Retina

Retinal surgery update

The latest advancements include small-gauge vitrectomy, laser, and implantable technologies.

BY ANDREW MATHIS, PHD, CONTRIBUTING EDITOR

Although anti-VEGF drugs have transformed the treatment arsenal for retinal disease, only surgery can provide a solution for some conditions. In particular, patients with diabetes often experience such advanced retinopathy that only vitrectomy (i.e., the surgical removal of the eye’s vitreous gel) can salvage some vision.

In addition, although anti-VEGF drugs and steroids can be quite effective in treating diabetic eye diseases and conditions such as retinal vein occlusions, many of the cutting-edge treatment paradigms still prescribe laser as a modality for treatment.

Finally, and perhaps most excitingly, a growing number of patients with more or less total vision loss are regaining some vision with surgically implanted microtechnologies. This article reviews the latest surgical trends in retina with a focus on small-gauge vitrectomy, laser, and implants.

Small-gauge vitrectomy

Vitrectomy as performed today takes a minimally invasive approach, with much of the “work” done with instruments inserted via trocars placed in the sclera. In keeping with the concept of minimally invasive surgery, the instruments themselves have decreased in size.

At the turn of the millennium, standard vitrectomy instruments were 20-gauge. Then, 23- and 25-gauge instruments (bearing in mind that size decreases as gauge size increases) followed over the past decade. The newest instruments are 27-gauge (approximately 0.41 mm). Introduced in Japan five years ago, two companies now distribute full 27-gauge suites in the United States: Alcon and Dutch Ophthalmic.

In studies examining 27-gauge systems, surgeons found that the only key difference between the 27-gauge system and the older 23- and 25-gauge systems is that the newer system was slightly slower due to pure fluid dynamics — fluid flows slower through a narrower channel.

This difference of 9.9±3.5 vs. 6.2±2.7 minutes for vitrectomy is quite significant, although longer procedures have not resulted in significant time differences between gauge sizes. Nevertheless, centers adopting 27-gauge vitrectomy suites may want to allow for more time between procedures, particularly in the flatter parts of the learning curve.

Laser treatment

Laser treatment of retinal disease, which began in the 1960s, is primarily used to treat macular edema, a common complication of diabetic retinopathy and retinal vein occlusion. In addition, in advanced cases of diabetic retinopathy, laser is used to eradicate the abnormal new blood vessels that form in the proliferative form of retinopathy.

Although macular edema is limited to the macula, which is responsible for central vision, diabetic retinopathy can affect different parts of the retina. Therefore, depending on the location to be treated, different types and modalities of laser might be used. New modalities introduced over the past decade can meet patient-specific needs, including greater comfort.

Micropulse breaks up a continuous-wave laser into microsecond pulses, thereby decreasing heat buildup on the retina and reducing patient discomfort. Although the technology has since been mostly superseded by pattern scan and navigated lasers, micropulse laser has undergone several innovations. The most important innovation subthreshold operates below the level of producing a visible laser burn on the retina. Also, micropulse laser remains the safest of the available modalities.

In 2006, Topcon introduced pattern scan laser (PASCAL), which is notable for its increased patient comfort owing to its lower energy use. The laser’s name comes from the predetermined pattern of spots that the laser creates on the retina, which also reduces treatment time. The other variety of laser treatment, called “focal” due to its precision, is not included with PASCAL systems.

PASCAL, the oldest modality discussed here, has also undergone the most modifications and innovations by a variety of manufacturers. Different wavelengths and patterns are now available, as well as limited ability on the part of the surgeon to navigate the laser and apply micropulses of laser.

Navigated laser (Navilas), introduced by OD-OS in 2009, combines both focal and pattern laser abilities with a camera and imaging system, including eye-tracking software. Importantly, Navilas clearly marks the optic nerve and fovea (the center of the macula, providing the most precise vision), helping the surgeon to avoid lasering these areas accidentally.

This modality, however, is also the most expensive and, reportedly, the most difficult, according to a 2013 Oman Journal of Ophthalmology article from Chhablani, et al. Therefore, it is the least likely of these lasers to appear in practices, even retina-specific practices.

Color fundus photo of a 65-year-old woman with diabetic macular edema, which can be treated with some of the newest laser treatment technologies.COURTESY MICHAEL JAVAHERI, MD

Implantable retinal technologies

Some retinal diseases — notably the advanced dry form of age-related macular degeneration and many of the inherited retinal dystrophies — remain untreatable and can cause permanent vision loss. For these patients, retina implants might offer an opportunity to regain some vision.

Implants are generally applied epiretinally or subretinally. Epiretinal implants sit on the inner surface of the retina with direct access to the retinal ganglion cells, which communicate visual information directly to the brain. In contrast, subretinal implants lie on the outer surface between the photoreceptors and the retinal pigment epithelium. They instead communicate directly with the photoreceptor cells, rather than the ganglion cells.

Several companies have implantable technologies in development, but only one, the Argus II implant (Second Sight), has FDA approval. An epiretinal implant, the Argus requires surgical implantation of an epiretinal prostheses to work as well as external equipment, including glasses, video processing unit, and cable. A camera installed within the glasses captures the visual information processed by the rest of the system.

A wireless epiretinal implant developed by Retina Implant AG received a CE Mark, the European equivalent of FDA approval, three years ago, but it is not yet available in the United States. Retina Implant AG also has a subretinal implant in development, as does Optobionics.

The relatively limited applicability of these devices and the fact that only the Argus is currently available in the United States means that ophthalmic professionals aren’t likely to see many cases of these implants being surgically applied. Nevertheless, implants represent a tremendous growth area for treatment of retinal diseases, and it is likely that the future will see an explosion of such devices.

Conclusion

Although surgery for retinal conditions is rarer than it used to be, it is still a common scenario in many practices.

Innovations, such as smaller surgical instruments, new types of lasers, and implantable technologies, continue to play a role in the field and represent significant advancements in the area of retinal surgery. OP