |
| % reduction, P | 27.7, <0.001 | 32.9, <0.001 | 23.1, <0.001 |
| n | 186 | 60 | 126 |
| 12 months | 15.1 ± 4.4 | 16.5 ± 5.6 | 14.6 ± 3.7 |
| % reduction, P | 30.1, <0.001 | 36.4, <0.001 | 24.3, <0.001 |
| n | 152 | 44 | 108 |
| 18 months | 14.7 ± 4.6 | 16.8 ± 6.3 | 14.0 ± 3.7 |
| % reduction, P | 32.1, <0.001 | 35.1, <0.001 | 27.2, <0.001 |
| n | 111 | 27 | 84 |
| 24 months | 15.3 ± 4.6 | 16.8 ± 2.8 | 14.9 ± 4.9 |
| % reduction, P | 29.1, <0.001 | 35.1, <0.001 | 22.8, 0.10 |
| N | 69 | 17 | 52 |
| 30 months | 15.1 ± 4.7 | 15.5 ± 5.3 | 15.0 ± 4.6 |
| % reduction, P | 30.2, 0.002 | 40.0, 0.02 | 22.2, 0.08 |
| N | 50 | 11 | 39 |
| 36 months | 15.0 ± 5.9 | 13.5 ± 2.9 | 15.3 ± 6.3 |
| % reduction, P | 30.6, 0.04 | 47.9, 0.005 | 20.4, 0.26 |
| N | 37 | 6 | 31 |
| 42 months | 13.1 ± 3.6 | 15.2 ± 3.6 | 12.3 ± 3.4 |
| % reduction, P | 39.1, 0.09 | 41.4, 0.14 | 36.3, 0.26 |
| N | 16 | 5 | 11 |
| 48 months | 12.0 ± 2.6 | 13.0 | 11.8 ± 3.0 |
| % reduction, P | 44.5, 0.36 | 49.8 | 39.0, 0.47 |
| n | 5 | 1 | 4 |
a Percent reduction and P values compare mean IOP at each visit to baseline using the generalized estimating equation models.
| Mean no. of glaucoma meds ± SD | |||
|---|---|---|---|
| All cases | Trabeculotomy-only cases | Trabeculotomy with CE cases | |
| Baseline | 3.1 ± 1.1 | 3.3 ± 1.1 | 3.0 ± 1.0 |
| n | 246 | 88 | 158 |
| 1 week | 2.0 ± 1.2 | 2.0 ± 1.4 | 1.9 ± 1.1 |
| % reduction, P a | 36.3, < 0.001 | 38.1, < 0.001 | 31.1, < 0.001 |
| n | 242 | 87 | 155 |
| 1 month | 2.1 ± 1.3 | 2.3 ± 1.5 | 2.0 ± 1.1 |
| % reduction, P | 31.1, < 0.001 | 28.5, < 0.001 | 32.8, < 0.001 |
| n | 243 | 86 | 157 |
| 3 months | 2.0 ± 1.3 | 2.5 ± 1.4 | 1.8 ± 1.2 |
| % reduction, P | 34.3, < 0.001 | 25.2, < 0.001 | 40.5, < 0.001 |
| n | 218 | 81 | 137 |
| 6 months | 2.0 ± 1.4 | 2.6 ± 1.5 | 1.7 ± 1.2 |
| % reduction, P | 35.1, < 0.001 | 19.8, < 0.001 | 42.8, < 0.001 |
| n | 186 | 60 | 126 |
| 12 months | 2.0 ± 1.4 | 2.6 ± 1.4 | 1.8 ± 1.3 |
| % reduction, P | 34.7, < 0.001 | 21.1, 0.04 | 40.2, < 0.001 |
| N | 152 | 44 | 108 |
| 18 months | 2.0 ± 1.4 | 2.5 ± 1.4 | 1.8 ± 1.3 |
| % reduction, P | 34.9, < 0.001 | 23.3, 0.04 | 38.0, < 0.001 |
| N | 111 | 27 | 84 |
| 24 months | 1.9 ± 1.3 | 2.2 ± 1.5 | 1.8 ± 1.3 |
| % reduction, P | 38.2, < 0.001 | 31.9, 0.07 | 39.5, < 0.001 |
| N | 69 | 17 | 52 |
| 30 months | 2.0 ± 1.6 | 2.0 ± 1.8 | 2.1 ± 1.5 |
| % reduction, P | 33.6, < 0.001 | 39.1, 0.05 | 30.6, < 0.001 |
| N | 50 | 11 | 39 |
| 36 months | 2.2 ± 1.4 | 3.0 ± 0.6 | 2.0 ± 1.5 |
| % reduction, P | 29.6, < 0.001 | 8.7, 0.08 | 32.3, < 0.001 |
| N | 37 | 6 | 31 |
| 42 months | 2.3 ± 1.1 | 3.0 ± 0.0 | 1.9 ± 1.2 |
| % reduction, P | 26.8, 0.004 | 8.7, 0.27 | 35.4, < 0.001 |
| N | 16 | 5 | 11 |
| 48 months | 2.6 ± 0.9 | 3.0 | 2.5 ± 1.0 |
| % reduction, P | 15.4, 0.26 | 8.7 | 15.4, 0.25 |
| n | 5 | 1 | 4 |
a Percent reduction and P values compare number of medications at each visit to baseline using the generalized estimating equation models.
Of the 88 cases of ab interno trabeculotomy-only, subgroup comparison of phakic patients (n = 43) as opposed to pseudophakic patients (n = 45) showed that the decrease in mean IOP from preoperative to 1 year and 2 years postoperatively was not significantly different in the two subgroups ( P = 0.26 at preoperative; P = 0.72 at 1 year; P = 0.54 at 2 years).
Subsequent glaucoma surgery was recommended in 66 cases (26.8%) at an average of 10 months (range, 2 days to 3.2 years) after the initial surgery. At the follow-up visit during which the recommendation for subsequent surgery was made, the mean IOP was 26.2 ± 9.4 mm Hg, which was higher than the mean IOP at 1 year for patients who did not require subsequent surgery (14.3 ± 3.7 mm Hg, P < 0.001). Trabeculectomy with mitomycin C was performed in 52 of the 66 cases, and a tube shunt was placed in one case. One patient underwent repeat ab interno trabeculotomy with improved success. In 12 of the 66 cases requiring second glaucoma surgery, the patients made the decision to defer further surgery despite medical advice.
Kaplan-Meier analysis ( Table 4 ; Figure ) was used to determine the success rate for all cases and also for the subgroups (ab interno trabeculotomy-only versus ab interno trabeculotomy with cataract extraction). At 24 months, the success rate (all cases) was 62% (95% confidence interval [CI], 56% to 68%) using Criteria A, and 22% (95% CI, 16–29) using Criteria B. When using Criteria A, cases of ab interno trabeculotomy combined with cataract extraction had a higher rate of success at 36 months after surgery compared to cases of ab interno trabeculotomy-only ( P < 0.001). For Criteria C and Criteria D, the success rate at 24 months for all cases was 72% (95% CI, 66–79), and 23% (95% CI, 18–30), respectively. At 24 months, cases of ab interno trabeculotomy combined with cataract extraction had a higher rate of success using Criteria A, B, and C ( P < 0.05) but not using Criteria D ( P = 0.432).
| Success criteria | Success rate (%) (95% confidence interval) | ||||||
|---|---|---|---|---|---|---|---|
| All cases (n = 246) | Ab interno trabeculotomy only cases (n = 88) | Ab interno trabeculotomy + CE cases (n = 158) | P b | ||||
| 1 yr | 2 yrs | 1 yr | 2 yrs | 1 yr | 2 yrs | ||
| A: IOP ≤21 mm Hg or IOP reduction ≥20% and no 2nd surgery | 63.8 (57.9-70.3) | 61.7 (55.6-68.4) | 38.4 (28.9-51.0) | 36.2 (26.7-49.2) | 77.4 (71.1-84.3) | 75.2 (68.4-82.7) | <0.001 |
| B: IOP ≤18 mm Hg and IOP reduction ≥20% and no 2nd surgery | 28.4 (22.9-35.3) | 21.7 (16.5-28.6) | 22.0 (14.3-34.1) | 20.0 (12.5-32.2) | 31.9 (25.0-40.8) | 22.9 (16.4-31.8) | 0.025 |
| C: IOP ≤21 mm Hg or IOP reduction ≥20% | 78.0 (72.6-83.7) | 71.9 (65.7-78.8) | 57.8 (47.1-70.9) | 47.1 (35.4-62.8) | 88.0 (82.9-93.4) | 83.8 (77.6-90.5) | <0.001 |
| D: IOP ≤18 mm Hg and IOP reduction ≥20% | 32.4 (26.6-39.5) | 23.0 (17.6-30.1) | 30.6 (21.5-43.5) | 21.8 (13.4-35.5) | 33.5 (26.4-42.5) | 23.7 (17.1-32.7) | 0.432 |
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