Purpose: To report a case of unusual complication of ring segments migrated infranasally after intrastromal corneal ring segment (ICRS) implantation. Major symptoms: Female subject, 49 years old. Preoperative best spectacle-corrected visual acuity (BSCVA) was 20/60 in left eye. The patient complained decreased visual acuity in both eyes without pain. Scanning-slit tomography/topography (Orbscan II, Bausch & Lomb, Rochester, NY) showed moderate inferior steepening. The central pachymetry was 429 µm as measured by optical coherence tomography (OCT, RTVue, Optovue Inc. Fremont, CA). The average corneal thickness within 6-9 mm annual zone was 509 µm (Orbscan II) with minimum 486 µm. The patient was unable to tolerate rigid gas permeable (RGP) contact lens and chose ICRS implantation to improve vision. Major surgical procedures: Two 0.45 mm ICRS were implanted (Intacs, Addition Technology, Inc., Des Plaines, IL). The corneal channels were created with a femtosecond laser (iFS, Abbott Medical Optics Inc., Santa Ana, CA). The channel depth was set at 356 microns, 70% of the average pachymetry within the 6-9mm diameter zone (Orbscan II). A single 10-0 nylon suture was used to close the wound. Findings: One day after surgery, the BSCVA was improved to 20/40. Slit lamp showed ring segments in proper position. On the one month follow-up, the patient complained of eye irritation. The BSCVA was 20/40-1. Slit lamp showed both ring segments migrated infranasally, causing the tips to overlap. At the point of overlap the intrastromal channels were widened and the tip of the inferotemporal segment had migrated centrally into the optical zone (Figure 1, 2). No edema or infiltration was observed. OCT showed that both segments remained within the lamellar plane of the channel, and the relative depth of ring segments was 76% as measured at the inner edge (Figure 3). To prevent further dissection into the optical zone, both segments were explanted. One day after removing the ICRS segment, BSCVA was 20/40+1. The corneal had returned to its preoperative appearance except for faint haze in the ICRS channel. Discussion: One of the most common complications of ICRS implantation is ring segment displacement. Two previous studies reported the complications after mechanical channel creation. Kanellopoulos et al reported in 2006 six out of 20 keratoconus cases (30%) had ring segments movement about 3-6 months postoperatively.1 Such high incidence was not reported in other studies. Zare et al reported in 2007 ring segments displacement occurred in three out of 30 keratoconus cases (10%) 3-5 months after ICRS implantation.2 The reported incidence of ring segment migration with femtosecond laser channel creation was much lower. Coskunseven et al reported in 2011 that among 850 eyes, ring segment movement was observed in 11 (1.3%) cases at 2 months postoperatively.3 In these reported cases of ring migration, the movement was within the surgically created channel or incisional wound, or associated with corneal thinning and melting superficial to the segments,1,2 or protrusion through the Descemet’s membrane, 4 or even perforation into the anterior chamber.5 Dissection through the lateral wall of the channel had not been explicitly described. In our case, dissection of the ring segments in the corneal stromal happened one month after ICRS implantation, which is earlier than the range of 2-6 months reported in previous studies.2,3,6 There was intra-channel rotation of one segment while the other segment dissection along the lamellar plane of the channel toward the optical zone, which had not been reported before. Several factors could have contributed to this pattern of dissection. One is the thickness of the segments. The 450 µm thick segments that was used was the maximum available, and only recently approved by the FDA for use in the US. The thicker segment and overlapping tip could have created greater stress to split the cornea along the lamellar plane. Another factor was the 76% depth. Inter-lamellar corneal fibers decrease posteriorly and therefore deeper lamellar planes are easier to dissection. Another factor was the relatively advanced nature of keratoconus in this case, with only 429 µm corneal thickness centrally. Although this is above the 400 µm minimum needed to qualify for Intacs, it is thinner than most cases of ICRS implantation.5,7 In conclusion, thick ICRS segments, deep implantation depth, and thin cornea may be the risk factors for lateral dissection and migration of ICRS segments. This suggests that ICRS may be safer for less advanced cases of keratoconus. Reference 1. Ertan A, Colin J. Intracorneal rings for keratoconus and keratectasia. J Cataract Refract Surg. Jul 2007;33(7):1303-1314. 2. Zare MA, Hashemi H, Salari MR. Intracorneal ring segment implantation for the management of keratoconus: safety and efficacy. J Cataract Refract Surg. Nov 2007;33(11):1886-1891. 3. Coskunseven E, Kymionis GD, Tsiklis NS, et al. Complications of intrastromal corneal ring segment implantation using a femtosecond laser for channel creation: a survey of 850 eyes with keratoconus. Acta Ophthalmol. Feb 2011;89(1):54-57. 4. Guell JL, Verdaguer P, Elies D, Gris O, Manero F. Acute corneal hydrops after intrastromal corneal ring segment implantation for keratoconus. J Cataract Refract Surg. Dec 2012;38(12):2192-2195. 5. Park S, Ramamurthi S, Ramaesh K. Late dislocation of intrastromal corneal ring segment into the anterior chamber. J Cataract Refract Surg. Nov 2010;36(11):2003-2005. 6. Kanellopoulos AJ, Pe LH, Perry HD, Donnenfeld ED. Modified intracorneal ring segment implantations (INTACS) for the management of moderate to advanced keratoconus: efficacy and complications. Cornea. Jan 2006;25(1):29-33. 7. Haddad W, Fadlallah A, Dirani A, et al. Comparison of 2 types of intrastromal corneal ring segments for keratoconus. J Cataract Refract Surg. Jul 2012;38(7):1214-1221.