Excimer laser "corneal shaping": a new technique for customized trephination in penetrating keratoplasty. First experimental results in rabbits

Laser-assisted corneal transplantation surgery

Corneal transplant surgeries have a broad range of indications with outcomes largely dependent on surgeon experience. Traditional manual techniques have certain limitations pertaining to the preparation of donor tissue and the recipient bed that might affect the predictability of visual outcomes. Use of lasers for keratoplasty procedures not only improves the repeatability and consistency of the technique, but also enables the surgeon to control the thickness and shape of the transplant tissue tailored to the specific condition. Despite the advantages, cost-effectiveness and technical know-how remain the major challenges. We discuss the various techniques of laser-assisted keratoplasties with respect to their methods, precision, and efficacy in various corneal indications.

Construction of tissue-engineered full-thickness cornea substitute using limbal epithelial cell-like and corneal endothelial cell-like cells derived from human embryonic stem cells

The aim of this study was to construct a full-thickness artificial cornea substitute in vitro by coculturing limbal epithelial cell-like (LEC-like) cells and corneal endothelial cell-like (CEC-like) cells derived from human embryonic stem cells (hESCs) on APCM scaffold. A 400 μm thickness, 11 mm diameter APCM lamella containing Bowman's membrane was prepared as the scaffold using trephine and a special apparatus made by ourselves. LEC-like cells and CEC-like cells, derived from hESCs as our previously described, were cocultured on the scaffold using a special insert of 24-well plates that enabled seeding both sides of the scaffold. Three or four layers of epithelium-like cells and a uniform monolayer of CEC-like cells could be observed by H&E staining. The thickness, endothelial cell density, and mechanical properties of the construct were similar to that of native rabbit corneas. Immunofluorescence analysis showed expression of ABCG2 and CK3 in the epithelium-like cell layers and expression of N-cadherin, ZO-1 and Na+/K + ATPase in the CEC-like cells. The corneal substitutes were well integrated within the host corneas, and the transparency increased gradually in 8-week follow-up after transplantation in the rabbits. These results suggest that the strategy we developed is feasible and effective for construction of tissue-engineered full-thickness cornea substitute with critical properties of native cornea.

Long-term refractive results of elliptical excimer laser penetrating keratoplasty (EELPK)

PURPOSE

To assess long-term refractive and visual outcome of elliptical excimer laser penetrating keratoplasty (EELPK).

METHODS

Inclusion criteria (17 eyes): (1) Primary central elliptical excimer laser penetrating keratoplasty in phakic eyes; (2) No other simultaneous procedure except cataract surgery in 6 eyes; (3) Interrupted sutures; (4) Complete sequence of follow-ups before EELPK, with all-sutures-in, with all-sutures-out; (5) No active inflammation at the time of EELPK. Best corrected visual acuity (BCVA), refractive and keratometric astigmatism, topographic surface regularity index (SRI), surface asymmetry index (SAI) were determined in 5.9+/-3.3 years follow-up.

RESULTS

BCVA improved from 0.2 preoperatively to 0.6 after suture removal (p<0.001). After suture removal, keratometric (4.9D/5.8D, p=0.01) and refractive cylinder (2.8D/4.4D; p<0.001) increased, and SRI and SAI decreased significantly (3.0/1.0; 1.9/0.9; p=0.01) compared to all-suture-in values.

CONCLUSIONS

EELPK is effective in improving visual acuity. Despite topographic regularization, an increase of refractive more than keratometric astigmatism may occur after suture removal.

[Non-contact donor cornea trephination with a flying spot excimer laser system]

BACKGROUND

One of the most common complications after mechanical penetrating keratoplasty is the occurrence of irregular astigmatism. We developed a method to prepare donor grafts for transplantation applying excimer laser techniques. The quality of the cut edges and exposure time were evaluated.

MATERIALS AND METHODS

The beam of an experimental excimer laser (OPTex, Lambda Physik) was homogenized and guided by an optical system including lenses and scanner mirrors. A special software was used to conduct the laser beam in a circular mode over the surface of the cornea. Corneas from porcine eyes were stabilized in an artificial anterior chamber. Twenty in vitro explants were trephinated applying our method and subsequently investigated by electron microscopy and histology.

RESULTS

All experiments provided regular and smooth cut edges. The average exposure time until perforation was 10.5 min (SD 2.7 min), the diameter of the grafts was 8.0 mm.

CONCLUSION

The experiments showed the possibility of non-contact trephination and generation of smooth cut edges with a rotating focussed excimer laser beam in a porcine cornea model. A major advantage of the system is the possibility of customized "tailored" grafts.