We report a case of a young patient with keratoconus, whose left eye presented with high myopia astigmatism (-2.25 -8.5 × 100) following penetrating keratoplasty. Femtosecond laser assisted arcuate keratotomy (FLAK) was performed and the patient’s astigmatism was significantly reduced after the procedure. However, the visual acuity was still limited by residual myopia astigmatism (-8.00 -3.75 × 110). A Toric implantable collamer lens (TICL) was used to this condition. The refraction after implantation improved to -0.50 -0.75 × 65 with an uncorrected distance visual acuity (UDVA) of 20/25 and a corrected distance visual acuity (CDVA) of 20/20. The combination of TICL implantation and FLAK is a candidate for correcting residual myopia astigmatism following PKP.

INTRODUCTION

Arcuate keratotomy (AK) is a procedure which has been widely used in correction of astigmatism after penetrating keratoplasty (PKP) [1,2]. However, AK has certain limitations such as low reproducibility and tendency to undercorrect [3,4]. Despite that the application of femtosecond laser in AK has improved its accuracy, this procedure is still not effective enough, as evidenced by the frequent occurrences of residual astigmatism or/and myopia [5,6]. Nonsurgical therapies such as spectacles and contact lenses are not always effective in correcting these residual refractive errors, because spectacles correction is unsuitable for high level of anisometropia, and the use of contact lenses is dependent on lens tolerance of patients. Laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) are common procedures for correcting these residual refractive errors are limited by the thickness of graft and therefore, are not appropriate in ameliorating high level of residual refractive errors after AK. Here, we present a case of high myopia astigmatism post-PKP, which was not completely corrected by femtosecond laser-assisted arcuate keratotomy (FLAK) alone, but was properly corrected by a combined therapy of FLAK and Toric implantable collamer lens (TICL implantation).

CASE REPORT

The patient was a 23-year-old man who had received PKP in his left eye. Three months after suture removal, the vision in his left eye could not be improved to a satisfying level due to high residual myopia astigmatism (Table 1). Regarding his right eye, the manifest refraction was -0.75 -0.75×60. The UDVA was 20/20. The examination of intraocular pressure (IOP), crystalline lens and retina was normal. AK was implemented under topical anesthesia with INTRALASE FS SYSTEM (Advanced Medical Optics) after receiving patient’s informed consent. The length and location of the arcuate incisions were determined based on the borders of the steep semi-meridians, which were identified by corneal topography [1] Parameter settings including posterior depth (469 µm, 80% depth of the thinnest corneal thickness), anterior diameter (6.0 mm), anterior energy (1.5 µJ), cut position 1 (35 degree), cut angle 1 (70 degree), cut position 2 (175 degree), cut angle 2 (90 degree), anterior side cut angle (120 degree) and anterior side cut spot separation (3μm). The astigmatism was obviously reduced (Figure 1), but with high residual myopia astigmatism remained (Table 1) 22 months after FLAK. Therefore, a TICL was implanted after another informed consent was signed. Preoperative examinations established the following parameters: corneal topography (50.7@25/47.0@115), anterior chamber depth (3.69 mm), white-to-white distance (11.5 mm), manifest refraction (-8.00 -3.75×110), IOP (11 mmHg) and endothelial cells density (ECD, 2196/mm²).

A final TICL (VTICMO 13.2 mm, -13.5 +4.0×023, STAAR surgical) was determined by the software provided

by manufacturer and it was implanted into the left eye of the patient under topical anesthesia (Figure 2).

The manifest refraction, UCVA and CDVA showed obvious improvements 3 months after TICL implantation compared with those before the procedure (Table 1). These significant improvements of his vision and refractive error were sustained at the 6-month follow-up. In addition, the ECD was 2106/mm² with a loss rate of 4.1% at 3-month follow-up and 2055/mm² with a loss rate of 6.4% at 6-month follow-up. No intraoperative or postoperative complications were observed at the follow-ups.

DISCUSSION

AK was considered as an effective way to reduce the high level of astigmatism after PKP [1,2]. In this study, we observed a reduction of refractive cylinder of 55.9%, which was consistent with previous reports [1,7-9]. The reduction of keratometric cylinder was 57%, which was also similar to those seen in other studies [7,8]. However, neither the UDVA nor the CDVA improved evidently (Table 1). It is worth noting that we observed an obvious myopia shift of spherical equivalent (SE) at 3-month follow-up. This trend of myopic shift development after AK was probably associated with the increase in central corneal curvature, which occurred due to the release of axial tension within the graft and a concomitant increase in the corneal vault. Another possible reason of this process was two large arcuate incisions (70 degree and 90 degree) performed on graft, which dramatically weakened the mechanical strength of graft and resulted in ectasia. Fortunately, this process stopped, and the topography and refraction were stable at the subsequent follow-ups.

Although there was a significant reduction in astigmatism after FLAK, the residual myopia astigmatism (-8.00 -3.75×110) was so high that the patient’s vision was still unsatisfactory, which was too high for refractive surgery to be safe. Severe anisometropia rendered spectacle correction infeasible, and the patient was intolerant of long-term use of contact lenses. We therefore performed TICL implantation to improve the results of FLAK. TICL implantation has been reported as a potential procedure for correcting myopia and astigmatism after PKP and anterior lamellar keratoplasty [10-12]. However, to our knowledge, the management of TICL implantation to correct high residual refractive errors after FLAK has not been reported.

The manifest refraction and visual acuity showed significant improvements and reached satisfactory levels after the surgery (Table 1). A low rate of ECD loss (6.4% at 6 months) similar to that reported by a previous study (5.11% at 6 months) [7] was observed in our case. No cataract, opacification and IOP elevation were observed during 6-month follow-up. However, Fernandes et al. [13] reported that 5.2% of eyes developed cataract after ICL implantation during at least 3-year follow-up. So we need to perform longer follow-ups to estimate the long-term safety of this treatment.

Although AK can effectively reduce severe astigmatism after PKP, the predictability of AK remains unsatisfactory and secondary treatments are usually inevitable. TICL implantation not only can accurately correct residual myopia astigmatism, especially high residual myopia astigmatism after AK, which is unsuitable to perform LASIK or PRK. It may also be a safer option than LASIK and PRK, which might be responsible for complications such as iatrogenic corneal ectasia [14] and the increased risk of graft rejection. Therefore, in our opinion, combining TICL implantation with FLAK is a candidate for the correction of high residual myopia astigmatism after PKP. The effectiveness, safety and predictability of this procedure are worthy of further studies.

ACKNOWLEDGEMENTS

Disclosure: Neither author has a financial or proprietary interest in any material or method mentioned.

Funding: No funding

Additional contributions: No additional contribution.

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