Geometric Properties of Donor Corneas After Mechanical Trephination in Deep Anterior Lamellar Keratoplasty

An analysis of factors associated with graft topographic outcomes after deep anterior lamellar keratoplasty

PURPOSE

To investigate the correlations between preoperative, operative, and postoperative factors and corneal graft topographic parameters after deep anterior lamellar keratoplasty (DALK) performed in keratoconus-affected eyes.

METHODS

This prospective, interventional study enrolled 44 eyes. Graft topographic parameters, including keratometric astigmatism and the surface regularity index (SRI), were assessed after complete suture removal. Univariate analyses were used to evaluate the effects of preoperative factors (donor quality, donor and recipient age, keratoconus severity), operative factors (graft size, donor button roundness, roundness and centration of the donor-recipient junction), and postoperative factors (time point of suture removal) on postoperative topographic parameters.

RESULTS

The roundness of the donor-recipient junction after complete suture removal had a significant association with the roundness of the donor button after trephination (P = 0.04) and the amount of graft decentration relative to the limbus (P = 0.03). A significant correlation was found between the value of graft decentration relative to the limbus and postoperative keratometric astigmatism (P = 0.001) and between the roundness of the donor-recipient junction and the postoperative SRI (P = 0.02). The flat axis of the keratometric astigmatism and the longer axis of the graft lay in the direction of graft displacement. Other investigated factors had no significant association with postoperative topographic indices.

CONCLUSION

Graft displacement relative to the limbus and roundness of the donor-recipient junction were the main predictors of graft astigmatism and regularity, respectively, after DALK. Noncircularity of the donor button after trephination could increase the graft surface irregularity indirectly by influencing the roundness of the surgical wound.

Appropriate stage of Descemet membrane removal during donor preparation in deep anterior lamellar keratoplasty

PURPOSE

To investigate the appropriate surgical stage for Descemet membrane (DM) removal during donor preparation in deep anterior lamellar keratoplasty (DALK).

METHODS

This study included 83 corneoscleral buttons that were used for DALK. The donor DM was removed randomly either before (group 1; 43 eyes) or after (group 2; 40 eyes) trephination. The time required for DM removal was recorded, and the geometric properties of cut buttons were evaluated after trephination. The intraoperative video recordings were reviewed to determine if the dissections were performed at the stroma-DM plane as it was intended. The time needed to remove the DM, the rate of correct dissection at the intended stroma-DM plane, and the roundness and precision of the donor cuts were compared between the groups.

RESULTS

The two groups were comparable in donor characteristics, including age, quality of the tissue, and trephination size. Time spent to remove DM was significantly shorter in group 1 (68.9 ± 48.2 s) than group 2 (117.7 ± 52.7 s, P = 0.001). DM stripping was performed incorrectly in 2 corneas (4.7%) in group 1 and in 12 corneas (30%) in group 2 (P = 0.01). No difference was found between the groups in the roundness and precision of donor button cuts.

CONCLUSIONS

DM removal before trephination did not detrimentally affect the geometric properties of punched donor tissues. When DM stripping was performed before trephination, the donor tissue was less traumatized and posterior graft surface was more likely to be regular; therefore, it is advisable to remove DM before trephination during donor preparation for DALK.

Configuration of recipient corneal cut after mechanical trephination in keratoconus

PURPOSE

To determine the roundness of recipient corneal cuts after mechanical trephination and to investigate possible factors that could affect the corneal bed configuration in deep anterior lamellar keratoplasty (DALK).

METHODS

This study enrolled 85 eyes with keratoconus that underwent DALK. Recipient corneas were partially trephined using a new, unused, disposable Hessburg-Barron suction trephine. Photographs that best represented the recipient corneal cut were selected, and ImageJ software was used to evaluate the roundness of recipient bed. The effect of potential variables on the roundness of cuts was investigated using the univariate analyses.

RESULTS

The mean patient age was 31.0 ± 9.0 years. The mean recipient trephine size was 8.04 ± 0.29 mm (range 7.5-8.50 mm). The recipient cut roundness was 0.922 ± 0.070, varying from 0.78 to 1.0. The roundness of the corneoscleral limbus (0.874 ± 0.074) which represented the shape of recipient cornea was the main predictor of the configuration of recipient cut (r = 0.84, P < 0.001). Other preoperative characteristics investigated were mean keratometry (P = 0.63), keratometric astigmatism (P = 0.18), central corneal thickness (P = 0.64), keratoconus severity (P = 0.37), and trephine size (P = 0.50) that demonstrated no significant associations with the roundness of cut.

CONCLUSIONS

The recipient corneal cut after mechanical trephination may not be circular. The roundness of recipient bed was primarily affected by the roundness of corneoscleral limbus, indicating that the shape of recipient cut tends to follow the original shape of the cornea.