Donor Descemet-off versus Descemet-on deep anterior lamellar keratoplasty: a confocal scan study

Ultrastructural Examination of the Corneal Interface after Predescemetic Deep Anterior Lamellar Keratoplasty (DALK) - A Case Report with Light and Transmission Electron Microscopy

PURPOSE

To examine corneal buttons with light and transmission electron microscopy (TEM) to visualize the interface area and highlight the ultrastructural corneal changes after deep anterior lamellar keratoplasty (DALK).

METHODS

Two patients underwent excimer laser-assisted penetrating repeat keratoplasty after predescemetic DALK. The corneal buttons were examined by light microscopy and TEM.

RESULTS

The light microscopic examination of the corneal buttons revealed fragments of a second Descemet's membrane in the central and midperipheral areas (Case 1). In both cases, visualization of the interface area was not possible by light microscopy. The donor and host stroma were tightly attached without dehiscence. TEM identified the interface area by irregularities in the collagen distribution between the donor and host stroma. The thickness of the remaining recipient corneal stroma measured approximately 30 µm (Case 1) and 100 µm (Case 2), respectively. In the host stroma, TEM revealed the absence or degeneration of keratocytes, accumulation of amorphous material between the collagen lamellae, and vacuolar inclusions dispersed in the stroma, forming a band-like zone anterior to Descemet's membrane.

CONCLUSION

The interface area after DALK has been mainly investigated by in vivo confocal microscopy. Light microscopy and TEM findings indicate remodeling processes after DALK that are associated with increased keratocyte degeneration and structural alterations of the extracellular matrix in the host stroma. The choice of surgical method may influence the postoperative morphological and functional outcome since these findings were primarily apparent in the remaining host stroma. Therefore, complete exposure of Descemet's membrane is an important prognostic factor for the postoperative visual outcome.

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.

Descemet's membrane macroperforation during interface irrigation in big bubble deep anterior lamellar keratoplasty

This report describes the macroperforation of descemet's membrane (DM) during irrigation of the interface following successful removal of stromal tissue in big bubble (BB) deep anterior lamellar keratoplasty (DALK). A 42-year-old woman with keratoconus underwent a BB DALK procedure. After successful formation of Type 2 bubble and removal of stromal tissue, interface irrigation was performed to remove residual viscoelastic. This led to a macroperforation of DM, and the case was converted to penetrating keratoplasty. To the best of our knowledge, this is the first report of such a complication in the literature. Recognition of a 2 bubble formation during pneumodissection should alert the surgeon to a high risk of DM rupture. We advise against the removal of DM from the donor in such cases as an added measure of safety.

Comparison of Descemet-On Versus Descemet-Off Deep Anterior Lamellar Keratoplasty in Keratoconus Patients: A Randomized Trial

PURPOSE

To compare the visual outcomes of Descemet membrane (DM)-on and DM-off after deep anterior lamellar keratoplasty (DALK) using the big-bubble (BB) technique in keratoconus patients.

METHODS

In this prospective trial, keratoconic eyes undergoing DALK procedures with the BB technique were randomized into 2 groups: a donor cornea without DM (group 1; 29 eyes) or with DM (group 2; 30 eyes). These groups were compared with respect to best-corrected visual acuity and contrast sensitivity while wearing gas permeable contact lenses and also endothelial cell counts.

RESULTS

There were no statistically significant differences between the 2 groups with regard to best-corrected visual acuity and contrast sensitivity using gas permeable contact lenses as well as endothelial cell counts at 3, 6, and 12 months. After 1 year, the mean (±SD) postoperative visual acuity CL (with contact lenses) was 0.05 (±0.01) in the DM-off group and 0.05 (±0.01) in the DM-on group (P = 0.956). Mean postoperative endothelial cell counts were 2425.0 (±123.7) and 2306.7 (79.9), respectively (P = 0.443), and corneal thicknesses were 527.9 (58.3) and 556.6 (47.3), respectively (P = 0.150). During the follow-up period, very few complications occurred and neither group had a predominance of adverse events at 3, 6, 12, or 24 months.

CONCLUSIONS

In conclusion, DALK procedures using the BB technique for keratoconus with DM-on or DM-off presented no significant differences regarding the visual outcomes or endothelial cell counts.