Purpose
Reporting treatment outcomes of slow coagulation transscleral cyclophotocoagulation (TSCPC) as an initial surgical intervention in pseudophakic patients with glaucoma.
Design
Retrospective case series.
Methods
This single academic center study reviewed 74 pseudophakic patients who had a diagnosis of glaucoma and no previous glaucoma surgeries (mean age 82.6 ± 12.5 years; mean follow-up 18.7 ± 9.1 months). The intervention used was slow coagulation continuous wave TSCPC (1250-mW power and 4-second duration). The primary outcome measure was surgical success defined as an intraocular pressure (IOP) of 6-21 mm Hg with a ≥20% reduction from baseline, no reoperation for glaucoma, and no loss of light-perception vision. Secondary outcome measures included glaucoma medication use, visual acuity (VA), and complications.
Results
IOP decreased from 27.5 ± 9.8 mm Hg preoperatively to 16.1 ± 6.3 mm Hg postoperatively ( P < .001). The preoperative number of glaucoma medications was 4.1 ± 0.9 and 3.1 ± 1.3 post-TSCPC ( P < .001). The cumulative probabilities of success at 1 and 2 years were 60.6 % and 58.5%, respectively. When patients were divided into 2 groups based on their baseline IOP being >21 mm Hg (high group) or ≤21 mm Hg (low group), success rates at 2 years were 64.9% and 45.5%, respectively ( P = .144). The mean logarithm of the minimum angle of resolution VA changed from 0.70 ± 0.64 to 1.04 ± 0.87 at the last follow-up visit ( P = .01). No serious complications were observed and most of the complications were mild and transient.
Conclusions
Slow coagulation TSCPC has good efficiency, especially in patients with baseline IOP >21 mm Hg, and safety profile as an initial surgical intervention in pseudophakic patients with glaucoma.
G laucoma is the leading cause of irreversible blindness worldwide. The management of glaucoma aims to lower intraocular pressure (IOP), which is the major modifiable risk factor for glaucoma progression. , Cyclodestructive procedures are used to control IOP by decreasing aqueous humor production. Cyclodestruction has evolved over the decades from a treatment option mostly used in patients with end-stage glaucoma with poor visual acuity (VA) or in those with a high risk of incisional surgery failure to an acceptably safe and efficacious procedure for a broad spectrum of patients, including those with good VA and as a primary glaucoma surgery.
In transscleral diode laser cyclophotocoagulation (TSCPC), laser energy applied to the sclera is absorbed by the melanin pigment in the ciliary processes, leading to coagulative necrosis of the ciliary body. Continuous wave (CW) delivery of diode laser energy is the most common approach, although significant interest exists for a newer modality of intermittent, known as micropulse (MP), laser energy delivery. Two approaches are commonly used to deliver laser energy using CW-TSCPC. One CW-TSCPC approach is the conventional “pop” technique, where laser energy is increased until an audible explosive, cavitating tissue–derived pop is heard, and then the laser power is reduced until pops are no longer audible. Laser treatment is then delivered circumferentially along the limbus. Another approach is known as slow coagulation CW-TSCPC, where a fixed lower amount of diode laser energy is delivered over a longer period.
Results comparing the outcomes of the slow coagulation approach with the conventional high-energy pop approach found a lower incidence of postoperative complications in the slow coagulation group and comparable IOP-lowering effects between both groups. This has encouraged providers to use slow coagulation TSCPC early in the disease process, at a time when the interest in optimizing cyclodestruction as minimally invasive glaucoma surgery is revived. Recent studies have shown the efficacy and safety profiles of slow coagulation CW-TSCPC in the management of primary glaucoma in patients with no previous history of incisional surgery (including cataract surgery).
We report on the outcomes of slow coagulation CW-TSCPC in a cohort of pseudophakic patients with different types of glaucoma. In this retrospective observational study, we evaluated the efficacy and safety profile of slow coagulation TSCPC as an initial surgical glaucoma treatment modality in pseudophakic patients with medically uncontrolled glaucoma.
Methods
Study Design and Participants
This study was approved by the University of Miami Institutional Review Board with a waiver of informed consent because of the study’s retrospective nature. All study methods adhered to the tenants of the Declaration of Helsinki and were conducted in accordance with the regulations of Health Insurance Portability and Accountability Act.
We performed a retrospective chart review of patients with glaucoma, regardless of glaucoma severity, who underwent slow coagulation TSCPC at the Bascom Palmer Eye Institute between February 2015 and June 2019. Subjects ≥18 years of age who underwent previous uncomplicated cataract extraction with intraocular lens implantation and had inadequate medically controlled glaucoma or intolerance to medical therapy were included in this study. Exclusion criteria were no light perception vision, patients who underwent complicated cataract surgery, phakic or aphakic patients, those with a history of incisional ocular surgeries (including glaucoma surgeries) other than cataract extraction, a previous cyclodestructive procedure, or follow-up <3 months after cyclophotocoagulation laser treatment.
The primary outcome measure was the cumulative rate of surgical success at 12 and 24 months. Failure was defined as IOP >21 mm Hg and reduced by <20% from baseline on 2 consecutive follow-up visits, IOP ≤5 mm Hg on 2 consecutive follow-up visits, loss of light perception vision, or reoperation for glaucoma. Additional TSCPC treatment was not considered a glaucoma reoperation and therefore not a failure as surgeons in our institution use TSCPC in a titratable fashion. Secondary outcome measures include IOP, the number of glaucoma medications, VA, and postoperative complications.
For all study participants, we collected demographic and clinical characteristics, preoperative and postoperative IOP measurements, the number of glaucoma medications, and best-corrected VA at 1, 3, 6, 12, 18, 24, 30, and 36 months of follow-up in addition to any postoperative complications observed during the follow-up period. Postoperative complications included postoperative anterior chamber inflammation (any degree of cells or flare), hypotony (IOP ≤5 mm Hg), cystoid macular edema (detected using optical coherence tomography), corneal decompensation, loss of light perception, pupillary changes, and conjunctival scarring. In patients who underwent glaucoma reoperation, the time of surgery and type of glaucoma surgical procedure were also collected.
Surgical Technique
Patients received retrobulbar anesthesia for all CW-TSCPC procedures. A G-Probe (Iridex Corp, Mountain View, California, USA) was used with power settings of 1250 mW of 810-nm infrared diode laser and a duration of 4 seconds. The G probe footplate was held perpendicular to the sclera, with the curved edge of the footplate placed at the limbus so that the laser beam was directed 1.2 mm posteriorly toward the ciliary processes. Balanced salt solution was used as a coupling agent. The number of laser applications was 16-20 for all study participants. Successive applications were spaced one-half the width of the G-Probe footplate apart, sparing the 3- and 9-o’clock meridians to avoid injury of the long ciliary blood vessels and nerves. All patients tolerated the procedure. After the procedure, shield and patch were applied. Postoperatively, prednisolone acetate 1% drops were used for 3-4 weeks. In general, steroid drops were started at 6-8 times a day for ≥1 week and then tapered slowly. Variations to this regimen were made at the surgeon’s discretion based on the patient’s response to treatment, including the use of sub-Tenon depot triamcinolone acetonide.
Statistical Analysis
Statistical analysis was performed using SPSS software (v 25.0; SPSS Inc, Chicago, Ilinois, USA). P < .05 was considered statistically significant. The dataset was divided into subjects who had a baseline, or pretreatment, IOP ≤21 mm Hg (the low IOP group) and those with a baseline IOP >21 mm Hg (the high IOP group). Dividing patients based on their pretreatment IOP was performed based on results from previous reports in the literature suggesting that the success rate of different surgical approaches is affected by the baseline IOP. In a recent report on the efficacy of slow coagulation CW-TSCPC in the management of primary phakic glaucoma patients with no previous history of incisional surgery, preoperative IOP was a significant predictor of IOP-lowering success. Similarly, the post hoc analysis from the results of the Primary Tube Versus Trabeculectomy (PTVT) study showed that the only significant predictor of postoperative failure was preoperative IOP, emphasizing its impact on the likelihood of success.
When calculating the number of glaucoma medications used at baseline, the use of oral carbonic anhydrase inhibitor was counted as 1 glaucoma medication and added to the number of topical glaucoma medications used. Statistically significant differences in the variables between the two baseline IOP groups were determined by conducting independent sample t tests. Patient preoperative IOP and the number of glaucoma medications were compared against respective postoperative values at every consecutive visit through paired t tests. For categorical (binary) variables, the Fisher exact test was used. Descriptive statistics were reported as mean ± standard deviation (SD) for continuous variables and as a percentage for categorical variables. The Kaplan-Meier survival analysis log-rank test was used to evaluate success. If an eye experienced multiple failure events, the time to the first failure was used for analysis. Cox proportional hazards models were used to assess the risk factors for failure including age, gender, and African ancestry.
Results
Baseline Characteristics
A total of 74 pseudophakic eyes of 74 patients who underwent slow coagulation TSCPC between 2015 and 2019 were included in the study. The baseline characteristics of the participants are presented in Table 1 . Eyes were stratified into 2 groups based on their baseline preoperative IOP: the high IOP group, including patients with pretreatment IOP >21 mm Hg, and the low IOP group, including those with pretreatment IOP ≤21 mm Hg.
| Characteristics | Total | Pretreatment IOP (mm Hg) | P Value | |
|---|---|---|---|---|
| >21 | ≤21 | |||
| Age (years) | .005 | |||
| Mean ± SD | 82.6 ± 12.5 | 85.5 ± 12.5 | 77.0 ± 10.9 | |
| Median (range) | 87.0 (46.0-103.0) | 90.0 (46.0-103.0) | 80.0 (55.0-93.0) | |
| Gender, n (%) | .19 | |||
| Male | 24 (32.4) | 13 (26.5) | 11 (44.0) | |
| Female | 50 (67.6) | 36 (73.5) | 14 (56.0) | |
| Race, n (%) | .79 | |||
| African American | 20 (27.0) | 14 (28.6) | 6 (24.0) | |
| Hispanic | 27 (36.5) | 15 (30.6) | 12 (48.0) | |
| White | 24 (32.4) | 17 (34.7) | 7 (28.0) | |
| Asian | 2 (2.7) | 2 (4.1) | 0 (0) | |
| Other | 1 (1.4) | 1 (2.0) | 0 (0) | |
| Laterality (right), n (%) | 29 (39.2) | 19 (38.8) | 10 (40.0) | 1.00 |
| IOP (mm Hg) | <.001 | |||
| Mean ± SD | 27.5 ±9.8 | 32.8 ± 7.5 | 17.2 ± 2.9 | |
| Range | 11-52 | 22-52 | 11-21 | |
| Glaucoma medications (n) | .07 | |||
| Mean ± SD | 4.1 ± 0.9 | 4.3 ± 0.9 | 3.6 ± 0.8 | |
| Range | 2.0-6.0 | 2.0-6.0 | 2.0-5.0 | |
| Glaucoma subtype, n (%) | 1.00 | |||
| POAG | 49 (66.2) | 32 (65.3) | 17 (68.0) | |
| CACG | 5 (6.8) | 2 (4.1) | 3 (12.0) | |
| PXFG | 11 (14.9) | 9 (18.4) | 2 (8.0) | |
| NTG | 2 (2.7) | 0 (0) | 2 (8.0) | |
| Uveitic | 3 (4.1) | 2 (4.1) | 1 (4.0) | |
| Other | 4 (5.4) | 4 (8.2) | 0 (0) | |
| HVF | ||||
| MD (mean ± SD) | −15.74 ± 10.20 | −15.92 ± 9.43 | −15.13 ± 8.51 | .726 |
| VA | ||||
| LogMAR (mean ± SD) | 0.70 ± 0.64 | 0.82 ± 0.70 | 0.46 ± 0.41 | .020 |
| Median | 0.54 | 0.60 | 0.30 | |
| Range | 0.00-2.60 | 0.00-2.60 | 0.00-1.30 | |
At the time of TSCPC, the mean ± SD age of the patients was 82.6 ± 12.5 years with a mean ± SD follow-up of 18.7 ± 9.0 months. Of the 74 enrolled patients, 50 patients (67.6%) were females, and 27 patients (36.5%) were Hispanic. In the overall cohort, the mean ± SD baseline IOP was 27.5 ± 9.8 mm Hg, the mean ± SD number of medications was 4.1 ± 0.9, and the mean ± SD logarithm of the minimum angle of resolution (logMAR) VA was 0.70 ± 0.64. The most common glaucoma diagnosis in the study was primary open-angle glaucoma, which was observed in 32 eyes (65.3%) in the high IOP group and 17 eyes (68.0%) in the low IOP group ( P = 1.00). The mean ± SD of mean deviation with Humphrey visual field testing was −15.92 ± 9.43 dB and −15.13 ± 8.51 dB in the high-IOP and low-IOP groups, respectively ( P = .726). The mean ± SD baseline IOP was 32.8 ± 7.5 mm Hg in the high IOP group and 17.2 ± 2.9 mm Hg in the low IOP group ( P < .001), while the mean ± SD number of glaucoma medications used at baseline was 4.3 ± 0.9 in the high IOP group and 3.6 ± 0.8 in the low IOP group ( P = .07). The mean logMAR VA was 0.82 ± 0.70 in the high IOP group and 0.46 ± 0.41 in the low IOP group ( P = .020). The treated patients received 17.97 laser spots on average (range 16-20, median 18).
In addition to the difference in baseline IOP, patients in the high IOP group were older and had worse baseline VA than the low IOP group. However, the 2 groups were similar with regard to other baseline demographic and clinical characteristics ( Table 1 ).
IOP and Medications Changes
IOP measurements and the number of medications at baseline, 1, 3, 6, 12, 18, 24, 30, and 36 months of follow-up for the overall cohort and the 2 groups are shown in Table 2 . The reduction in the number of patients at follow-up timepoints in Table 2 was mainly related to missed visits or reoperation for glaucoma. Table 3 compares the baseline and last follow-up visit parameters. Clinical parameters of the patients who underwent additional glaucoma surgery were excluded from the analysis after glaucoma reoperation.
| Total | Pretreatment IOP (mm Hg) | P Value | ||
|---|---|---|---|---|
| >21 | ≤21 | |||
| Baseline | ||||
| IOP (mm Hg) a | 27.5 ± 9.8 | 32.8 ± 7.5 | 17.2 ± 2.9 | <.001 |
| No. of glaucoma medications a | 4.1 ± 0.9 | 4.3 ± 0.9 | 3.6 ± 0.8 | .07 |
| Patients with follow-up (n) | 74 | 49 | 25 | |
| 1 months | ||||
| IOP (mm Hg) a | 17.5 ± 6.6 | 19.1 ± 6.9 | 14.3 ± 4.6 | .002 |
| No. of glaucoma medications a | 3.2 ± 2.7 | 3.7 ± 3.1 | 2.3 ± 1.5 | .047 |
| Patients with follow-up (n) | 74 | 49 | 25 | |
| 3 months | ||||
| IOP (mm Hg) a | 17.3 ± 5.8 | 18.7 ± 6.1 | 14.7 ± 4.3 | .005 |
| No. of glaucoma medications a | 3.0 ± 1.4 | 3.3 ± 1.4 | 2.5 ± 1.3 | .018 |
| Patients with follow-up (n) | 73 | 48 | 25 | |
| 6 months | ||||
| IOP (mm Hg) a | 16.0 ± 5.9 | 17.6 ± 6.5 | 13.1 ± 3.1 | <.001 |
| No. of glaucoma medications a | 3.1 ± 1.3 | 3.3 ± 1.3 | 2.7 ± 1.2 | .033 |
| Patients with follow-up (n) | 71 | 46 | 25 | |
| 12 months | ||||
| IOP (mm Hg) a | 15.8 ± 6.4 | 16.7 ± 7.5 | 14.4 ± 3.6 | .18 |
| No. of glaucoma medications a | 3.2 ± 1.3 | 3.4 ± 1.3 | 3.0 ± 1.3 | .26 |
| Patients with follow-up (n) | 60 | 37 | 23 | |
| 18 months | ||||
| IOP (mm Hg) a | 14.9 ± 6.2 | 16.0 ± 6.9 | 12.7 ± 3.9 | .10 |
| No. of glaucoma medications a | 3.3 ± 1.1 | 3.4 ± 1.1 | 3.1 ± 1.1 | .38 |
| Patients with follow-up (n) | 42 | 28 | 14 | |
| 24 months | ||||
| IOP (mm Hg) a | 15.2 ± 4.2 | 16.3 ± 4.2 | 13.3 ± 3.6 | .054 |
| No. of glaucoma medications a | 3.4 ± 1.1 | 3.4 ± 0.9 | 3.3 ± 1.6 | .77 |
| Patients with follow-up (n) | 31 | 20 | 11 | |
| 30 months | ||||
| IOP (mm Hg) a | 13.2 ± 5.2 | 13.9 ± 5.5 | 10.7 ± 3.1 | .36 |
| No. of glaucoma medications a | 3.5 ± 10.0 | 3.5 ± 0.8 | 3.7 ± 1.5 | .81 |
| Patients with follow-up (n) | 13 | 10 | 3 | |
| 36 months | ||||
| IOP (mm Hg) a | 14.7 ± 2.9 | 14.8 ± 3.3 | 14.0 b | .83 |
| No. of glaucoma medications a | 3.5 ± 0.8 | 3.4 ± 0.9 | 4.0 b | .57 |
| Patients with follow-up (n) | 6 | 5 | 1 | |
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