Research Update on Laser Trabeculoplasty
A literature search reveals interesting findings from 2016.
Utilization of laser trabeculoplasty increased after the 2001 introduction of selective laser trabeculoplasty (SLT) but later plateaued and has begun to decrease again.1 Despite efficacy comparable to that of prostaglandin analogue monotherapy and minimal side effects,2,3 SLT’s role in the stepped management of glaucoma has not yet become clear. Data published in 2016 may help clarify the optimal use of trabeculoplasty in glaucoma management.
ARGON AND SELECTIVE LASER TRABECULOPLASTY
Only 16 articles related to argon laser trabeculoplasty (ALT) were indexed into PubMed in 2016. Of these, just four included data on the procedure, none of which added significantly to eye care providers’ understanding of ALT’s safety, efficacy, or optimal use.
AT A GLANCE
• The research published in 2016 updated eye care providers’ understanding of selective laser trabeculoplasty (SLT).
• Perhaps most importantly, a series of studies by independent research teams established beyond a doubt that repeat SLT safely reduces IOP in previously treated eyes.
• A small case series suggests that surgeons should proceed with caution when performing SLT on eyes with pseudoexfoliation and/or heavily pigmented angles.
In contrast, a similar search for SLT identified 53 articles, 32 of which reported new data on the procedure. Some findings from last year were interesting. Perhaps most importantly, a series of studies by independent research teams established beyond a doubt that repeat SLT safely reduces IOP in previously treated eyes. Collectively, these articles4-6—coupled with others published prior to 20167-9—demonstrated that repeat SLT lowers IOP to the same level achieved by initial SLT. Several studies suggested that the IOP reduction provided by repeat SLT endures longer than that seen with initial SLT,5,6,8 although this observation remains unexplained.
One intriguing study described significant IOP reductions when SLT was administered transsclerally to the perilimbal region without the use of a goniolens or coupling agent.10 In this randomized comparison with conventional SLT in patients with primary open-angle glaucoma who were on medical therapy, the mean IOP reductions achieved at 6 months were statistically comparable (4.71 and 5.14 mm Hg in the transscleral and conventional groups, respectively; P = .744). These results should be interpreted with caution, as this was a small study (27 subjects completed the trial) and no power analysis was reported.
Finally, a cautionary tale: surgeons should proceed carefully when performing SLT on eyes with pseudoexfoliation and/or heavily pigmented angles. In a case series of five eyes with exfoliation glaucoma, SLT was complicated by posttreatment IOP spikes.11 All five eyes required trabeculectomy, and two required subsequent tube shunt implantation. Two eyes developed corneal endothelial failure requiring endothelial transplantation. These observations are consistent with a prior report of four cases of post-SLT IOP spikes (three requiring surgical intervention), all in eyes with heavily pigmented angles.12 SLT can be safely performed in eyes with heavy meshwork pigmentation (as in both pigment dispersion and exfoliation syndromes), but some modifications to the standard approach are recommended. These include a lower power than is routinely used and staging the treatment over two 180º sessions rather than treating all 360º in a single setting.
Watch it Now
Steven Vold, MD, and Tony Realini, MD, MPH, discuss his research on selective laser trabeculoplasty in African-derived patient populations in the developing world.
MICROPULSE LASER TRABECULOPLASTY
Unlike the continuous-wave laser beam utilized in ALT, micropulse laser trabeculoplasty breaks the wave (diode 532- or 577-nm) into duty cycles that include a brief pulse of laser energy followed by a rest cycle to allow tissue cooling and to prevent thermal tissue damage. No studies relevant to this approach were indexed into PubMed in 2016, but earlier articles suggest generally modest IOP reductions (approximately 20% or less).13-15
These new studies provide valuable information to guide therapeutic decision making in glaucoma management. SLT is efficacious, safe, and repeatable. It eliminates the need for daily dosing adherence. In addition, the procedure is cost-effective compared to medical therapy (when known nonadherence is considered).16 This procedure should therefore be considered a first-line intervention for IOP reduction in most eyes with ocular hypertension or open-angle glaucoma.
1. Arora KS, RObin AL, Corcoran KJ, et al. Use of various glaucoma surgeries and procedures in Medicare beneficiaries from 1994 to 2012. Ophthalmology. 2015;122:1615-1624.
2. McIlraith I, Strasfeld M, Colev G, Hutnik CM. Selective laser trabeculoplasty as initial and adjunctive treatment for open-angle glaucoma. J Glaucoma. 2006;15:124-130.
3. Katz LJ, Steinmann WC, Kabir A, et al. Selective laser trabeculoplasty versus medical therapy as initial treatment of glaucoma: a prospective, randomized trial. J Glaucoma. 2012;21:460-468.
4. Francis BA, Loewen N, Hong B, et al. Repeatability of selective laser trabeculoplasty for open-angle glaucoma. BMC Ophthalmol. 2016;16:128.
5. Durr GM, Harasymowycz P. The effect of repeat 360-degree selective laser trabeculoplasty on intraocular pressure control in open-angle glaucoma. J Fr Ophtalmol. 2016;39(3):261-264.
6. Polat J, Grantham L, Mitchell K, Realini T. Repeatability of selective laser trabeculoplasty. Br J Ophthalmol. 2016;100:1437-1441.
7. Khouri AS, Lari HB, Berezina TL, et al. Long term efficacy of repeat selective laser trabeculoplasty. J Ophthalmic Vis Res. 2014;9(4):444-448.
8. Avery N, Ang GS, Nicholas S, Wells A. Repeatability of primary selective laser trabeculoplasty in patients with primary open-angle glaucoma. Int Ophthalmol. 2013;33:501-506.
9. Hong BK, Winer JC, Martone JF, et al. Repeat selective laser trabeculoplasty. J Glaucoma. 2009;18:180-183.
10. Geffen N, Ofir S, Belkin A, et al. Transscleral selective laser trabeculoplasty without a gonioscopy lens. J Glaucoma. 2017;26(3):201-207.
11. Bettis DI, Whitehead JJ, Farhi P, Zabriskie NA. Intraocular pressure spike and corneal decompensation following selective laser trabeculoplasty in patients with exfoliation glaucoma. J Glaucoma. 2016;25:e433-437.
12. Harasymowycz PJ, Papamatheakis DG, Latina M, etal. Selective laser trabeculoplasty (SLT) complicated by intraocular pressure elevation in eyes with heavily pigmented trabecular meshworks. Am J Ophthalmol. 2005;139:1110-1113.
13. Lee JW, Yau GS, Yick DW, Yuen CY. MicroPulse laser trabeculoplasty for the treatment of open-angle glaucoma. Medicine (Baltimore). 2015;94(49):e2075.
14. Babalola OE. Micropulse diode laser trabeculoplasty in Nigerian patients. Clin Ophthalmol. 2015;9:1347-1351.
15. Rantala E, Valimaki J. Micropulse diode laser trabeculoplasty — 180-degree treatment. Acta Ophthalmologica. 2012;90:441-444.
16. Stein JD, Kim DD, Peck WW, et al. Cost-effectiveness of medications compared with laser trabeculoplasty in patients with newly diagnosed open-angle glaucoma. Arch Ophthalmol. 2012;130:497-505.
Tony Realini, MD, MPH
• professor of ophthalmology, West Virginia University Eye Institute, Morgantown, West Virginia
• (304) 598-6884; email@example.com