Abstract
LASIK (laser-assisted in situ keratomileusis) is a common laser refractive procedure for myopia and astigmatism, involving permanent removal of anterior corneal stromal tissue by excimer ablation beneath a hinged flap. Correction of refractive error is achieved by the resulting change in the curvature of the cornea and is limited by central corneal thickness, as a thin residual stromal bed may result in biomechanical instability of the cornea. A recently developed alternative to LASIK called Refractive Lenticule Extraction (ReLEx) utilizes solely a femtosecond laser (FSL) to incise an intrastromal refractive lenticule (RL), which results in reshaping the corneal curvature and correcting the myopia and/or astigmatism. As the RL is extracted intact in the ReLEx, we hypothesized that it could be cryopreserved and re-implanted at a later date to restore corneal stromal volume, in the event of keratectasia, making ReLEx a potentially reversible procedure, unlike LASIK. In this study, we re-implanted cryopreserved RLs in a non-human primate model of ReLEx. Mild intrastromal haze, noted during the first 2 weeks after re-implantation, subsided after 8 weeks. Refractive parameters including corneal thickness, anterior curvature and refractive error indices were restored to near pre-operative values after the re-implantation. Immunohistochemistry revealed no myofibroblast formation or abnormal collagen type I expression after 8 weeks, and a significant attenuation of fibronectin and tenascin expression from week 8 to 16 after re-implantation. In addition, keratocyte re-population could be found along the implanted RL interfaces. Our findings suggest that RL cryopreservation and re-implantation after ReLEx appears feasible, suggesting the possibility of potential reversibility of the procedure, and possible future uses of RLs in treating other corneal disorders and refractive errors.
Highlights
Myopia remains a significant ocular disability and economic burden by virtue of its high prevalence in most populations [1]
This study evaluated the long term tissue response associated with Refractive Lenticule Extraction (ReLEx) surgery, and the safety, efficacy and long-term outcome of autologous, cryopreserved refractive lenticule (RL) re-implantation following a myopic correction in a non-human primate model of ReLEx surgery, with an emphasis on determining the potential for reversibility with regards to restoration of corneal thickness, curvature and refractive status
This study suggests that anatomical restoration of the cornea by lenticule re-implantation following ReLEx surgery is a viable option
Summary
Myopia remains a significant ocular disability and economic burden by virtue of its high prevalence in most populations [1]. While LASIK remains a highly successful procedure, side effects such as post-operative glare and haloes, and dry eye symptoms have been documented [11,12,13,14]. The latter probably relating to a neurotrophic state due to transection of afferent sensory nerves in the anterior layers of the cornea stroma [14]. Biomechanical instability resulting from excessive stromal bed thinning can result in visual loss and significant ocular morbidity in the form of post-LASIK keratectasia in patients with undetected form fruste keratoconus or excessively thin residual stromal beds [15]. The incidence of corneal ectasia after LASIK is estimated at 0.2% to 0.6% [15,16]
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