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First Author: N.Lagali SWEDEN
Co Author(s): M. Koulikovska M. Rafat S. Akhtar M. Griffith P. Fagerholm
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To evaluate the performance of a femtosecond laser-enabled intra-stromal surgical model for testing the integration of bioengineered implants designed to replace corneal stromal tissue.
Laser Surgery Suite, Department of Ophthalmology, Division of Clinical and Experimental Medicine, Linköping University, Sweden.
An Intralase iFS 150kHz femtosecond laser was used to remove and replace thick sections of mid-stromal tissue from the cornea, while minimizing disturbance to the epithelium and endothelium. In this technique, a mid-stromal disc of tissue is cut by successive lamellar procedures, and subsequently removed via a small slit-like opening in the epithelium. A bioengineered stromal replacement material is then inserted into the stromal cavity through the same opening. This technique was validated in 20 rabbits, consisting of a control autograft group and 3 groups where biomaterial type and thickness varied. Implants were monitored in vivo for 8 weeks postoperatively, using photography, optical coherence tomography, and in vivo confocal microscopy. Bio-integration was examined ex-vivo by immunohistology and electron microscopy.
Tissue extraction and insertion was successful in all cases, with minimal impact on epithelium, endothelium, or subepithelial nerves. Healing was rapid, suture-free and irritation-free. Implants were retained in all corneas at 8 weeks. The thickest implants thinned partially over time but retained clarity, while thinner implants and control allografts retained shape, thickness, and clarity. Some interface haze formed early as implants attached to the surrounding stroma. Early cell migration into implants was noted, and the detailed collagen structure of implants and interface regions could be analyzed.
A model of femtosecond laser-assisted intra-stromal keratoplasty has been validated. The model enables evaluation and screening of bioengineered materials for eventual corneal transplantation. Surgical replacement of stromal tissue alone, without the requirements of suturing or re-epithelialization, results in rapid healing while minimizing denervation and possible immune response.