Pellucid marginal degeneration is a rare, bilateral, progressive ectatic disorder characterized by an arcuate band of thinning in the peripheral cornea with protrusion above the thinning. Although ectatic cornea maintains its transparency, patients with pellucid marginal degeneration suffer from visual deterioration due to high irregular astigmatism.1,2 Both ametropia and corneal thinning correction remain fundamental therapeutic targets because of common unsatisfactory rigid contact lens fitting and controversial outcomes of standard penetrating keratoplasty as a result of marked corneal profile change and eccentric graft placement, respectively.1,2
Intracorneal ring segments (ICRSs) are widely used in surgical treatment of keratoconus and pellucid marginal degeneration; full-ring implantation and ICRS 355° implantation have demonstrated their efficacy in the management of keratectasias.3–6 Recent studies have shown that reimplanted refractive lenticules obtained during small incision lenticule extraction (SMILE) can be safely used in the treatment of different types of ametropia and keratoconus.7,8
A 43-year-old man who was intolerant to contact lenses was referred to our clinic complaining about significantly decreased visual acuity in both of his eyes, with worse visual acuity in his right eye. During the past 5 years, he had noticed a progressive visual impairment. He had a history of subtotal thyroidectomy with no subsequent medication use. Using slit-lamp examination, corneal topography, pachymetric mapping, and anterior segment optical coherence tomography, he was diagnosed as having pellucid marginal degeneration. The day of the first examination, the patient presented with uncorrected distance visual acuity (UDVA) of 0.02 (decimal) and corrected distance visual acuity (CDVA) of 0.4.
The surgery was performed after the patient gave written informed consent. A refractive lenticule with a maximum thickness of 100 µm, minimum thickness of 15 µm, and diameter of 7 mm for subsequent implantation was obtained from the patient, who had undergone a bilateral myopic SMILE procedure earlier that day (negative serologic test results received, as was written informed consent for donation). Lenticules were placed into balanced salt solution in a sterile Petri dish; the time between SMILE and lenticule implantation was 1.5 hours. Figure A (available in the online version of this article) demonstrates the positions of the ICRS in the intrastromal tunnel and the lenticule in the stromal pocket and their respective relationships.
This diagram (A = front view; B = cross-section) demonstrates the positions of the intracorneal ring segment in the intrastromal tunnel and the lenticule in the stromal pocket and their respective relationships. The lamellar graft is pictured in gray. The zones of the intrastromal tunnel and stromal pocket are clearly outlined with gray lines.
Video 1 (available in the online version of this article) demonstrates the surgical technique. A 360° intrastromal tunnel at a depth of 350 µm and two incisions at the 3- and 9-o'clock positions were created in the recipient's cornea by a VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany) (Figure 1A). Tunnel dimensions were 5.4 µm (inner diameter) and 8 µm (outer diameter). Lamellar dissection was performed centrifugally from the tunnel toward the limbus through the ectatic zone, thus creating a stromal pocket in the region of the thinning, encompassing 4 clock hours (from the 4- to 8-o'clock positions) (Figure 1B). The refractive lenticule was folded in half like a taco and implanted into the stromal pocket inferiorly (Figures 1C–1D). A 359° ICRS with thickness of 300 µm, inner diameter of 6 mm, and outer diameter of 7.2 mm (Scientific Experimental Production Ltd., Fyodorov's Eye Microsurgery Complex, Moscow, Russia) was inserted into the circular channel via incision (Figure 1E), then closed with two 10-0 nylon sutures (Figure 1F).
Intraoperative photographs. (A) Femtosecond laser tunnel creation. (B) Manual dissection through the thinned part of the cornea from the tunnel toward the limbus. (C) Refractive lenticule folded in half prior to insertion. (D) Lenticule implantation through the corneal incision into the stromal pocket. (E) Implantation of a 359° intracorneal ring segment after the lenticule placement. (F) Corneal incisions sutured with 10-0 nylon.
The patient was prescribed topical moxifloxacin, dexamethasone, and nepafenac. An early postoperative period slit-lamp examination revealed mild stromal edema that resolved after the first week and Descemet's folds that disappeared in 2 days. The lamellar graft was visible in the intrastromal pocket in the zone of corneal thinning with a clear delineation line, and the ICRS was present in the tunnel (Figures 2A–2D). Corneal thickness in the thinnest zone increased to 624 µm (Figures 2B and 2E). By 3 months postoperatively, the UDVA had improved to 0.5 (decimal) and the CDVA to 0.7. Corneal topography demonstrated a decrease in simulated keratometry values (by 9.50 diopters [D] at 170° and 5.00 D at 80°) and astigmatism reduction from 14.88 D preoperatively to 10.38 D postoperatively (Figures 2C and 2F).
Preoperative and 3-month postoperative slit-lamp photographs, anterior segment optical coherence tomography (AS-OCT), and corneal topography images. (A) Zone of thinning in the lower peripheral cornea, (B) the same zone on AS-OCT imaging, and (C) corneal topography demonstrating simulated keratometry readings of 50.75 diopters (D) in the steep meridian and 35.87 D in the flat meridian with 14.88 D of astigmatism. Reinforced cornea with clearly visible lamellar graft on both (D) slit-lamp photograph and (E) AS-OCT. (F) Corneal topography shows a decrease in astigmatism by 4.50 D and in simulated keratometry values by 9.50 D in the steep meridian and by 5.00 D in the flat meridian.
ICRS implantation, which is widely used in keratoconus management, has demonstrated its efficacy in significantly decreasing spherical and cylindrical refractive components and increasing both UDVA and CDVA with stable postoperative refraction in pellucid marginal degeneration.3,4 Similar results were obtained with a full-ring implantation that have shown greater sphere reduction than ICRS implantation and comparable cylinder reduction.6 Nonetheless, persisting corneal thinning may provoke further disease progression with recurring refractive errors, ICRS displacement, and mechanical corneal injury.
In this case report, surgical treatment aimed to correct refractive errors and corneal thinning. For this purpose, intrastromal lamellar keratoplasty with simultaneous ICRS 359° implantation was performed. The use of the VisuMax femtosecond laser allowed creation of a 360° intrastromal tunnel at a definite depth, taking into account thinning band localization. Dissection from the tunnel toward the limbus was done manually to diminish the risk of perforation while dissecting the thinnest part of the cornea (dissection was performed in one corneal layer).
The refractive lenticule with specified thickness obtained during a myopic SMILE procedure the same day was used as a donor lamellar graft for implantation into the zone of thinning, allowing not only correction of corneal thinning but also further centration of the ICRS. The safety of allogeneic implantation of refractive lenticules has been demonstrated in various studies.7
An ICRS with an arc length of 359° provided a decrease in induced corneal astigmatism by 4.50 D with a significant decrease in simulated keratometry values and allowed the optical center of the cornea to remain intact. An ICRS with an arc length of 359° was preferred in this case due to its flattening and arc shortening properties that are comparable to full ring implants, and because it allows gradient redistribution of corneal tension force, thus affecting the cylindrical component of refraction.3,4
Despite the lack of long-term observation, the new technique described in this case report was successful for this specific patient and therefore might be effective and safe in severe stages of disease. We believe that its use in early and moderate stages of pellucid marginal degeneration will allow better visual outcomes. Intrastromal lamellar keratoplasty combined with ICRS implantation provides simultaneous cylinder reduction and reinforcement of the thinned cornea. Refractive lenticules obtained with a myopic SMILE procedure can be preserved or used fresh, which makes this procedure an unlimited source of stromal tissue. Intraoperative optical coherence tomography guidance should improve surgical accuracy and exclude the possibility of thinned stroma zone maintenance during lenticule implantation.
- Jinabhai A, Radhakrishnan H, O'Donnell C. Pellucid corneal marginal degeneration: a review. Cont Lens Anterior Eye. 2011;34:56–63. doi:10.1016/j.clae.2010.11.007 [CrossRef]
- Moshirfar M, Edmonds JN, Behunin NL, Christiansen SM. Current options in the management of pellucid marginal degeneration. J Refract Surg. 2014;30:474–485. doi:10.3928/1081597X-20140429-02 [CrossRef]
- Mularoni A, Torreggiani A, di Biase A, Laffi GL, Tassarini G. Conservative treatment of early and moderate pellucid marginal degeneration: a new refractive approach with intracorneal rings. Ophthalmology. 2005;112:660–666. doi:10.1016/j.ophtha.2004.10.050 [CrossRef]
- Piñero DP, Alio JL, Morbelli H, et al. Refractive and corneal aberrometric changes after intracorneal ring implantation in corneas with pellucid marginal degeneration. Ophthalmology. 2009;116:1656–1664. doi:10.1016/j.ophtha.2009.06.002 [CrossRef]
- Jadidi K, Mosavi SA, Nejat F, Naderi M, Janani L, Serahti S. Intrastromal corneal ring segment implantation (keraring 355°) in patients with central keratoconus: 6-month follow-up. J Ophthalmol. 2015;2015:916385.
- Jabbarvand M, Hashemian H, Khodaparast M, Bazvand F, Beheshtnejad A. Outcome of complete intrastromal ring implantation using femtosecond laser in pellucid marginal degeneration. Eye (Lond). 2015;29:783–790. doi:10.1038/eye.2015.33 [CrossRef]
- Lazaridis A, Messerschmidt-Roth A, Sekundo W, Schulze S. Refractive lenticule implantation for correction of ametropia: case reports and literature review. Klin Monbl Augenheilkd. 2017;234:77–89.
- Mastropasqua L, Nubile M, Salgari N, Mastropasqua R. Femtosecond laser–assisted stromal lenticule addition keratoplasty for the treatment of advanced keratoconus: a preliminary study. J Refract Surg. 2018;34:36–44. doi:10.3928/1081597X-20171004-04 [CrossRef]