EX-PRESS Glaucoma Filtration Device: Management of Complications

Microfluidics in the eye: a review of glaucoma implants from an engineering perspective

Glaucoma is a progressive optic neuropathy in the eye, which is a leading cause of irreversible blindness worldwide and currently affects over 70 million individuals. Clinically, intraocular pressure (IOP) reduction is the only proven treatment to halt the progression of glaucoma. Microfluidic devices such as glaucoma drainage devices (GDDs) and minimally invasive glaucoma surgery (MIGS) devices are routinely used by ophthalmologists to manage elevated IOP, by creating an artificial pathway for the over-accumulated aqueous humor (AH) in a glaucomatous eye, when the natural pathways are severely blocked. Herein, a detailed modelling and analysis of both the natural microfluidic pathways of the AH in the eye and artificial microfluidic pathways formed additionally by the various glaucoma implants are conducted to provide an insight into the causes of the IOP abnormality and the improvement schemes of current implant designs. The mechanisms of representative glaucoma implants have been critically reviewed from the perspective of microfluidics, and we have categorized the current implants into four groups according to the targeted drainage sites of the AH, namely Schlemm's canal, suprachoroidal space, subconjunctival space, and ocular surface. In addition, we propose to divide the development and evolution of glaucoma implant designs into three technological waves, which include microtube (1st), microvalve (2nd) and microsystem (3rd). With the emerging trends of minimal invasiveness and artificial intelligence in the development of medical implants, we envision that a comprehensive glaucoma treatment microsystem is on the horizon, which is featured with active and wireless control of IOP, real-time continuous monitoring of IOP and aqueous rate, etc. The current review could potentially cast light on the unmatched needs, challenges, and future directions of the microfluidic structural and functional designs of glaucoma implants, which would enable an enhanced safety profile, reduced complications, increased efficacy of lowering IOP and reduced IOP fluctuations, closed-loop and on-demand control of IOP, etc.

Minimally Invasive Glaucoma Surgery: A Review of the Literature

Minimally invasive glaucoma surgery (MIGS) has emerged as a novel approach in the glaucoma treatment spectrum, offering a range of diverse procedures and devices aimed at reducing intraocular pressure (IOP). MIGS can be broadly classified into several categories: those that enhance trabecular outflow (Trabectome, iStent, Hydrus Microstent, Kahook Dual Blade, high frequency deep sclerotomy, and gonioscopy-assisted transluminal trabeculotomy), those that augment suprachoroidal outflow (CyPass Microstent and iStent Supra), those that target Schlemm's canal (TRAB360 and the OMNI Surgical System, Streamline, and Ab Interno Canaloplasty), and conjunctival bleb-forming procedures (EX-PRESS Glaucoma Filtration Device, Xen Gel Stent and PreserFlo MicroShunt). MIGS is considered to have a shorter surgical time and fewer severe complications when compared to traditional glaucoma surgeries such as trabeculectomy and glaucoma drainage device implantation (Ahmed, Baerveldt, and Molteno valves). This literature review comprehensively examines the distinct MIGS devices and procedures, their underlying mechanisms, and clinical outcomes, emphasizing the importance of evaluating the efficacy and complications of each approach individually. As the field of MIGS continues to evolve, it is crucial to prioritize high-quality, long-term studies to better understand the safety and effectiveness of these innovative interventions in glaucoma management.

The Role of Automated Peripheral Iridectomy Combined with Phacoemulsification and Mini Ex-PRESS Shunt Implantation in Patients with Chronic Angle Closure Glaucoma

Purpose

To evaluate the role of automated peripheral iridectomy as an adjunctive tool combined with phacoemulsification and ExPRESS shunt implantation in management of cases with chronic angle closure glaucoma.

Setting

Magrabi eye hospital.

Methods

This prospective study included 22 eyes of 22 patients with chronic angle closure glaucoma and cataract who underwent Ex-PRESS shunt implantation, cataract extraction and surgical peripheral iridectomy at the site of shunt implantation in the period between January 2018 and April 2020.

Results

After surgery, the mean IOP was 11.3±1.2 mm Hg, 14.5±1.6 mm Hg, 14.8±2.1 mm Hg, 15.3±1.9 mm Hg and 17.4±1.8 mm Hg at 7 days, 1 month, 3 months, 6 months and 12 months, respectively. All postoperative IOP was significantly lower compared with preoperative IOP (P = 0.001). There was a significant decrease in the number of medications required after surgery. The baseline mean number of medications was 3.4±0.02 (range from 1 to 4), while postoperatively the mean number of medications decreased to 0.7±0.01 at 12 months (P < 0.01). The qualified success rate was 6/22 eyes, and the complete success rate was 16/22 (72.7%) at 12 months, respectively.

Conclusion

The combined phacoemulsification and Ex-PRESS shunt implantation with automated peripheral iridectomy is an effective and safe procedure to treat chronic angle closure glaucoma.

Deadbolt cataract due to misplanted minishunt

A 62-year-old woman with stable unilateral glaucoma in the left eye presented for a cataract consultation. In 2010, laser peripheral iridotomies (LPI) were performed on both eyes by a different provider. Her postoperative course was complicated by a recalcitrant steroid response with a highest intraocular pressure (IOP) of 65 mm Hg in the left eye. A trabeculectomy with a glaucoma minishunt (EX-PRESS, Alcon) was then performed by that provider (Supplemental Figure 1, http://links.lww.com/JRS/A603). Thereafter, IOP control of the left eye was normalized and maintained without topical antiglaucoma medications. Historically, her right eye has been always her better eye. Recently, she noticed metamorphopsia in her left eye. Her ocular history was also notable for high refractive errors requiring continuous spectacles wear, possible mild refractive amblyopia of the left eye, history of submacular choroidal nevus with drusen in the right eye, and an epiretinal membrane (ERM) with macular pucker in the left eye. Her husband is an optician. Both inquire about refractive cataract surgery options to correct astigmatism and presbyopia; both have reservations regarding cost and visual quality associated with diffractive optic intraocular lenses (IOLs). Her deteriorating visual acuity in both eyes affects her ability to work. Her corrected distance visual acuity was 20/40 in both eyes (pinhole, no help) while wearing spectacles according to a prescription of -8.50 diopters (D) +1.50 D × 106 for the right eye and -13.00 D +3.25 D × 057 for the left eye. Her corrected near visual acuity was 14/14 in both eyes with the abovementioned prescription and a +3.00 D add. Central corneal thickness was 618 µm in the right eye and 631 µm in the left eye. IOP was 20 mm Hg in the right eye and 10 mm Hg in the left eye on no antiglaucoma medications. Pertinent findings on slitlamp examination included bilateral dermatochalasis, a shallow diffuse thick bleb superiorly in the left eye only, patent LPI superiorly in both eyes, nuclear sclerotic and cortical cataracts in both eyes (with prominent focal spoke superiorly left eye only) (Figure 1, A-C). Fundus photos show posterior vitreous detachment in both eyes, ERM with macular pucker in the left eye, and submacular choroidal nevus (2.5 × 3.0 disc diameter size) with overlying drusen in the right eye (Supplemental Figure 2, A, http://links.lww.com/JRS/A604). Gonioscopy revealed open angles in both eyes, albeit with focal narrowing without synechiae superiorly in the left eye only (Figure 1, D-FJOURNAL/jcrs/04.03/02158034-202207000-00020/figure1/v/2022-06-24T130746Z/r/image-tiff). Most importantly, however, the distal tip of the minishunt was not positioned as expected in the anterior chamber; rather, it was noted to pierce the peripheral iris near the iris root superiorly. Most of the minishunt shaft and spur were positioned in the posterior chamber with the distal tip penetrating into the superior aspect of the capsular bag and cataract in the left eye-like a deadbolt. Visual field testing showed a full field in the right eye and an inferior nasal step in the left eye (Supplemental Figure 2, B, http://links.lww.com/JRS/A604). In addition to slitlamp, gonioscopic, and fundus photos, we also obtained optical coherence tomography of the macula and nerve (Supplemental Figure 2, C, http://links.lww.com/JRS/A604), optical biometry, ultrasound biomicroscopy, endothelial cell counts, and corneal topography (Supplemental Figure 3, http://links.lww.com/JRS/A605). How would you counsel this patient regarding her glaucoma condition, the misplanted minishunt, and her cataract surgery and IOL options? How would you manage the misplanted minishunt? What surgical approaches or specific techniques would you consider for cataract removal and visual rehabilitation?

Ex-PRESS® surgery versus trabeculectomy for primary open-angle glaucoma with low preoperative intraocular pressure

PURPOSE

To compare surgical outcomes between Ex-PRESS® surgery (EXP) and trabeculectomy (Trab) for primary open-angle glaucoma (POAG) with low preoperative intraocular pressure (IOP).

PATIENTS AND METHODS

This was a retrospective non-randomized study. We included POAG patients with preoperative IOP ≤ 16 mmHg who were taking tolerance glaucoma medications. We compared the surgical outcomes, postoperative IOP, number of glaucoma medications, reduction rate of corneal endothelial cell density (ECD), visual acuity, and postoperative complications between POAG patients who underwent EXP (34 eyes) or Trab (38 eyes) and could be followed up for > 2 years.

RESULTS

Both surgeries significantly decreased the IOP (p < 0.001): At 2 years, EXP provided decreases from 13.4 ± 2.3 to 10.2 ± 3.1 mmHg, and Trab provided decreases from 13.5 ± 2.0 to 8.9 ± 3.2 mmHg. No significant differences were observed in the postoperative IOP (p = 0.076), number of postoperative medications (p = 0.263), success rate (p = 0.900), reduction rate of ECD (p = 0.410), or difference in visual acuity (p = 0.174). The reduction rate of IOP was significantly high in the Trab group (p = 0.047).

CONCLUSIONS

Both surgeries significantly decreased IOP and were useful surgical methods for low-IOP glaucoma. Our results suggest that trabeculectomy can decrease IOP more than Ex-PRESS surgery but might have more complications.