Purpose
To assess the effect of selective laser trabeculoplasty (SLT) following failed phacoemulsification cataract extraction combined with ab interno trabeculectomy (AIT) using the Trabectome (phaco-trabectome).
Design
Randomized, interventional case series.
Methods
Retrospectively, the medical records of patients who underwent SLT between March 2010 and July 2012 by 1 surgeon at a single center after a failed phaco-AIT were evaluated. Inclusion criteria were age ≥18 years with no upper limit and prior failed phaco-AIT attributable to glaucoma progression. Exclusion criterion was performance of any additional glaucoma procedure with influence on intraocular pressure (IOP) during follow-up and a follow-up after surgery of <3 months. Success was defined by reduction of IOP of >3 mm Hg and 20% and number of antiglaucoma medications equal to or less than baseline. Main outcome measures were IOP, antiglaucoma medications, time to failure, and Kaplan-Meier survival curve.
Results
Fourteen eyes of 13 subjects were included. Mean follow-up after SLT was 12.9 ± 8.7 months. Total laser energy was 59.5 ± 8.7 mJ. Baseline IOP was 17.9 ± 3.3 mm Hg and number of antiglaucoma medications at baseline was 2.0 ± 1.0. All SLT procedures failed. Median time to failure after SLT was 3.6 ± 0.8 (range 2.1-5.1) months. Number of antiglaucoma medications did not change.
Conclusions
In eyes in which the IOP was no longer controlled following phaco-trabectome, SLT had a limited duration of significant IOP-lowering effect. Other alternatives, such as incisional filtration surgery, should be considered following failed phaco-trabectome.
Ab interno trabeculectomy using the Trabectome (Neomedix, Tustin, California, USA) is an incisional surgical procedure during which 60-140 degrees of nasal trabecular meshwork is removed, allowing a direct communication between the anterior chamber and collecting channels. When performed in isolation, Trabectome has a limited success rate. Following a failed Trabectome, a subsequent trabeculectomy has the same success rate as a primary trabeculectomy. The combination of phacoemulsification cataract extraction and Trabectome (phaco-trabectome) has a greater success rate. If phaco-trabectome fails, it is unknown if it is necessary to move to trabeculectomy or if a less invasive intervention can be effective.
Laser trabeculoplasty involves the delivery of electromagnetic energy to the trabecular meshwork to enhance aqueous drainage and lower intraocular pressure (IOP). Laser trabeculoplasty is most commonly performed with either argon (wavelength, 488-514 nm; also known as argon laser trabeculoplasty [ALT]) or Q-switched, frequency-doubled neodymium–yttrium-aluminum-garnet (Nd:YAG; wavelength, 532 nm; also known as selective laser trabeculoplasty [SLT]) lasers. In direct comparisons, similar treatment areas of ALT and SLT have been shown to be equivalent with regard to intraocular pressure (IOP) lowering. As an initial primary therapy, ALT has a statistical advantage over topical beta-blockers with regard to IOP control and visual field preservation; primary SLT has equivalent IOP lowering to topical prostaglandin analogues. As adjunctive therapy, SLT lowers IOP in pseudophakic eyes with intact posterior capsules and glaucoma occurring after complicated cataract surgery. ALT works equally well on phakic and pseudophakic eyes. ALT is effective even after failed trabeculectomy. We hypothesized that SLT would be effective following failed phaco-trabectome.
Methods
All study-related analyses were approved by the institutional review board of the Massachusetts Eye and Ear Infirmary, Harvard Medical School (Boston, Massachusetts, USA). The analyses were conducted in adherence with the Declaration of Helsinki and the Health Insurance Portability and Accountability Act. A waiver of consent/HIPAA authorization was granted in accordance with the regulations of the Common Rule and HIPAA Privacy Rule. As part of their routine medical care, all patients had given informed consent for both their phaco-trabectome and SLT. Retrospectively, the medical records of all patients who underwent SLT between March 1, 2010 and July 31, 2012 by 1 surgeon (D.J.R.) after a failed phaco-trabectome procedure were identified by billing records and the surgeon’s personal logs.
Baseline patient data were collected, such as age at the time of surgery, gender, ethnicity, central corneal thickness, refractive error, type of glaucoma, and prior IOP-lowering surgery. Study data were collected once before surgery and then at 2 weeks and 1, 3, 6, 9, and 12 months after surgery, then every 6 months after 1 year. At each study visit, best-corrected visual acuity (BCVA), IOP, and the numbers of antiglaucoma medications (AGM) were collected for comparison. The baseline IOP was defined as the average of the 2 measurements immediately before the surgery. The individuals acquiring the IOP measurements were not masked. Mean deviation (MD) and pattern standard deviation (PSD) were collected from the Humphrey visual field (HVF; Carl Zeiss Meditec Inc., Dublin, California, USA) testing preoperatively. The HVF was graded analog to the Hodapp-Anderson-Parrish scale.
Inclusion and Exclusion Criteria
Inclusion criteria were age ≥18 years with no upper limit and prior failed phaco-trabectome as the initial (ie, primary) and only incisional surgical procedure for the management of open-angle glaucoma (primary open-angle or pseudoexfoliation glaucoma). Failed phaco-trabectome was defined as either IOP above the target range or glaucomatous progression of the optic nerve and/or visual field irrespective of the IOP. Exclusion criterion was performance of any glaucoma procedure prior to phaco-trabectome, or any glaucoma other than primary open-angle or pseudoexfolitation glaucoma, and a follow-up of less than 3 months after SLT.
Selective Laser Trabeculoplasty Technique
SLT was performed with an Ocular Latina SLT Gonio Laser lens (Ocular Inc., Bellevue, Washington, USA) to focus the laser (Coherent Selecta 7000 laser; Coherent, Inc, Palo Alto, California, USA) onto the pigmented trabecular meshwork ( TM ). The SLT laser is a frequency-doubled Q-switched Nd:YAG laser (wavelength 532 nm, pulse duration of 3 nsec, and spot size of 400 mm). Immediately before the procedure, a topical α agonist (apraclonidine 0.5%) and a topical anesthesia (proparacaine 0.5%) were administered to the treatment eye. Initially, laser treatment was started at a power between 0.8 and 1.2 W. The treatment energy was then titrated until “champagne bubbles” were achieved. Aside from the area of trabecular meshwork that was ablated exposing the posterior wall of the Schlemm canal as a result of the prior Trabectome, the remaining trabecular meshwork was treated. In all cases, between 90 and 120 degrees of nasal trabecular meshwork had been ablated by the Trabectome procedure. Postoperatively, the patients were treated with prednisolone acetate 1% eye drops 4 times daily for 1 week.
Definitions of Failure and Success
Complete success was evaluated as defined by reduction of IOP of >3 mm Hg and >20% of baseline, and number of antiglaucoma drugs ≤ baseline. Qualified success was defined as reduction of IOP of >3 mm Hg and >20% of baseline (definition 1) or reduction of IOP of >20% of baseline (definition 2). Failure was the opposite of success. Definition of failure included the criteria of IOP ≤5 mm Hg (“hypotony”) on 2 consecutive follow-up visits after 1 month, additional glaucoma surgery with influence on IOP (laser or incisional) during follow-up, or loss of light perception vision. Date of failure is the first date out of 2 consecutive examinations on which the definitions of success are not met starting with month 1 after the SLT procedure.
Statistical Analysis
All statistical analyses were carried out using SPSS software version 20.0 (IBM Inc, Chicago, Illinois, USA). Paired-sample Student t tests were used to determine significant differences at each study visit compared to baseline and Kaplan-Meier survival statistics was used to assess time to failure. A P value less than 0.05 was considered to be statistically significant. All visual acuities were converted to logarithm of the minimal angle of resolution visual acuity for statistical analysis. Continuous variables were expressed as mean ± standard deviation (95% confidence interval) and categorical variables were expressed as absolute numbers (percentage).
Results
Fourteen eyes from 13 people (8 women and 5 men; 4 right and 10 left eyes) met the inclusion criteria. None were excluded. Time to failure of phaco-trabectome was 22.8 ± 13.4 months. Reasons for failure of prior phaco-trabectome were an IOP outside of target range in 12 cases and IOP outside target range in addition to progression of visual field defects in 2 cases. The average amount of trabecular meshwork that had been ablated as part of the Trabectome was 89.3 ± 29.0 degrees. Prior to phaco-trabectome, 3 eyes had ALT, 1 eye had SLT, and 2 eyes had both ALT and SLT. Mean age was 74.8 ± 9.4 years. Ten eyes (76.9%) had a diagnosis of open-angle glaucoma and 3 eyes (23.1%) had pseudoexfolitation glaucoma. One patient (7.7%) was of African-American descent; all others were of European descent ( Table 1 ).
| Characteristic | Value |
|---|---|
| Age at intervention (years) | 74.8 ± 9.4 (69.4-80.3) |
| Gender | |
| Female | 8 (61.5%) |
| Male | 5 (38.5%) |
| Ethnicity | |
| African-American descent | 1 (7.7%) |
| European descent | 12 (92.3%) |
| Eye | |
| OD | 4 (28.6%) |
| OS | 10 (71.4%) |
| Refractive error before cataract surgery | |
| Spherical error | −1.62 ± 3.0 (−3.4 to 0.2) |
| Cylindrical error | −1.0 ± 1.0 (−1.6 to −0.4) |
| Axial length (mm) | 24.8 ± 1.2 (24.1-25.4) |
| Baseline BCVA (logMAR) | 0.20 ± 0.22 (0.08-0.33) |
| Baseline IOP (mm HG) | 17.9 ± 3.3 (16.0-19.7) |
| Baseline AGM (n) | 2.8 ± 1.0 (2.2-3.3) |
| Baseline MD (dB) | −8.6 ± 9.5 (−14.3 to −2.8) |
| Baseline PSD (dB) | 4.3 ± 4.6 (1.5-7.0) |
| Hodapp-Anderson-Parrish score | |
| Early defect | 5 (35.7%) |
| Moderate defect | 5 (35.7%) |
| Severe defect | 2 (14.3%) |
| N/A | 2 (14.3%) |
| CCT (μm) | 524.4 ± 30.4 (502.6-5546.2) |
| Baseline cup-to-disc ratio | 0.83 ± 0.11 (0.76-0.89) |
| Glaucoma diagnosis | |
| POAG | 10 (76.9%) |
| PXFG | 3 (23.1%) |
| Previous IOP-lowering surgery | |
| ALT | 3 (21.4%) |
| SLT | 1 (7.1%) |
| ALT and SLT | 2 (14.3%) |
| None | 8 (57.1%) |
The average number of SLT shots was 55.3 ± 7.5 and total laser energy was 59.5 ± 8.7 mJ. Mean follow-up after SLT was 12.9 ± 8.7 months. All SLT procedures failed ( Figure ). Median time to failure after SLT was 3.6 ± 0.8 (2.1-5.1) months for complete success and 3.8 ± 0.8 (2.3-5.4) months for both qualified successes based on definitions 1 and 2. Success rates for complete success were 92.9% at 1 month, 57.1% at 2 months, 42.9% at 3 months, 30.8% at 4 months, 23.1% between 6 and 10 months, and 0% after 11 months. Success rates for both definitions of qualified success were 92.9% at 1 month, 57.1% at 2 months, 42.9% at 3 months, 30.8% between 4 and 5 months, 15.4% between 6 and 7 months, 7.7% between 8 and 10 months, and 0% after 11 months. Baseline IOP was 17.9 ± 3.3 mm Hg and number of antiglaucoma medications at baseline was 2.8 ± 1.0. IOP remained unchanged at week 2 compared with baseline and was lowered in the cases that met the criteria of success at 1 month (14.0 vs 17.9 mm Hg, P = .030). During the entire follow-up, number of antiglaucoma medications and BCVA did not change ( Table 2 ).
