Abstract
To report a case of a 20-year-old woman who developed massive and progressive corneal remodeling in both eyes after bilateral PRK with mitomycin and CXL as an elective refractive procedure for mild keratoconus. The patient had 6 years of follow up, initially presenting with focal steepening of up to 20 diopters on both eyes one-and-a-half- years postoperatively that spontaneously reversed over the next five years while the high order aberrations worsened. At the present time, the patient depends on bilateral scleral contact lenses for her day-to-day activities. The use of combined elective PRK with mitomycin and prophylactic CXL could lead to progressive corneal deformation. Additional reports would help to establish the role of this combination procedure among the armamentarium to visually rehabilitate patients with keratoconus.
1
Introduction
Keratoconus (KC) is a corneal disease with stromal weakening, thinning and distortion. Disease management includes non-surgical interventions such as spectacles and contact lens, and surgical interventions such intracorneal ring segment implantation, lamellar keratoplasty, penetrating keratoplasty, among others. Additionally, the simultaneous use of surface ablation with mitomycin C (MMC) and corneal cross-linking (CXL) has been advocated to improve corneal contour in patients with keratoconus. , We present a case of bilateral simultaneous photorefractive keratectomy (PRK) with MMC and CXL in which corneal scarring and progressive corneal distortion that worsened over several years needing scleral contact lenses for visual rehabilitation.
2
Case report
2.1
Initial assessment
A 20-year-old woman patient had a preoperative uncorrected visual acuity (UCVA) of 0.3 LogMAR and 0.6 LogMAR in her right and left eyes. The refraction was +0.75–2.00 × 75 and + 0.75–2.00 × 105 with corrected distance visual acurity (CDVA) of 0.2 LogMAR OU. The Scheimpflug imaging technology (Pentacam, Oculus Gmbh, Wetzlar, Germany) showed an inferior crab-claw pattern in each eye, with a thinnest corneal point of 423 μm and 449 μm respectively ( Figs. 1A and 2 A ) . Her two-year old glasses formula was the same as the preoperative refraction but we were not sure if she was progressing since no sequential preoperative topographies/tomographies were available. She had a history of allergic conjunctivitis and volunteered to rub her eyes frequently. After informed consent was obtained, PRK with CXL and MMC was performed in a modified Athens protocol to improve her refractive parameters in February 16 of 2012.
2.2
Surgical procedure
After topical anesthesia, the corneal epithelium was removed with 20% ethanol for 40 seconds using a 9.0-mm-diameter well. The Esiris excimer laser (Schwind eye-tech-solutions GmbH, Kleinostheim) was programmed to treat the higher-order aberrations (HOA) in both eyes using a corneal wavefront profile. The ablation profile was calculated based on measurements of the wavefront corneal topography (Keratron Scout, Optikon, Roma, Italy). The ablation was superior and inferior in an attempt to steepen the vertical meridian (a printout of the ablation pattern for the right eye was found in the surgical report but poor definition does not allow for publication here).
In the right eye, a 54 μm ablation of HOA was performed. The ablation diameter was 5.0 mm (deeper superiorly than inferiorly) with an additional 0.4 mm transition zone. No refractive correction was input into the laser due to thickness considerations. We were cognizant that the HOA stromal ablation could be different than the corneal-epithelial-surface-topography-measured wavefront but that was the software available to us. Mitomycin C 0.02% for 120 seconds was applied after the excimer laser application. The cornea was soaked with 0.1% riboflavin with 20% dextran (no hypotonic riboflavin was available in the country at the time), one drop every 3 minutes for 30 minutes and one drop of riboflavin was applied every 5 minutes while irradiating. The thinnest of 10 central and paracentral ultrasound pachymetry readings (Sonogage Inc, Cleveland, OH, USA) was 404 μm before irradiation. Ultraviolet A (UVA) of 365 nm (3 mW/cm 2 ) was used (IROC, Peschke, Switzerland). Given the borderline pachymetry, the UVA application time was empirically reduced to 20 minutes (3.6 J/cm2)A bandage contact lens was placed at the end.
A similar procedure was done in the left eye. The thinnest pre-UVA application ultrasonic pachymetry was 405 μm. Forty-three μm of HOA were treated (in a similar ablation profile as described above) along with half of the refractive error according to the laser nomogram for mixed astigmatism (Plano – 0.60 × 105°) for a total of 56 μm total ablation. The rest of the procedure was done similarly to the right eye.
Postoperative regimen consisted of a plano bandage contact lens (Soflens 66®, Bausch & Lomb), gatifloxacin (Zymaran®, Allergan, Irvine, CA) and fluorometholone (FML®, Allergan, Irvine, CA) four times a day for one week.
2.3
Clinical follow-up
Four days after the procedure there was a 1 mm epithelial defect and trace superficial haze in the right eye, and a deep central dense haze in the left eye. The epithelium in both eyes closed one week after surgery and the contact lenses were removed. One month after the procedure the UDVA was 0.2 and 0.4 and CDVA was 0.2 LogMAR in both eyes with a refraction of +1.50–1.75 × 130 and + 1.75–2.50 × 20. At this time, the right eye presented with mild haze and left eye a dense deep-stromal haze and blurred vision. She was compliant with the postoperative steroid regimen, protected herself from UV light for three months as instructed and did not use ascorbic acid as she was not instructed to do so.
One year after, the UDVA was 0.5 and 0.4, CDVA was 0.30 LogMAR in right eye (−0.25 – 7.00 × 78) and non-refractable OS. There was a deep central stromal haze in both eyes. Eighteen months postop the differential Scheimpflug axial corneal maps showed bilateral corneal steepening close to 20 diopters in both eyes ( Fig. 1 ABD and 2 ABD), despite bilateral full-thickness stromal scarring evident on the en-face Scheimpflug images. ( Fig. 3 A and B). Similar findings were seen on the differential Scout (Keratron Scout, Optikon, Roma, Italy) corneal topography ( Fig. 4 A and B.) Despite the corneal ectasia, because the presence of 100% corneal haze we decided to observe the patient.
