Pneumatic Dissection for Large-Diameter (9-mm) Deep Anterior Lamellar Keratoplasty in Eyes With Previous Anterior Lamellar Keratoplasty

Main issues in deep anterior lamellar keratoplasty: A systematic narrative review

Deep anterior lamellar keratoplasty (DALK) has emerged as a transformative approach in managing corneal pathologies, notably keratoconus (KC), providing a viable alternative to penetrating keratoplasty (PK). This systematic review explores the intricacies of DALK, comparing its preoperative, intraoperative, and postoperative considerations with PK. Extensive literature searches revealed a wealth of data regarding DALK's advantages and challenges, with an emphasis on graft survival, visual outcomes, and complications. In the preoperative phase, DALK showcases its versatility, catering to a wide spectrum of patients, including those with KC and ocular surface disorders. Intraoperatively, it offers innovative techniques to address emphysema, bubble formation, and Descemet's membrane perforation, all while maintaining a strong focus on patient-centered outcomes. Postoperatively, DALK's lower rejection rates and decreased complications underscore its potential superiority over PK, although unique challenges such as graft failure from nonimmunologic factors demand vigilant management. This comprehensive review not only serves as a valuable resource for ophthalmic surgeons but also sheds light on the evolving landscape of corneal transplantation, highlighting DALK's role as a transformative force in the field.

Large-diameter deep anterior lamellar keratoplasty: A narrative review

Deep anterior lamellar keratoplasty (DALK) involves the selective replacement of diseased corneal stroma while preserving healthy unaffected endothelium. While DALK has failed to gain widespread popularity, improved visual and refractive outcomes of large-diameter grafts, which patients directly perceive following suture removal, may represent a compelling reason to shift toward DALK. Since the unaffected host endothelium is retained, DALK offers the opportunity to use large-diameter grafts, which reliably achieves maximum visual potential without an increased risk of immune-mediated stromal rejection. In this narrative review, we evaluate the current evidence on large-diameter DALK including surgical technique and clinical outcomes.

High Astigmatism After Conventional Diameter Deep Anterior Lamellar Keratoplasty in Keratoconus Can Be Successfully Managed With Repeat Wide Diameter Deep Anterior Lamellar Keratoplasty

PURPOSE

The aim of this study was to describe a new surgical technique to replace a conventional diameter (≤8 mm) deep anterior lamellar keratoplasty (DALK) graft with associated high astigmatism refractory to corneal-based astigmatic procedure/intolerance to contact lenses with a larger diameter (≥9 mm) DALK graft to improve best spectacle-corrected visual acuity (BSCVA).

METHODS

Two eyes from 2 keratoconic patients at Southend University Hospital between December 2019 and June 2021 with a minimum follow-up of 17 months were evaluated. The primary outcome of interest was Snellen BSCVA with a secondary outcome of topographic cylinder.

RESULTS

Patient 1 had undergone initial 8 mm diameter DALK, with residual keratometric astigmatism of nearly 12 diopters (D) postoperatively despite numerous astigmatic interventions, with a BSCVA of 6/60, before undergoing 9 mm diameter repeat modified DALK. After suture removal and subsequent in-the-wound blunt manual relaxing incisions, the patient had a final keratometric astigmatism of 3.5 D, manifest refraction of plano/-3.50 × 175, and a BSCVA of 6/9. Patient 2 had undergone initial 7.75 mm diameter DALK, with residual keratometric astigmatism of 10.5 D with a BSCVA of counting fingers. The patient underwent 9 mm repeat modified DALK with final residual keratometric astigmatism of 3.1 D after suture removal, manifest refraction of -1.00/-2.75 × 25, and BSCVA of 6/9.

CONCLUSIONS

Wide diameter DALK (>9 mm) is effective in the management of conventional diameter DALK (≤8 mm) associated high astigmatism in keratoconus. Creation of a peripheral posterior stromal shoulder also allows safe further titration of residual astigmatism if needed.

Repeat deep anterior lamellar keratoplasty (DALK) for failed primary DALK

Purpose

To evaluate the effectiveness of repeat deep anterior lamellar keratoplasty (DALK) in patients of previous failed DALK.

Methods

: A retrospective analysis of records of seven patients who had undergone repeat DALK following the failure of the primary DALK was done. The indications for repeat surgery, time elapsed since the first surgery, and pre- & postoperative best-corrected visual acuity (BCVA) were noted for all the patients.

Results

The follow-up period ranged between one- to four-year post repeat DALK. The indication of primary DALK was keratoconus with vernal keratoconjunctivitis (VKC) (n = 3), corneal amyloidosis (n = 2), Salzman nodular keratopathy (n = 1), and healed keratitis (n = 1). The need for repeat surgery arose when the BSCVA dropped to less than 20/200. The time interval elapsed since the first surgery ranged from two months to four years. Postoperatively, the BSCVA improved from 20/120 to 20/30 at the end of one-year post repeat DALK in all except one patient. All regrafts were clear at the most recent examination, performed after a mean period of 18 months after the secondary graft. No complication was encountered during the resurgery. The dissection of the host bed was easier in the second surgery owing to weaker adhesions.

Conclusion

The prognosis for repeat DALK for failed DALK is excellent, and the outcomes of secondary grafts were comparable to those of primary DALK grafts. Re DALK offers the advantage of an easier dissection and lower chances of graft rejection compared to penetrating keratoplasty.

Outcomes of Conventional 8.0-mm Versus Large 9.0-mm Diameter Deep Anterior Lamellar Keratoplasty for Keratoconus

PURPOSE

The purpose of the study was to compare the clinical outcomes of large 9.0-mm diameter and conventional 8.0-mm big-bubble deep anterior lamellar keratoplasty (DALK).

METHODS

In this comparative, retrospective interventional case series, medical records of 124 cases of large 9.0-mm diameter DALK from January 2017 to December 2019 and 133 conventional 8.0-mm DALK from January 2014 to December 2016 performed by a single surgeon for the indication of keratoconus were reviewed. Main outcome measures were best spectacle-corrected visual acuity (BSCVA), refractive astigmatism (RA), and postoperative complication rates.

RESULTS

Postoperative logarithm of the minimum angle of resolution BSCVA did not significantly differ between 9.0-mm and 8.0-mm DALK at any time points. Although the cumulative percentage of eyes achieving Snellen BSCVA of 20/40 or better was comparable between groups (9.0-mm DALK: 93%, 8.0-mm DALK: 90%, P = 0.571), the cumulative percentage of eyes achieving 20/20 or better (9.0-mm DALK: 44%, 8.0-mm DALK: 26%, P = 0.01) and 20/25 or better (9.0-mm DALK: 74%, 8.0-mm DALK: 59%, P = 0.03) was significantly higher in the 9.0-mm DALK group. RA was significantly lower in the 9.0-mm DALK group compared with the 8.0-mm DALK group during all time points (P < 0.001). The percentage of eyes with RA less than or equal to 4.0 D was significantly lower in the 9.0-mm DALK patients (90%) compared with in 8.0-mm DALK group (72%) (P = 0.002). Postoperative complication rates were similar between groups.

CONCLUSIONS

Compared with conventional 8.0-mm DALK, large 9.0-mm DALK can provide superior visual outcomes at higher levels of Snellen BSCVA and significantly lower degrees of astigmatism without an increased risk of immune rejection and graft failure.

Deep Anterior Lamellar Keratoplasty: Current Status and Future Directions

ABSTRACT

Deep anterior lamellar keratoplasty (DALK) involves selective replacement of diseased corneal stroma while preserving normal healthy endothelium. Despite several well-recognized advantages, the uptake of DALK has remained sluggish with an adoption rate that has plateaued over the past decade. Misconceptions such as the rarity of complications of penetrating keratoplasty, lack of standardization of the DALK technique, and limited substantial benefit in visual and refractive outcomes are frequently cited as arguments against performing DALK. This brief review discusses the recent findings that refute these perceived barriers; describes contemporary techniques, tools, and modifications in the surgical approach; and evaluates the evidence regarding the clinical outcomes of DALK.

Ultrastructural Alterations of Grafted Corneal Buttons: The Anatomic Basis for Stromal Peeling Along a Natural Plane of Separation

PURPOSE

To examine the ultrastructure of the natural plane of separation in grafted corneas and evaluate the outcomes of stromal peeling.

DESIGN

Interventional case series.

METHODS

In this multicenter study, stromal peeling was attempted in 96 consecutive eyes with unsatisfactory vision following penetrating keratoplasty (PK) for keratoconus (n = 79), herpetic keratitis (n = 11), and granular dystrophy (n = 6). Stromal exchange was performed by (1) 9 mm partial-thickness trephination; (2) creation of a corneal flap across the PK wound; (3) opening of the stromal component of the PK wound until a smooth, translucent natural plane was identified; (4) severing the attachment of the PK scar; (5) stromal peeling along the identified plane; and (6) suturing of donor lamella. Grafted corneas from cases that mandated conversion to PK were processed for transmission electron microscopy.

RESULTS

The natural plane of separation was identified in all cases. Stromal exchange was successfully completed in 84 cases (87.5%). Snellen visual acuity ≥20/40 and ≥20/25 was reached in 93% and 72% of cases at 3 years (n = 49) and 86% and 62% at 4 years (n = 21) postoperatively. Mean endothelial cell loss at 1 year was 6.6% ± 9.5%. Stromal peeling occurred along a plane lined with a continuous layer of keratocytes separating pre-Descemet membrane (DM) stroma, DM, and endothelium from the anterior stroma. Pre-DM stroma was made of poorly organized lamellae containing widely spaced, randomly arranged collagen fibrils.

CONCLUSIONS

Ultrastructural alterations in the stromal microarchitecture of grafted corneas provide evidence of a natural plane of separation identified intraoperatively. Stromal peeling can be successfully performed in post-PK eyes with various stromal pathology.