Epithelial ingrowth occurs minimally in primary laser in situ keratomileusis (LASIK) cases, but incidence ranges from 1.7% to 23.3% for relifts.1–3 The incidence of ingrowth following small-incision lenticule extraction (SMILE), although poorly reported, is believed to be lower than for LASIK due to the absence of the flap.4 If left untreated, epithelial ingrowth can obstruct vision by inducing corneal astigmatism or obstructing vision by migrating toward the visual axis. Resulting epithelial defects or superficial punctate keratitis can result in irritation or a foreign body sensation. Risk factors associated with an increased risk for epithelial ingrowth following LASIK include history of recurrent erosions, hyperopic treatments, epithelial basement membrane dystrophy, and type 1 diabetes.5 Flap trauma, including relifts, has also been reported to increase the risk.1 Although rare, difficult dissections and repeated insertion of the instruments into the incision have been reported to contribute to ingrowth formation following SMILE.6 In response to the need of a specialized instrument for the treatment of epithelial ingrowth following SMILE and LASIK, we have designed an innovative scraping tool that allows the manual removal of epithelial cells from the SMILE pocket without converting to a flap and under the LASIK flap without having to lift the flap fully and risk trauma or striae.
The instrument features a 10 cm long and 4 mm wide handle with a blunt end angled tip at one end and a biconcave curette tip on the opposite end (Figure 1). The instrument is designed to be used following lenticule extraction to remove cellular debris from the pocket or for manual removal of epithelial ingrowth following SMILE or LASIK.
For removal of epithelial ingrowth following SMILE, the blunt end angled tip is designed to lift the edge of the SMILE incision. The curette tip can then be used to manually scrape the epithelial cells from the pocket using a windscreen wiper motion. Once the cells are loose, they can be collected in the curette and removed from the SMILE pocket, especially from the 6 o'clock position where it is difficult to remove by flushing. Video 1 (available at https://links.lww.com/JC9/A369) shows the instrument being used for a patient undergoing primary SMILE to remove cellular debris from the pocket following lenticule removal. No intra- or postoperative complications were experienced for this patient. The instrument had previously been trialed on 4 patients presenting with issues ranging from cell removal to fiber removal. No patients have experienced complications (including corneal trauma or infection).
Following LASIK, the curette tip can be used to lift the edge of the section of the flap with cells present. The curette tip can then be used to remove epithelial cells from the stromal surface below the flap. This can be performed without lifting the whole flap. Video 2 (available at https://links.lww.com/JC9/A370) shows the instrument being used to partially lift a LASIK flap and to remove epithelial cells from the stromal bed. This was performed on a patient who had undergone primary myopic LASIK performed by a different surgeon 25 years previously. The patient had experienced flap complications at the time of the initial LASIK and had developed corneal scarring and cell deposits. Following the removal of the epithelial cells, the patient achieved an uncorrected visual acuity of 20/30, and cells were no longer detectable on slitlamp examination.
Although the attached videos were filmed on the laser bed under the observation light with magnification, we suggest that when performed on a cooperative patient, the procedures can be performed using a slitlamp for better visualization and magnification using local anesthesia. Verbal consent was obtained before filming each procedure.
Epithelial ingrowth can be prevented by longer courses of postoperative steroids and cleaning the edge of the flap cut with a sponge to remove loose epithelium before replacing the flap. Current treatments include manual removal and YAG laser. For SMILE, the small incision makes manual removal difficult, and flushing the pocket can push debris into the 6 o'clock position trapping it inside. Converting the cap into a flap has been suggested as a way to expose the stromal bed and to aid in manual removal; however, this introduces the added risks associated with flap formation.7 We propose the use of this instrument as a way to manually scrape epithelial cells from the anterior and posterior surface of the pocket simultaneously. The advantage of this method is that it avoids flushing the pocket and flap formation, reducing the risk for complications. Furthermore, the design is based on a modified SMILE lenticule dissector, and therefore, the learning curve when adopting the instrument is minimal.
Manual removal of epithelial cells following LASIK involves relifting the flap and scraping the treatment surface with a blade or similar instrument. Although effective, this comes with a risk for infection, and the recurrence rate is high, around 23%.1 Sealing of the flap edge with hydrogel ocular sealant or other sealants has been reported to prevent recurrence even after multiple scrapings.8 In cases in which the ingrowth is stable and corrected distance visual acuity has not been compromised, photorefractive keratectomy can be used to treat the induced astigmatism to correct visual acuity without removing the ingrowth. If removal is deemed beneficial, the innovative instrument described here allows for successful removal while only lifting the section of the flap with cell deposits. This reduces the risk for further complications including trauma, striae formation, and recurrence of ingrowth. As only one instrument is required, the risk for infection is also likely to be reduced.
WHAT WAS KNOWN
- Epithelial ingrowth is a known complication of LASIK and SMILE.
- Current treatment of epithelial ingrowth following SMILE involves flushing the pocket or converting the cap to a flap and lifting the complete flap following LASIK.
WHAT THIS PAPER ADDS
- A modified lenticule dissector with a curette tip can be used to manually scrape epithelial cells from the pocket without converting to a flap and lifting the edge partially to remove the cells from under the LASIK flap.
1. Wang MY, Maloney RK. Epithelial ingrowth after laser in situ keratomileusis. Am J Ophthalmol 2000;129:746–751
2. Caster AI, Friess DW, Schwendeman FJ. Incidence of epithelial ingrowth in primary and retreatment laser in situ keratomileusis. J Cataract Refract Surg 2010;36:97–101
3. McAlinden C, Moore JE. Retreatment of residual refractive errors with flap lift laser in situ keratomileusis. Eur J Ophthalmol 2011;21:5–11
4. Maharana P, Asif M, Bafna R, Mehta J, Reddy J, Titiyal J, Sharma N. Complications of small incision lenticule extraction. Indian J Ophthalmol 2020;68:2711–2722
5. Ting DSJ, Srinivasan S, Danjoux JP. Epithelial ingrowth following laser in situ keratomileusis (LASIK): prevalence, risk factors, management and visual outcomes. BMJ Open Ophthalmol. 2018;3:e000133
6. Piccinini P. A challenging case: managing epithelial ingrowth after SMILE. 2017. https://crstodayeurope.com/case-studies/a-challenging-case-managing-epithelial-ingrowth-after-smile-2/
. Accessed May 30, 2022
7. Kankariya VP, Gogri PY, Dube AB, Mohiuddin SM, Madia T, Vaddavalli PK. CIRCLE software for management of epithelial ingrowth after SMILE. J Refract Surg 2021;37:776–780
8. Thulasi P, Kim SW, Shetty R, Randleman JB. Recalcitrant epithelial ingrowth after SMILE treated with a hydrogel ocular sealant. J Refract Surg 2015;31:847–850