Deep Anterior Lamellar Keratoplasty Over Penetrating Keratoplasty for Host Rim Thinning and Ectasia

Characterisation of ectasia after penetrating keratoplasty in keratoconus eyes using anterior segment optical coherence tomography

BACKGROUND/AIMS

Ectasia of the cornea can occur decades after penetrating keratoplasty (PK), especially in keratoconus eyes. The purpose of this study was to characterise ectasia after PK by morphological findings in anterior segment optical coherence tomography (AS-OCT).

METHODS

In this retrospective, single-centre case series, 50 eyes of 32 patients with a history of PK at an average of 25±10 years earlier were included. The eyes were classified either as ectatic (n=35) or as non-ectatic (n=15). The main parameters included central corneal thickness (CCT), lowest corneal thickness at the interface (LCTI), anterior chamber depth, graft-host interface angle at the thinnest point and host cornea-iris angle. Furthermore, steep and flat keratometry readings obtained by AS-OCT (CASIA-2, Tomey) and Scheimpflug tomography (Pentacam, Oculus) were assessed. OCT findings were correlated with clinical grading of ectasia.

RESULTS

There was a highly significant difference in LCTI, graft-host interface angle and anterior chamber depth (in pseudophakic eyes) between the groups. The ratio calculated by the quotient of LCTI divided by CCT was significantly lower in ectatic than non-ectatic eyes (p<0.001). In eyes with an LCTI/CCT ratio of ≤0.7, the OR for the occurrence of a clinical detectable ectasia was 2.4 (CI 1.5 to 3.7). Steep keratometry values were significantly higher in ectatic eyes.

CONCLUSION

AS-OCT is a helpful tool to recognise and quantify ectasia in post-PK eyes objectively.

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.

Post Penetrating Keratoplasty Ectasia: Incidence, Risk Factors, Clinical Features, and Treatment Options

BACKGROUND: Corneal transplantation in keratoconus (KC) patients is generally considered to be successful with a high grade of patient satisfaction. Long-term studies suggest a 6% to 11% probability of KC recurrence manifested by keratometric instability and progressive corneal ectasia. METHODS: We propose to review the frequency, risk factors for the development, and the surgical options for the correction of high irregular astigmatism due to late graft ectasia following penetrating keratoplasty (PK). RESULTS: Post-keratoplasty ectasia is characterized by increasing corneal steepening with myopic shift and high irregular astigmatism, developing years or decades after PK, mostly occurring in KC patients. Contact lenses may adequately improve the visual acuity; however, because these patients are often elderly and intolerant to hard contact lenses, ultimately a surgical correction is proposed to the patient. Compressive suture and corneal wedge resection may improve corneal astigmatism, but the outcomes are unpredictable and often temporary. For this reason, a larger PK graft is often proposed for surgical rehabilitation with the consequence of removing more of the recipient’s healthy endothelium and exposing the patient to a renewed immunogenic stimulus and short-term graft failure for endothelial decompensation. More recently, lamellar keratoplasty using various techniques has been proposed as an alternative to PK in order to maximize the visual outcomes and minimize the complications. CONCLUSIONS: Management of advanced corneal ectasia is a significant challenge for corneal surgeons. Many surgical approaches have been developed, so there is a large arsenal of surgical operations to correct post-PK ectasia. Among them, large-diameter anterior lamellar keratoplasty may be a viable, safer, and effective alternative to PK for the correction of post-keratoplasty ectasia.

Bowman's layer transplantation in advanced keratoconus; 18-months outcomes

PURPOSE

To assess the outcome of isolated Bowman's layer transplantation (BLT) in advanced keratoconus in the patients not suitable for ultra violet cross-linking and intra stromal corneal ring segments.

STUDY DESIGN

Nonrandomized Quasi-Experimental.

MATERIALS AND METHODS

Mid corneal stromal dissection followed by implantation of manually isolated bowman layer from a donor into the recipient stromal pocket was performed in the Department of Ophthalmology Khyber Teaching Hospital Peshawar from September 2018 to October 2018 and followed up over 18 months.

RESULTS

Eleven eyes of 11 patients, 8 male and 3 female within the age range of 7-28 years with progressive keratoconus went under BLT All keratometry values decreased after surgery. Mean anterior pre-operative SimK changed from 69.05 ± 10.85 D to 61.14 ± 6.23 D at 18 months post-operatively (P = 0.005). Means pre-operative Kmax value decreased from 77.24 ± 7.58 D to 71.07 ± 5.37 D at 18 months post-operatively (p = 0.060). The mean pre-operative posterior keratometry value changed from - 10.03 ± 0.88 to - 8.96 ± 1.06 D at 18 months post-operatively (P = 0.002). Mean pre-operative thinnest corneal thickness increased from 281.64 ± 196.86 um to 355.27 ± 19.17 um at 18th months post-operatively (P = 0.001). Pachymetry p-value pre-operative to 18 months (P = 0.001) was statistically significant. Mean anterior SimK at 6 months post-operatively, 60.55 ± 5.56D changed to 61.14 ± 6.23D at 18 months post-operatively (P = 0.000), Kmax at 6 months postoperative 71.60 ± 5.01 D changed to 71.07 ± 5.37 D at 18 months post-operatively (P = 0.008). Both anterior K values at 6 months and 18 months post-operatively showed less significant change, and the same was true for Kmax data at 6 months and 18 months post-operatively. P-values at 6 months to 18 months post-operatively for cornea back data remained (P = 0.001) unchanged. No complications were observed intra-operatively or post-operatively.

CONCLUSION

Bowman layer transplantation is a unique surgical treatment for advanced keratoconus to stabilize progressive ectasia with fewer complications avoiding the need for penetrating or deep anterior lamellar keratoplasty.

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.

Stromal peeling for deep anterior lamellar keratoplasty in post-penetrating keratoplasty eyes

Background/aims

To evaluate the clinical outcomes of deep anterior lamellar keratoplasty performed by stromal peeling in eyes that have previously undergone penetrating keratoplasty (PK) for keratoconus.

Methods

Standardised stromal exchange included (1) 9 mm trephination of the recipient bed outside the old PK wound, (2) creation of a partial anterior corneal flap through lamellar dissection across the PK wound, (3) opening the stromal component of the old PK wound using blunt-tipped Vannas scissors until a plane of separation is reached, (4) severing the attachment of the PK surgical scar from the recipient host, (5) peeling the stroma of the PK graft from the underlying tissue and (6) suturing the donor anterior corneal lamella prepared by microkeratome dissection (450 µm depth, 9 mm diameter). Main outcome measures were success rate, best spectacle-corrected visual acuity (BSCVA) and endothelial cell loss (ECL).

Results

Of 21 post-PK eyes, stromal exchange succeeded in all but three cases, which were converted to a two-piece mushroom PK. After complete suture removal, mean BSCVA significantly improved from 0.95±0.39 logMAR preoperatively to 0.23±0.17 logMAR (p<0.001). Mean ECL was 5.4±23.2%. Double anterior chamber formation occurred in eight cases (44%), which all resolved after a single re-bubbling.

Conclusion

In post-PK eyes, stromal exchange can be performed by means of simple peeling without deep anterior lamellar dissection of the previous PK graft. Large-diameter (9 mm) repeat keratoplasty through stromal peeling yields excellent visual outcomes and minimal ECL. Double anterior chamber formation may complicate the postoperative course, but prompt intervention allows successful management.

Corneal transplantation after failed grafts: Options and outcomes

Corneal transplantation is the most commonly performed human tissue transplantation procedure worldwide. Because of the large number of transplants, corneal graft failure has become one of the most common indications for corneal transplantation. The relatively recently developed lamellar transplant techniques have brought about specific potential complications leading to graft failure that may require different approaches to repeat transplantation other than penetrating keratoplasty. On the other hand, these new lamellar techniques also provide novel ways of rescuing failed penetrating grafts, with potential advantages over successive penetrating keratoplasties, such as reduced intraoperative risks and faster visual rehabilitation. We summarize the incidence and risk factors of graft failure for penetrating and lamellar (stromal and endothelial) corneal transplants and discuss the various surgical alternatives currently available to rescue such failed grafts, with a focus on the reported outcomes and limitations.

Treatment options for advanced keratoconus: A review

Traditionally, the mainstay of treatment for advanced keratoconus (KC) has been either penetrating or deep anterior lamellar keratoplasty (PK or DALK, respectively). The success of both operations, however, has been somewhat tempered by potential difficulties and complications, both intraoperatively and postoperatively. These include suture and wound-healing problems, progression of disease in the recipient rim, allograft reaction, and persistent irregular astigmatism. Taken together, these have been the inspiration for an ongoing search for less troublesome therapeutic alternatives. These include ultraviolet crosslinking and intracorneal ring segments, both of which were originally constrained in their indication exclusively to eyes with mild to moderate disease. More recently, Bowman layer transplantation has been introduced for reversing corneal ectasia in eyes with advanced KC, re-enabling comfortable contact lens wear and permitting PK and DALK to be postponed or avoided entirely. We offer a summary of the current and emerging treatment options for advanced KC, aiming to provide the corneal specialist useful information in selecting the optimal therapy for individual patients.