Deep Anterior Lamellar Keratoplasty in Keratoconic Patients with versus without Vernal Keratoconjunctivitis

Suture-related complications after deep anterior lamellar keratoplasty for keratoconus

PURPOSE

The purpose of this study is to determine the incidence of suture-related complications, their risk factors, and effects on the clinical outcomes after deep anterior lamellar keratoplasty (DALK) for keratoconus.

METHODS

In this retrospective, comparative, interventional study, the records of consecutive patients with keratoconus who underwent DALK were reviewed for suture-related complications. Univariate analyses were used to identify risk factors for suture complications. We compared groups with and without suture-related complications to evaluate the effects of these complications on clinical outcomes after DALK.

RESULTS

Of the 633 DALKs, 438 eyes (69.2%) developed suture complications including loose sutures (32.7%), spontaneous suture rupture (30%), sterile suture abscesses (22.8%), suture tract vascularization (16.4%), suture erosion (10.3%), and suture cheese wiring (6.8%). Vernal keratoconjunctivitis increased the incidence of sterile suture infiltration, premature suture loosening, and suture tract vascularization. Loose suture was observed more commonly in larger graft size, while spontaneous suture rupture was associated with late suture removal. There was no statistically significant difference in postoperative outcomes including visual acuity, refraction, graft rejection, and failure in eyes with and without suture complications. However, suture-related complications were directly associated with sight-threatening ocular morbidities, including graft rejection (39 eyes), ulcer (1 eye), and failure (2 eyes).

CONCLUSION

Suture-related complications frequently occurred after DALK for keratoconus. Ocular surface inflammation, large grafts, and late suture removal increased the risk of suture-related complications. While these complications had no negative impact on clinical outcomes in the majority of cases, some of them led to sight-threatening morbidity, underlining the importance of early diagnosis and treatment.

Refractive surgery after deep anterior lamellar keratoplasty: a review of the literature

PURPOSE

The main objective of this work is to present an updated review of the different surgical procedures for the correction of residual refractive errors following deep anterior lamellar keratoplasty (DALK) surgery.

METHODS

A review of the literature was conducted using PubMed, Web of Science, and Scopus databases. The search was conducted in January 2022 and was limited to articles published in peer-reviewed journals. The information extracted from each publication included sample size, mean follow-up time, pre- and post-operative uncorrected (UDVA) and corrected distance visual acuity (CDVA), pre- and post-operative refraction and spherical equivalent (SE), safety and efficacy indexes and complications.

RESULTS

Residual ametropias, mainly high astigmatism and myopia, and the resulting anisometropia are likely to occur following DALK. They become a limiting factor and may lead to unsatisfactory visual restoration, therefore affecting patients' quality of vision and life. Alternative surgical interventions may be required to treat this residual ametropia, such as corneal refractive surgery or intraocular lens implantation. A total of 47 relevant articles were studied in detail. Different refractive surgery techniques have been shown to be effective and safe for the correction of ametropia following the DALK procedure and to improve the patient's quality of vision, although more research is needed to confirm long-term results.

CONCLUSION

The final refractive technique will depend on different factors, such as the amount of ametropia, the condition of the cornea or the patient's individual needs, economics, and occupational demands.

Update on Pediatric Corneal Diseases and Keratoplasty

Managing pediatric corneal disorders is challenging as the prognosis of pediatric keratoplasty depends on several factors. Advancements in the genetic basis of congenital corneal diseases and investigations in congenital corneal conditions provide a better understanding of pediatric corneal conditions. Surgeons performing keratoplasty in children now have a choice of various techniques. Evolving surgical techniques of anterior lamellar and endothelial keratoplasties has expanded the management interventions in these pediatric corneal morbidity conditions; however, considerable concerns still exist in association with corneal transplantation in infants and children. Outcomes in pediatric keratoplasty depend upon the preoperative indications, the timing of surgical intervention, intraoperative and postoperative factors including the patient/care givers' compliance. Factors such as low scleral rigidity, higher rate of graft failure, need for frequent examinations under anesthesia, and difficulty in optimal visual acuity assessment still remain a considerable challenge in pediatric scenarios. In children, deprivation amblyopia as a result of the corneal opacification can adversely affect visual development, causing dense amblyopia. Outcomes to surgical interventions for management of corneal opacification in children is further compromised by the pre-existing amblyopia apart from the concerns of refractive outcome of the graft. Graft rejection, graft infection, amblyopia, and glaucoma continue to be serious concerns. In recent years both anterior and posterior lamellar keratoplasty techniques are being increasingly performed in pediatric eyes, which offer advantages in the form of lower risk of graft rejection. The timing of surgery, careful case selection, cautious intraoperative approach, and optimal postoperative management can improve the anatomical and functional outcome in difficult cases.

Vernal keratoconjunctivitis and keratoconus

PURPOSE OF REVIEW

Vernal keratoconjunctivitis (VKC) is a severe allergic inflammatory disease affecting the conjunctiva in children and young adults. Keratoconus (KC) is a progressive corneal disease characterized by thinning of the corneal stroma, increased and asymmetric corneal curvature, with a potential for significant visual deterioration and is one of the most common corneal complications of VKC. We aimed to review the association of these two diseases, with focus on the mechanisms, prevalence, natural history and treatment strategies of KC associated with VKC.

RECENT FINDINGS

KC is a common complication of VKC. KC prevalence can be as high as 26.8% among VKC patients, whereas abnormal corneal topography may appear in up to 71% of them. It is more severe and progresses faster in the setting of VKC (P < 0.05), with remarkable visual deterioration and with an increased need for keratoplasty. Crosslinking treatment and corneal transplantation appear to be as effective for KC patients with VKC as compared to the patients without VKC. However, postoperative complications are higher in patients with VKC and demand close monitoring, tight control of local inflammation and prompt awareness with consequent restrain of eye rubbing.

SUMMARY

Patients with VKC should be closely monitored for KC. Prompt recognition of VKC and KC allows tight control of KC pathogenesis mechanisms, timely management of KC progression and preservation of vision and quality of life of young patients.

Penetrating Keratoplasty Versus Deep Anterior Lamellar Keratoplasty in Children and Adolescents With Keratoconus

PURPOSE

To compare the outcomes of penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK) for pediatric keratoconus.

DESIGN

Retrospective comparative interventional case series.

METHODS

This study included consecutive pediatric keratoconus cases (≤18 years of age) who received PK (n=45) or DALK (n=54) in 2 different time periods. Postoperative best spectacle-corrected visual acuity (BSCVA), refraction, and complications were compared between the study groups.

RESULTS

The mean follow-up was 83.3±46.1 and 63.3±45.6 months in the PK and DALK groups, respectively (P = .10). Postoperatively, BSCVA was 0.20±0.19 logMAR in the PK group and 0.26±0.19 logMAR in the DALK group (P = .11), with a BSCVA of ≥20/40 in 91.1% and 83.3% of eyes, respectively (P = .25). Two groups were comparable regarding postoperative refractive outcomes. Graft epitheliopathy and suture-associated complications were more commonly encountered after DALK, which was attributable to the effect of low-quality grafts on the clinical outcomes of DALK. Ten PK eyes (22.2%) and 9 DALK eyes (16.7%) experienced at least 1 episode of graft rejection within 5 years of corneal transplantation (P = .49). Rejection was reversible in 93.1% and 100% of episodes in the PK and DALK groups, respectively (P = .63). At the postoperative year 5, 95.6% of grafts in the PK group and 98.2% in the DALK group remained clear (P = .45).

CONCLUSION

No significant difference was observed in the outcomes between PK and DALK in pediatric keratoconus. Low-quality donor tissues in DALK increased the incidence of graft epithelial problems and suture-related complications as compared to PK.

Comparison of penetrating keratoplasty and deep anterior lamellar keratoplasty in keratoconus eyes with vernal keratoconjunctivitis

Purpose:

The purpose of the study is to compare outcomes after penetrating keratoplasty (PK) against deep anterior lamellar keratoplasty (DALK) for keratoconus in patients with vernal keratoconjunctivitis (VKC).

Methods:

Keratoconic patients with VKC who received PK (n = 55, group 1) or DALK (n = 62, group 2) were retrospectively enrolled. The Student’s t test, Mann–Whitney test, Fisher’s exact test, chi-square test, and Kaplan–Meier survival curve were used to compare outcomes between the groups.

Results:

The follow-up period was 59.4 ± 44.1 and 62.4 ± 38.9 months in groups 1 and 2, respectively (p = 0.70). Postoperative best spectacle-corrected visual acuity was 0.24 ± 0.18 and 0.29 ± 0.19 logMAR, respectively (p = 0.13). Graft rejection occurred in 34.6% and 25.8% of eyes in groups 1 and 2, respectively (p = 0.30). Groups 1 and 2 were comparable in the rates of cataract (3.6% and 12.9%, respectively, p = 0.07) and high intraocular pressure (3.6% and 8.1%, respectively, p = 0.31). Compared with the eyes with inactive VKC, PK eyes that experienced postoperative disease reactivation had a higher rate of suture abscesses (10.9% versus 50.0%, respectively, p = 0.01) and suture-tract vascularization (6.5% versus 33.3%, respectively, p = 0.03). Similarly, disease reactivation significantly increased suture abscesses from 27.3% to 51.7% (p = 0.03) and suture-tract vascularization from 18.2% to 49.6% (p = 0.005) in the DALK group. The graft survival rates were 95.3% in group 1 and 87.9% in group 2 at the 4-year follow-up, with mean durations of 14.4 and 11.1 months, respectively (p = 0.20).

Conclusion:

The results indicate no difference in outcomes between PK and DALK for keratoconus in patients with VKC. Postoperative VKC reactivation increased the rate of suture-related problems after both techniques of keratoplasty.

Corneal neovascularisation following deep anterior lamellar keratoplasty for corneal ectasia: incidence, timing and risk factors

BACKGROUND

The purpose of this study was to evaluate the incidence, timing and risk factors of corneal neovascularisation (NV) after deep anterior lamellar keratoplasty (DALK) for corneal ectasia.

METHODS

This study included 616 eyes who underwent DALK between 2012 and 2020 in two tertiary referral centres. In one centre topical corticosteroids were discontinued after complete suture removal 1 year after surgery, whereas in the other they were discontinued 3-4 months after surgery. The presence and severity of corneal NV was ascertained based on slit lamp photographs. Potential risk factors for corneal NV were evaluated using the Cox proportional hazards model.

RESULTS

The cumulative incidence of corneal NV was 8.7% at 1 year after surgery and 13.2% at 5 years. Mean time interval from surgery to development of corneal NV was 12.8±16.2 months, with 68.9% of cases occurring before complete suture removal. Early discontinuation of topical steroids, older age and ocular allergy were associated with an increased risk of developing corneal NV (respectively, HR=2.625, HR=1.019, HR=3.726, all p<0.05).

CONCLUSIONS

The risk of corneal NV is higher in the first year following DALK. Early discontinuation of topical steroids, ocular allergy and older age are significant predictors of corneal NV.

The Human Tissue-Engineered Cornea (hTEC): Recent Progress

Each day, about 2000 U.S. workers have a job-related eye injury requiring medical treatment. Corneal diseases are the fifth cause of blindness worldwide. Most of these diseases can be cured using one form or another of corneal transplantation, which is the most successful transplantation in humans. In 2012, it was estimated that 12.7 million people were waiting for a corneal transplantation worldwide. Unfortunately, only 1 in 70 patients received a corneal graft that same year. In order to provide alternatives to the shortage of graftable corneas, considerable progress has been achieved in the development of living corneal substitutes produced by tissue engineering and designed to mimic their in vivo counterpart in terms of cell phenotype and tissue architecture. Most of these substitutes use synthetic biomaterials combined with immortalized cells, which makes them dissimilar from the native cornea. However, studies have emerged that describe the production of tridimensional (3D) tissue-engineered corneas using untransformed human corneal epithelial cells grown on a totally natural stroma synthesized by living corneal fibroblasts, that also show appropriate histology and expression of both extracellular matrix (ECM) components and integrins. This review highlights contributions from laboratories working on the production of human tissue-engineered corneas (hTECs) as future substitutes for grafting purposes. It overviews alternative models to the grafting of cadaveric corneas where cell organization is provided by the substrate, and then focuses on their 3D counterparts that are closer to the native human corneal architecture because of their tissue development and cell arrangement properties. These completely biological hTECs are therefore very promising as models that may help understand many aspects of the molecular and cellular mechanistic response of the cornea toward different types of diseases or wounds, as well as assist in the development of novel drugs that might be promising for therapeutic purposes.

Management of corneal complications in vernal keratoconjunctivitis: A review

Vernal keratoconjunctivitis (VKC) is a chronic, bilateral, allergic conjunctivitis with episodes of acute exacerbations. Although VKC has a self-limiting course, chronic recurrent inflammation can cause long-term visual impairment due to corneal complications including shield ulcers, infectious keratitis, keratoconus, corneal opacities, and limbal stem cell deficiency. The initial step in the management of corneal involvement is medical treatment of the acute stage of VKC and prevention of recurrences. Giant papillae not responding to medical treatment can be removed surgically in the case of corneal involvement. Shield ulcer with no inflammatory plaque usually heals with appropriate medical therapy. For shield ulcer with inflammatory plaque, however, surgical debridement with or without amniotic membrane transplantation might be necessary. Keratoconus may develop in chronic and severe VKC. An annual evaluation of these patients with corneal topography and/or tomography is essential for early detection of keratoconus and its timely management that includes collagen cross-linking and intrastromal corneal ring segment implantation. Corneal transplantation may be required in the advanced stage of keratoconus. Both penetrating keratoplasty and deep anterior lamellar keratoplasty can result in excellent visual outcomes in keratoconic eyes with concomitant VKC. Appropriate management of inflammation in the perioperative period is crucial for achieving successful outcomes after corneal transplantation. Limbal stem cell deficiency, a rare complication of long-standing and severe VKC, might be treated with living-related conjunctival limbal allograft.

Approaches toward enhancing survival probability following deep anterior lamellar keratoplasty

The greatest advantage of deep anterior lamellar keratoplasty over full-thickness corneal transplantation is the elimination of graft failure caused by endothelial rejection. Despite this advantage, a deep anterior lamellar keratoplasty graft can fail because of several factors, such as complications related to the donor-recipient interface, graft epithelial abnormalities, graft vascularization, stromal graft rejection, and recurrence of herpetic keratitis. Increased deep anterior lamellar keratoplasty graft survival is mainly built upon optimization of the ocular surface to provide a hospitable environment for the graft. Any predisposing factors for graft epithelial abnormalities, corneal neovascularization, and preexisting vernal keratoconjunctivitis should be identified and treated preoperatively. Prompt recognition and appropriate treatment of interface-related complications and stromal graft rejection usually result in good anatomic outcomes, with no detrimental effects on vision.

Graft rejection-like reactions in the early postoperative period after deep anterior lamellar keratoplasty for keratoconus: a retrospective study

Background

Deep anterior lamellar keratoplasty (DALK) is indicated to correct high astigmatism in patients with keratoconus (KC) and no evidence of Descemet’s membrane rupture. However, some patients with KC experience graft rejection-like inflammatory reactions within 2 months (usually in the first week) after DALK. The aim of this study was to identify the characteristics and influencing factors of these reactions by reviewing the records of patients who underwent DALK or penetrating keratoplasty (PKP) for KC or other corneal problems.

Methods

We retrospectively reviewed the medical records of patients who underwent DALK for KC (DALK/KC), PKP for KC (PKP/KC), or DALK for other corneal problems (DALK/non-KC) at Ban Buntane Hotokukai Hospital between January 2006 and December 2015 and who were followed for more than 1 year. We collected data on the characteristics and incidence of severe inflammatory graft reactions in the early postoperative phase (ie, within 2 months after keratoplasty) and visual outcomes after these inflammatory reactions.

Results

Postoperative inflammatory reactions characterized by persistent epithelial defects, loose suture with infiltration, and vessel invasion occurred in seven of eleven DALK/KC patients, three of 50 DALK/non-KC patients, and none of five PKP/KC patients. These reactions were nonresponsive to topical steroids, and suture removal was required. Although a clear corneal graft in the pupillary area was obtained and best-corrected visual acuity was good after the resolution of inflammation, a risk of corneal astigmatism remained.

Conclusion

The incidence of these reactions in the early postoperative period is high after DALK for KC. These reactions do not respond well to topical steroids, and suture removal may be required, which may cause high astigmatism after the inflammation subsides. Lamellar keratoplasty should be considered carefully for patients with KC.

Pentacam HR Indices Variation in Normal Corneas with Different Corneal Thickness

Purpose

To evaluate the effect of variable corneal thickness on Pentacam HR diagnostic indices in normal corneas.

Methods

Retrospective study was conducted at Al Watany Eye Hospital, Cairo, Egypt. Consecutive 160 eyes of young myopic subjects without KC were evaluated using Pentacam HR (WaveLight Allegro Oculyzer II, Erlangen, Germany). The elevation- and thickness-based indices were recorded. Enrolled corneas were categorized into three groups according to TCT quartiles; group 1 (39 eyes) included corneas with TCT <523 µm, group 2 (81 eyes) with TCT between 523 and 564 µm, while group 3 (40 eyes) enrolled TCT >564 µm. The possible effect of pachymetry on Pentacam HR indices was assessed using partial correlation tests.

Results

In normal corneas, back elevation from best fit sphere (BE from BFS) and that from best fit toric ellipsoid (BFTE) were the elevation indices that showed statistically significant differences among groups (P=0.013 and 0.019, respectively). Regarding pachymetric indices, maximum pachymetry progression index (PPI max) showed statistical significance (P=0.001). Partial correlations, after excluding age and refractive error effects, showed that TCT was correlated with BE from BFS, BE from BFTE, and PPI max (P=0.001, 0.001,0.002, respectively).

Conclusions

Some Pentacam HR indices varied with different corneal thickness in normal corneas. This necessitates inclusion of pachymetric subgroups in the normative database. The use of the more robust indices (average pachymetry progression index and front elevations) is recommended in relatively thin or thick corneas.

Graft survival rate of deep anterior lamellar keratoplasty for keratoconus: A meta-analysis

BACKGROUND

Deep anterior lamellar keratoplasty (DALK) is an optional treatment for patients with keratoconus, and the associated graft survival rate varies. Herein, we aimed to explore the graft survival rate of DALK in patients with keratoconus.

METHODS

PubMed, Web of Science, and ProQuest databases were searched to retrieve the related articles. General data, clinical characters, and graft survival rates were obtained directly from the included studies and analyzed by meta-analysis.

RESULTS

A total of 12 articles were included. The merged 1-, 3-, and 5-year graft survival rates were 100% (99.9-100%, P < .001), 92.9% (89.8-95.9%, P < .001), and 90.4% (86.0-0.948%, P < .001), respectively. Lower heterogeneity was shown in each subgroup that was divided neither according to the sample number nor number of surgeons.

CONCLUSION

The survival rate slightly decreases year by year, but the overall trend seems relatively stable. Ensuring that all DALK procedures are performed by a single surgeon might be helpful to improve the graft survival rate after surgery.

Characteristic of entire corneal topography and tomography for the detection of sub-clinical keratoconus with Zernike polynomials using Pentacam

The study aimed to characterize the entire corneal topography and tomography for the detection of sub-clinical keratoconus (KC) with a Zernike application method. Normal subjects (n = 147; 147 eyes), sub-clinical KC patients (n = 77; 77 eyes), and KC patients (n = 139; 139 eyes) were imaged with the Pentacam HR system. The entire corneal data of pachymetry and elevation of both the anterior and posterior surfaces were exported from the Pentacam HR software. Zernike polynomials fitting was used to quantify the 3D distribution of the corneal thickness and surface elevation. The root mean square (RMS) values for each order and the total high-order irregularity were calculated. Multimeric discriminant functions combined with individual indices were built using linear step discriminant analysis. Receiver operating characteristic curves determined the diagnostic accuracy (area under the curve, AUC). The 3rd-order RMS of the posterior surface (AUC: 0.928) obtained the highest discriminating capability in sub-clinical KC eyes. The multimeric function, which consisted of the Zernike fitting indices of corneal posterior elevation, showed the highest discriminant ability (AUC: 0.951). Indices generated from the elevation of posterior surface and thickness measurements over the entire cornea using the Zernike method based on the Pentacam HR system were able to identify very early KC.

Stem Cells in the Limbal Stroma

The corneal stroma contains a population of mesenchymal cells subjacent to the limbal basement membrane with characteristics of adult stem cells. These 'niche cells' support limbal epithelial stem cell viability. In culture by themselves, the niche cells display a phenotype typical of mesenchymal stem cells. These stromal stem cells exhibit a potential to differentiate to multiple cell types, including keratocytes, thus providing an abundant source of these rare cells for experimental and bioengineering applications. Stromal stem cells have also shown the ability to remodel pathological stromal tissue, suppressing inflammation and restoring transparency. Because stromal stem cells can be obtained by biopsy, they offer a potential for autologous stem cell treatment for stromal opacities. This review provides an overview of the status of work on this interesting cell population.