Ocular Hypertension in Blacks

Ocular hypertension occurs when intraocular pressure (IOP) is greater than the normal range with no evidence of vision loss or damage to the optic nerve. Individuals with ocular hypertension have an increased risk for glaucoma. The mean normal IOP is 15 mmHg and the mean IOP of untreated glaucoma is 18 mmHg. Elevated IOP commonly occurs in patients over the age of 50 and is often due to enlargement of the lens, narrowing of the angle, iridolenticular apposition, and pigment liberation that obstructs the trabecular meshwork. Cataract surgery and lensectomy can lower IOP and reduce the risk of glaucoma. The global wealth inequality of Blacks has created health inequities that have led to decreased access to surgical care contributing to higher rates of blindness from glaucoma. Greater education on the benefits of early cataract surgery and trabecular bypass for higher risk patients, as well as addressing wealth and health inequities, can help to bend the curve of blindness from glaucoma.

Controversies in the Use of MIGS

Minimally invasive glaucoma surgery (MIGS) has fulfilled an unmet need in the management of glaucoma. This chapter highlights some controversial issues regarding the use of MIGS in clinical practice, including (1) whether there is sufficient evidence to advocate combining MIGS with cataract surgery over cataract surgery alone, (2) the merits and drawbacks of different approaches to trabecular bypass and canal-based MIGS procedures, (3) the effect of MIGS on endothelial cell loss, (4) suprachoroidal MIGS devices and whether there is still a role for these procedures, and (5) a comparison between subconjunctival MIGS and trabeculectomy. Several questions are still left unanswered and hopefully, further research and more clinical experience with these new technologies will help improve surgical outcomes for patients.

XEN Gel Implant

Among all the novel glaucoma surgical devices, the XEN Gel Implant (Allergan plc, Dublin, Ireland) is the only one which uses an ab-interno approach to drain aqueous to the subconjunctival space, similar to conventional filtration surgery. Most MIGS procedures target the Schlemm’s canal and the collector channels which can be difficult to locate. The patency of the downstream drainage system cannot be accurately assessed and the episcleral venous pressure cannot be routinely measured, leading to unpredictable surgical outcomes for trabecular bypass surgery. In contrast, subconjunctival aqueous drainage is more effective at lowering the intraocular pressure, as is evidenced by the efficacy of trabeculectomy which has a long track record. The main advantages of the XEN Gel Implant over other filtering procedures include its less invasive surgical procedure and the favorable safety profile, fast visual recovery, and short surgery duration, rendering this implant particularly suited for patients who are unable to tolerate a long surgical duration or a delayed visual recovery. Although designed as a stand-alone procedure, XEN implantation can be combined with phacoemulsification in patients with concurrent cataract. Although its pressure-lowering ability appears to be superior to trabecular bypass and suprachoroidal MIGS devices, there are surgical nuances which can be difficult to master and the pre- and postoperative management is critical in the success of the XEN Glaucoma Treatment System.

Comparison of a second-generation trabecular bypass (iStent inject) to ab interno trabeculectomy (Trabectome) by exact matching

Purpose To achieve a highly balanced comparison of trabecular bypass stenting (IS2, iStent inject) with ab interno trabeculectomy (T, Trabectome) by exact matching. Methods Fifty-three IS2 eyes were matched to 3446 T eyes. Patients were matched using exact matching by baseline intraocular pressure (IOP), the number of glaucoma medications, and glaucoma type, and using nearest neighbor matching by age. Individuals without a close match were excluded. All surgeries were combined with phacoemulsification. Results A total of 78 eyes (39 in each group) could be matched as exact pairs with a baseline IOP of 18.3 ± 5.1 mmHg and glaucoma medications of 2.7 ± 1.2 in each. IOP in IS2 was reduced to 14.6 ± 4.2 mmHg at 3 months and in T to a minimum of 13.1 ± 3.2 mmHg at 1 month. In IS2, IOP began to rise again at 6 months, eventually exceeding baseline. At 24 months, IOP in IS2 was 18.8 ± 9.0 mmHg and in T 14.2 ± 3.5 mmHg. IS2 had a higher average IOP than T at all postoperative visits (p < 0.05 at 1, 12, 18 months). Glaucoma medications decreased to 2.0 ± 1.5 in IS2 and to 1.5 ± 1.4 in T. Conclusion T resulted in a larger and sustained IOP reduction compared with IS2 where a rebound occurred after 6 months to slightly above preoperative values.