March 2019, Volume XXXII, No 12

Ophthalmology

Advances in treating eye disease

A look at new FDA-approved devices

he field of ophthalmology continues to change dramatically, with advancements in technology—tested and approved following clinical trials—drastically improving treatment options for patients facing vision-threatening eye disease. New FDA-approved prostheses and devices, implanted surgically, hold great promise for patients with glaucoma and those with damage or injury to the iris.

CustomFlex Artificial Iris

In May 2018, the U.S. Food and Drug Administration approved the first prosthetic iris in the U.S. The surgically implanted device treats patients whose iris (the colored part of the eye around the pupil) is missing or damaged. Typical reasons for the iris to be missing are trauma or a congenital condition called aniridia.

Congenital aniridia is a rare genetic disorder in which the iris is completely or partially absent. It affects approximately 1 in 50,000 people in the U.S. With the iris missing, the amount of light entering the eye is extreme, and those with aniridia have sensitivity to light and glare with loss of vision.

The CustomFlex Artificial Iris can also be used to treat iris defects due to trauma, intraoperative damage to the iris during cataract surgery to treat intraoperative floppy iris syndrome due to alpha-one blockers such as tamsulosin, or in patients with small iris melanomas that have been removed surgically.

The iris plays an important part in our vision, adjusting incoming light as we change environments. An absent or partially functioning iris can cause extreme light sensitivity and glare, and even impact the sharpness of vision by allowing abnormal light scatter.

The CustomFlex Artificial Iris is made of thin, foldable medical-grade silicone and is custom-sized and colored for each individual patient. A surgeon makes a small incision, inserts the device under the incision, unfolds it, and smooths out the edges using surgical instruments. The prosthetic iris is held in place by the anatomical structures of the eye or, if needed, by sutures.

Colors are created to replicate those in the iris of the patient’s uninjured or unaffected eye (if one is present). The silicone prosthesis is made in Germany and takes approximately two months to customize for the patient.

The safety and effectiveness of the CustomFlex Artificial Iris was demonstrated primarily in a non-randomized clinical trial of 389 adult and pediatric patients with aniridia or other iris defects. The study measured patients’ self-reported decrease in severe sensitivity to light and glare post-procedure, health-related quality of life, and satisfaction with the cosmetic improvement or appearance of the prosthesis. Following the procedure, more than 70 percent of patients reported significant decreases in light sensitivity and glare, as well as an improvement in health-related quality of life. In addition, 94 percent of patients were satisfied with the artificial iris’ appearance.

The study found low rates of adverse events associated with the device or the surgical procedure. Complications can occur such as dislocation of the iris, especially if the zonules were damaged along with the initial damage to the iris. Increased intraocular pressure (IOP) or glaucoma is more common in patients with damage to the iris because the trabecular meshwork is in close contact with the iris. Inflammation such as uveitis or adhesion of the residual native iris to the cornea or lens (synechiae) can occur. Bleeding is not uncommon during the surgery, and swelling of the retina (cystoid macular edema), corneal edema, or retinal detachment can occur in eyes with difficult underlying issues such as prior trauma.

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The findings were similar to those from a 32-patient retrospective case-series published in the May 2016 issue of Ophthalmology. Both studies reported a low rate of adverse events associated with the device and surgical procedure. Complications included dislocation, strands of device fiber in the eye, increased IOP, and iritis.

Prior to the FDA approval, Minnesota Eye Consultants (MEC) had been involved with Artificial Iris research studies for 18 years, treating 35 eyes within the most recent Artificial Iris research study (2013–2018). Altogether, MEC has performed this procedure over 90 times since 2000, often under the compassionate use process, under which the FDA allows practitioners to use medications or procedures that have not yet been approved when no comparable or satisfactory alternative therapy options are available.

Glaukos iStent inject and Ivantis Hydrus

In 2018 the FDA approved two new minimally invasive glaucoma surgery (MIGS) devices designed to lower intraocular pressure by improving aqueous outflow through the eye’s natural physiological outflow pathway. Both of these implanted stent devices improve aqueous outflow through the trabecular meshwork.

Glaucoma is one of the most common causes of irreversible blindness worldwide. The primary pathophysiology is permanent injury to the optic nerve, a collection of delicate axons that communicate vision-related neurologic impulses between the retina and the occipital cortex of the brain. Glaucomatous damage to this delicate network of neural tissue results from eye pressure, most often due to sluggish drainage of aqueous humor from the eye’s natural outflow pathways.

By enhancing the eyes’ natural physiological outflow pathways, the iStent inject (Glaukos), approved in June, and the Hydrus (Ivantis), approved in August, provide a therapeutic mechanism in stark contrast to more traditional glaucoma surgeries that completely bypass the natural outflow pathways.

While the traditional glaucoma surgeries have greater efficacy than those that enhance physiological outflow, the increased efficacy comes at a steep price, namely significantly more risk. Accordingly, they have been reserved for those with far advanced disease. Newer, safer procedures allow earlier surgical intervention. Surgeons can now individualize surgical risk for patients specific to their disease severity. Those at high risk for glaucoma-related blindness are candidates for the more invasive traditional surgery, while those at lower risk for functional impairment are candidates for the newer, minimally invasive procedures, typically performed simultaneously with cataract surgery.

The opportunity to combine safe glaucoma procedures with cataract surgery has changed the glaucoma management paradigm in recent years. For most patients with glaucoma, medicines and laser treatments are used to manage the condition until a visually significant cataract develops, at which time surgeons can address both of these common conditions. Cataract and glaucoma are among the most common ocular comorbidities. The glaucoma specialists at Minnesota Eye Consultants have been very involved in the development of each device, either as investigators or as medical monitors for the multicenter trials.

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To date there have been five prospective, randomized trials comparing cataract surgery alone to cataract surgery performed in conjunction with one of these MIGS procedures. One of the important takeaways from each of these trials has been that cataract surgery itself lowers intraocular pressure and is a meaningful intervention for patients with mild to moderate glaucoma. Removing the native lens (cataract) allows the iris-ciliary complex to assume a more posterior position, an anatomic change that improves outflow. By combining cataract surgery with a safe, minimally invasive stenting procedure, surgeons are able to augment that favorable effect on intraocular pressure, without adversely affecting the elegance and precision of modern cataract surgery.

Because iStent and Hydrus also improve physiologic outflow, the effect tends to be additive. With MIGS surgery, we can augment the pressure-lowering effect of cataract surgery in a synergistic and safe fashion, while retaining the well-known benefits of cataract surgery—including improved visual function—and reduce dependence on spectacles.

The recently completed iStent inject study was conducted at 41 sites with 380 subjects receiving phacoemulsification (which emulsifies the lens with ultrasound) plus iStent inject and 118 patients receiving phaco alone. Smaller than 0.5 mm, the iStent inject is the smallest device ever implanted in human subjects. The recently reported FDA trial efficacy endpoints at 24 months were a >20 percent reduction in diurnal IOP (primary endpoint) and the mean reduction in diurnal IOP (secondary endpoint). At 24 months, 75.3 percent of the iStent inject cohort achieved a 20 percent or greater reduction in unmedicated IOP, compared to 61.9 percent of the phaco-only cohort. At 24 months, the iStent inject cohort had a mean unmedicated IOP reduction of 6.9 mmHg, compared to a 5.4-mmHg reduction in the phaco-only cohort. Importantly, there were no meaningful between-group differences in safety parameters. Surgeons at Minnesota Eye Consultants recently implanted the first iStent inject devices in the nation following FDA approval earlier this year.

The Hydrus trial (HORIZON) was a prospective, multicenter randomized trial in which 369 individuals received a Hydrus shunt in addition to phaco, while 187 received phaco only. The primary endpoint at 24 months was a 20 percent reduction in diurnal IOP; the secondary endpoint was the change in mean diurnal IOP. At 24 months, 77.2 percent of the Hydrus group had at least a 20 percent drop in DIOP; 57.8 percent of the phaco-only group achieved that endpoint. The mean reduction in DIOP was 7.6 mmHg at 24 months for the Hydrus group and 5.3 mmHg for the phaco-only group.

Improved safety is perhaps the most important feature of the iStent and Hydrus approach. Other procedures may prove to be more efficacious, but none are likely to be proven safer. There will be proponents of both canal devices. Some surgeons might prefer the iStent inject because it’s a “stealth” approach and the least-tissue-disruptive canal intervention. On the other hand, some surgeons may prefer the Hydrus design, and the fact that you can more easily verify that it’s exactly where you want it to be in the canal because of its 8 mm length and the fact that you can see it through the translucent inner wall. Each procedure adds greatly to the rapidly expanding portfolio of glaucoma surgical options.

Thomas Samuelson, MD, is a partner and attending surgeon at Minnesota Eye Consultants. He specializes in glaucoma, cataract, and refractive surgery and performs iStent inject procedures at Minnesota Eye Consultants locations in Bloomington and Minnetonka.

David Hardten, MD, FACS, is a partner and attending surgeon at Minnesota Eye Consultants. He specializes in cornea, cataract, and refractive surgery and performs Artificial Iris cases at Minnesota Eye Consultants locations in Bloomington and Minnetonka. 

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David Hardten, MD, FACS, is a partner and attending surgeon at Minnesota Eye Consultants. He specializes in cornea, cataract, and refractive surgery and performs Artificial Iris cases at Minnesota Eye Consultants locations in Bloomington and Minnetonka.