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Reviving the lost art of manual Intacs implantation
Without a femtosecond laser, the operation is quick and safe and features a gentle learning curve.
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Intracorneal ring segments are among the best treatments currently available for patients with moderate keratoconus. Several types exist, but in the United States, the Intacs segment is the only FDA-approved model.
Intacs (CorneaGen) are not a new technology, which is an advantage because it means there are decades worth of publications corroborating their safety and efficacy. The average keratoconic cornea flattens 4 D in response to Intacs implantation. Practically, this produces a gain of two or more Snellen lines in two-thirds of patients treated. This visual benefit is realized almost immediately (ie, the first postoperative day), meaning that patient satisfaction with the procedure is typically high. In addition, the power of spectacle correction is often reduced, and contact lens tolerance is likewise improved. Furthermore, Intacs alone have a reported success rate of more than 90% when it comes to stabilizing the shape of corneas in patients with previously progressive keratoconus. When the procedure is combined with cross-linking, either simultaneously or sequentially, nearly all operated eyes experience an arrest in the course of their disease.
The surgery is quick and painless, reimburses well, is covered by most insurances, and entails only a brief and mild postoperative recovery. Why, then, is Intacs implantation not more commonly performed?
In our opinion, part of the problem is the misconception that a femtosecond laser is required to dissect the intrastromal channels into which the Intacs segments will be placed. This belief is limiting because many corneal specialists lack access to or familiarity with a femtosecond laser, without which they mistakenly regard Intacs implantation as impracticable.
Fortunately, however, Intacs implantation may be performed quickly and easily sans laser. Of course, the originally described technique featured a manual stromal dissection of the intrastromal channels. Since then, every large-scale study comparing the outcomes of manual vs. femtosecond surgery has found no difference in patient outcomes. In fact, there may even be some rationale for preferring the manual technique as safer because it involves only blunt dissection between the lamellar fibers of the patient’s cornea, whereas the laser actually cuts through the cornea, theoretically weakening it.
The technique for manual Intacs implantation is simple and straightforward (See video).
Source: Katelyn Joubert, BS, Philip Dockery, MPH, and Jack S. Parker, MD, PhD
In brief, the operation proceeds as follows (Figure 1). After either retrobulbar or general anesthesia, the corneal thickness is measured using a hand-held pachymeter in the vicinity of the planned incision. An 11-mm zone marker is used to create an impression on the corneal epithelial surface (a), and a gentian violet-marked Sinskey hook is used to place an ink dot on the center of this impression (b). Then, a dedicated incision and placement device is aligned with this central ink dot and used to mark the location for the incision and intrastromal channels (c). A guarded micrometer diamond blade fashions a radial incision in the cornea to a depth of 80% of what was previously measured by the hand-held pachymeter (d). Next, the vacuum centering guide is placed over the cornea, and the suction is engaged to hold the eye in position (e). A pocketing hook bluntly dissects a small stromal pocket at the base of the cornea’s radial incision (f), a centering glide is placed into the pocket (g), and the metallic stromal dissectors are then threaded into the vacuum centering guide, inserted underneath the glide and rotated between corneal lamellar fibers to create the channels (h). Then, the Intacs segments are fed through the mouth of the radial incision and pushed through the channels into position to complete the operation (i). While most incisions self-seal nicely, if appreciable wound gape is encountered, it can be closed with a fibrin adhesive or a single 10-0 nylon stitch. The entire process usually takes about 5 minutes.
Especially when combined with cross-linking, Intacs implantation has shown a remarkable ability to achieve significant, durable corneal flattening and meaningful improvements in patient vision and contact lens comfort/fit. With a manual technique, the operation is quick and safe, and it features a surprisingly gentle learning curve. Contrary to popular belief, you do not need a laser to get started — only 5 minutes and a willingness to learn something new.
- References:
- Bedi R, et al. J Refract Surg. 2012;doi:10.3928/1081597X-20120509-01.
- Fahd DC, et al. J Cataract Refract Surg. 2015;doi:10.1016/j.jcrs.2014.10.037.
- Kang MJ, et al. Sci Rep. 2019;doi:10.1038/s41598-018-36668-7.
- Kouassi FX, et al. J Fr Ophtalmol. 2012;doi:10.1016/j.jfo.2011.03.014.
- Kymionis GD, et al. Open Ophthalmol J. 2009;doi:10.2174/1874364100903010077.
- Parker JS, et al. Surv Ophthalmol. 2015;doi:10.1016/j.survophthal.2015.02.004.
- Rabinowitz YS, et al. J Refract Surg. 2006;doi:10.3928/1081-597X-20061001-06.
- For more information:
- Jack S. Parker, MD, PhD, can be reached at Parker Cornea, 700 18th St. South, Suite 503, Birmingham, AL 35233; email: jack.parker@gmail.com.
Disclosures: The authors report no relevant financial disclosures.