HIGHLIGHTS
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Approximately 10% of patients who underwent tube surgery required further operations within 6 months.
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Many patients who underwent tube shunt surgery required further operation.
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Valved and non-valved tube shunts had similar rates of reoperation.
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Reoperation and control eyes fared similarly in terms of interocular pressure and visual acuity endpoints.
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Unplanned reoperation needs further study prior to widespread use in ophthalmology.
Purpose
The purpose of this study was to determine the rate of unplanned returns to the operating room (OR) within 180 days and at any time postoperatively after valved and non-valved tube shunt surgery.
Design
Retrospective case-control study.
Methods
A review of 357 eyes that underwent tube shunt surgery (151 valved, 206 non-valved) was conducted at an academic glaucoma service between January 2014 and December 2016. A control eye was time matched for each eye that underwent reoperation.
Results
The reoperation rate within 180 days was 16 of 151 (10.6%) for valved and 25 of 206 (12.1%) for non-valved tube shunts and at any time postoperatively was 31 of 151 (20.5%) for valved, and 47 of 206 (22.8%) for non-valved tube shunts. Mean postoperative follow-up was 2.8 ± 1.1 years. The most common reoperations within 180 days and at any time postoperatively after valved tube shunt surgery were tube revisions (43.8% within 180 days, 38.7% any time) and external cyclophotocoagulation (CPC) (31.3% within 180 days, 38.7% anytime). The most common reoperations within 180 days after non-valved tube shunt surgery were tube revisions (32.0%), external CPC (12.0%), and vitrectomy with anterior chamber washout (12.0%) and at any time postoperatively were tube revision (34.0%), external CPC (31.9%), and tube explant (12.8%). At last follow-up, eyes that returned to the OR and controls were similar in terms of mean intraocular pressure (IOP), proportion of eyes meeting target IOP, and change in visual acuity.
Conclusions
More than 20% of eyes undergoing tube shunt surgery returned to the OR at any time postoperatively with a mean follow-up of nearly 3 years, with more than 10% of eyes undergoing reoperation within the first 180 days. Rates of reoperation were similar between valved and non-valved tube shunts.
Graphical Abstract
This retrospective case-controlled study examined the rate of unplanned return to the operating room after attending-performed and attending supervised tube shunt surgery at a single academic center. A considerable number of patients who underwent tube shunt implants required additional surgery; reoperation rates were similar between eyes that received valved versus those that received non-valved tube shunts. These findings provide information for the postoperative course after tube shunt surgery, which may be important in setting appropriate surgeon and patient expectations.
S tudies of unplanned return to the operating room (OR) within ophthalmology have almost exclusively focused on resident-performed surgeries, most commonly cataract and vitreoretinal surgeries. Among glaucoma surgeries, Hsia and associates examined complication and reoperation rates after resident-performed glaucoma procedures, and the present authors recently reported on unplanned returns to the OR after trabeculectomies performed by attendings and fellows.
Although relatively new to the ophthalmic literature, unplanned returns to the OR have been investigated as a quality metric across multiple surgical fields, including general surgery, colorectal surgery, vascular surgery, and pediatric neurosurgery. Unplanned returns to the OR have been shown to be associated with prolonged hospitalization and mortality, both of which are used as quality measurements in surgical fields. , Furthermore, unplanned returns to the OR are a metric that can be broadly applicable to an array of surgeries, are an objective, non-discretionary measurement, and can be easily identified from electronic health records, making it an attractive potential quality measurement.
Understanding the patient-, surgeon-, and procedure-specific factors that are associated with unplanned return to the OR in glaucoma surgeries can inform efforts to improve upon the current standard of care. This study set out to identify factors that are associated with unplanned return to the OR after tube shunt surgery at an academic glaucoma service. The results of this study may help predict which patients are at increased risk for postoperative complications and unplanned reoperation.
METHODS
This was a retrospective case-control study examining the outcomes of tube shunt surgery performed by glaucoma specialists at the Wilmer Eye Institute from January 2014 through December 2016. The study protocol was reviewed and approved by the Johns Hopkins University School of Medicine Institutional Review Board. The study adhered to the Declaration of Helsinki.
Patients included in the study were identified by searching billing records for procedures linked to current procedural terminology codes 66179 or 66180. Inclusion criteria included post-operative follow-up of at least 180 days, patients 18 years or older at the time of surgery, and undergoing no other glaucoma-related surgery (trabeculectomy, tube shunt, bleb needling, or trabeculotomy) in the same eye within the year preceding the index surgery. If both eyes of the same patient underwent tube shunt surgery within the study period, the first eye that met inclusion criteria was selected for the study. In the few cases in which a patient underwent multiple tube shunt surgeries in the same eye within the study period, only the first tube shunt surgery that met inclusion criteria was included.
For each patient who was identified as having had an unplanned reoperation at any time post-operatively related to a direct complication from their tube shunt surgery or progression of their glaucoma, a control patient that had undergone tube shunt surgery and was time-matched within 1 month was selected by a Web-based random number generator (Google, Alphabet Inc., Menlo Park, CA) for comparison. In this study, an unplanned return to the OR was defined as a second glaucoma surgery in the study eye that was not already scheduled prior to or at the time of the original tube shunt surgery. Multiphase tube shunt implantations were not counted as unplanned reoperations.
Clinical data were extracted from the electronic medical record: age at the time of surgery, sex, race, eye laterality, type of glaucoma, history of incisional eye surgery, highest recorded intraocular pressure (IOP), visual acuity (VA), number of glaucoma eyedrops, and use of oral IOP-lowering medications at the visit prior to surgery. Combination eyedrops were counted as 2 glaucoma medications. The target IOP most recently documented by the treating surgeon was recorded. Surgical details recorded included the surgeon, whether the surgery was combined with a cataract extraction, model of tube implant, and location of tube implant. Details documented in the medical record from the postoperative course that were recorded included any postsurgical complications (choroidal effusion, tube-corneal touch, endophthalmitis, flat anterior chamber, elevated IOP refractory to medical therapy, hyphema, hypotony, hypotony maculopathy, extraocular motility problems, pupillary/ciliary block, suprachoroidal hemorrhage, tube exposure, tube migration, wound leak, blebitis at the site of a prior trabeculectomy, or other), any postoperative treatment for the complication, and whether the complication resolved spontaneously or required intervention. Finally, whether a reoperation was performed at any time in the postoperative period, the time frame in which it was performed, reason for reoperation, type of reoperation surgery, number of additional reoperations, and the final VA, IOP, number of eye drops, and use of oral IOP-lowering medication at the last follow-up visit were recorded. Last follow-up was defined as the last clinical examination recorded on or before March 31, 2019. Throughout the analysis of postoperative complications, eyes experiencing multiple postoperative complications at once were counted once in the “any complications” category and counted multiple times among the further breakdown of specific postoperative complications. Postoperative hypotony was based on clinician assessment as recorded in the medical record, rather than an IOP cutoff value and included keywords such as “hypotony” or “IOP too low.” Postoperative hypotony maculopathy was similarly based on clinician judgement and typically included retinal changes affecting the patient’s vision. For this paper, we did not require a macular optical coherence tomography image to confirm maculopathy. Most IOP measurements on the glaucoma service were performed using applanation tonometry, most often by experienced technicians, although some measurements were with the iCare tonometer (Icare, Raleigh, North Carolina, USA). Snellen VA was converted to its logarithm of the minimum angle of resolution (logMAR) equivalent to assess changes in VA.
The tube shunt implants were either the Baerveldt BG 101-350 (B350; Johnson & Johnson Vision, Santa Ana, California, USA), the Baerveldt BG 103-250 (B250; Johnson & Johnson Vision), or the Ahmed FP7 glaucoma valve (AGV; New World Medical, Rancho Cucamonga, California, USA). Most tubes were covered with an irradiated, split-thickness corneal patch graft prior to conjunctival closure. Baerveldt tubes were variably modified by being tied off, having a ripcord suture inserted, and being fenestrated anterior to the tube ligation. The tubes were classified as either “valved” (AGV) or “non-valved” (B350 and B250) for analysis in this study. Tube revision surgery included a variety of techniques aimed at modifying the existing tube shunt to improve its function or address complications, including tying the tube shunt with suture, flushing, repositioning, lengthening or shortening the tube, creating new fenestrations, and/or resuturing the conjunctiva.
STATISTICAL METHODS
The primary outcome was whether an unplanned reoperation, related either to the patient’s glaucoma or as a result of a postoperative complication, was performed within 180 days of the original surgery. A second measure was whether a reoperation occurred at any time postoperatively. Student’s t -test was used to compare the mean follow-up time; the mean baseline IOP between the reoperation and control cases for each type of tube shunt and between eyes undergoing valved versus non-valved tube shunt; and the mean change in logMAR between the clinic visit just prior to tube shunt surgery and the last follow-up visit. The Wilcoxon rank-sum test was used to compare mean age at surgery, mean target IOP, mean number of glaucoma eyedrops being used prior to surgery, and mean number of additional surgeries following reoperation, as well as the mean IOP and mean number of glaucoma eyedrops at the last follow-up visit between the reoperation and control groups for each type of tube shunt. Pearson’s χ 2 test was used to compare eye laterality, sex, race, type of glaucoma, prior incisional and glaucoma surgery, lens status, surgeon, location of the tube shunt implant, and whether eyes attained their target IOP level at last follow-up between the reoperation and control cases for each type of tube shunt, as well as eye laterality, sex, race, type of glaucoma, lens status, history of prior incisional and glaucoma surgery, and reason for reoperation between eyes undergoing valved versus non-valved tube shunt. Kaplan-Meier survival analysis was performed, with failure defined as an unplanned return to the OR. The log-rank test was used to compare Kaplan-Meier survival curves between the valved and non-valved tube shunts.
To identify factors associated with unplanned reoperation both within 180 days and at any time in the postoperative period, 31 factors for tube shunt surgery were initially tested for inclusion in Cox proportional hazards models, and factors with univariate significance P ≤.10 were used to construct multivariate models. All types of tube shunt implants were combined in these models. These models were systematically tested by dropping the variables with the largest P values, and the most parsimonious model, identified as the model with the lowest Akaike information criterion, was chosen as the final model. A hazard ratio greater than 1 indicates a higher chance of failure compared with the reference group.
The 31 factors initially tested for inclusion in the models were age at surgery, sex, race, eye laterality, type of glaucoma, maximum IOP prior to initiation of therapy, target IOP, number of preoperative glaucoma eye drops, use of preoperative oral IOP-lowering medications, prior incisional eye surgery (trabeculectomy, tube shunt, cataract surgery, complex cataract surgery, or pars plana vitrectomy), whether cataract extraction was combined with the tube shunt surgery, whether the tube implant was valved or not, tube implant location, surgeon, postsurgical complications (choroidal effusion, flat anterior chamber, hyphema, hypotony, suprachoroidal hemorrhage, tube migration, wound leak, bleb leak, or blebitis at the site of a previous trabeculectomy, or other complications), and postsurgical treatment to address the complication (bandage contact lens). Postoperative endophthalmitis was not included in the model given that it was a rare complication.
A P value <.05 was considered statistically significant. In situations in which multiple statistical comparisons were made, the P value threshold of .05 was adjusted by dividing the threshold by the number of statistical comparisons. These situations included the comparisons of follow-up time, age at surgery, eye laterality, sex, race, type of glaucoma, prior incisional surgery, prior glaucoma surgery, baseline IOP, target IOP, and number of preoperative glaucoma eyedrops between the reoperation and control cases for each type of tube shunt and between eyes that underwent valved versus non-valved tube shunt, as well as comparisons between the reoperation and control cases of change in logMAR, IOP, and number of glaucoma eyedrops at the last follow-up visit. Study data were collected and managed using Research Electronic Data Capture (REDCap; Vanderbilt University, Nashville, Tennessee, USA). , All statistical analyses were performed using Stata version 15 software (StataCorp, College Station, Texas, USA).
RESULTS
RATE OF UNPLANNED RETURN TO THE OR
Of the 357 included tube shunt surgeries performed during the study period, 151 surgeries were valved tube shunts, and 206 surgeries were non-valved tube shunts. Forty-seven (22.8%) of the non-valved tube shunts and 31 (20.5%) of the valved tube shunts returned to the OR at any time postoperatively for an unplanned reoperation related either to glaucoma or a complication of tube shunt surgery (mean follow-up 2.8 ± 1.1 years). Twenty-five eyes (12.1%) with non-valved tube shunts and 16 eyes (10.6%) with valved tube shunts underwent reoperations within the first 180 postoperative days. The cumulative rate of return to the OR stratified early in the postoperative period is shown in Figure 1 .
For both valved and non-valved tube shunts, reoperation and control eyes did not vary in terms of mean age at the time of surgery, eye laterality, race, sex, type of glaucoma, history of prior incisional or glaucoma surgery, lens status, mean baseline IOP, mean target IOP, or mean number of glaucoma eyedrops being used prior to surgery ( Table 1 ).
| Non-Valved (Baerveldt) Tubes | Valved (Ahmed) Tubes | |||
|---|---|---|---|---|
| Reoperations | Controls | Reoperations | Controls | |
| n | 47 | 44 | 31 | 34 |
| Mean ± SD follow-up time, yrs | 2.7 ± 1.2 | 3.1 ± 1.1 | 2.6 ± 1.1 | 2.9 ± 1.1 |
| Mean ± SD age, yrs a | 63.3 (13.1) | 64.9 (16.2) | 54.2 (15.9) | 57.1 (17.5) |
| % OD | 49 | 56 | 45 | 59 |
| Males | 55 | 32 | 52 | 38 |
| Race | ||||
| White | 18 (38) | 19 (43) | 13 (42) | 19 (56) |
| Black | 22 (47) | 21 (48) | 15 (48) | 14 (41) |
| Asian | 5 (11) | 2 (5) | 2 (6) | 0 (0) |
| Hispanic | 1 (2) | 0 (0) | 0 (0) | 1 (3) |
| Other | 2 (4) | 2 (5) | 1 (3) | 0 (0) |
| Type of glaucoma | ||||
| OAG a | 31 (66) | 25 (57) | 8 (26) | 8 (24) |
| ACG | 2 (4) | 2 (5) | 2 (6) | 4 (12) |
| Uveitic/inflammatory | 7 (15) | 8 (18) | 3 (10) | 5 (15) |
| PXF | 0 (0) | 1 (2) | 1 (3) | 1 (3) |
| NVG a | 4 (9) | 2 (5) | 13 (42) | 9 (26) |
| Pigmentary | 1 (2) | 0 (0) | 0 (0) | 0 (0) |
| Traumatic | 1 (2) | 2 (5) | 1 (3) | 1 (3) |
| Suspected | 0 (0) | 3 (7) | 0 (0) | 1 (3) |
| Other | 1 (2) | 1 (2) | 3 (10) | 5 (15) |
| Prior incisional surgery | 39 (83) | 33 (75) | 20 (65) | 22 (65) |
| Previous glaucoma surgery | ||||
| Any a | 25 (53) | 26 (59) | 7 (23) | 11 (32) |
| Previous trab a | 22 (47) | 23 (52) | 6 (19) | 7 (21) |
| Previous tube | 6 (13) | 4 (9) | 2 (6) | 4 (12) |
| Other (trab revision, tube revision, CPC) | 3 (6) | 6 (14) | 1 (3) | 0 (0) |
| Mean ± SD baseline IOP | 37.5 ± 11.5 | 35.9 ± 9.8 | 47.5 ± 12.3 | 46.6 ± 10.3 |
| Lens status | ||||
| Phakic | 21 (45) | 18 (41) | 16 (52) | 15 (44) |
| Pseudophakic | 22 (47) | 26 (59) | 14 (45) | 17 (50) |
| Aphakic | 4 (9) | 0 (0) | 1 (3) | 2 (6) |
| Mean ± SD target IOP a | 14.9 ± 3.1 | 15.9 ± 3.1 | 18.4 ± 3.3 | 16.7 ± 2.9 |
| Mean ± SD glaucoma eyedrops prior to surgery | 3.1 ± 1.3 | 3.3 ± 0.8 | 2.5 ± 1.5 | 2.8 ± 1.4 |
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