Comparison of sulfur hexafluoride and air for donor attachment in Descemet stripping endothelial keratoplasty in patients with pseudophakic bullous keratopathy

Comparison of efficacy of three gases for anterior chamber tamponade in Descemet's membrane endothelial keratoplasty

PURPOSE

To compare the efficacy of three different gases for intraocular tamponade: 100% air, 10% perfluoropropane (C3F8), and 10% sulfur hexafluoride (SF6), in Descemet's membrane endothelial keratoplasty (DMEK).

MATERIALS AND METHODS

The medical records of 138 patients who underwent DMEK were reviewed retrospectively, with the primary outcome being the rebubbling rate in the first week following surgery. Other clinical outcomes, such as best-corrected visual acuity (BCVA), central corneal thickness (CCT), incidence of rebubbling after the first week, endothelial cell density (ECD), graft detachment, graft failure, pupillary block, and intraocular pressure (IOP) changes were also analyzed.

RESULTS

Of the 138 patients, 57 were in group 1 (treated with air), 44 in group 2 (treated with 10% C3F8), and 37 in group 3 (treated with 10% SF6). Group 3 showed significantly lower rates of graft detachment and rebubbling compared to groups 1 and 2 (P<0.001). However, there was no significant difference in postoperative BCVA among the groups. At one year, the mean endothelial cell loss was 32% in group 1, 30% in group 2, and 33% in group 3 (P=0.715). One patient in group 1 experienced pupillary block and increased IOP, while there were no such occurrences in the other groups. There was no difference between the groups in terms of graft failure.

CONCLUSION

The use of 10% SF6 in DMEK surgery may be a good option due to its efficacy in preventing graft detachment, low rebubbling rate, and potential for minimizing complications.

Comparison of 20% SF6 and 6% C3F8 Gas for Anterior Chamber Tamponade in Endothelial Keratoplasty

PURPOSE

The aim of this study was to compare the rates of rebubbling after Descemet membrane endothelial keratoplasty (DMEK) and Descemet stripping endothelial keratoplasty (DSEK) between patients who had anterior chamber (AC) graft tamponade with 20% sulfur hexafluoride gas (SF6) and 6% perfluoropropane gas (C3F8).

METHODS

The charts of 431 patients undergoing EK from June 8, 2010, to April 16, 2023, were reviewed. Patients undergoing EK alone as well as combined procedures with cataract extraction and intraocular lens implantation were included. Eyes with tube shunts, anterior chamber intraocular lenses, and large peripheral iridotomy with posterior loss of bubble, and patients undergoing cyclophotocoagulation or synechialysis were excluded. All rebubble procedures were performed within 1 month after initial surgery.

RESULTS

A total of 346 eyes using SF6 and 167 eyes using C3F8 were analyzed. Overall, 46 eyes (9%) required rebubbling; 33 eyes (10%) in the SF6 group and 13 eyes (8%) in the C3F8 group. For those patients undergoing DMEK, the odds of requiring rebubbling in the C3F8 group were about 22% lower than that of patients in the SF6 group (operating room [OR]: 0.782; P < 0.001). For patients undergoing DSEK, however, the gas type did not significantly affect rebubbling rates (P = 0.99).

CONCLUSIONS

For DMEK, utilization of 6% C3F8 as an AC tamponade was associated with a significantly lower odds of graft rebubbling compared with 20% SF6. Gas type did not result in a significant difference for DSEK. Utilization of 6% C3F8 for graft tamponade could be considered to reduce graft detachment rates in DMEK.

Descemet membrane endothelial keratoplasty: Update on preoperative considerations, surgical techniques, and outcomes

Descemet membrane endothelial keratoplasty (DMEK) is the closest to the physiological replacement of endothelial cells. In the initial years, the technique was surgically challenging. Over the years, with better understanding and modifications in the surgical steps, the technique has evolved as an alternative to more popular procedure Descemet stripping endothelial keratoplasty. The article highlights the various preoperative, intraoperative, and postoperative nuances of DMEK. Additionally, it summarizes the various comparative and noncomparative studies on DMEK outcomes.

Graft detachments in endothelial keratoplasty

Graft detachment is the most common complication of endothelial keratoplasty. With the ongoing advancements in the field of endothelial keratoplasty, our understanding of risk factors of graft detachments and its management has been evolving. Various prevention measures have been described in literature including presoaking the donor graft, anterior chamber tamponade, venting incisions, sutures to prevent dislocation of graft. Management of a detached graft involves secondary interventions such as rebubbling, suturing and regrafts. In this review, we discuss graft detachment in different types of endothelial keratoplasty techniques including Descemet stripping endothelial keratoplasty, Descemet stripping automated endothelial keratoplasty and Descemet's membrane endothelial keratoplasty; with emphasis on incidence, risk factors, preventive measures and their management.

Factors Associated With Graft Detachment After Primary Descemet Stripping Automated Endothelial Keratoplasty

PURPOSE

To identify risk factors associated with postoperative graft detachment after Descemet stripping automated endothelial keratoplasty (DSAEK).

METHODS

In this retrospective institutional cohort study, the study group included all consecutive eyes that underwent primary DSAEK between January 2005 and October 2015 at Villa Serena-Villa Igea private hospitals (Forlì, Italy) and developed postoperative graft detachment (n = 45). The control group included all eyes that underwent primary DSAEK during the same period and did not develop graft detachment (n = 1167). The main outcome measure was whether or not postoperative graft detachment occurred.

RESULTS

Main indications for surgery included Fuchs endothelial dystrophy (525/1212 = 41%), pseudophakic bullous keratopathy (422/1212 = 35%), and a failed penetrating keratoplasty (PK) graft (190/1212 = 16%). Postoperative graft detachment occurred in 45 of 1212 (3.7%) eyes. Medically treated glaucoma, previous trabeculectomy, previous aqueous shunt procedure, and failed PK were all associated with an increased risk for graft detachment in univariate analysis. No particular lens status at the time of graft implantation was significantly associated with graft detachment, including the presence of an anterior chamber intraocular lens [odds ratio (OR), 1.5; 95% confidence interval (CI), 0.35-6.46, P = 0.58] or aphakia at the time of graft transplantation (OR, 1.37; 95% CI, 0.41-4.57, P = 0.74). Cataract removal during surgery was not associated with an increased risk for detachment (OR, 0.77; 95% CI, 0.39-1.5, P = 0.47). Previous trabeculectomy (OR, 4.21; 95% CI, 1.53-11.56, P = 0.005) and a previous failed PK graft (OR, 3.04; 95% CI, 1.6-5.78, P = 0.001) were the only independent risk factors for graft detachment in multivariate analyses.

CONCLUSIONS

Previous PK and trabeculectomy are independent risk factors for postoperative graft detachment in primary DSAEK.

Incidence of cystoid macular edema after Descemet's stripping automated endothelial keratoplasty

AIM

To determine the incidence of cystoid macular edema (CME) after Descemet's stripping automated endothelial keratoplasty (DSAEK).

METHODS

This study included all consecutive patients operated in a Spanish tertiary reference hospital over a period of four years. A total of 55 eyes from 47 patients matched the selection criteria. CME was diagnosed clinically at the slit-lamp and confirmed by optical coherence tomography.

RESULTS

Six cases of CME were diagnosed postoperatively, which represented an incidence of 11%. Three patients had previously undergone DSAEK alone (7%; 3/41) and the other three, DSAEK combined with phacoemulsification (21%; 3/14). Five out of six patients with CME responded to standard therapy.

CONCLUSION

CME is a possible complication after DSAEK and can be treated with standard therapy. CME appears more frequently when DSAEK is combined with phacoemulsification and posterior chamber (PC) intraocular lens (IOL) implantation. Intraoperative damage to the corneal endothelial cells might play a role in the pathogenesis of CME. As long as the causes remain unclear, we recommend administering prophylaxis when risk factors are present or when combined surgery is planned.

The effect of air, SF6 and C3F8 on immortalized human corneal endothelial cells

PURPOSE

While anterior chamber air bubbles aid attachment during posterior lamellar surgery only for few days, these periods can be prolonged with gases in non-expanding concentrations. To test the effects of different gas compositions on immortalized human corneal endothelial cells (HCEC-12), we utilized Transwell inserts with semipermeable membranes as an artificial anterior chamber model.

METHODS

Human corneal endothelial cells (HCEC-12) were cultured on Transwell inserts for 24 hr, then flipped, burdened and sunk with titanium rings in medium (M1), as well as filled with 2 ml of air (A), 20% sulphur hexafluoride (SF6) (S), or 12% C3F8 (C). After gas exposition for 24, 48 and 120 hr, cells were evaluated by live/dead staining, cell viability assay and Ki67 immunohistochemistry.

RESULTS

Proliferation was significantly reduced (Ki67-positive fraction; M1, 14.8 ± 2.0%; A, 7.9 ± 1.4%; S, 8.1 ± 1.3%; C, 9.9 ± 2.3%; p-values; A, S, C versus M1 < 0.01), the total cell number decreased and the percentage of dead cells increased under gas exposition, independently of the type of gas (120 hr cell count/2.25 cm² : M1 = 660.8 ± 57.0 cells; A = 125.5 ± 17.4 cells, S = 123.5 ± 17.0 cells, C = 118.8 ± 16.6 cells; p-value: M versus A/S/C < 0.001; 120 hr dead cells: M = 2.6 ± 1.0%, A = 8.4 ± 2.7%, S = 9.5 ± 3.2%, C = 11.3 ± 3.1%; p-value: M1 versus A/S/C < 0.01). Medium (M1)-control also proved significantly higher cell viability values in comparison with the gases, which did not differ significantly among them (120 hr luminescence: M1 = 1752.2 ± 91.4, A = 433.0 ± 30.3, S = 507.8 ± 23.3, C = 523.8 ± 20.3; p-value: M1 versus A/S/C < 0.01).

CONCLUSIONS

Gas exposition led to a reduction in proliferation and an increase in cell death in HCEC-12, independently of the gas composition.

[Influence of 20 % sulfur hexafluoride (SF6) on human corneal endothelial cells : An in vitro study]

BACKGROUND

In posterior lamellar keratoplasties, such as Descemet membrane endothelial keratoplasty (DMEK) and Descemet's stripping automated endothelial keratoplasty (DSAEK) an air bubble is left inside the anterior chamber to promote graft attachment during the early postoperative period. In the case of insufficient graft adhesion a renewed intracameral air injection is often necessary. The use of sulfur hexafluoride diluted with air (SF6 20 %) as an alternative to pure air may further enhance graft attachment and reduce the rebubbling rate. The effect of SF6 20 % on corneal endothelium is currently unclear and was therefore examined in vitro.

MATERIAL AND METHODS

For this study 12 human corneoscleral discs were mounted in artificial anterior chambers, the systems were continuously filled with culture medium and the anterior chambers with air (n = 5) or SF6 20 % (n = 7) as tamponade. After 6 days of storage in the incubator endothelial cell density, toxicity on endothelial cells and corneal thickness were evaluated.

RESULTS

There were no significant differences in endothelial cell loss (p = 1.000), endothelial cell count (p = 0.648), toxicity on endothelial cells (p = 0.048) and central corneal thickness (p = 0.905) between the two groups after 1 week. The level of significance was defined as p ≤ 0.05 and adjusted to p ≤ 0.0056 according to the Bonferroni correction for multiple testing.

CONCLUSION

The use of SF6 20 % as tamponade in the anterior chamber for posterior lamellar keratoplasty can be proposed as a safe alternative to pure air filling related to endothelial cell loss. Increased toxic effects on the corneal endothelium by SF6 20 % were not detected in this study; however, further prospective clinical trials are needed to examine the long-term effects in humans.

Impact of Introducing 2 Simple Technique Modifications on the Descemet Membrane Endothelial Keratoplasty Learning Curve

Purpose

To analyze the impact of performing premarking of the Descemet roll and using SF6 20% on a surgeon's Descemet membrane endothelial keratoplasty (DMEK) learning process.

Methods

A total of 30 consecutive eyes with endothelial dysfunction undergoing DMEK during the learning curve of a surgeon were retrospectively analyzed. Prior to the study, the surgeon had already performed 10 DMEKs. The first 15 consecutive patients were included in group 1 (no premarking and air tamponade) and the other 15 consecutive patients were included in group 2 (premarking and SF6 tamponade). Main outcome parameters were best-corrected visual acuity (BCVA), endothelial cell density (ECD) loss at 6 months, and intraoperative and postoperative complications.

Results

Among the 2 groups, BCVA and ECD loss at 6 months were similar. However, there was a statistically significant reduction in primary graft failure (40% vs 0%) and need of rebubbling due to complete or partial graft detachment (40% vs 6%) when comparing group 1 versus group 2. In group 1, half of the patients needing rebubbling had primary graft failure.

Conclusions

Based on our personal experience, premarking the graft to assess orientation and using a SF6 gas tamponade dramatically reduces the risk of primary graft failure and the need for rebubbling even during the first stages of the learning curve. These findings should encourage surgeons to safely change from Descemet stripping automated endothelial keratoplasty to DMEK.