SLT: The Next “Refractive Surgeon’s Laser”?

David A. Goldman, M.D.

About Author

One of the most frustrating consults a refractive/cornea specialist can receive is the older glaucoma patient on multiple drops referred for eye irritation. In most of these cases the problem is chronic rather than acute, and is a result of the multiple eye drops which are necessary to prevent further vision loss. At this stage of disease, it is very difficult to reverse the damage that has been done. Patients return frequently, frustrated that their problem has not been "fixed". Unfortunately, simply discontinuing their drops is not a viable option, in spite of evidence that the drops are the offending agents. Multiple studies have shown the prevalence of ocular surface disease to be higher in patients on glaucoma drops,¹ and further work has shown a direct correlation between the number of drops and frequency of eye discomfort.² While preservatives such as BAK have been shown to worsen tear film breakup times, drops such as carteolol can result in faster tear film breakup times for at least two hours.³In addition to discomfort, disruption of a healthy ocular surface can lead to blurred vision, and irregular refractions/topographies. This last effect is what has made refractive surgeons pay particular attention to the ocular surface. It is much more commonplace today to pre-treat patients with topical, or even oral, medications with the intent of decreasing ocular surface inflammation to ensure good visual outcomes and comfortable eyes. Most refractive surgeons are using femtosecond, YAG, and excimer lasers for their patients, but could SLT be the next refractive surgeon’s laser?

For my practice the answer was a resounding 'YES'. At first I would recommend SLT for those glaucoma patients referred to be who had already developed significant ocular surface disease, but gradually I started to recommend it more. For ophthalmologists in today’s climate of decreasing reimbursements and decreasing LASIK volume, we are looking for ways to increase practice revenue. While ALT laser has often been utilized primarily by glaucoma specialists, SLT laser offers many advantages that make it appealing to all ophthalmologists. Most importantly, it works; in a study by Nagar et al SLT was found equally effective as latanoprost.⁴ ALT requires precise location of its spots (and with them thermal energy burns) to ensure a good effect. SLT laser, however, incorporates a larger spot size that is more forgiving for those less comfortable with gonioscopy. This is because the SLT laser incorporates a Q-switched frequency doubled YAG operating at 532 nm – this laser only destroys pigmented trabecular meshwork cells while not causing thermal injury to collateral tissue. This is an excellent advantage as it preserves the structural integrity of the eye and conjunctiva should the patient require cataract surgery or filtering surgery down the road. Another advantage of this technology is that it can be used once or repeated as necessary and remains effective. Dr. Brian Francis and colleagues recently conducted a retrospective review of repeat SLT and found "an equivalent IOP lowering of the second SLT to the first. The SLT 2 group had a lower baseline, but when we did a subanalysis with selected matched baselines, the effect was almost exactly the same."

Another advantage for refractive surgeons incorporating this technology is that their practice is already well prepared for performing laser surgery; rooms are clean and set at appropriate temperature/humidity to maximize product lifetime. Furthermore, refractive surgeons who have satellite offices appreciate that patients are very willing to travel for a one time procedure. For those that do not want to, however, the SLT laser platform is very amenable to transport between offices.

Besides getting patients off of glaucoma drops, SLT laser can be instituted as primary therapy. A retrospective chart review was conducted in which investigators collected data on 1,363 eyes that underwent SLT as primary therapy from a total of more than 3,000 eyes treated with SLT for more than eight years. Long-term reduction in mean IOP was 31%, from a mean of 18.8 to 13.0 mm Hg, and 93% of eyes treated with primary SLT required no further intervention. Further, only 6% of eyes required one repeat SLT, and 1% of eyes required medications to control the IOP.^{5, 6, 7, 8, 9, 10}

For today's practicing refractive surgeons, revenue has on average significantly decreased. LASIK volume has decreased nationwide, and with downfalls in the economy patients are less willing to pay for presbyopic intraocular lenses. By incorporating technology such as SLT into a refractive practice, income sources become more diversified and more stable. Refractive surgeons who have already incorporated this technology agree, "As a cornea and glaucoma specialist, I have found many refractive patients who would benefit from lower intraocular pressure. These patients typically prefer SLT because of their active lifestyle and the convenience of not needing eye drops. Having SLT available has allowed me to diversify my practice, provide a valuable service to my patients, and increase revenue. It is only natural for patients with glaucoma to seek laser eye surgeons for laser eye surgery like SLT. We were surprised by how many patients that could benefit from SLT were passing through our clinic as LASIK or cataract consults. By incorporating SLT, we have increased patient satisfaction, provided an important service to our patients, and grown our practice." notes John Berdahl, MD (Sioux Falls, SD). Dr. Jai Parekh (Paterson, NJ) agrees, "I started doing SLTs a few years ago…it's added immense value to our patients, practice, and reputation. There is no doubt that SLT, as either an adjunctive, rescue, or primary therapy in our glaucoma patients is clinically and cost-effective. In the days of polypharmacy and its associated costs in our ever-growing baby-boomer glaucoma practices, we must strive to provide our patients with the best therapies at a reasonable cost. Our patients yearn for us to be cutting-edge but not at the expense of their wallets. SLT is certainly in the armamentarium of the modern-day, fiscally-prudent anterior segment surgeon." Furthermore, the SLT laser incorporates traditional YAG technology so that one laser platform can perform both SLT and/or YAG capsulotomies. This is important to consider as replacing a YAG laser with an SLT laser should not require any more office space. Additionally the lasers, such as Lumenis' Selecta Duet, can switch modes with the flip of a switch, allowing if desired both YAG capsulotomies and SLT to be performed in one setting without moving the patient, thereby greatly increasing patient flow.

Of course, this is an excellent service for the patient. By decreasing the patient's requirement for eye drops, their lifestyle is now not only easier but also less costly as they no longer need their monthly medications. The 5-year cumulative costs for glaucoma patients were calculated to be approximately $6,571 and $6,363, respectively, for medications and filtering surgery compared with $4,838 for laser trabeculoplasty.¹¹ As our baby boomer generation ages, the need for glaucoma treatment will increase exponentially, and performing a reimbursable procedure in place of writing a nonprofit script will certainly affect a practice's bottom line. Patient compliance is also removed from the equation, so when that patient forgets their drop (which is much more often than we'd like to believe), they will no longer have to worry about any potential harm. Furthermore, their ocular irritation and blurred vision can now improve. This again is of particular importance to refractive surgeons, whether their refractive procedure involves LASIK, phakic IOLs, presbyopic lenses, or traditional cataract surgery. If this treatment is initiated in the early stages of glaucoma, rather than after decades of drops have affected the lid margin, therapeutic benefits can be maximized. By reducing the use of drops that are detrimental to the ocular surface, SLT laser will ultimately make both patients and their physicians pleased. With benefits that greatly outweigh the risks, SLT laser is a practice builder that will likely be commonplace in LASIK suites within the next few years.

REFERENCES:

1. Schmier JK, et al. Characteristics of respondents with glaucoma and dry eye in a national panel survey. Clin Ophthalmol. 2009;3:645-650
2. Fechtner R, et al. Prevalence of ocular surface disease symptoms in glaucoma patients on IOP-lowering medications. Presented at: Annual Meeting of the American Glaucoma Society; March 8, 2008; Washington DC
3. Baudouin C, et al. Short-term comparative study of topical 2% carteolol with and without benzalkonium chloride in healthy volunteers. Br J Ophthalmol. 1998;82(1):39-42
4. M Nagar, A Ogunyomade, D P S O’Brart, F Howes, and J Marshall. A randomised, prospective study comparing selective laser trabeculoplasty with latanoprost for the control of intraocular pressure in ocular hypertension and open angle glaucoma. Br. J. Ophthalmology, Nov 2005; 89:1413 – 1417
5. Jindra LF,Gupta A.Selective laser trabeculoplasty is effective in maintaining lower intraocular pressure and fewer medications over the long term in patients with glaucoma.Poster presented at:The AAO Annual Meeting;October 15-18,2005:Chicago,IL.
6. Jindra LF,Miglino E,Gupta A.Effectiveness of selective laser trabeculoplasty as primary,secondary,and repeat treatment in patients with glaucoma.Poster presented at:The ASCRS Annual Symposium on Cataract,IOL and Refractive Surgery;April 27-May 2,2007:San Diego,CA.
7. Jindra LF,Donnelly JA,Gupta,A,et al.Selective laser trabeculoplasty as primary and secondary therapy in patients with glaucoma:8 year experience.Poster presented at:The ARVO Annual Meeting;May 2-6,2010:Fort Lauderdale,FL.
8. Jindra LF,Gupta A,Miglino EM.Five year experience with selective laser trabeculoplasty as primary therapy in patients with glaucoma.Poster presented at:The AAO Annual Meeting;November 10-13,2007;New Orleans,LA.
9. Jindra LF,Gupta A,Miglino EM.Selective laser trabeculoplasty as primary therapy in patients with glaucoma. Poster presented at:The ASCRS Annual Symposium on Cataract,IOL and Refractive Surgery;April 4-9,2008;Chicago,IL.
10. Jindra LF,Donnelly JA,Miglino EM.Demonstrating the long-term efficacy of selective laser trabeculoplasty as a primary treatment.Poster presented at:XXVII Congress of the European Society for Cataract and Refractive Surgery; September 12-16,2009;Barcelona Spain
11. Cantor LB,Katz LJ,Cheng JW,et al.Economic evaluation of medication,laser trabeculoplasty and filtering surgeries in treating patients with glaucoma in the US.Curr Med Res Opin.2008;24(10):2905-2918