Deep anterior lamellar keratoplasty in the management of keratoconus

Incidence and Clinical Features of Immunologic Rejection After Deep Anterior Lamellar Keratoplasty

PURPOSE

The aim of this study was to investigate the incidence and clinical features of immunologic rejection after deep anterior lamellar keratoplasty (DALK).

METHODS

This study included 411 patients (464 eyes, median age [interquartile range; IQR] 55.8 years [36.1-69.5]) who underwent DALK at Tokyo Dental College between June 1997 and 2021. Of 411 patients, 24 (24 eyes [5.2%], 51.9 years [IQR 31.6-65.4]) developed immunologic rejection. We characterized the clinical features, risk factors associated with immunologic rejection, and prognosis.

RESULTS

The interval between DALK and immunologic rejection was 14.5 (range, 5-78) months. Immunologic rejection occurred after cessation/reduction of topical steroid in 9 (47.4%) and suture removal in 4 eyes (21.1%). The postoperative duration of topical steroid use in eyes with immunologic rejection was significantly shorter (10.0 months, [IQR 6.0-14.0]) than those without immunologic rejection (28.3 [IQR 15.8-42.7], P = 0.001). Immunologic rejection manifested as stromal edema in 19 (100.0%), ciliary hyperemia in 17 (89.5%), keratic precipitates in 13 (68.4%), epithelial edema in 13 (68.4%), infiltration in 9 (47.4%), corneal opacity in 4 (21.1%), and Descemet membrane detachment in 2 eyes (10.5%). After treatment, corneal clarity was restored in 17 eyes (89.5%); however, immunologic rejection led to corneal endothelial decompensation in 2 eyes (10.5%). Endothelial cell density decreased from 1795.7 ± 722.6 to 1651.6 ± 655.6 cells/mm 2 after immunologic rejection ( P = 0.074).

CONCLUSIONS

Post-DALK immunologic rejection was associated with specific clinical triggers such as reduction/cessation of topical steroids or suture removal.

Replace or Regenerate? Diverse Approaches to Biomaterials for Treating Corneal Lesions

The inner structures of the eye are protected by the cornea, which is a transparent membrane exposed to the external environment and subjected to the risk of lesions and diseases, sometimes resulting in impaired vision and blindness. Several eye pathologies can be treated with a keratoplasty, a surgical procedure aimed at replacing the cornea with tissues from human donors. Even though the success rate is high (up to 90% for the first graft in low-risk patients at 5-year follow-up), this approach is limited by the insufficient number of donors and several clinically relevant drawbacks. Alternatively, keratoprosthesis can be applied in an attempt to restore minimal functions of the cornea: For this reason, it is used only for high-risk patients. Recently, many biomaterials of both natural and synthetic origin have been developed as corneal substitutes to restore and replace diseased or injured corneas in low-risk patients. After illustrating the traditional clinical approaches, the present paper aims to review the most innovative solutions that have been recently proposed to regenerate the cornea, avoiding the use of donor tissues. Finally, innovative approaches to biological tissue 3D printing and xenotransplantation will be mentioned.

Bubbling With Confidence: A Study of Numerous Deep Anterior Lamellar Keratoplasty Cases Using Anwar's Big Bubble Technique

PURPOSE

This study aims to assess the postoperative results, variability, and complications of a hundred deep anterior lamellar keratoplasty cases. Study design and duration: This is an observational study. The study was conducted at Pak International Medical College (PIMC) for a duration of four years (January 2019-January 2023).

METHODOLOGY

Our study collected information on a hundred cases of deep anterior lamellar keratoplasty (DALK) utilizing Anwar's big bubble technique, consisting of patients with keratoconus, superficial corneal scars, and macular dystrophy. Consenting patients had their pre and postoperative visual acuities and keratometry readings recorded. Overall success and complications were recorded and compared with the present literature.

RESULTS

Big bubble formation was achieved in 87% (n = 87) eyes and not achieved in 13% (n=13). There was a significant reduction in keratometry values after the procedures as well as improved vision in all patients, with 84% reporting significant improvement. Descemet membrane exposure was achieved in 91% (n=91). Complications included the failure of Anwar's big bubble formation in 13% (n=13) patients and the failure to expose Descemet's in nine patients (9%).

CONCLUSION

DALK using the big bubble technique is a safe and effective procedure in patients with corneal diseases who have a healthy Descemet membrane and endothelium.

Management and prevention of corneal graft rejection

The management of an episode of corneal graft rejection (CGR) is primarily by corticosteroids. Immunomodulators are useful for long-term immunosuppression and in dealing with cases of high-risk (HR) corneal grafts. The classical signs of CGR following penetrating keratoplasty (PKP) include rejection line, anterior chamber (AC) reaction, and graft edema. However, these signs may be absent or subtle in cases of endothelial keratoplasty (EK). Prevention of an episode of graft rejection is of utmost importance as it can reduce the need for donor cornea significantly. In our previous article (IJO_2866_22), we had discussed about the immunopathogenesis of CGR. In this review article, we aim to discuss the various clinical aspects and management of CGR.

Deep Anterior Lamellar Keratoplasty: Can All Ruptures Be Fixed?

PURPOSE

The aim of this study was to report our experience in managing different types of Descemet membrane (DM) ruptures during deep anterior lamellar keratoplasty (DALK).

METHODS

This study was a retrospective, consecutive, interventional case series of 1573 DALK procedures conducted on 1244 patients, performed between 2002 and 2017. Inclusion criteria consisted of a minimum of 24-month follow-up. DM rupture incidence, location, and surgical approach for repair were recorded. Postoperative measures were investigated only in eyes that experienced DM ruptures and included best spectacle-corrected visual acuity, endothelial cell loss, double anterior chamber, pupillary block, need for rebubbling, graft clarity, and rejection episodes.

RESULTS

One thousand four hundred forty-three eyes met the inclusion criteria. DM ruptures occurred in 119 eyes (8.25%). Seventy-eight percent of DM ruptures were microruptures (≤2 mm), and they occurred more frequently during manual DALK cases. Macroruptures were less frequent (22%), and they occurred more frequently during subtotal and total anterior lamellar keratoplasty (STALK-TALK) cases. In general, DM ruptures mainly occurred in the peripheral cornea (95% of cases). One hundred (84%) of the 119 ruptures resolved by the first postoperative day. Nineteen cases (16%) developed double anterior chamber; all resolved by using different strategies. No intraoperative penetrating keratoplasty conversion was recorded. Pupillary block occurred in 7 cases (5.9%), but no Urrets-Zavalia syndrome was observed. The average postoperative endothelial cell loss was 410 ± 39 cells/mm 2 (19%) at 1-year follow-up, and there was no significant difference between cases requiring a rebubbling and cases that did not ( P = 0.896). All grafts but one were clear at the last follow-up. Graft failure from endothelial decompensation occurred in this lone case (0.8%).

CONCLUSIONS

It is worth trying to repair all DM ruptures in DALK, and immediate penetrating keratoplasty conversion should be avoided. Understanding the physiomechanical mechanisms in DALK allows to correctly choose a proper rescue strategy to successfully repair DM ruptures.

Femtosecond Laser-Assisted Big-Bubble Deep Anterior Lamellar Keratoplasty

Purpose

To determine whether type 1 big-bubble (BB) formation is influenced by the sequence of incisions created with the Victus femtosecond laser (FSL) enabled with software version 3.4 (SV 3.4) during deep anterior lamellar keratoplasty (DALK).

Materials and Methods

Consecutive FSL-assisted DALK BB procedures were performed on 20 human donor corneas: 10 shaped by tunnel incision followed by lamellar incision (tunnel-lamellar group, TL) and 10 in the reverse order (lamellar-tunnel group, LT). The BB type was assessed by evaluating dynamic air movement during air inflation; bubble diameter and floor thickness were measured by anterior segment optical coherence tomography.

Results

Overall, a type 1 BB formed in 85% of eyes: 100% in the TL group and 70% in the LT group. In the LT group, a type 2 BB formed in 2 corneas and one cornea was perforated during cannula insertion. Type 1 BB was achieved after one attempt in 90% of eyes in the TL group and in 57% in the LT group.

Conclusion

Shaping the tunnel before rather than after lamellar incision may be more effective for obtaining a type 1 BB by air injection.

Total or subtotal full thickness recipient bed cut to repair donor-recipient curvature disparity in cases of DM rupture with manual DALK

PURPOSE

To report how to manage a specific type of Descemet's membrane (DM) rupture during manual DALK with a concurrent donor-recipient disparity of curvature.

METHODS

Case report of two patients that had DM rupture during manual DALK with a concurrent donor-recipient disparity of curvature; the recipient bed was flatter (post-infectious scar, case 1) and steeper (keratoglobus, case 2) than the donor. Preoperative diagnosis, clinical exam, and best spectacle correct visual acuity (BSCVA) have been reported. A subtotal full-thickness circular cut of the recipient bed was performed to resolve a persistent double AC in case 1 (recipient flatter than donor). A total full-thickness circular cut of the recipient bed, creating a graft made by a DALK allograft and a "DSEK autograft," was performed to avoid a refractory double AC in case 2 (recipient steeper than donor). Evaluated outcomes included postoperative BSCVA, endothelial cell count (ECC), graft clarity, rejection, and presence/absence of double AC.

RESULTS

Surgery was successful in resolving/avoiding double AC. VA improved in both cases. No episodes of rejection were recorded. Graft remained clear at the last follow-up (6 years for case 1 and 4 years for case 2).

CONCLUSION

The existence of a donor-recipient curvature disparity should be investigated as a possible underlying mechanism of refractory double AC. Total or subtotal full thickness recipient bed cut may be considered to repair donor-recipient curvature disparity in cases of DM rupture occurring during manual DALK. Repairing the DM rupture and avoiding a conversion to PK in high-risk transplant cases are crucial.

Femtosecond Laser-Assisted Small Incision Sutureless Intrastromal Lamellar Keratoplasty (SILK) for Corneal Transplantation in Keratoconus

PURPOSE

To describe a femtosecond laser-assisted small incision sutureless intrastromal lamellar keratoplasty in an eye with severe keratoconus and report on the outcome with a 1-year follow-up.

METHODS

A 20-year-old man with a history of keratoconus presented for evaluation at the Tilganga Institute of Ophthalmology, Kathmandu, Nepal. The patient had previously undergone a deep anterior lamellar keratoplasty in the left eye. Examination of the right eye revealed an uncorrected distance visual acuity (UDVA) of counting fingers with a manifest refraction of -5.00 -3.50 × 170, giving a corrected distance visual acuity (CDVA) of 20/80. Thinnest pachymetry was 425 µm and progression of both anterior and posterior corneal elevation tomography and maximum keratometry was noted compared to examination 2 years prior. The VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany) was used to prepare the donor and recipient cornea. The donor graft was inserted into the recipient through the 3-mm small incision. No sutures were applied.

RESULTS

At 2 weeks postoperatively, UDVA was 20/50 with a manifest refraction of -1.00 -5.00 × 145 (20/32). One year postoperatively, UDVA was 20/80 with a manifest refraction of -2.50 -3.50 × 125 (20/40^-2), with the maximum keratometry decreasing from 64.08 to 56.74 diopters.

CONCLUSIONS

This femtosecond laser-assisted sutureless intrastromal corneal transplantation technique may provide an option to improve the quality of vision for some patients with keratoconus, affording a simpler postoperative follow-up course compared to traditional anterior lamellar or full-thickness corneal transplantation. [J Refract Surg. 2019;35(10):663-671.].

Outcome of therapeutic deep anterior lamellar keratoplasty in advanced Acanthamoeba keratitis

Purpose

To report and analyze the outcomes of therapeutic deep anterior lamellar keratoplasty (DALK) in patients with advanced Acanthamoeba keratitis (AK).

Methods

Medical records of microbiologically confirmed AK, underwent DALK from 2004 to 2017, were reviewed and the data related to early and late outcome including complications were retrieved. Outcome of cases with largest diameter of infiltrate ≥8 mm at the time of surgery (advanced keratitis) were analyzed and compared with those with less severe keratitis (infiltrate size less than 8 mm).

Results

Out of 23 patients of AK in whom DALK was performed, ten (43.4%) patients had advanced keratitis. Mean age of these patients was 38.7 ± 8.6 years (range, 25 to 56). Median visual acuity at presentation was 2.78 (IQR, 1.79-3.0) that improved to 1.79 (IQR, 0.70-2.78) postoperatively. Early complications included recurrence of AK in 2 (20%), Descemet's membrane detachment in 5 (50%), and persistent epithelial defect in 3 (30%) cases. Overall, 6 (60%) grafts failed, whereas 4 (40%) patients had clear graft at their last follow-up. Median follow-up of these cases was 5 months (IQR, 1.4-11.4). One graft developed stromal rejection, which resolved with increased dose of corticosteroids. In comparison, DALK performed for less severe keratitis (N = 13) had 1 (7.6%) recurrence and 2 (15.8%) grafts failure (OR, 8.25). The probability of one-year graft survival and eradication of infection was 32% and 74.1%, respectively, in advanced cases compared to 91.6% and 83.9% in less severe cases.

Conclusion

Outcome of DALK in advanced Acanthamoeba keratitis is less favorable compared to those carried out for less severe keratitis cases.

The correlation between keratoconus and eye rubbing: a review

Keratoconus is a non-inflammatory disorder which is gradual in development; corneal thinning and ectatic protrusion characterizes it. Keratoconus prevalence varies between different regions depending on several factors that affecting its prevalence. There are risk factors for developing keratoconus such as demographic and environmental factors. It was suggested that eye rubbing was associated with the development of keratoconus. The main aim of this review was to summarize the literature data about keratoconus and to identify the role of eye-rubbing in the aetiology of the disease. A number of 24 articles was reviewed through the PubMed, Google Scholar and Research Gates. There are many keywords used such as keratoconus, aetiology of keratoconus, eye rubbing, keratoconus prevalence, keratoconus and eye rubbing correlation. We concluded that eye rubbing causes the thinning of keratocyte, and the degree of effect of eye rubbing depends on the period and force of performing eye rubbing. It is recommended to avoid eye rubbing to prevent keratoconus, this can be achieved by avoiding itching and treating dryness of the eye and avoiding wearing eye lenses.

Immunologic Stromal Rejection After Deep Anterior Lamellar Keratoplasty With Grafts of a Larger Size (9 mm) for Various Stromal Diseases

PURPOSE

To evaluate the rate and outcomes of immunologic stromal rejection occurring after large deep anterior lamellar keratoplasty (DALK) and the effect of the underlying disease on the cumulative probability of rejection.

METHODS

This was a retrospective chart review of all eyes that underwent a 9-mm DALK at Ospedali Privati Forlì (Forlì, Italy). On the basis of preoperative diagnosis, eyes were assigned to group 1: keratoconus, group 2: stromal disease with a low risk for rejection, or group 3: stromal disease with a high risk for rejection. The cumulative probability of experiencing a rejection episode over time was assessed by Kaplan-Meier analysis and was compared among the 3 groups using the log-rank test. Values of corrected distance visual acuity, central corneal thickness, and endothelial cell density before and 6 months after rejection were compared.

RESULTS

Twenty of 377 eyes (5.3%) experienced an episode of stromal rejection [17/265 (6.4%) in group 1, 2/71 (2.8%) in group 2, and 1/41 (2.4%) in group 3]. The mean time interval between DALK and the rejection onset was 11.8 months (range 1-24). The cumulative probability of rejection episodes did not differ significantly among the 3 groups. All episodes resolved within 6 months after the onset, with no significant differences between prerejection and 6-month postrejection values of corrected distance visual acuity, central corneal thickness, and endothelial cell density.

CONCLUSIONS

The rate of immunologic stromal rejection after large 9-mm DALK is within the range reported in the literature for conventional DALK, regardless of the indication for surgery.

Anti-CD40 antibody-mediated costimulation blockade promotes long-term survival of deep-lamellar porcine corneal grafts in non-human primates

BACKGROUND

Corneal xenotransplantation is an effective solution for the shortage of human donor corneas, and the porcine cornea may be a suitable candidate for the donor cornea because of its optical similarity with humans. However, it is necessary to administer additional immunosuppressants to overcome antigenic differences. We aimed to investigate the feasibility of porcine corneas with anti-CD40 antibody-mediated costimulation blockade in a clinically applicable pig-to-non-human primate corneal xenotransplantation model.

METHODS

Five Chinese rhesus macaques underwent deep-lamellar corneal transplantation using clinically acceptable sized (7.5 mm diameter) porcine corneal grafts. The anti-CD40 antibody was intravenously administered on a programmed schedule. Graft survival, central corneal thickness, and intraocular pressure were evaluated. Changes in effector and memory T and B cell subsets and anti-αGal and donor-specific antibodies were investigated in the blood, and the changes in complement levels in the aqueous humor and blood were evaluated. Memory cell profiles in the anti-CD40 antibody-treated group were compared with those from the anti-CD154 antibody-treated group or rejected controls presented in our previous report. The changes in anti-αGal, non-αGal, and donor-specific antibodies after 6 months were compared with baseline values.

RESULTS

Anti-CD40 antibody-mediated costimulation blockade resulted in the successful survival of xenocorneal grafts (>389, >382, >236, >201, and >61 days), with 80% reaching 6 months of survival. Injection of anti-CD40 antibody considerably reduced the infiltration of inflammatory cells into the grafts and significantly blocked the complement response in the aqueous humor (P=.0159, Mann-Whitney U test). Systemic expansion of central or effector memory T cells was abrogated in the anti-CD40 antibody-treated primates compared with those in the rejected controls (P<.05, Mann-Whitney U test) or those in the anti-CD154 antibody-treated primates (P>.05, Mann-Whitney U test). The levels of anti-αGal, non-αGal, and donor-specific antibodies at 6 months were not significantly increased compared with baseline levels (P>.05, Wilcoxon signed rank test).

CONCLUSIONS

An anti-CD40 antibody-mediated blockade appears to be effective immunosuppressive approach for porcine corneal deep-lamellar xenotransplantation in primates.

Evidence against ZNF469 being causative for keratoconus in Polish patients

PURPOSE

Keratoconus (KTCN) is a degenerative disorder characterized by stromal thinning and protrusion of the cornea, resulting in severe impairment of visual function. A recent study proposed that rare heterozygous mutations in ZNF469 determine KTCN aetiology.

METHODS

To investigate the contribution of ZNF469 to KTCN, we Sanger sequenced ZNF469 in 42 unrelated Polish patients with KTCN and 49 Polish individuals with high myopia (HM) and compared the results with whole-exome sequencing (WES) data performed in 268 Polish individuals without ocular abnormalities.

RESULTS

The average number of ZNF469 non-synonymous variants was 16.31 and 16.0 for individuals with KTCN and HM, respectively (p = 0.3724). All identified variants were previously reported. Alternative allele frequency (AAF) was determined based on the WES results. Among missense variants, only one (rs528085780) has AAF ≤ 0.001 and was identified in one patient with sporadic KTCN. However, the resulting Arg1864Lys substitution was not predicted to be deleterious.

CONCLUSION

In summary, we have not found a significant enrichment of sequence variants in ZNF469 in Polish patients with KTCN. High prevalence of ZNF469 variants identified in our KTCN group is typical for a common genetic variation observed in general population. Our findings indicate that variation in ZNF469 is not responsible for KTCN and other genetic variants are involved in the development and progression of this disease in Polish patients.

Keratoconus: tissue engineering and biomaterials

Keratoconus (KC) is a bilateral, asymmetric, corneal disorder that is characterized by progressive thinning, steepening, and potential scarring. The prevalence of KC is stated to be 1 in 2000 persons worldwide; however, numbers vary depending on size of the study and regions. KC appears more often in South Asian, Eastern Mediterranean, and North African populations. The cause remains unknown, although a variety of factors have been considered. Genetics, cellular, and mechanical changes have all been reported; however, most of these studies have proven inconclusive. Clearly, the major problem here, like with any other ocular disease, is quality of life and the threat of vision loss. While most KC cases progress until the third or fourth decade, it varies between individuals. Patients may experience periods of several months with significant changes followed by months or years of no change, followed by another period of rapid changes. Despite the major advancements, it is still uncertain how to treat KC at early stages and prevent vision impairment. There are currently limited tissue engineering techniques and/or "smart" biomaterials that can help arrest the progression of KC. This review will focus on current treatments and how biomaterials may hold promise for the future.