Clinical evaluation of Toric phakic posterior chamber intraocular collamer lens implantation for ametropia following deep anterior lamellar keratoplasty for keratoconus

Background

Postoperative ametropia, especially large astigmatism after deep anterior lamellar keratoplasty (DALK) for keratoconus often results in poor visual acuity. Though postoperative ametropia can be corrected by wearing glasses or performing corneal refractive surgery, the visual quality of patients is still poor, and the operations are difficult to implement because of insufficient corneal thickness. Toric intraocular collamer lens (TICL) implantation appears to have good corrective efficacy on severe astigmatism, but the research on the eyes after DALK is still less.

Objective

This study was to evaluate the efficacy and safety of TICL implantation for the ametropic eyes following DALK for keratoconus.

Methods

This study protocol was approved by Ethic Commission of Nanjing Drum Tower Hospital, and written informed consent was obtained from each patient prior to any medical procedure. A self-controlled serial observational research was carried out. Eight ametropic eyes of 8 patients who received the DALK for keratoconus before 18 months were enrolled in Nanjing Drum Tower Hospital from August 2011 to March 2012, with the spherical diopter range from 0 D to -7.5 D and cylindrical diopter range from -2.5 D to -6.0 D. TICL implantation was performed on the eyes. The eye examinations were carried out before surgery and 1 week, 3 months, 6 months, 1 year and 2 years after surgery, including uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), comprehensive optometry, corneal astigmatism degree, the central corneal thickness and anterior chamber depth (ACD), corneal endothelial cell counts (ECD), intraocular pressure. The examination outcomes were compared before and after surgery. The intraoperative and postoperative complications were observed to evaluate the safety of TICL implantation for the ametropic eyes following DALK for keratoconus.

Results

The UCVA and BCVA were obviously improved at 6 months after TICL implantation in comparison with before surgery and maintained stable during the follow-up duration. The mean spherical diopter was from -0.5 D to -1.0 D and the mean cylindrical diopter was from -0.5 D to -2.0 D after surgery. The corneal endothelial cell counts were (2 520.2±307.2), (2 496.2±306.2), (2 469.6±304.5), (2 432.0±305.4), (2 383.4±309.4)/mm², and the intraocular pressures were (14.57±3.75), (16.62±4.21), (16.57±3.56), (15.66±3.37), (15.13±3.48) mmHg, showing insignificant differences among different time points (F=0.375, P=0.825; F=9.871, P=0.394). No significant differences were found in mean ACD and intraocular pressure between before and after surgery (t=1.56, P=0.16). The axial deviation of TICL was less than 10° in all the operated eyes 6 months after surgery. No intraoperative and postoperative complications were found during the follow-up duration.

Conclusions

TICL implantation is a safe and effective alternative and viable approach to myopic and astigmatism patients following DALK for keratoconus.

[Key words]Lens implantation, intraocular; Phakic intraocular lens; Ametropia/surgery; Astigmatism/surgery; Keratoconus/surgery; Corneal transplantation/complications; Treatment outcome; Toric intraocular collamer lens