A colleague recently asked me what my surgical recommendations would be for a young glaucoma patient. The patient was a 40-year-old female, a lawyer with moderate glaucoma having already undergone selective laser trabeculoplasty (SLT) with little success. She had normal vision with pressures in the upper 20s on 3 drops.

This question is very pertinent to a small but significant glaucoma population in the prime of their lives. Juvenile open-angle glaucoma (JOAG), a subset of primary open-angle glaucoma (POAG), estimated to affect 1 in 50,000 individuals, is seen in patients who are between approximately 10 and 35 years old.^1,2

Diagnosis

There are several questions and exam findings to tackle before proceeding to a recommendation in these cases. I believe it is crucial to first examine the angle. I have seen countless “open-angle” glaucoma patients that were in fact chronic angle-closure patients. Ensuring the angle is open is the first critical step to properly treating this or any glaucoma patient.

Assuming the angle is open, the next crucial question, which may actually be difficult to ascertain, is when did the patient’s glaucoma start. This question is difficult because often these young patients’ glaucoma is discovered at an advanced stage due to the symptom of vision loss or with a lucky eye exam early in the disease course. The exact time the IOP became elevated is often impossible to determine. Although difficult to definitively answer, this question is pertinent as it has the potential to differentiate the diagnosis as JOAG. These diseases tend to respond differently and surgical success, and options may change depending on this difference.

JOAG can demonstrate an autosomal dominant inheritance. Research has shown an association between JOAG and a gene mutation in the GLCC1A locus containing the genes TIGR (trabecular meshwork induced glucocorticoid response) and MYOC (myocilin protein).^2,3 Histopathologic study of the trabecular meshwork in these patients has shown accumulated extracellular material in the trabecular spaces, as well as abnormally compact trabecular meshwork.⁴ These patients, in addition to younger age and family history, will typically present with very high IOP. Unfortunately, due to the lack of early symptoms, the presenting symptom is typically vision loss, which accompanies severe cupping. In addition to an open angle, gonioscopic findings can include a high iris insertion and iris processes. It important to rule out other causes, such as pigmentary dispersion, uveitis, traumatic glaucoma, and steroid-induced glaucoma, either with a detailed exam or by history.

Treatment

The treatment of JOAG had traditionally focused on trabecular bypass surgeries, such as tubes and trabeculectomy. In addition, incisional limited goniotomies or external trabeculotomies have also been employed. These procedures often lead to unfortunate side effects in these young patients.

Recently, the treatment paradigm has changed considerably. Given that the primary dysgenesis in these patients is located at the trabecular meshwork, work was sought toward a targeted, more efficient and safer procedure. Treatment using a 6-0 Prolene suture to create a 360° external goniotomy in congenital glaucoma was first described in 1995.⁵ This required an external approach, sacrificing valuable conjunctival real estate that might be needed for future surgeries. In 2014, Grover et al described a procedure they termed gonioscopy-assisted transluminal trabeculotomy (GATT) as a treatment for POAG. This method used either an iTrack catheter (Ellex) or Prolene suture to perform the same procedure but via an ab-intero approach.⁶ A year later, they published the results using the same technique in congenital and juvenile glaucoma.⁷ In this study of 14 eyes, with at least 1 year of follow-up, the IOP successfully decreased from an average of 27.3 mmHg to 14.8 mmHg with an average medication reduction from 2.6 to 0.86. This new technique has completely changed how I approach these patients.

As one recent case of mine describes, this technique can be quite successful. This particular patient presented initially in her early 20s with elevated IOP and advanced visual field loss in her left eye. She was initially treated with a trabeculectomy in this eye. For many years this was successful, and her healthy right eye showed no signs of glaucoma. At the age of 35 she started to develop elevated IOP in her right eye. She presented to my clinic 2 years ago with an IOP of 25 on 4 drops in the right eye and 13 mmHg in the eye that had received trabeculectomy. She had a very constricted field in her previously treated left eye (Figure 1). Her right eye did not yet show any damage. Her previous ophthalmologist had suggested that she undergo a trabeculectomy in her right eye. Since she had had bleb-related irritation and challenges in her left eye, she came to me searching for another option.

We had a long discussion regarding her options. The trabeculectomy had worked well in her first eye, but she was hoping to avoid this fate in her good eye. We discussed the GATT procedure and she elected to proceed with this option. She underwent an uneventful surgery using the iTrack catheter (Figure 2). Following her surgery, she was able to discontinue all eye drops with an IOP in the low teens in her right eye. Unfortunately, 1 year later, the trabeculectomy in her left eye started to fail, and her IOP had risen to 20 mmHg on 4 drops. We again discussed surgical options. We discussed either a bleb revision or an attempted GATT. The sclerotomy of her trabeculectomy had been created though Schlemm’s canal, presenting potential difficulties. She elected to proceed with a GATT in this eye as well. Although the catheter was unable to pass 360 degrees, we were able to create a 270-degree goniotomy. It has now been a year since her second surgery and her IOP is 13 in both eyes on no medications. She is ecstatic that she was able to avoid more invasive procedures. She does, however, admit that she misses her prostaglandin-induced long eyelashes.

With this background, we can return to my colleague’s question. It is likely that this 40-year-old, similar to my patient, does in fact have a milder form of JOAG. It is likely that she has been suffering from elevated IOP for some time and is now just progressing to the point of needing surgery. I feel that an ab-interno goniotomy is the ideal surgery for this patient.

Since the advent of GATT, there have been additional surgical techniques developed to accomplish an ab-interno goniotomy. Omni (Sight Sciences) and Kahook Dual Blade (KDB; New World Medical) are 2 such options. The Omni device treats 180° of the angle at a time by delivering a microcatheter into the canal via an access canula that enters the eye through a clear corneal incision. Up to 360° of trabecular meshwork can be cut with the Omni device with 2 passes of the catheter. The KDB has a dual blade that enters the eye in much the same way as the Omni. It differs in that it excises the entire inner wall of the canal by removing a strip of trabecular meshwork, rather than simply cutting through it. This theoretically should reduce the risk of the remaining leaflets scarring back into place. One major drawback to the KDB, however, is that it is limited to 90° to 100° through 1 incision. By making additional corneal incisions, additional portions of the canal can be treated, but this is still likely limited to 180°.

Conclusion

Whether employing GATT, Omni, or KDB, an ab-interno goniotomy is the best first step for young patients suffering from glaucoma. If this procedure fails, the option to move on to the more traditional surgeries is not compromised because the ab-interno approach has been used. Despite a high rate of hyphema, recovery is usually quick and free of the irritation of sutures or bleb formation. Often, an ab-interno goniotomy can be curative. This new surgical approach has revolutionized the treatment paradigm for these patients. The ability to seemingly cure glaucoma while avoiding potentially disastrous bleb-related complications has brought about a better option for these patients in the prime of their lives. GP

References

1. Turalba AV, Chen TC. Clinical and genetic characteristics of primary juvenile-onset open-angle glaucoma (JOAG). Semin Ophthalmol. 2008;23(1):19-25.
2. Albert DM, Miller JW, Azar DT, Blodi BA, Cohan JE, Perkins T. Juvenile open angle glaucoma. In: Albert D, Miller J, Azar D, Blodi B, eds. Albert & Jakobiec’s Principles & Practice of Ophthalmology. 3rd ed. Philadelphia, PA: Elsevier; 2008.
3. Bruttini M, Longo I, Frezzotti P, et al. Mutations in the myocilin gene in families with primary open-angle glaucoma and juvenile open-angle glaucoma. Arch Ophthalmol. 2003;121(7):1034-1038.
4. Tawara A, Inomata H. Developmental immaturity of the trabecular meshwork in juvenile glaucoma. Am J Ophthalmol. 1984;15:98(1):82-97.
5. Beck AD, Lynch MG. 360 degrees trabeculotomy for primary congenital glaucoma. Arch Ophthalmol. 1995;113(9):1200-1202.
6. Grover DS, Godfrey DG, Smith O, Feuer WJ, Montes de Oca I, Fellman RL. Gonioscopy-assisted transluminal trabeculotomy, ab interno trabeculotomy: technique report and preliminary results. Ophthalmology. 2014;121(4):855-861.
7. Grover DS, Smith O, Fellman RL, et al. Gonioscopy assisted transluminal trabeculotomy. Br J Ophthalmol. 2015;99(8):1092-1096.

Jacob W. Brubaker, MD, is a glaucoma specialist with Sacramento Eye Consultants in Sacramento, California. He reports consultancy to and research for New World Medical. Reach him at jbrubaker@saceye.com.