Immunologic rejection of the central graft after limbal allograft transplantation combined with penetrating keratoplasty

The outcomes of corneal sight rehabilitating surgery in Stevens-Johnson syndrome: case series

PURPOSE

To summarize the outcomes of corneal sight rehabilitating surgery in Stevens-Johnson syndrome (SJS).

METHODS

This is a retrospective analysis of a consecutive case series. Twenty-four eyes of 18 SJS patients were included in this study. The ocular parameters, surgical procedures, postoperative complications, and additional treatments of the cases were reviewed.

RESULTS

A total of 29 corneal sight rehabilitating surgeries, which consists of 9 keratoplasties, 8 Keratolimbal allograft (KLAL) and 12 combined surgeries (keratoplasty and KLAL simultaneously) were performed on the 24 eyes. All patients were treated with glucocorticoid eyedrops and tacrolimus eyedrops for anti-rejection treatment without combining systemic immunosuppression, except two patients who were prescribed prednisone tablets for the management of systemic conditions. The mean follow-up period was 50.6 ± 28.1 months. The optimal visual acuity (VA) (0.74 ± 0.60 logarithm of the minimum angle of resolution [logMAR]) and endpoint VA (1.06 ± 0.82 logMAR) were both significantly better than the preoperative VA (1.96 ± 0.43 logMAR) (95% CI, p = 0.000). 57.1% patients (8/14) were no longer in the low vision spectrum, and 88.9% patients (8/9) were no longer blind. The mean epithelialization time was 7.1 ± 7.6 weeks. The success rate was 86.7%. Additional treatments for improving epithelialization included administration of serum eyedrops (n = 10), contact lens (n = 15), amniotic membrane transplantation (n = 6), and tarsorrhaphy (n = 8). Complications included delayed epithelialization (n = 4, over 12 weeks), glaucoma (n = 11), and severe allograft opacity (n = 4). Only one graft rejection was observed.

CONCLUSIONS

Keratoplasty and KLAL can remarkably enhance VA and improve low vision or even eliminate blindness for ocular complications of SJS. The outcome of the surgeries was correlated with the preoperative ocular situation and choice of operative methods.

Case Report: Simultaneous penetrating keratoplasty with autologous simple limbal epithelial transplantation as an alternative to keratoprosthesis

Introduction and importance: This case report highlights the multidisciplinary approach required to achieve successful anatomical and functional outcomes, in an eye with total limbal stem cell deficiency (LSCD) associated with underlying corneal scarring and thinning. Presentation of case: A 59-year-old gentleman had poor visual recovery in the right eye (RE) following accidental carbide blast, 1-year before presenting to us. The visual acuity was counting fingers and clinical examination revealed cicatricial entropion involving the upper eyelid, total LSCD, corneal scarring with a central descemetocele and cataract in the RE. Prior to ocular surface reconstruction, entropion correction was performed. Three months later, penetrating keratoplasty combined with cataract surgery and intraocular lens implantation (penetrating keratoplasty (PK) triple), with autologous simple limbal epithelial transplantation (SLET) was performed. The visual acuity was 20/100, 18 months after the surgery, with a clear well-epithelized corneal graft and stable ocular surface. Discussion: LSCD is caused by a decrease in the population and /or function of the limbal epithelial stem cells. Limbal stem cell transplantation (LSCT) is warranted in eyes with total LSCD. In eyes with coexisting corneal scarring, LSCT alone may be inadequate to restore the vision. These eyes require simultaneous or sequential lamellar or full-thickness corneal transplantation for visual rehabilitation. Though, the existing literature favors a sequential approach, where LSCT is performed first followed by corneal transplantation, under certain circumstances such as a thin underlying cornea like in our case, corneal transplantation may have to be combined with LSCT to achieve optimal outcomes. Conclusion: Combining autologous SLET with PK can be performed for visual rehabilitation in eyes with unilateral total LSCD and underlying corneal thinning. Corneal and limbal graft survival is prolonged if existing adnexal comorbidities are addressed before any surgical intervention is planned and adequate time interval is allowed for the surface inflammation to subside.

Case Report: Simultaneous penetrating keratoplasty with autologous simple limbal epithelial transplantation as an alternative to keratoprosthesis

Introduction and importance: This case report highlights the multidisciplinary approach required to achieve successful anatomical and functional outcomes, in an eye with total limbal stem cell deficiency (LSCD) associated with underlying corneal scarring and thinning. Presentation of case: A 59-year-old gentleman had poor visual recovery in the right eye (RE) following accidental carbide blast, 1-year before presenting to us. The visual acuity was counting fingers and clinical examination revealed cicatricial entropion involving the upper eyelid, total LSCD, corneal scarring with a central descemetocele and cataract in the RE. Prior to ocular surface reconstruction, entropion correction was performed. Three months later, penetrating keratoplasty combined with cataract surgery and intraocular lens implantation (penetrating keratoplasty (PK) triple), with autologous simple limbal epithelial transplantation (SLET) was performed. The visual acuity was 20/100, 18 months after the surgery, with a clear well-epithelized corneal graft and stable ocular surface. Discussion: LSCD is caused by a decrease in the population and /or function of the limbal epithelial stem cells. Limbal stem cell transplantation (LSCT) is warranted in eyes with total LSCD. In eyes with coexisting corneal scarring, LSCT alone may be inadequate to restore the vision. These eyes require simultaneous or sequential lamellar or full-thickness corneal transplantation for visual rehabilitation. Though, the existing literature favors a sequential approach, where LSCT is performed first followed by corneal transplantation, under certain circumstances such as a thin underlying cornea like in our case, corneal transplantation may have to be combined with LSCT to achieve optimal outcomes. Conclusion: Combining autologous SLET with PK can be performed for visual rehabilitation in eyes with unilateral total LSCD and underlying corneal thinning. Corneal and limbal graft survival is prolonged if existing adnexal comorbidities are addressed before any surgical intervention is planned and adequate time interval is allowed for the surface inflammation to subside.

Outcomes of Combined Penetrating Keratoplasty and Limbal Stem Cell Transplantation: A Meta-Analysis on Simultaneous Versus Sequential Surgery

PURPOSE

The objective of this study is to perform a systematic review and meta-analysis of the published studies on limbal stem cell transplantation (LSCT) combined with penetrating keratoplasty (PK) performed either simultaneously or sequentially.

METHODS

An extensive search was conducted in the MEDLINE and Google Scholar databases. Prospective and retrospective trials and case series reporting on the outcomes of LSCT with PK were included. Primary outcomes were the stability of the ocular surface and the rejection and/or failure of the corneal graft.

RESULTS

A total of 209 eyes from 13 studies were included in the simultaneous group and 489 eyes from 33 studies in the sequential group. Ocular surface stability was 88% [95% confidence interval (CI), 79%-96%] for sequential cases and 64% (95% CI, 43%-82%) for simultaneous cases ( P = 0.001). The graft failure rate was 15% (95% CI, 6%-26%) for sequential cases and 44% (95% CI, 31%-58%) for simultaneous cases ( P < 0.001). For cases performed sequentially, subgroup analysis revealed a stable ocular surface in 97% (95% CI, 91%-100%) of autograft cases and 63% (95% CI, 45%-80%) of allograft cases ( P < 0.001). The graft failure rate in sequential cases was 7% (95% CI, 0%-18%) for autografts and 34% (95% CI, 18%-52%) for allografts ( P < 0.001).

CONCLUSIONS

Sequential LSCT followed by PK demonstrated superior results in terms of ocular surface stability and graft retention compared with simultaneous LSCT and PK. Limbal stem cells of autologous origin fare better than allogeneic ones in sequential cases.

Long-Term Outcomes of Allogeneic Ocular Surface Reconstruction: Keratolimbal Allograft (KLAL) Followed by Penetrating Keratoplasty (PK)

Purpose

Long-term results of the patients with total LSCD, who had undergone keratolimbal allograft (KLAL) for limbal reconstruction followed by penetrating keratoplasty (PK).

Methods

The study analyzes surgical treatment of 43 eyes with severe ocular surface disorders. All subjects underwent KLAL to achieve suitable conditions for consecutive PK. Due to failures of primary treatment in 17 eyes (39%), the KLAL was repeated. PK was performed in all the patients at 9-12 months after KLAL. As a retrospective study we analyzed data from the medical records including the preoperative and postoperative best corrected visual acuity, corneal clarity, surgical outcomes and complications, postoperative intraocular pressure, graft rejection, and other comorbidities and complications.

Results

The preoperative visual acuity ranged from light perception to 0.01. The final improvement of visual acuity within a gain of one or more lines with the Snellen chart, including the results of successive surgical treatments after PK, was achieved in 23 operated eyes (53%). Early graft rejection was observed in 4 eyes (9%). In 3 eyes, it was manifested as endothelial rejection, and in 1 eye, as combined endothelial and epithelial rejection. PK failure requiring repetitive PK was present in 14 eyes (32%). Phthisis bulbi developed in 6 eyes (14%). Glaucoma or ocular hypertension was reported in 25 eyes (58%). A majority were treated with up to 3 topical agents or referred for trabeculectomy in 3 cases, transscleral cyclophotocoagulation in 2 eyes, and EX-PRESS glaucoma shunt implantation in 3 cases.

Conclusions

Successful KLAL carries a high risk of subsequent PK failure. Visual function remains the second aim of treatment; the primary one is to stabilize the surface.

Anterior segment optical coherence tomographic characterisation of keratic precipitates

BACKGROUND/OBJECTIVES

Anterior segment optical coherence tomography (AS-OCT) can be used to visualise keratic precipitates (KPs) on the corneal endothelium. However, there has been no correlation between characteristic clinical appearances of KPs and AS-OCT morphology. We wished to assess the potential diagnostic role of AS-OCT in patients presenting with inflammatory eye disease and KPs.

SUBJECTS/METHODS

Six patients with inflammatory KPs were compared to one patient with infective interface keratitis following Descemet Membrane Endothelial Keratoplasty (DMEK) and one patient with endothelial pigment. AS-OCT was performed in each case and morphological features of the KPs were compared. Reflectivity of KPs was also compared numerically by measuring their relative lightness.

RESULTS

AS-OCT images in acute and active inflammation generally demonstrated hyperreflective KP variants in comparison to conditions with moderate or longstanding inflammation. In the patient with infective interface keratitis, KPs were evident on the endothelial surface but no changes could be identified at the graft-host interface. There were no significant differences between infective and inflammatory KPs to help distinguish between the two. Endothelial pigment deposits were clearly differentiated from keratic precipitates with smaller, poorly defined deposits on the endothelium surface which were isoreflective to the cornea.

CONCLUSION

Hyperreflective KPs could be suggestive of newly deposited KPs and active inflammation; they may also be increased in KPs of herpetic origin. AS-OCT should not be used to differentiate infective infiltrate from inflammatory KPs if a patient were to present with post-operative inflammation and interface infection should still be suspected even if only endothelial deposits are identified on AS-OCT. AS-OCT may be used as a diagnostic and monitoring tool to assess response to treatment in cases where anterior segment inflammation of uncertain aetiology is present.

Early Results of Penetrating Keratoplasty in Patients With Unilateral Chemical Injury After Simple Limbal Epithelial Transplantation

PURPOSE

To evaluate clinical outcomes of sequential PKP in eyes with unilateral chemical injury, which have previously undergone autologous simple limbal epithelial transplantation (SLET) at a tertiary eye center in North India.

METHODS

This is a single-center, retrospective, noncomparative interventional case series reviewing patients with unilateral limbal stem cell deficiency treated by SLET and sequential PKP between 2012 and 2017. The primary outcome was defined as allograft survival, defined as a completely epithelialized, clear, avascular graft. The secondary outcome was improvement in best-corrected visual acuity by 2 lines or any complications.

RESULTS

Seven eyes of 7 patients, all aged below 40 years, who underwent SLET followed by PKP for unilateral ocular surface injury were included. Most of the patients were male (71.4%), and alkali injury (42.8%) was the most common cause of limbal stem cell deficiency. The mean duration between SLET and PK was 9.5 ± 11.9 months (2-36 mo), and the mean follow-up duration after PKP was 15.1 ± 5.4 months (6-21 mo). A successful outcome after SLET was achieved in all 7 patients and clear grafts in 6 patients, with a graft survival rate of 85% at 6 months. Visual success was noted in 4 patients. Poor vision in 3 patients was due to glaucoma, amblyopia, and graft failure.

CONCLUSIONS

PKP was found to have a good outcome when the surface has been stabilized by SLET as an initial procedure in unilateral ocular chemical injury. The visual outcome was restricted mainly by other causes such as glaucoma and amblyopia.

Outcomes of Keratoplasty After Ocular Surface Stem Cell Transplantation

PURPOSE

To investigate the long-term outcomes of penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK) after ocular surface stem cell transplantation (OSST).

METHODS

An observational retrospective review was performed on all patients who underwent OSST followed by either PK or DALK with a minimum of 6-month follow-up.

RESULTS

One hundred two eyes fulfilled the inclusion criteria. The mean time to keratoplasty after OSST was 19 months, and the mean follow-up was 57 months after keratoplasty. A Kaplan-Meier analysis demonstrated 92% graft survival at year 1, 77% at year 2, 62% at year 3, 55% at year 4, and 54% at year 5. During the study period, a total of 44 grafts failed. The mean time to graft failure was 32 months. Preoperative median best-corrected visual acuity for all eyes was 20/550, which improved to 20/100 (P < 0.001) at 1 year postoperatively, 20/60 (P < 0.001) at 2 years, and 20/100 (P < 0.001) at last follow-up.

CONCLUSIONS

Without addressing the underlying stem cell deficiency, keratoplasty in patients with total limbal stem cell deficiency will ultimately fail in all cases. OSST with either subsequent PK or DALK provides successful visual outcomes with an acceptable complication profile.

Systemic immunosuppression in limbal stem cell transplantation: best practices and future challenges

The objective of this study was to evaluate systemic immunosuppression regimens used for patients undergoing ocular surface stem cell transplantation, including their benefits and adverse effects in the adjunctive management of limbal stem cell deficiency (LSCD). A systematic literature review was conducted using the MEDLINE and EMBASE databases (1980-2015). Data were collected on surgical intervention(s), type of immunosuppressive agent(s), duration of immunosuppression, percentage with stable ocular surface at last follow-up, mean follow-up time, and demographics. Data were also collected on adverse ocular and systemic outcomes. Sixteen reports met the inclusion criteria. There were no randomized controlled studies. Three studies were noncomparative prospective case series, whereas the majority were retrospective case series. Bilateral severe LSCD was the most common disease (50%), and keratolimbal allograft was the most common intervention (80%). Immunosuppressive regimens showed a progression from early studies using oral cyclosporine to later studies using combinations of mycophenolate mofetil and tacrolimus. Most studies included a course of high-dose systemic corticosteroids. For patients adherent to long-term systemic immunosuppression, stable ocular surface rates of 70%-80% at last follow-up were reported. Adverse effects included hypertension, diabetes mellitus, and biochemical abnormalities managed with pharmacotherapy or discontinuation of offending agents. There were no cases of mortality related to immunosuppression. However, the current literature does not elucidate which immunosuppressive regimen is most efficacious for different categories of LSCD or graft types. Evidence-based guidelines for systemic immunosuppression in limbal allograft therapy would benefit from randomized controlled and/or additional prospective studies. Long-term immunosuppression would benefit from close collaboration between ophthalmologists and transplant specialists to individualize treatments.

Establishment of Novel Limbus-Derived, Highly Proliferative ABCG2+/ABCB5+ Limbal Epithelial Stem Cell Cultures

Homeostasis and regeneration of corneal epithelia are sustained by limbal epithelial stem cells (LESCs); thus, an LESC deficiency is a major cause of blindness worldwide. Despite the generally promising results of cultivated LESC transplantation, it has been limited by variations in long-term success rates, the use of xenogeneic and undefined culture components, and a scarcity of donor tissues. In this study, we identified the culture conditions required to expand LESCs in vitro and established human limbus-derived highly proliferative ABCG2⁺/ABCB5⁺ double-positive LESCs. These LESCs exhibited the LESC marker profile and differentiated into corneal epithelial cells. In addition, cultured LESCs expressed high levels of the stem cell markers Sox2, Oct4, c-Myc, and Klf4, had high telomerase activity, and had stable, normal genomes. These results suggest that our novel cultivation protocol affects the phenotype and differentiation capacity of LESCs. From the limbus, which contains a heterogenous cell population, we have derived highly proliferative ABCG2⁺/ABCB5⁺ double-positive cells with the ability to differentiate into corneal epithelial cells. This study opens a new avenue for investigation of the molecular mechanism of LESC maintenance and expansion in vitro and may impact the treatment of corneal disease, particularly corneal blindness due to an LESC deficiency.

Diagnostic criteria for limbal stem cell deficiency-a systematic literature review

The diagnosis of limbal stem cell deficiency (LSCD) is often based on clinical manifestations with or without the use of tests to demonstrate the presence of goblet cells or of specific epithelial markers on the corneolimbal surface. This systematic review looks at the various diagnostic methods used in the diagnosis of LSCD in published interventional studies. The design is a systematic literature review. We did a systematic search on MEDLINE and PUBMED for articles published in English between January 1, 2003, and December 31, 2013. We collected data on diagnostic methods used to diagnose LSCD (clinical findings, impression cytology, immunohistochemistry for various epithelial markers, or in vivo confocal microscopy). Forty-six studies (mostly retrospective/interventional case series) met the inclusion criteria. All of the studies used clinical features as evidence of LSCD: discomfort, impaired vision, irregular epithelium, unstable tear film, persistent epithelial defects, scarring, fibrovascular pannus, neovascularization, keratinization, calcification, and opacification of the cornea. Eighteen studies (39.1%) used an additional test for the diagnosis; 17 studies (37.0%) used impression cytology for goblet cells, 4 studies (8.7%) used immunohistochemistry for epithelial markers, and 2 studies (4.3%) use in vivo confocal microscopy. The diagnosis of LSCD was made in most cases on clinical grounds alone. In some studies, diagnostic tests were used, but these varied considerably from study to study. Comparison of effectiveness of various interventions requires standardized diagnostic methods. Consensus on the diagnostic criteria for LSCD is essential and needs to be reached by the interested care providers.

Stevens-Johnson syndrome: The role of an ophthalmologist

Stevens-Johnson syndrome (SJS) is an acute blistering disease of the skin and mucous membranes. Acute SJS leads to the acute inflammation of the ocular surface and chronic conjunctivitis. If not properly treated, it causes chronic cicatricial conjunctivitis and cicatricial lid margin abnormalities. Persistent inflammation and ulceration of the ocular surface with cicatricial complications of the lids leads to chronic ocular sequelae, ocular surface damage, and corneal scarring. The destruction of the glands that secrete the tear film leads to a severe form of dry eye that makes the management of chronic SJS difficult. The option that is routinely used for corneal visual rehabilitation, keratoplasty, is best avoided in such cases. We describe the management strategies that are most effective during the acute and chronic stages of SJS. Although treatments for acute SJS involve immunosuppressive and immunomodulatory therapies, amniotic membrane transplantation is also useful. The options for visual rehabilitation in patients with chronic SJS are undergoing radical change. We describe the existing literature regarding the management of SJS and highlight recent advances in the management of this disorder.

Reconstruction of functional ocular surface by acellular porcine cornea matrix scaffold and limbal stem cells derived from human embryonic stem cells

Limbal stem cells (LSCs) derived from human embryonic stem cells (hESCs) hold great potential for cell-based therapies for ocular surface diseases. The cell-based therapies mainly depend on an appropriate differentiation proposal with a high efficiency and on a suitable scaffold. In this study, we aimed to establish a feasible and efficient strategy for inducing hESCs into LSC-like cells by the LSC conditioned medium. The induced cells possessed the similar morphologic characteristics and expression of normal LSCs and showed a strong clonogenic and proliferative capacity in vitro. To construct a tissue-engineering corneal graft, these differentiated cells were seeded on an acelluar porcine corneal matrix (APCM), which maintained the corneal basement membrane in vitro. After 14 days culture, these induced cells gave rise to stratified epithelial cell sheets on the APCM and the basal cells still kept LSC characteristics. In rabbit total limbal stem cell deficiency (LSCD) models, the tissue-engineering graft had the potential to reconstruct the damaged ocular surface and alleviated the invasion of corneal neovascularization. These findings indicated that the engraftment constructed with the APCM scaffold and hESC-derived LSCs might be a potential therapy option for ocular surface regeneration in LSCD cases.

Phenotypic evaluation of severely damaged ocular surface after reconstruction by cultured limbal epithelial cell transplantation

OBJECTIVE

To report the clinical outcome of autologous cultured limbal epithelial cell transplantation (CLECT) followed by deep anterior lamellar keratoplasty (DALK) in paediatric eyes and to correlate the clinical outcome with the phenotype of rejuvenated corneal epithelium.

METHODS

Four patients with total limbal stem cell deficiency (LSCD) underwent autologous CLECT. Cultivated cell sheets were transplanted onto the damaged ocular surface followed by DALK surgery. Excised corneal buttons were subjected to histopathological analysis. Data recorded included age, sex, laterality, nature of injury, follow-up period, severity of stem cell deficiency, visual acuity, Schirmer's test and impression cytology.

RESULTS

At a mean follow-up period of 19.5 ± 7.4 (range 9-26) months after CLECT, all 4 eyes showed epithelialized and clinically stabilized ocular surface. Manual DALK was performed in all 4 eyes, with a mean follow-up of 9.75 ± 4.5 (range 5-15) months. All eyes exhibited smooth and clear corneal epithelium with improved visual acuity. Excised corneal buttons demonstrated organized corneal epithelial morphology and showed expression of cornea-specific CK3/12 marker.

CONCLUSION

Restoration of severely damaged ocular surface following chemical injury by using 2-stage meticulous approaches offers a new modality for the treatment of severe LSCD. Transplantation of cultivated autologous limbal epithelial cell sheet followed by DALK surgery can efficiently restore the corneal phenotype with improved vision.

Lamellar keratoplasty and keratolimbal allograft for mustard gas keratitis

PURPOSE

To report the clinical outcomes of lamellar keratoplasty (LKP) in patients with delayed-onset mustard gas keratitis and to compare visual acuity and graft survival rates between subgroups with simultaneous or sequential keratolimbal allograft and LKP.

DESIGN

Retrospective, comparative, interventional case series.

METHODS

Fifty-two eyes of 37 male survivors of chemical warfare with mustard gas keratitis who underwent LKP were included. The results were evaluated with respect to best spectacle-corrected visual acuity (BSCVA), refractive error and keratometry readings, and graft clarity. Thirty-two eyes required stem cell transplantation (keratolimbal allograft), which was performed before or concomitant with LKP. The groups with sequential and concomitant intervention were compared regarding BSCVA, refraction, corneal graft surface stability, and stem cell and corneal graft survival rates.

RESULTS

The mean patient age at the time of surgery was 43.4 ± 8.2 years, and the mean follow-up period was 41.4 ± 19.6 months. The mean preoperative BSCVA was 0.51 ± 0.48 logarithm of the minimal angle of resolution units, which increased to 0.33 ± 0.18 logarithm of the minimal angle of resolution units (P = .03). The mean preoperative spherical equivalent refractive error was -2.40 ± 1.5 diopters, which remained unchanged after surgery (-1.52 ± 3.7 diopters; P = .77). No significant difference between the sequential and simultaneous subgroups was found with regard to postoperative BSCVA, refraction, keratometry readings, or corneal graft survival (90.3% and 89.9%, respectively; P = .68). However, the latter group had statistically better stem cell graft survival (40.0% vs 100% at month 41, respectively; P = .02).

CONCLUSIONS

LKP is an effective method of corneal transplantation in mustard gas victims. When stem cell and corneal transplantation are indicated, the simultaneous approach can yield better results than staged intervention.

Update on limbal stem cell transplantation

Limbal epithelial stem cells are the primary source of corneal epithelial cell regeneration. Limbal stem cell deficiency (LSCD) can develop in traumatic, immunologic, or genetic diseases that affect the ocular surface. LSCD leads to conjunctivalization, with corneal vascularization and opacification and subsequent loss of vision. Limbal stem cell transplantation is a surgical treatment to address LSCD and restore a corneal epithelial phenotype. Based on the source of cells, limbal transplant can be autologous or allogenic. Many surgical techniques are defined according to the source of the stem cells and the carrier tissues that are used. More recently, ex vivo expanded bioengineered epithelial cells have been used to reconstruct the corneal surface using autologous cells to eliminate the risk of rejection. Before transplantation, a systematic exam of the lids, eyelashes, fornices, and aqueous tears is mandatory and every effort should be made to optimize ocular surface health and control inflammation to enhance the chances of graft survival. Postoperative care is also another major determinant of success. Any factor that destabilizes the ocular surface needs to be addressed. In addition, systemic and topical immunosuppressants are also needed in all allograft recipients. In addition to pre-operative and postoperative care and the surgery itself, the etiology of LSCD also has an impact on the outcome. The prognosis of inflammatory diseases such as Stevens-Johnson syndrome is the worst among disorders causing LSCD.

Stem cells in clinical practice: applications and warnings

Stem cells are a relevant source of information about cellular differentiation, molecular processes and tissue homeostasis, but also one of the most putative biological tools to treat degenerative diseases. This review focuses on human stem cells clinical and experimental applications. Our aim is to take a correct view of the available stem cell subtypes and their rational use in the medical area, with a specific focus on their therapeutic benefits and side effects. We have reviewed the main clinical trials dividing them basing on their clinical applications, and taking into account the ethical issue associated with the stem cell therapy.

Corneal Epithelial Cultures Generated from Organ-Cultured Limbal Tissue: Factors Influencing Epithelial Cell Growth

PURPOSE

To explore the in vitro proliferative potential of human limbal epithelial cells after 31 degrees C organ-culture storage and to investigate putative factors influencing it.

METHODS

185 cultures of limbal explants were carried-out either from full-thickness explants (n = 102) or from enzymatically dissociated cells (n = 83) seeded on a feeder layer of human keratocytes. Epithelial outgrowth was assessed by phase contrast microscopy using a computerized image analysis software. Cell phenotype was evaluated by transmission electron microscopy and immunocytology. Univariate and multivariate analysis were performed to determine factors influencing epithelial growth in culture.

RESULTS

An epithelial outgrowth of 100 square mm or more was observed in 52% of cultures, (average growth area: 440 +/- 256 mm at three weeks). Corneal epithelial phenotype was confirmed by transmission electron microscopy, and cytokeratin pattern. Cytokeratine 19, deltaNp63, nestin and vimentin positive staining revealed undifferentiated epithelial cells in both explant and cell suspension cultures at three weeks. Short death to cornea retrieval time (p < 0.03) and female donors (p < 0.01) were associated with higher cell growth. Enzymatic treatment of explants by trypsin, but not dispase, decreased cell proliferation at two (p < 0.03) and three weeks (p < 0.04). Donor age, duration of corneal storage, and source of the explant did not influence the cell growth.

CONCLUSION

Organ-culture conditions can preserve limbal cell mitotic potential if limbal tissue is excised early after circulatory arrest. Human keratocytes can be used as a feeder layer allowing epithelial cells to maintain poorly differentiated phenotype in culture. Further investigations are needed to explain the influence of the donor sex on epithelial cell growth in culture.

Living-related conjunctival-limbal allograft for chronic or delayed-onset mustard gas keratopathy

PURPOSE

To determine the long-term outcomes of living-related stem cell transplantation in patients with delayed or chronic mustard gas keratopathy (MGK).

MATERIALS AND METHODS

In this noncomparative interventional case series, 21 consecutive patients with advanced delayed or chronic MGK received living-related conjunctival-limbal allograft and were followed up for at least 1 year. All subjects received immunosuppression with systemic cyclosporine. Main outcome measures were reduction of subjective complaints, corneal epithelial healing, and regression of corneal neovascularization adjacent to the transplant area.

RESULTS

Twenty-five eyes of 21 patients (all male), including 4 patients who received bilateral grafts, were operated. Mean age at the time of surgery was 35.8 +/- 3.8 years, mean interval between mustard gas exposure and surgery was 12.2 +/- 3.5 years, and mean follow-up was 37.2 +/- 18.5 months. Average size of the donor lenticule was 71.16 +/- 17.34 degrees. Simultaneous penetrating and lamellar keratoplasty were performed in 5 and 2 eyes, respectively. All patients consistently reported marked subjective improvement. Mean time for epithelial healing was 7.76 +/- 3.2 days. Visual acuity was 1.35 +/- 0.81 LogMAR before surgery, which improved to 0.59 +/- 0.34 LogMAR 3 months after the procedure (P < 0.001). Mean visual acuity at final examination was 0.82 +/- 0.49 LogMAR (P = 0.001). Acute stem cell rejection was observed in 10 (40%) eyes, which improved by increasing the dose of topical and systemic steroids. Chronic stem cell rejection was diagnosed in 8 (32%) eyes, which led to failure in 5 (20%) eyes.

CONCLUSIONS

Living-related conjunctival-limbal allograft is effective in stabilizing the ocular surface in patients with delayed or chronic MGK.

A systematic literature review of surgical interventions for limbal stem cell deficiency in humans

PURPOSE

To evaluate the relative benefits and to identify any adverse effects of surgical interventions for limbal stem cell deficiency (LSCD).

DESIGN

Systematic literature review.

METHODS

We searched the following electronic databases from January 1, 1989 through September 30, 2006: MEDLINE, EMBASE, Science citation index, BIOSIS, and the Cochrane Library. In addition, reference lists were scanned to identify any additional reports. The quality of published reports was assessed using standard methods. The main outcome measure was improvement in vision of at least two Snellen lines of best-corrected visual acuity (BCVA). Data on adverse outcomes also were collected.

RESULTS

Twenty-six studies met the inclusion criteria. There were no randomized controlled studies. All 26 studies were either prospective or retrospective case series. For bilateral severe LSCD, keratolimbal allograft was the most common intervention with systemic immunosuppression. Other interventions included eccentric penetrating keratolimbal allografts and cultivated autologous oral mucosal epithelial grafts. An improvement in BCVA of two lines or more was reported in 31% to 67% of eyes. For unilateral severe LSCD, the most common surgical intervention was contralateral conjunctival limbal autograft, with 35% to 88% of eyes gaining an improvement in BCVA of two lines or more. The only study evaluating partial LSCD showed an improvement in BCVA of two lines or more in 39% of eyes.

CONCLUSIONS

Studies to date have not provided strong evidence to guide clinical practice on which surgery is most beneficial to treat various types of LSCD. Standardized data collection in a multicenter LSCD register is suggested.

Corneal Graft Rejection

Penetrating keratoplasty is the most widely practiced type of transplantation in humans. Irreversible immune rejection of the transplanted cornea is the major cause of human allograft failure in the intermediate and late postoperative period. This immunological process causes reversible or irreversible damage to the grafted cornea in several cases despite the use of intensive immunosuppressive therapy. Corneal graft rejection comprises a sequence of complex immune responses that involves the recognition of the foreign histocompatibility antigens of the corneal graft by the host's immune system, leading to the initiation of the immune response cascade. An efferent immune response is mounted by the host immune system against these foreign antigens culminating in rejection and graft decompensation in irreversible cases. A variety of donor- and host-related risk factors contribute to the corneal rejection episode. Epithelial rejection, chronic stromal rejection, hyperacute rejection, and endothelial rejection constitute the several different types of corneal graft rejection that might occur in isolation or in conjunction. Corneal graft failure subsequent to graft rejection remains an important cause of blindness and hence the need for developing new strategies for suppressing graft rejection is colossal. New systemic pharmacological interventions recommended in corneal transplantation need further evaluation and detailed guidelines. Two factors, prevention and management, are of significant importance among all aspects of immunological graft rejection. Preventive aspects begin with the recipient selection, spread through donor antigenic activity, and end with meticulous surgery. Prevention of corneal graft rejection lies with reduction of the donor antigenic tissue load, minimizing host and donor incompatibility by tissue matching and suppressing the host immune response. Management of corneal graft rejection consists of early detection and aggressive therapy with corticosteroids. Corticosteroid therapy, both topical and systemic, is the mainstay of management. Addition of immunosuppressive to the treatment regimen helps in quick and long term recovery. Knowledge of the immunopathogenesis of graft rejection may allow a better understanding of the immunological process thus helping in its prevention, early detection and management.

Changes Observed in Keratolimbal Allograft

OBJECTIVE

To study the incidence and clinical characteristics of presumed immunologic reactions in limbal grafts after keratolimbal allograft(KLAL).

METHODS

A total of 121 KLALs performed in consecutive 85 eyes of 78 patients with total limbal stem-cell deficiency were analyzed retrospectively. Mean follow-up period was 46.6 months. Three types of limbal graft changes classified as epithelial defects, acute edema, and vascular engorgement were analyzed as probable signs of immunologic rejection.

RESULTS

One or more changes in limbal grafts were observed after 16 KLALs (13.1%). All but 1 eye used systemic and local immunosuppression using corticosteroid and cyclosporine A, and most of the changes developed within 3 months postoperatively. All but 2 eyes developed epithelial breakdown in the central cornea, and 12 corneas underwent conjunctivalization. The rate of corneal epithelialization in eyes with limbal graft changes was significantly worse than those without the changes (P < 0.0001). Histologic examination in eyes with the limbal graft changes revealed high incidence of lymphocyte infiltration.

CONCLUSIONS

Presumed limbal graft rejection occurred in approximately 13% of cases after KLAL. Suppression of the immune reaction remains a key to success in KLAL.

Survival analysis of conjunctival limbal grafts and amniotic membrane transplantation in eyes with total limbal stem cell deficiency

PURPOSE

To evaluate the survival of conjunctival limbal grafts and amniotic membrane transplantation (AMT) for total limbal stem cell deficiency (LSCD) and the influence of several parameters as cause of LSCD, dry eye, keratinization, eyelid abnormalities, HLA compatibility, systemic immunosuppression, and keratoplasty (PKP) on surgical outcome.

DESIGN

Prospective, noncomparative, interventional case series.

METHODS

Thirty-three eyes of 31 patients with total LSCD that underwent conjunctival limbal grafts and AMT at the Department of Ophthalmology, Federal University of São Paulo were included in this study. Cumulative graft survival as well as the influence of several variables on surgical outcome was analyzed.

RESULTS

Ten eyes (30%) underwent conjunctival limbal autograft and 23 (70%) underwent conjunctival limbal allograft from living HLA-matched donor. Graft survival was seen in 13 eyes (40%) at 1 year and in 11 eyes (33.3%) at 2 years, with a cumulative survival of 33% after a mean follow-up time of 33 months. Increase in postoperative visual acuity was observed in 20 eyes (60.6%) during this period. Marked impact on graft survival was observed for patients with Stevens-Johnson syndrome, dry eye, keratinization, eyelid abnormalities, and allogeneic conjunctival limbal transplantation (independently of HLA compatibility) (P < .05). Preoperative dry eye was the most important prognostic parameter for surgical outcome (P < .001).

CONCLUSIONS

Conjunctival limbal grafts associated with AMT are useful for restoring corneal epithelium phenotype in eyes with total LSCD. However, the cumulative survival declines substantially over a 2-year period. Considering all investigated variables, dry eye was the most important prognostic parameter.

Keratolimbal allograft in corneal reconstruction

The replenishment of corneal epithelial SC is a crucial step for reconstructing the ocular surface in patients suffering from devastating ocular surface diseases manifesting with total LSCD. KLAL is one of such procedures and has a long track record and a long follow-up for patients with bilateral total LSCD. This review summarizes the literature experiences and outline new strategies that are important to enhance the success of this procedure. Further research is needed to fully understand the biological processes involved in allogeneic tissue transplantation for preserving epithelial SC adhesion, migration, and survival.

Donor source affects the outcome of ocular surface reconstruction in chemical or thermal burns of the cornea11The authors do not have any proprietary interest in the products mentioned used in this study

PURPOSE

To study the association between surgical approach and postoperative results in chemical and thermal burns of the cornea.

DESIGN

Retrospective, interventional, noncomparable case series.

PARTICIPANTS

Thirty-two eyes of 32 patients with chemical (n = 27) or thermal (n = 5) burns of the cornea that were associated with total limbal dysfunction. Eight eyes had a history of previous keratoplasty.

INTERVENTION

Patients were treated by amniotic membrane transplantation combined with either conjunctivolimbal autograft transplantation (autograft group, n = 11) or keratolimbal allograft transplantation (allograft group, n = 21). Fifteen eyes had simultaneous penetrating keratoplasty (simultaneous group), and 6 had keratoplasty several months after ocular surface reconstruction (2-step group).

MAIN OUTCOME MEASURES

Reconstruction of the corneal surface by corneal epithelium, clarity of the cornea, and incidence of postoperative complications. The outcome was compared between the autograft and allograft groups and also between the simultaneous and 2-step groups.

RESULTS

At final examination, 17 eyes (53.1%) showed stable corneal epithelialization. Preoperative conditions were similar in the autograft and allograft groups and also in the simultaneous and 2-step groups. The autograft group showed significantly better results than the allograft group in both corneal epithelialization (Kaplan-Meier analysis, P = 0.003) and clear cornea (P = 0.010). Although the incidences of corneal epithelialization and clear corneas did not significantly differ between the simultaneous and 2-step groups, the former had a higher rate of endothelial rejection in the central graft (P = 0.019).

CONCLUSIONS

In chemical or thermal burns of the cornea with monocular involvement, autografting should be considered as a first choice of surgery. Even in eyes with opaque corneal stroma, it may be safer to perform ocular surface reconstruction first, followed by keratoplasty as a secondary procedure.

Ocular surface reconstruction update

Ocular surface reconstruction (OSR) is now a standard procedure in the treatment of severe ocular surface disorders. The past few years have revealed the long-term results of patients who were operated on during the early stages of OSR development, and we now have a more realistic view of the benefits and limits of the procedure. On the other hand, further understanding of the physiologic role played by the amniotic membrane (AM) has opened doors to further refined techniques in treating these patients. This review will introduce some of the major contributions made during the past years in the advancement of OSR. Clinically, we are at a stage of reviewing the pros and cons of the various transplantation techniques. Identification of factors crucial for a successful OSR procedure will further improve surgical results. Basic researchers are on the verge of identifying the so-called limbal stem cells, and further understanding of AM physiology will lead the way to tissue engineering techniques as another alternative in OSR surgery.

Long-term outcome of keratolimbal allograft with or without penetrating keratoplasty for total limbal stem cell deficiency

PURPOSE

To evaluate the long-term outcome of ocular surface reconstruction, including keratolimbal allograft (KLAL) and amniotic membrane transplantation (AMT) with or without penetrating keratoplasty (PKP), in patients with nonambulatory vision secondary to total limbal stem cell deficiency (LSCD).

DESIGN

Retrospective, non-comparative interventional case series.

PARTICIPANTS

Thirty-nine eyes in 31 consecutive patients with total LSCD, as defined by impression cytology, who had a preoperative best-corrected visual acuity of less than 20/200 and a minimum follow-up of 12 months. Patients were divided into three groups: group 1 (16 eyes) with chemical burns, group 2 (9 eyes) with Stevens-Johnson syndrome (SJS), and group 3 (14 eyes) with other causes of LSCD, including ocular cicatricial pemphigoid, atopic keratoconjunctivitis, and aniridia.

INTERVENTION

All patients underwent KLAL and AMT by one surgeon (SCGT). If needed, PKP was performed at the same surgical setting using tissue from the same donor.

MAIN OUTCOME MEASURES

Cumulative rates of survival of ambulatory vision (> or = 20/200), survival of KLAL, survival of PKP, and incidence of complications.

RESULTS

Fifty-three KLAL with AMT procedures were performed in 39 eyes, of which 23 eyes received simultaneous PKP at the time of the first KLAL. The mean follow-up was 34.0 +/- 21.5 months (range, 12-117.6). The mean period of ambulatory vision was 23.9 +/- 20.9 months (range, 0-104). The overall survival of ambulatory vision was 53.6% at 3 years and 44.6% at 5 years. The survival of ambulatory vision was significantly worse in SJS compared with other causes (67%, 81%, and 92% for groups 1, 2, and 3, respectively; P = 0.06 for group 1 versus 2, P = 0.0008 for group 1 versus 3). KLAL performed alone resulted in higher survival of ambulatory vision at 2 years (86.1% +/- 9.1%) compared with KLAL with PKP (46.9% +/- 10.6%, P = 0.100). The survival of PKP was significantly worse in SJS compared with the other causes (20.0% +/- 17.9% compared with 55.6% +/- 11.7%, respectively, P = 0.028). After 2 years, the survival of the second KLAL was better than that of the first: 68.2% +/- 15.4% compared with 27.3% +/- 13.4%, respectively (P = 0.041).

CONCLUSIONS

Ambulatory vision for a period of more than 2 years can be achieved by KLAL with or without PKP in eyes with severe ocular surface disorders caused by total LSCD. However, a progressive decline of the visual outcome and graft survival is evident with time. Performing PKP simultaneously with KLAL may be associated with a less favorable outcome. The failure of KLAL is associated with the loss of donor cells in the recipient. Augmentation of ocular surface defense is essential in securing the success of KLAL and PKP. Future modifications of the surgical procedure and of the immune suppressive protocols may improve survival of the allogeneic grafts and the final visual outcome.

Limbal stem cell transplantation for the treatment of subepithelial amyloidosis of the cornea (gelatinous drop-like dystrophy)

PURPOSE

Subepithelial amyloidosis of the cornea, or gelatinous drop-like corneal dystrophy (GDD), is a severe form of corneal stromal amyloidosis predominantly found in the Japanese population. GDD causes severe visual disturbances with irritating symptoms, and keratoplasty is inevitably complicated by early recurrence. This study was conducted to evaluate the efficacy of limbal stem cell transplantation (LSCT) for the treatment of GDD.

METHODS

Nine consecutive eyes of seven patients with GDD were treated with LSCT. Limbal grafts were obtained from cadaver eyes. All eyes underwent lamellar or penetrating keratoplasty simultaneously with LSCT. Intensive epithelial management and immunosuppression therapy was performed.

RESULTS

With a mean observation period of 4 years, eight (88.9%) of nine eyes did not show any signs of recurrence. Five grafts remained clear, and seven eyes had an improvement in vision. Glaucoma and rejection were observed in five and three eyes, respectively, and two eyes with glaucoma required surgical intervention.

CONCLUSIONS

Limbal stem cell transplantation is effective for the prevention of recurrence in GDD. Control of intraocular pressure and rejection are the keys to long-term maintenance of clear grafts.