Early surgical intervention with stent advantageous for certain glaucomas

Dr. VoldIt is well known that with most disease, the earlier it is detected, the better the outcome prognosis. Along with early detection comes the need for early treatment.

Traditionally, options for glaucoma have been limited. Medications can be effective when used properly, though patients are notorious for compliance issues.¹

Micro-invasive glaucoma surgery (MIGS) procedures are useful in controlling IOP without introducing significant adverse events--overall improving the quality of life of patients.

While medical therapy traditionally preceded surgical treatment, I strongly feel that patients benefit significantly when MIGS intervention is introduced earlier in the disease process. With newer-generation, extended-range-of-vision IOLs now available, patients with dysfunctional lens syndrome or mild cataracts should consider undergoing refractive lens exchange with placement of a trabecular micro-bypass stent (iStent, Glaukos) to treat their glaucoma before permanent damage occurs.

The trabecular meshwork

David L. Epstein, MD, performed extensive research in the area of aqueous outflow, believing it was key to treatment of glaucoma.²

While Dr. Epstein focused on the impact of pharmaceuticals on the trabecular meshwork, I believe that the use of a stent to bypass the outflow resistance is consistent with his findings. This has been proven in clinical trials that show placement of a single trabecular micro-bypass stent reduces both IOP and the need for medications^3-7 in the short and long term.⁸

The stent works well for patients with early mild-to-moderate glaucoma. Dr. Epstein believed the normal aging process caused a gradual decrease of aqueous outflow through the trabecular meshwork. The more advanced the glaucoma and the longer patients are on topical glaucoma medication, the more damage there is to the trabecular meshwork and outflow system.

The trabecular meshwork is a complex system that undergoes significant change with age and the onset of glaucoma. This includes a considerable increase in the accumulation of extracellular material which intensifies resistance in the outflow pathways.^9,10 In turn, decreases in outflow facility can be triggered by changes in the extracellular environment and may be a factor in IOP increases.^11-13

Therefore, it is logical to begin treatment earlier, before damage becomes too severe. As the natural path of aqueous flow is through the trabecular meshwork and Schlemm’s canal, when the trabecular meshwork becomes clogged the outflow of aqueous is blocked. Opening that pathway with a stent allows for the aqueous outflow to be restored and IOP reduced.

However, patients who have had glaucoma for a sustained period may have a trabecular network that is too clogged for a stent to help. Those who find that the stent is ineffective may not be selecting the right patients for this treatment.

3 merits of early stent intervention

Merits of early stent intervention

By intervening earlier in the glaucomatous-disease process, patients avoid many of the challenges associated with medical treatment.

1. Medical compliance is a significant issue for many patients with glaucoma. 

Factors impacting adherence to drug therapy include medication costs, forgetfulness, and local and systemic drug side effects. If patients are unable to take their glaucoma medication consistently, its efficacy is adversely affected.

2. Due to the healthier trabecular outflow system often present in earlier disease, the stent potentially offers improved efficacy than what might be achievable in at least some patients with more advanced disease.

The risk-benefit ratio of placing an stent is extremely high in these patients. In fact, the safety profile and postoperative management of combined cataract and stent surgery is nearly identical to that of cataract surgery alone. Many surgeons consider the safety profile of the stent to be the gold standard in all of incisional glaucoma surgery. Even within the trabecular bypass category of procedures, the stent appears to largely avoid the risk of bleeding sometimes associated with more ablative angle procedures.

With early intervention, it is common to achieve mid-teen IOPs with glaucoma medications completely eliminated, utilizing a single stent. As imaging technologies and surgeon-targeted stent placement improves, surgical outcomes have the potential to stop the glaucomatous-disease process in its tracks.

3. By combining stent implantation with cataract surgery, not only will IOP control be improved, but patient quality of vision will also be enhanced.

Monofocal or toric IOLs provide outstanding distance vision to most glaucoma patients. When intervening early in the glaucomatous-disease process, extended-range-of-vision multifocal IOLs can be utilized safely and offer glaucoma patients a significantly improved quality of life.

By waiting until patients have more advanced visual field loss due to less than adequate glaucoma management, patients miss out tremendously on what these kinds of lenses have to offer. Accommodative IOLs offer enhanced range of vision, even in patients with more moderate-to-advanced glaucomas.

Conclusion

Conclusion

The stent has changed the entire glaucoma treatment paradigm-treating glaucoma patients medically until they have nearly lost fixation is no longer acceptable to patients. Clinicians are more commonly approaching glaucoma as a surgical disease.

Although topical medications and laser therapy will certainly continue to have roles in the treatment of glaucoma, the stent makes early surgical intervention appealing to both patients and surgeons. In select patients with early glaucoma and visually significant cataract, utilizing the stent as a first-line therapy is not only a viable option, but potentially the preferred treatment.

Once the stent inject is approved as a stand-alone therapy, I suspect the role of this proven approach will continue to expand within patients with early glaucoma, thereby preventing the need for filtration surgery, such as trabeculectomy or tube shunt surgery, during a patient’s lifetime.

Steven D. Vold, MD

E: svold@voldvision.com

Dr. Vold is founder of Vold Vision in Fayetteville and Bentonville, AR. Dr. Vold is a consultant to Glaukos.

References

1. Okeke CO, Quigley HA, Jampel HD, et al. Adherence with topical glaucoma medication monitored electronically the Travatan Dosing Aid study. Ophthalmology. 2009;116:191-199.

2. Kent C. Glaucoma Drugs: The search for new options. 16 March 2007. Review of Ophthalmology. Available at: https://www.reviewofophthalmology.com/article/glaucoma-drugs-the-search-for-new-options

3. Samuelson TW, Katz LJ, Wells JM, Duh Y-J, Giamporcaro JE. Randomized evaluation of the trabecular micro-bypass stent with phacoemulsification in patients with glaucoma and cataract. Ophthalmology. 2011;118:459-467. doi: 10.1016/j.ophtha.2010.07.007.

4. Fea AM. Phacoemulsification versus phacoemulsification with micro-bypass stent implantation in primary open-angle glaucoma. J Cataract Refract Surg. 2010;36:407-412. doi: 10.1016/j.jcrs.2009.10.031.

5. Craven ER, Katz LJ, Wells JM, Giamporcaro JE, for the iStent Study Group Cataract surgery with trabecular micro-bypass stent implantation in patients with mild-to-moderate open-angle glaucoma and cataract: Two-year follow-up. J Cataract Refract Surg. 2012;38:1339-1345. doi: 10.1016/j.jcrs.2012.03.025.

6. Fea AM, Pignata, G, Bartoli E, et al. Prospective, randomized, double-masked trial of trabecular bypass stent and cataract surgery vs. cataract surgery alone in primary OAG: long-term data. Presented at the 2012 European Society of Cataract and Refractive Surgeons, Milan, Italy, September 2012.

7. Arriola-Villalobos P, Martínez-de-la-Casa JM, Díaz-Valle D, et al. Combined iStent trabecular micro-bypass stent implantation and phacoemulsification for coexistent open-angle glaucoma and cataract: a long-term study. Br J Ophthalmol. 2012;96:645-649.

8. Neuhann T. Trabecular micro-bypass stent implantation during small-incision cataract surgery for open-angle glaucoma or ocular hypertension: Long-term results. J Cataract Refract Surg. 2015;41:
2664-2671.

9. Lütjen-Drecoll E, Rohen JW. Functional morphology of the trabecular meshwork. In: Bilyk J, Tasman W, Jaeger EA, editors. Duane’s Foundations of Clinical Ophthalmology on CD-ROM. Vol. 1. Lippincott Williams & Wilkins, Vol; Philadelphia: 2006. pp. 1-28. Section 1, Ocular Anatomy, Embryology, and Teratology.

10. Lütjen-Drecoll E, Shimizu T. Rohrbach M, Rohen JW: Quantitative analysis of “plaque material” in the inner and outer wall of Schlemm’s canal in normal and glaucomatous eyes. Exp Eye Res. 1986;42:443-455.

11. Gabelt BT, Kaufman PL. Changes in aqueous humor dynamics with age and glaucoma. Prog Retin Eye Res. 2005;24:612-637.

12. Tian B, Geiger B, Epstein DL, Kaufman PL. Cytoskeletal involvement in the regulation of aqueous humor outflow. Invest Ophthalmol Vis Sci. 2000;41:619-623.

13. Gabelt BT, Gottanka J, Lütjen-Drecoll E, Kaufman PL. Aqueous humor dynamics and trabecular meshwork and anterior ciliary muscle morphologic changes with age in rhesus monkeys. Invest Ophthalmol Vis Sci. 2003;44:2118-2125.