Lenticules for intrastromal corneal implantation

Abstract

Decellularized and shaped corneal tissue lenticules from allograft and/or xenograft sources and methods of obtaining such lenticules are disclosed. The lenticules are particularly useful as intrastromal lenticular implants in keratoplasty procedures, in which a hinged flap is formed in a patient's cornea and folded back along its hinge to expose the stromal bed of the cornea. The shaped lenticule is then applied to the stromal bed and the flap returned to its original position yielding a new curvature for the cornea and resulting in a desired refractive correction. Fine-tuning of the new refractive power can be achieved by laser ablation either at the same time as implantation or at later time in the event of regression or tonus changes. Methods of decellularizing cornea tissue are disclosed to reduce potential immunogenic reactions on the part of the patient to the implanted lenticule. The lenticules can be further treated to remove immunogenic epitopes. In addition, the posterior and/or anterior surfaces of the lenticule can be treated to assist in intrastromal seating of the lenticule and/or to reduce the likelihood of dislodgement. The methods of forming lenticules can further include preserving at least a portion of the Bowman's membrane. The smoothness of the Bowman's membrane surface also makes it less likely that reopening the flap will dislodge the lenticule.

Description

BACKGROUND OF THE INVENTION[0001]Vision disorders caused by abnormal refractive conditions, e.g. ammetropia, can be a significant problem for patients of all ages and can often be treated with subtractive laser ablation procedures or keratoplasty. Recently, additive techniques have been developed which can be used in conjunction with subtractive (ablative) techniques. Additive techniques typically involve the transplantation of a lenticule into a patient's cornea after a flap has been cut and folded back to expose an intrastromal region of the cornea. The shape of the lenticule modifies the optical power of the patient's cornea by changing its curvature. The flap can then be replaced on top of the lenticule. A few weeks later, if a change in the tonus of eye occurs, the patient can be assessed and a second step performed, which involves re-lifting the flap and performing refractive ablation of the lenticule with a laser.[0002]However, several problems limit wider acceptance of addit...

AI Technical Summary

Benefits of technology

[0007]Importantly, by preserving the top stromal surface, the anterior surface of the lenticule will exhibit a different texture than the other (posterior) surface because this naturally anterior segment of the cornea is denser and smoother due to natural condensation of the outermost layers of stromal tissue. The posterior surface (opposite to anterior surface or Bowman's membrane) will be rougher due to lesser stromal tissue density and the fact that it is formed by mechanical or laser cutting of the tissue. This difference in roughness can be especially advantageous when the lenticule is used for intrastromal implantation because it is highly desirable that the lenticule be strongly adherent to the stromal bed. If a less than optimal refractive result is observed post procedure, the flap may need to be folded back again to permit further keratoplasty (re-sculpting of the lenticule) by laser ablation or the like. Any movement of the lenticule from its original position in the stromal bed could compromise the effectiveness of this keratoplasty. Moreover, the smoothness of the Bowman's membrane surface of the lenticule also makes it less likely that reopening the flap will dislodge the lenticule.

Problems solved by technology

Vision disorders caused by abnormal refractive conditions, e.g. ammetropia, can be a significant problem for patients of all ages and can often be treated with subtractive laser ablation procedures or keratoplasty.

However, several problems limit wider acceptance of additive (lenticular) techniques.

First, the availability of donor human corneas to form lenticules is quite limited.

Additionally, the lenticules, themselves, are difficult to manipulate and prone to movement, especially if the flap must be re-lifted to perform a subsequent ablative procedure.