In vivo confocal microscopy in diagnosis of limbal stem cell deficiency

The inferocentral whorl region and its directional patterns in the corneal sub-basal nerve plexus: A review

There has been a growing application of in vivo confocal microscopy (IVCM) in the examination of corneal microstructure, including different corneal layers and corneal nerve fibers in health and in pathological conditions. Corneal nerves forming the sub-basal nerve plexus (SBNP) beneath the corneal basal epithelial cell layer in particular have been intensively researched in health and disease as a marker for corneal neurophysioanatomical and degenerative changes. One intriguing feature in the SBNP that is found inferior to the corneal apex, is a whorl-like pattern (or vortex) of nerves, which represents an anatomical landmark. Evidence has indicated that the architecture of this 'whorl region' is dynamic, changing with time in healthy individuals but also in disease conditions such as in diabetic neuropathy and keratoconus. This review summarizes the known information regarding the characteristics and significance of the whorl region of nerves in the corneal SBNP, as a potential area of high relevance for future disease monitoring and diagnostics.

In Vivo Confocal Microscopy in Limbal Stem Cell Deficiency After Mesenchymal Stem Cell Transplantation: A Sub-analysis from a Phase I-II Clinical Trial

INTRODUCTION

The aim of this work is to evaluate the effect of mesenchymal stem cell transplantation (MSCT) and cultivated limbal epithelial transplantation (CLET) therapies on the limbus of patients suffering from limbal stem cell deficiency (LSCD).

METHODS

A sub-analysis of a phase I-II randomized, controlled, and double-masked clinical trial was performed to assess the changes in the anatomical structures of the limbus. In vivo confocal microscopy (IVCM) analysis was carried out in LSCD eyes before and 12 months after allogeneic MSCT or CLET. Epithelial phenotype of the central cornea, as well as the presence of transition zones and palisades of Vogt in the limbus, were assessed using Wilcoxon test.

RESULTS

Twenty-three LSCD (14 MSCT and nine CLET) eyes were included. The epithelial phenotype of the central cornea improved significantly (p < 0.001) from 15 (eight MSCT, seven CLET) and eight (six MSCT, two CLET) LSCD eyes showing conjunctival and mixed phenotypes, respectively, to eight (five MSCT, three CLET), five (two MSCT, three CLET), and ten (seven MSCT, three CLET) eyes showing conjunctival, mixed, and corneal phenotypes, respectively. Transition areas and palisades of Vogt were observed in at least one quadrant in nine (five MSCT, four CLET) and 16 (nine MSCT, seven CLET), and in four (two MSCT, two CLET) and six (three MSCT, three CLET) LSCD eyes before and after surgery, respectively. Changes in the transition zones and palisades were solely significant (p = 0.046) for the nasal and inferior quadrants, respectively.

CONCLUSIONS

MSCT and CLET improved the central corneal epithelial phenotype despite only minor changes in the anatomical structures of the limbus, as detected by IVCM technology.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT01562002.

Management of limbal stem cell deficiency by amnion-assisted conjunctival epithelial redirection using vacuum-dried amniotic membrane and fibrin glue

PURPOSE

To study the outcome of a modified amnion-assisted conjunctival epithelial redirection (ACER) technique using vacuum-dried amnion (Omnigen) and fibrin glue for managing total limbal stem cell deficiency (LSCD).

METHOD

A retrospective, interventional case series of all patients with total LSCD who underwent limbal stem cell transplant (LSCT) using the modified ACER procedure between 2016 and 2019. The outcome was defined as: (1) success: complete corneal re-epithelialisation without conjunctivalisation; (2) partial success: sub-total corneal re-epithelialisation with partial non-progressive conjunctivalisation sparing the visual axis and (3) failure: conjunctivalisation affecting the visual axis.

RESULTS

Ten patients (six men), with a mean age of 46.2±18.4 years, were included. The mean follow-up was 23.0±13.9 months. Causes of LSCD were chemical eye injury (30%), congenital aniridia-related keratopathy (30%), ocular surface malignancy (20%), Steven-Johnson syndrome (10%) and contact lens overuse (10%). 50% were bilateral. The time from diagnosis to ACER (for acquired causes) was 45.6±44.4 months. 80% of patients achieved a complete/partial success following ACER and 20% of patients required repeat LSCT. Auto-LSCT was associated with a significantly higher chance of success than allo-LSCT (p=0.048). The mean best-corrected-visual-acuity (logMAR) improved significantly from 1.76±0.64 preoperatively to 0.94±0.94 at final follow-up (p=0.009). Omnigen was available off-the-shelf stored at room temperature and its transparency enabled visualisation of the healing epithelium beneath.

CONCLUSION

LSCT using the modified ACER serves as an effective ocular surface reconstruction technique in managing total LSCD and improving vision. Vacuum-dried amnion provides advantages of easy handling, transparency and storage at room temperature.

Diagnostic Algorithm for Surgical Management of Limbal Stem Cell Deficiency

BACKGROUND

Limbal stem cell deficiency (LCSD) presents several challenges. Currently, there is no clearly defined systematic approach to LSCD diagnosis that may guide surgical tactics.

METHODS

The medical records of 34 patients with LSCD were analyzed. Diagnostic modalities included standard (visometry, tonometry, visual field testing, slit-lamp biomicroscopy with corneal fluorescein staining, Schirmer test 1, ultrasonography) and advanced ophthalmic examination methods such as anterior segment optical coherence tomography, in vivo confocal microscopy, impression cytology, and enzyme-linked immunoassay.

RESULTS

Standard ophthalmological examination was sufficient to establish the diagnosis of LSCD in 20 (58.8%) cases, whereas advanced evaluation was needed in 14 (41.2%) cases. Depending on the results, patients with unilateral LSCD were scheduled to undergo glueless simple limbal epithelial transplantation (G-SLET) or simultaneous G-SLET and lamellar keratoplasty. Patients with bilateral LSCD with normal or increased corneal thickness were enrolled in the paralimbal oral mucosa epithelium transplantation (pLOMET) clinical trial.

CONCLUSIONS

Based on the diagnostic and surgical data analyzed, the key points in LSCD diagnosis were identified, helping to guide the surgeon in selecting the appropriate surgical procedure. Finally, we proposed a novel step-by-step diagnostic algorithm and original surgical guidelines for the treatment of patients with LSCD.

A Review of the Diagnosis and Treatment of Limbal Stem Cell Deficiency

Limbal stem cell deficiency (LSCD) can cause significant corneal vascularization and scarring and often results in serious visual morbidity. An early and accurate diagnosis can help prevent the same with a timely and appropriate intervention. This review aims to provide an understanding of the different diagnostic tools and presents an algorithmic approach to the management based on a comprehensive clinical examination. Although the diagnosis of LSCD usually relies on the clinical findings, they can be subjective and non-specific. In such cases, using an investigative modality offers an objective method of confirming the diagnosis. Several diagnostic tools have been described in literature, each having its own advantages and limitations. Impression cytology and in vivo confocal microscopy (IVCM) aid in the diagnosis of LSCD by detecting the presence of goblet cells. With immunohistochemistry, impression cytology can help in confirming the corneal or conjunctival source of epithelium. Both IVCM and anterior segment optical coherence tomography can help supplement the diagnosis of LSCD by characterizing the corneal and limbal epithelial changes. Once the diagnosis is established, one of various surgical techniques can be adopted for the treatment of LSCD. These surgeries aim to provide a new source of corneal epithelial stem cells and help in restoring the stability of the ocular surface. The choice of procedure depends on several factors including the involvement of the ocular adnexa, presence of systemic co-morbidities, status of the fellow eye and the comfort level of the surgeon. In LSCD with wet ocular surfaces, autologous and allogeneic limbal stem cell transplantation is preferred in unilateral and bilateral cases, respectively. Another approach in bilateral LSCD with wet ocular surfaces is the use of an autologous stem cell source of a different epithelial lineage, like oral or nasal mucosa. In eyes with bilateral LSCD with significant adnexal issues, a keratoprosthesis is the only viable option. This review provides an overview on the diagnosis and treatment of LSCD, which will help the clinician choose the best option amongst all the therapeutic modalities currently available and gives a clinical perspective on customizing the treatment for each individual case.

Cell Morphology as an In Vivo Parameter for the Diagnosis of Limbal Stem Cell Deficiency

PURPOSE

The aim of this study was to investigate basal epithelial cell morphology (CM) in the central cornea and limbal areas of eyes with limbal stem cell deficiency (LSCD).

METHODS

This was a prospective, cross-sectional comparative study. We developed a CM scoring system based on basal epithelial cell phenotypes graded from 0 (normal) to 3 (severe morphologic alterations); this system was evaluated by 2 independent masked observers. The CM score was compared with the LSCD clinical score, mean best-corrected visual acuity, and in vivo laser scanning confocal microscopy parameters used to stage LSCD (ie, basal epithelial cell density, basal epithelial thickness, and subbasal corneal nerve fiber length density).

RESULTS

One hundred sixty-eight eyes with LSCD and 63 normal eyes were included. Compared with the control group, the LSCD group had significantly higher mean (±SD) CM scores in the central cornea (1.8 ± 0.7 vs. 0.5 ± 0.4, respectively; P = 0.01) and limbal areas (1.6 ± 0.2 vs. 1.3 ± 0.0, respectively; P < 0.05). The mean CM score in the central cornea was positively correlated with the clinical score (P < 0.01, r = 0.66) and negatively correlated with the best-corrected visual acuity (P < 0.01, r = 0.42). The CM scores were positively correlated with all other in vivo laser scanning confocal microscopy parameters in the central cornea and limbal areas (all P < 0.001).

CONCLUSIONS

Basal epithelial CM is altered in the central cornea and limbus of eyes with LSCD and thus can be used to stage the clinical severity of the disease.

Biomarkers of in vivo limbal stem cell function

PURPOSE

To evaluate in vivo parameters as biomarkers of limbal stem cell function and to establish an objective system that detects and stage limbal stem cell deficiency (LSCD).

METHODS

A total of 126 patients (172 eyes) with LSCD and 67 normal subjects (99 eyes) were included in this observational cross-sectional comparative study. Slit-lamp biomicroscopy, in vivo laser scanning confocal microscopy (IVCM), and anterior segment optical coherence tomography (AS-OCT) were performed to obtain the following: clinical score, cell morphology score, basal cell density (BCD), central corneal epithelial thickness (CET), limbal epithelial thickness (LET), total corneal nerve fiber length (CNFL), corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), and tortuosity coefficient. Their potential correlations with the severity of LSCD were investigated, and cutoff values were determined.

RESULTS

An increase clinical score correlated with a decrease in central cornea BCD, limbal BCD, CET, mean LET, maximum LET, CNFL, CNFD, CNBD, and tortuosity coefficient. Regression analyses showed that central cornea BCD, CET and CNFL were the best parameters to differentiate LSCD from normal eyes (Coef = 3.123, 3.379, and 2.223; all p < 0.05). The rank correlation analysis showed a similar outcome between the clinical scores and the central cornea BCD (ρ = 0.79), CET (ρ = 0.82), and CNFL (ρ = 0.71). A comprehensive LSCD grading formula based on a combination of these parameters was established.

CONCLUSIONS

A comprehensive staging system combining clinical presentation, central cornea BCD, CET, and CNFL is established to accurately and objectively diagnose LSCD and stage its severity.

The Corneal Changes in Diabetic Patients

Diabetes mellitus (DM) represents a systemic disorder which afects different organs. Ocular complications of the DM are the worldwide leading cause of blindness. The most common complications are diabetic retinopathy, diabetic cataract, neovascular glaucoma. Recently many investigations point out that DM can cause comlications at ocular surface as well. Condition such as decreased corneal sensitivity, dry eye or neurotrophic corneal ulceraction are the main clinical manifestations of the diabetic keratopathy (DK). Untreated, these conditions can lead to serious visual acuity decrease. Pathological processes, based on chronic inflammation, due to chronic hyperglycemia, are the main step in the process of DK development. Adequate treatment of the main disease - DM is an imperative in maintaining the healthy cornea without subjective sensations of diabetic patients.

Human limbal epithelial stem cell regulation, bioengineering and function

The corneal epithelium is continuously renewed by limbal stem/progenitor cells (LSCs), a cell population harbored in a highly regulated niche located at the limbus. Dysfunction and/or loss of LSCs and their niche cause limbal stem cell deficiency (LSCD), a disease that is marked by invasion of conjunctival epithelium into the cornea and results in failure of epithelial wound healing. Corneal opacity, pain, loss of vision, and blindness are the consequences of LSCD. Successful treatment of LSCD depends on accurate diagnosis and staging of the disease and requires restoration of functional LSCs and their niche. This review highlights the major advances in the identification of potential LSC biomarkers and components of the LSC niche, understanding of LSC regulation, methods and regulatory standards in bioengineering of LSCs, and diagnosis and staging of LSCD. Overall, this review presents key points for researchers and clinicians alike to consider in deepening the understanding of LSC biology and improving LSCD therapies.

High-Resolution Optical Coherence Tomography Angiography Characteristics of Limbal Stem Cell Deficiency

This study aimed to identify the anterior segment high-resolution optical coherence tomography (HR-OCT) and HR-OCT angiography (HR-OCTA) features suggestive of limbal stem cell deficiency (LSCD) as confirmed by both impression cytology (IC) and in vivo confocal microscopy (IVCM). This was a single-centre prospective cross-sectional study including 24 eyes of 22 patients with clinical suspicion of LSCD based on peripheral superficial corneal vascularisation and scarring. On IC and IVCM, performed and interpreted by blinded observers, 12 eyes each were diagnosed with and without LSCD. Additionally, 10 eyes of 5 healthy volunteers with no ocular pathology were also imaged. The 136 HR-OCT/A images of these 34 eyes were analysed with respect to 12 imaging parameters; the parameters most suggestive of LSCD were identified and the sensitivity and specificity were calculated. In the LSCD group, the most common aetiology was ocular chemical burns (83%), whereas in the non-LSCD group, the most common aetiology was viral keratitis (67%). Multiple logistic regression analysis revealed that mean epithelial reflectivity, mean stromal reflectivity, and mean superficial vascular density were the parameters that were diagnostic of LSCD on HR-OCT/A (p < 0.0001). A ratio of the mean epithelial reflectivity to stromal reflectivity of >1.29 corresponded with a high sensitivity (91.7%) and specificity (98.75%); while a mean superficial vascular density score of >0.38 corresponded with a sensitivity of 97.9% and specificity of 73.8%. In conclusion, HR-OCT/A as a non-invasive imaging modality could prove to be a useful tool for confirming the diagnosis of LSCD, with potential clinical and research applications.

Treatment of Capecitabine Corneal Side Effects With Autologous Blood-derived Serum Eye Drops

BACKGROUND/AIM

To describe the clinical progress and management of ocular side effects in a 35-year-old patient with metastatic breast cancer who underwent oral chemotherapy with capecitabine and lapatinib.

MATERIALS AND METHODS

Slit lamp evaluation revealed bilateral perikeratic hyperemia, perilimbal conjunctival edema associated with corneal marginal infiltrates and epithelial and anterior stromal defects in both eyes. Slit lamp examination, in vivo confocal microscopy and anterior-segment optical coherence tomography were highly suggestive for limbal stem cell deficiency. The decision to administer autologous blood- derived serum eye drops was made.

RESULTS

Following administration of autologous blood-derived serum eye drops, corneal marginal infiltrates, epithelial and stromal defects significantly regressed in both eyes after only 10 days. Chemotherapy was resumed and serum eye drops were prescribed simultaneously.

CONCLUSION

Autologous blood-derived serum eye drops may be an adequate therapeutic choice for bilateral corneal lesions detected as ocular side effects of capecitabine.

Histopathological Characteristics of Limbal Stem Cell Deficiency Secondary to Chronic Vernal Keratoconjunctivitis

PURPOSE

To describe the histopathological characteristics of limbal stem cell deficiency (LSCD) due to chronic vernal keratoconjunctivitis (VKC).

METHODS

This retrospective study included 14 eyes of 13 patients who underwent simple limbal epithelial transplantation for total LSCD from 2017 to 2018. The histological characteristics of the excised fibrovascular pannus were compared between 2 groups of 7 eyes, each with LSCD due to VKC and chemical burns (CB). Histological characteristics and type of inflammation were studied using special stains and immunohistochemistry. Fisher exact test was used to detect the statistical significance of the histological differences between both groups.

RESULTS

Epithelial hypertrophy, epithelial downgrowth, and eosinophilic infiltration were noted in all eyes in the VKC group (7/7, 100%). Epithelial hypertrophy was noted in 3 of the 7 (42.8%) eyes in the CB group, whereas epithelial downgrowth and eosinophilic infiltrates were absent. The average chronic inflammatory score of the pannus (5.28) was higher in VKC than in CB (3.85; P = 0.1080). The presence of goblet cells was higher in the CB group (5/7, 1.4%) than in the VKC group (3/4, 2.8%), although not statistically significant. Other histological differences between the groups were not statistically significant.

CONCLUSIONS

The histopathological features of LSCD in VKC reveal some distinctive characteristics. These include the presence of epithelial downgrowth, eosinophilic infiltration, and epithelial solid and cystic implants. Although this information may be used to establish the diagnostic criteria for VKC as the cause of LSCD, further studies are needed to elucidate the reasons behind these unique findings.

Bilateral Limbal Stem Cell Alterations in Patients With Unilateral Herpes Simplex Keratitis and Herpes Zoster Ophthalmicus as Shown by In Vivo Confocal Microscopy

Purpose

The purpose of this study was to investigate the limbal changes in the palisades of Vogt (POV) in patients with herpes simplex keratitis (HSK) and herpes zoster ophthalmicus (HZO) with the application of in vivo confocal microscopy (IVCM).

Methods

We enrolled 35 eyes of 35 consecutive patients with HSK and 4 patients with HZO in this observational study. Thirty-five participants were also recruited from a healthy population as the control group. All subjects were examined by IVCM in addition to routine slit-lamp biomicroscopy. The IVCM images of the corneal basal epithelial cells, corneal nerve, and the corneoscleral limbus were acquired and then were analyzed semiquantitatively.

Results

The rate of absent and atypical POV was significantly higher in the affected eyes of patients with HSK than in the contralateral eyes and eyes of controls (88.57% vs. 65.71% vs. 17.14%, P < 0.01). In the HZO group, the rate of absent and atypical POV was 100% in the affected eyes and 50% in the contralateral eyes. When compared to the contralateral unaffected eyes and control eyes, the average density of the central basal epithelial cells and the sub-basal nerve plexus density and the total number of nerves in the central area of the affected eyes were significantly lower in the HSK group (1541 ± 704.4 vs. 2510 ± 746.8 vs. 3650 ± 746.1 cells/mm², P < 0.0001). Spearman's rank correlation showed that the presence of absent and atypical POV had a significant negative correlation with central corneal basal epithelial cells (r_s = −0.44979, P < 0.0001), the density of total nerves (r_s = −0.49742, P < 0.0001), and the total nerve numbers (r_s = −0.48437, P < 0.0001). A significant positive correlation was established between the presence of absent and atypical POV and HSK severity in affected eyes in the superior, inferior, nasal, and temporal quadrants (r_s = 0.68940, r_s = 0.78715, r_s = 0.65591, and r_s = 0.75481, respectively, P < 0.0001) and the contralateral eyes (r_s = 0.51636, r_s = 0.36207, r_s = 0.36990, r_s = 0.51241, correspondingly, P < 0.0001).

Conclusions

Both eyes of patients with unilateral HSK and HZO demonstrated a profound and significant loss of limbal stem cells, which may explain the fact that HSK and HZO are risk factors for limbal stem cell deficiency (LSCD) in both eyes. The loss of LSCs was strongly correlated with the sub-basal nerve plexus and central basal epithelial cell alterations as shown by IVCM.

Clinical outcomes of modified simple limbal epithelial transplantation for limbal stem cell deficiency in Chinese population: a retrospective case series

Objective

To report the clinical outcomes of a novel surgical technique, namely simple limbal epithelial transplantation (SLET), for the treatment of limbal stem cell deficiency (LSCD).

Methods

Thirteen patients (13 eyes) with LSCD who underwent autologous (10 eyes) or allogeneic (3 eyes) modified SLET between 2018 and 2021 were enrolled in this study. Grades of symblepharon, corneal conjunctivalization, vascularization, opacification, and visual acuity (VA) were evaluated preoperatively and postoperatively. In 2 cases, in vivo confocal microscopy (IVCM) and impression cytology (IC) were performed to assess the proliferation and degeneration of limbal tissue.

Results

At a postoperative follow-up of 6.5±5.3 (range, 2–20) months, 10 (10/13, 76.92%) eyes maintained a successful outcome. The grades of symblepharon, corneal conjunctivalization, vascularization, and opacification were significantly improved after SLET (P<0.05). Two-line improvement in VA was found in 6 (6/10, 60%) eyes of the successful cases. Recurrence of LSCD occurred in 3 (3/13, 23.08%) eyes, and conjunctival cyst occurred in 1 patient. After SLET, the morphology and structure of corneal epithelial cells and epithelial transition around the limbal tissue fragments were detected by IVCM and IC.

Conclusions

Our findings suggest that the SLET is a safe and effective technique for the treatment of LSCD. The corneal stroma and hAM can provide protection and nutrition for the limbal stem cells (LSCs) without negatively influencing the clinical outcomes. IVCM and IC after SLET can evaluate the effectiveness of surgery and the transition of LSCs and corneal epithelial cells.

Neuronal-epithelial cell alignment: A determinant of health and disease status of the cornea

PURPOSE

How sensory neurons and epithelial cells interact with one another, and whether this association can be considered an indicator of health or disease is yet to be elucidated.

METHODS

Herein, we used the cornea, Confetti mice, a novel image segmentation algorithm for intraepithelial corneal nerves which was compared to and validated against several other analytical platforms, and three mouse models to delineate this paradigm. For aging, eyes were collected from 2 to 52 week-old normal C57BL/6 mice (n ≥ 4/time-point). For wound-healing and limbal stem cell deficiency, 7 week-old mice received a limbal-sparing or limbal-to-limbal epithelial debridement to their right cornea, respectively. Eyes were collected 2-16 weeks post-injury (n=4/group/time-point), corneas procured, immunolabelled with βIII-tubulin, flat-mounted, imaged by scanning confocal microscopy and analyzed for nerve and epithelial-specific parameters.

RESULTS

Our data indicate that nerve features are dynamic during aging and their curvilinear arrangement align with corneal epithelial migratory tracks. Moderate corneal injury prompted axonal regeneration and recovery of nerve fiber features. Limbal stem cell deficient corneas displayed abnormal nerve morphology, and fibers no longer aligned with corneal epithelial migratory tracks. Mechanistically, we discovered that nerve pattern restoration relies on the number and distribution of stromal-epithelial nerve penetration sites.

CONCLUSIONS

Microstructural changes to innervation may explain corneal complications related to aging and/or disease and facilitate development of new assays for diagnosis and/or classification of ocular and systemic diseases.

In Vivo Confocal Microscopy of the Corneal-Conjunctival Transition in the Evaluation of Epithelial Renewal after SLET

Examination of the corneal surface by in vivo confocal microscopy (IVCM) allows for objective identification of corneal and conjunctival cell phenotypes to evaluate different epithelialization patterns. Detection of a corneal-conjunctival epithelial transition could be considered as a sign of restored epithelial function following simple limbal epithelial transplantation (SLET). This is a prospective, interventional case series. We assessed patients with limbal stem cell deficiency (LSCD) by IVCM, preoperatively and at monthly intervals following SLET. Sectors in the central and peripheral cornea were scanned. Immediately upon detection of multi-layered cells with the epithelial phenotype in the central cornea and confirmation of epithelial transition in all corneal sectors, the decision for keratoplasty was taken. Ten patients were enrolled. After SLET, epithelial phenotype in the central cornea and an epithelial transition were identified within six and nine months in seven and one patients, respectively. One patient was a partial success and one failed. Five patients underwent keratoplasty, with stable results up to 12 months. Identification of the epithelial transition zone by IVCM permits assessment of the efficacy of SLET, enabling subsequent planning of keratoplasty for visual rehabilitation. The stability of the corneal surface following keratoplasty confirms that the renewal of the corneal epithelium was effectively retained.

Corneal Epithelial Thickness Measured Using Anterior Segment Optical Coherence Tomography as a Diagnostic Parameter for Limbal Stem Cell Deficiency

OBJECTIVE

Using anterior segment optical coherence tomography (AS-OCT), we investigated the epithelial thickness (ET) of the central cornea and limbal regions in patients with limbal stem cell deficiency (LSCD) as a diagnostic and staging parameter.

DESIGN

Prospective, cross-sectional study.

METHODS

The central corneal epithelium thickness (CET) and maximum limbal epithelium thickness (mLET) were measured in the superior, inferior, nasal, and temporal limbus on AS-OCT images of the normal and eyes with LSCD. CET was obtained by 1-point (OCT-CET1) and 3-point measurement (OCT-CET3). The values of OCT-CET1 and OCT-CET3 were compared to the CET obtained with in vivo confocal microscopy (IVCM-CET).

RESULTS

Sixty-eight eyes of 50 patients with LSCD and 52 eyes of 34 normal subjects were included. The mean (±standard deviation) OCT-CET3 was 55.0 ± 3.0 μm (range, 50.6-62.0 μm) in the control group and 41.6 ± 10.8 μm (range, 0-56.3 μm) in the LSCD group (P < .001). OCT-CET3 had a better correlation with IVCM-CET (r = 0.91) than did OCT-CET1 (r = 0.87, P = .001). The degree of reduction in OCT-CET3 increased in more advanced clinical stages of LSCD (all P < .001). The OCT-CET3 cutoff value that suggests LSCD was 46.6 μm. Compared with the control group, the LSCD group had decreases in mLET in all 4 limbal regions (all P < .001). The sensitivity and specificity of OCT-CET3 is the highest among all mLET in detecting LSCD.

CONCLUSIONS

Both CET and mLET were thinner in patients with LSCD than in normal subjects. OCT-CET3 appears to be a reliable parameter to confirm LSCD when there is clinical suspicion.

Short-Term Results Analysis in the Allogenic Transplantation of Limbal Stem Cells Expanded on Amniotic Membrane in Patients with Bilateral Limbal Stem Cell Deficiency

Purpose: The objective of this study was to describe the short-term results of allogenic transplantation of limbal stem cells expanded on amniotic membrane for the ocular surface reconstruction. Methods: Prospective nonrandomized, nonmasked study in a single ophthalmological center. Ten patients with bilateral total limbal stem cell deficiency (LSCD) were included. Expression and presence of ABCB5 and Δp63α in amniotic membrane-cultured limbal epithelial stem cells were analyzed, in relationship with clinical changes after allogenic transplantation. An objective evaluation was performed to determine corneal transparency and superficial vascularization. Results: In a median follow-up time of 11.6 months, 7 patients (70%) were considered as failure compared with the preoperative status. ABCB5 and Δp63α are expressed in similar amount in the limbal epithelial cells expanded in vitro and transplanted in patients with bilateral LSCD. Conclusions: Transplantation of allogenic epithelial limbal cells expanded in amniotic membrane could be considered in patients with LSCD due to burns or congenital etiologies such as aniridia, but its benefit is limited for patients with immunologic diseases.

Corneal alteration and pathogenesis in diabetes mellitus

The incidence of diabetes mellitus (DM) and its complications have increased considerably worldwide. Diabetic keratopathy is the major complication of the cornea characterized by delayed corneal wound healing, decreasing corneal epithelial sensitivity, and recurrent corneal ulcers. There is accumulating evidence that diabetic keratopathy is correlated with the hyperglycemic state. Different corneal components may produce different alterations under hyperglycemia. In addition, diabetic nerve alteration may become a novel biomarker of early-stage DM. Abnormalities of the corneal nerve plexus have been associated with diabetic inflammatory states. There is rapidly growing evidence based on investigations of diabetic corneal nerves through in vivo confocal microscopy. Understanding the molecular pathogenesis caused by hyperglycemia may assist in the identification of novel biomarkers, as well as therapeutic targets for early treatment. This review mainly summarizes recent findings on corneal alteration and pathogenesis in DM.

Immune reactions after modern lamellar (DALK, DSAEK, DMEK) versus conventional penetrating corneal transplantation

In the past decade, novel lamellar keratoplasty techniques such as Deep Anterior Lamellar Keratoplasty (DALK) for anterior keratoplasty and Descemet stripping automated endothelial keratoplasty (DSAEK)/Descemet membrane endothelial keratoplasty (DMEK) for posterior keratoplasty have been developed. DALK eliminates the possibility of endothelial allograft rejection, which is the main reason for graft failure after penetrating keratoplasty (PK). Compared to PK, the risk of endothelial graft rejection is significantly reduced after DSAEK/DMEK. Thus, with modern lamellar techniques, the clinical problem of endothelial graft rejection seems to be nearly solved in the low-risk situation. However, even with lamellar grafts there are epithelial, subepithelial and stromal immune reactions in DALK and endothelial immune reactions in DSAEK/DMEK, and not all keratoplasties can be performed in a lamellar fashion. Therefore, endothelial graft rejection in PK is still highly relevant, especially in the "high-risk" setting, where the cornea's (lymph)angiogenic and immune privilege is lost due to severe inflammation and pathological neovascularization. For these eyes, currently available treatment options are still unsatisfactory. In this review, we will describe currently used keratoplasty techniques, namely PK, DALK, DSAEK, and DMEK. We will summarize their indications, provide surgical descriptions, and comment on their complications and outcomes. Furthermore, we will give an overview on corneal transplant immunology. A specific focus will be placed on endothelial graft rejection and we will report on its incidence, clinical presentation, and current/future treatment and prevention options. Finally, we will speculate how the field of keratoplasty and prevention of corneal allograft rejection will develop in the future.

Diagnostic criteria for limbal stem cell deficiency before surgical intervention-A systematic literature review and analysis

An accurate diagnosis of limbal stem cell deficiency (LSCD) is the premise of an appropriate treatment; however, there is no consensus about the diagnostic criteria for LSCD. We performed a systematic literature search of the peer-reviewed articles on PubMed, Medline, and Ovid to investigate how LSCD was diagnosed before surgical intervention. The methods used to diagnose LSCD included clinical presentation, impression cytology, and in vivo confocal microscopy. Among 131 eligible studies (4054 eyes), 26 studies (459 eyes, 11.3%) did not mention the diagnostic criteria. In the remaining 105 studies, the diagnosis of LSCD was made on the basis of clinical examination alone in 2398 eyes (62.9%), and additional diagnostic tests were used in 1047 (25.8%) eyes. Impression cytology was used in 981 eyes (24.2%), in vivo confocal microscopy was used in 29 eyes (0.7%), and both impression cytology and in vivo confocal microscopy were used in 37 eyes (0.9%). Our findings suggest that only a small portion of patients underwent a diagnostic test to confirm the diagnosis of LSCD. Treating physicians should be aware of the limitations of clinical examination in diagnosing LSCD and perform a diagnostic test whenever possible before surgical intervention.

A proof-of-concept clinical trial using mesenchymal stem cells for the treatment of corneal epithelial stem cell deficiency

Ocular stem cell transplantation derived from either autologous or allogeneic donor corneoscleral junction is a functional cell therapy to manage extensive and/or severe limbal stem cell deficiencies that lead to corneal epithelial failure. Mesenchymal stem cells have been properly tested in animal models of this ophthalmic pathology, but never in human eyes despite their potential advantages. We conducted a 6- to 12-month proof-of-concept, randomized, and double-masked pilot trial to test whether allogeneic bone marrow-derived mesenchymal stem cell transplantation (MSCT], n = 17) was as safe and as equally efficient as allogeneic cultivated limbal epithelial transplantation (CLET), (n = 11) to improve corneal epithelial damage due to limbal stem cell deficiency. Primary endpoints demanded combination of symptoms, signs, and the objective improvement of the epithelial phenotype in central cornea by in vivo confocal microscopy. This proof-of-concept trial showed that MSCT was as safe and efficacious as CLET. Global success at 6-12 months was 72.7%-77.8% for CLET cases and 76.5%-85.7% for MSCT cases (not significant differences). Central corneal epithelial phenotype improved in 71.4% and 66.7% of MSCT and CLET cases, respectively at 12 months (P = 1.000). There were no adverse events related to cell products. This trial suggests first evidence that MSCT facilitated improvement of a diseased corneal epithelium due to lack of its stem cells as efficiently as CLET. Consequently, not only CLET but also MSCT deserves more preclinical investigational resources before the favorable results of this proof-of-concept trial could be transformed into the larger numbers of the multicenter trials that would provide stronger evidence. (ClinicalTrials.gov number, NCT01562002.).

Global Consensus on Definition, Classification, Diagnosis, and Staging of Limbal Stem Cell Deficiency

PURPOSE

Despite extensive knowledge gained over the last 3 decades regarding limbal stem cell deficiency (LSCD), the disease is not clearly defined, and there is lack of agreement on the diagnostic criteria, staging, and classification system among treating physicians and research scientists working on this field. There is therefore an unmet need to obtain global consensus on the definition, classification, diagnosis, and staging of LSCD.

METHODS

A Limbal Stem Cell Working Group was first established by The Cornea Society in 2012. The Working Group was divided into subcommittees. Four face-to-face meetings, frequent email discussions, and teleconferences were conducted since then to obtain agreement on a strategic plan and methodology from all participants after a comprehensive literature search, and final agreement was reached on the definition, classification, diagnosis, and staging of LSCD. A writing group was formed to draft the current manuscript, which has been extensively revised to reflect the consensus of the Working Group.

RESULTS

A consensus was reached on the definition, classification, diagnosis, and staging of LSCD. The clinical presentation and diagnostic criteria of LSCD were clarified, and a staging system of LSCD based on clinical presentation was established.

CONCLUSIONS

This global consensus provides a comprehensive framework for the definition, classification, diagnosis, and staging of LSCD. The newly established criteria will aid in the correct diagnosis and formulation of an appropriate treatment for different stages of LSCD, which will facilitate a better understanding of the condition and help with clinical management, research, and clinical trials in this area.

Classification of Limbal Stem Cell Deficiency Using Clinical and Confocal Grading

PURPOSE

To grade the severity of limbal stem cell deficiency (LSCD) based on the extent of clinical presentation and central corneal basal epithelial cell density (BCD).

METHODS

This is a retrospective observational comparative study of 48 eyes of 35 patients with LSCD and 9 eyes of 7 normal subjects (controls). Confocal images of the central cornea were acquired. A clinical scoring system was created based on the extent of limbal and corneal surface involvement. LSCD was graded as mild, moderate, and severe stages based on the clinical scores. The degree of BCD reduction was given a score of 0 to 3.

RESULTS

Compared with BCD in controls, BCD decreased by 23.0%, 40.4%, and 69.5% in the mild, moderate, and severe stages of LSCD classified by the clinical scoring system, respectively. The degree of BCD reduction was positively correlated with larger limbal and corneal surface involvement and when the central visual axis was affected (all P ≤ 0.0005). Mean corrected distance visual acuity logarithm of the minimum angle of resolution was 0.0 ± 0.0 in control eyes, 0.2 ± 0.5 in mild LSCD, 0.6 ± 0.4 in moderate LSCD, and 1.6 ± 1.1 in severe LSCD (P < 0.0001). There was a significant correlation between a higher clinical score and corrected distance visual acuity logarithm of the minimum angle of resolution (rho = 0.82; P < 0.0001) and a greater decrease in BCD (rho = -0.78; P < 0.0001).

CONCLUSIONS

A clinical scoring system was developed to assess the extent of clinical presentation of LSCD. A classification system to grade the severity of LSCD can be established by combining the BCD score with the clinical score.

[In vivo confocal microscopy and optical coherence tomography as innovative tools for the diagnosis of limbal stem cell deficiency (French translation of the article)]

The limbus is the anatomical and functional barrier between corneal and conjunctival epithelia. It is characterized by presence of the limbal stem cell niche which allows corneal homeostasis to be maintained. Limbal stem cell deficiency is characterized by a dual process: insufficient regeneration of corneal epithelium, which cannot therefore assure its function of physiological support, associated with corneal invasion by conjunctival proliferation. Diagnosis is currently made via routine clinical examination, corneal impression cytology and in vivo confocal microscopy (IVCM). Slit lamp examination shows abnormal limbal anatomy, thin and irregular epithelium with late fluorescein staining, and superficial vascularization. With its high resolution, IVCM allows identification of limbal and corneal epithelial changes at a cellular level in en face views, parallel to the corneal surface, but with a restricted viewing field of the corneal surface. It shows a poor transition between the corneal and conjunctival epithelia, associated with a loss of the normal corneal epithelial stratification, low basal cell and sub-basal nerve plexus densities, even with sub-epithelial fibrosis. Optical coherence tomography in central cornea and at the limbus, with scans in different orientations, allows a quick, global and non-invasive analysis of normal eyes and those with limbal stem cell deficiency. It shows a thin limbal epithelium, lacking normal thickening, featuring absence of stromal undulations and limbal crypts in cross-sections and sections parallel to the limbus, lack of visible limbal crypts in en face sections, loss of clear transition between the hyporeflective corneal epithelium and the hyperreflective conjunctival epithelium, and hyperreflective sub-epithelial fibrosis.

Limbal Stem Cell Transplantation: Clinical Results, Limits, and Perspectives

Limbal stem cell deficiency (LSCD) is a clinical condition characterized by damage of cornea limbal stem cells, which results in an impairment of corneal epithelium turnover and in an invasion of the cornea by the conjunctival epithelium. In these patients, the conjunctivalization of the cornea is associated with visual impairment and cornea transplantation has poor prognosis for recurrence of the conjunctivalization. Current treatments of LSCD are aimed at replacing the damaged corneal stem cells in order to restore a healthy corneal epithelium. The autotransplantation of limbal tissue from the healthy, fellow eye is effective in unilateral LSCD but leads to depauperation of the stem cell reservoir. In the last decades, novel techniques such as cultivated limbal epithelial transplantation (CLET) have been proposed in order to reduce the damage of the healthy fellow eye. Clinical and experimental evidence showed that CLET is effective in inducing long-term regeneration of a healthy corneal epithelium in patients with LSCD with a success rate of 70%–80%. Current limitations for the treatment of LSCD are represented by the lack of a marker able to unequivocally identify limbal stem cells and the treatment of total, bilateral LSCD which requires other sources of stem cells for ocular surface reconstruction.

Simultaneous penetrating keratoplasty and amniotic membrane transplantation in eyes with a history of limbal stem cell deficiency

PURPOSE

To describe the outcomes of simultaneous penetrating keratoplasty (PK) and amniotic membrane transplantation (AMT) performed both as a ring-shaped graft and as a temporary patch in eyes with a history of limbal stem cell deficiency (LSCD).

METHODS

Prospective observational case series including 48 simultaneous PK/AMT procedures (48 patients) in eyes with a history of partial or total LSCD. Patients with total LSCD were first treated with limbal stem cell transplantation. The preoperative indication was graft failure in 58.3% of cases. Most recipients (89.6%) were at high-risk for rejection.

RESULTS

The mean graft reepithelialization time was 29.2±30.8 days. Graft reepithelialization was achieved in 30 days in 70.8% of cases. No AMT-related adverse events were observed. The mean time from keratoplasty-to-last visit was 84.5±54.5 months. The 3-year graft survival rate was 62.5%. Recurrence of corneal epithelial defects after graft reepithelialization (47.9%) was associated with lower graft survival (P=0.004). In eyes with successful grafts at the last visit, the mean LogMAR visual acuity was 1.90 (20/1575)±5 lines before keratoplasty and 0.89 (20/155)±10 lines at 5 years. A ring of amniotic membrane was visible between the graft stroma and the corneal epithelium on slit-lamp examination and optical coherence tomography in all successful cases.

CONCLUSIONS

In this series of eyes with a history of LSCD and at high-risk of rejection, simultaneous PK and AMT were associated with satisfactory graft survival and no additional adverse events.

Femtosecond Laser-Assisted Stromal Lenticule Addition Keratoplasty for the Treatment of Advanced Keratoconus: A Preliminary Study

PURPOSE

To investigate the in vivo effect of a novel femtosecond laser-assisted procedure termed stromal lenticule addition keratoplasty for advanced keratoconus.

METHODS

Ten patients with stage III and IV stable keratoconus were included. Negative meniscus-shaped stromal lenticules were produced from corneoscleral eye bank buttons with a refractive lenticule extraction procedure with a 500-kHz VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany). Recipient corneas underwent a modified femtosecond laser flap-cut procedure to produce an intrastromal pocket and lenticules were implanted. Patients were followed up for 6 months after surgery with determination of uncorrected (UDVA) and corrected (CDVA) distance visual acuity, subjective refraction and topographic corneal curvature changes, anterior segment optical coherence tomography (AS-OCT), and in vivo confocal microscopy.

RESULTS

Comparison of preoperative and 6-month postoperative UDVA and CDVA showed statistically significant improvements (P = .024 and .007, respectively) from 1.58 ± 0.36 to 1.22 ± 0.37 and from 1.07 ± 0.17 to 0.70 ± 0.23 logMAR. Eight of 10 eyes showed an improvement in UDVA (P < .001) that ranged between one and three lines, whereas all but one eye presented improved CDVA. Corneal topography documented a decrease between preoperative and 6-month postoperative anterior mean curvature (AVG-K at 3 mm) and anterior Q values (P = .005). AS-OCT showed a significant increase in thickness of the central and mid-peripheral cornea produced by the lenticule implantation (P = .005).

CONCLUSIONS

The stromal lenticule addition keratoplasty procedure was clinically efficient in improving the corneal shape and vision in patients with keratoconus. Negative meniscus-shaped lenticule addition induced a flattening of the cone while increasing corneal thickness. [J Refract Surg. 2018;34(1):36-44.].

A Case of Corneal Neovascularization Misdiagnosed as Total Limbal Stem Cell Deficiency

PURPOSE

To report a case of corneal neovascularization misdiagnosed as total limbal stem cell deficiency (LSCD).

METHODS

This is a case report of a 61-year-old woman who has a history of bilateral idiopathic scleritis, keratitis, and uveitis for more than 20 years. She was diagnosed with total LSCD in her left eye based on clinical presentation alone and was confirmed as a candidate for limbal transplantation at several major tertiary eye care centers in the United States. After referral to the Stein Eye Institute, in vivo confocal microscopy (IVCM) and anterior segment optical coherence tomography (AS-OCT) were performed to clarify the diagnosis.

RESULTS

Slit-lamp examination of the left eye revealed 360-degree severe thinning at the limbus and peripheral corneal pannus and neovascularization that spared the central cornea, a smooth epithelium without fluorescein staining at the central cornea, an uneven surface, and pooling of fluorescein at the peripheral cornea accompanied by minimal fluorescein staining of the sectoral peripheral epithelium. IVCM showed that epithelial cells in the central cornea exhibited a corneal phenotype and that the morphology of the epithelium in all limbal regions except the nasal limbus was normal. Epithelial cellular density and thickness were within the normal range. AS-OCT showed severe thinning in the limbus and a normal epithelial layer in the cornea and limbus. Based on the findings of IVCM and AS-OCT, we concluded that the patient had minimal LSCD, and limbal stem cell transplantation was not recommended.

CONCLUSIONS

Clinical presentation alone is insufficient to correctly diagnose LSCD in complex cases. Additional diagnostic tests, such as IVCM, are necessary to confirm the diagnosis before any surgical intervention.

Emerging Therapeutic Strategies for Limbal Stem Cell Deficiency

Identification and characterization of the limbal epithelial stem cells (LESCs) has proven to be a major accomplishment in anterior ocular surface biology. These cells have been shown to be a subpopulation of limbal epithelial basal cells, which serve as the progenitor population of the corneal epithelium. LESCs have been demonstrated to play an important role in maintaining corneal epithelium homeostasis. Many ocular surface diseases, including intrinsic (e.g., Sjogren's syndrome) or extrinsic (e.g., alkali or thermal burns) insults, which impair LESCs, can lead to limbal stem cell deficiency (LSCD). LSCD is characterized by an overgrowth of conjunctival-derived epithelial cells, corneal neovascularization, and chronic inflammation, eventually leading to blindness. Treatment of LSCD has been challenging, especially in bilateral total LSCD. Recently, advances in LESC research have led to novel therapeutic approaches for treating LSCD, such as transplantation of the cultured limbal epithelium. These novel therapeutic approaches have demonstrated efficacy for ocular surface reconstruction and restoration of vision in patients with LSCD. However, they all have their own limitations. Here, we describe the current status of LSCD treatment and discuss the advantages and disadvantages of the available therapeutic modalities.

Spectral-domain Optical Coherence Tomography in Limbal Stem Cell Deficiency. A Case-Control Study

PURPOSE

To evaluate the efficacy of optical coherence tomography (OCT) as a noncontact method for imaging the ocular surface in limbal stem cell deficiency (LSCD) and normal eyes.

DESIGN

Retrospective case-control study.

METHODS

Setting: Institutional.

STUDY POPULATION

Twenty-two eyes with LSCD (study group, 22 patients) and 10 normal eyes (control group, 10 patients).

OBSERVATION PROCEDURES

Spectral-domain (SD)-OCT and confocal microscopy in both the limbal and central corneal zones.

MAIN OUTCOME MEASURES

Pachymetry data from the central cornea, presence of the palisades of Vogt, limbal crypts, and clear transition between the hyporeflective corneal epithelium and the hyperreflective conjunctival epithelium assessed on cross sections parallel and perpendicular to the limbus and en face sections of the limbal region. Parallel, perpendicular, and en face limbal scores were calculated by adding results of the 4 limbal quadrants.

RESULTS

Both the difference between the minimal and the maximal epithelial thicknesses and the epithelial thickness standard deviation were significantly higher in the study group (mean, 47 μm/10 μm) compared with the control group (mean, 8 μm/2 μm). The parallel, perpendicular, and en face limbal scores were significantly lower in the study group (0.1/0.6/0.2) compared with the control group (7.4/4.8/3.5). Poorer visual acuity was significantly associated with higher standard deviation and difference between minimal and maximal corneal epithelial thicknesses (r_s, +0.81/+0.77) and lower parallel, perpendicular, and en face limbal scores (-0.82/-0.73/-0.82).

CONCLUSIONS

SD-OCT of both the central cornea and limbus with various section orientations is a valuable imaging modality allowing noninvasive and rapid overall precise assessment of both normal and LSCD eyes.

Cornea and anterior eye assessment with slit lamp biomicroscopy, specular microscopy, confocal microscopy, and ultrasound biomicroscopy

Current corneal assessment technologies make the process of corneal evaluation extremely fast and simple, and several devices and technologies show signs that help in identification of different diseases thereby, helping in diagnosis, management, and follow-up of patients. The purpose of this review is to present and update readers on the evaluation of cornea and ocular surface. This first part reviews a description of slit lamp biomicroscopy (SLB), endothelial specular microscopy, confocal microscopy, and ultrasound biomicroscopy examination techniques and the second part describes the corneal topography and tomography, providing up-to-date information on the clinical recommendations of these techniques in eye care practice. Although the SLB is a traditional technique, it is of paramount importance in clinical diagnosis and compulsory when an eye test is conducted in primary or specialist eye care practice. Different techniques allow the early diagnosis of many diseases, especially when clinical signs have not yet become apparent and visible with SLB. These techniques also allow for patient follow-up in several clinical conditions or diseases, facilitating clinical decisions and improving knowledge regarding the corneal anatomy.

The Role of Limbal Epithelial Stem Cells in Regulating Corneal (Lymph)angiogenic Privilege and the Micromilieu of the Limbal Niche following UV Exposure

The cornea is a clear structure, void of blood, and lymphatic vessels, functioning as our window to the world. Limbal epithelial stem cells, occupying the area between avascular cornea and vascularized conjunctiva, have been implicated in tissue border maintenance, preventing conjunctivalisation and propagation of blood and lymphatic vessels into the cornea. Defects in limbal epithelial stem cells are linked to corneal neovascularisation, including lymphangiogenesis, chronic inflammation, conjunctivalisation, epithelial abnormalities including the presence of goblet cells, breaks in Bowman's membrane, persistent epithelial defects and ulceration, ocular surface squamous neoplasia, lipid keratopathy, pain, discomfort, and compromised vision. It has been postulated that pterygium is an example of focal limbal deficiency. Previous reports showing changes occurring in limbal epithelium during pterygium pathogenesis suggest that there is a link to stem cell damage. In this light, pterygium can serve as a model disease of UV-induced stem cell damage also characterised by corneal blood and lymphangiogenesis. This review focuses on the role of corneal and limbal epithelial cells and the stem cell niche in maintaining corneal avascularity and corneal immune privilege and how this may be deregulated following UV exposure. We present an overview of the PUBMED literature in the field as well as recent work from our laboratories.

In Vivo Analysis of Prostaglandins-induced Ocular Surface and Periocular Adnexa Modifications in Patients with Glaucoma

BACKGROUND/AIM

Prostaglandin analogues (PGAs) are a first-line medical treatment for glaucoma because of their powerful intraocular pressure (IOP) lowering effect, few systemic side-effects (SEs), and the once daily administration. Despite the high systemic safety profile, the chronic use of PGAs may induce periocular and ocular surface (OS)-related side effects, which affect a significant proportion of glaucomatous patients. In this review, we summarize the current knowledge about SEs of PGAs on periocular structures and OS, and their implications in clinical practice.

MATERIALS AND METHODS

A comprehensive literature search on the PubMed platform was performed. Two hundred fifty articles fulfilling key words were identified, of which 180 were excluded since they did not concern the effects of PGAs on the periocular tissues and OS, or because of their limited relevance. The following key words were used and combined, to narrow-down the literature: "prostaglandin" and "ocular surface," which identified 184 unique publications, of which 68 were selected; "prostaglandin" and "periocular" which identified 46 unique publications, of which 11 were selected. An additional search was conducted using "prostaglandin" and "Meibomian glands (MGs)", which identified twenty unique publications, of which 8 were selected. Thus, a total of 70 articles were chosen based on their relevance and were included in this review.

RESULTS

Prostaglandin-associated peri-orbitopathy, skin pigmentation and hypertrichosis, eyelash growth, and MGs dysfunction are the most frequent modifications of periocular tissues. They are induced by the tissue accumulation of PGAs, and FP receptor stimulation. Without preservatives, PGAs act as stimulators of conjunctival goblet cells, which are the main source of ocular surface mucoproteins, and seem to increase conjunctival epithelium microcysts proposed as in vivo hallmark of the trans-scleral aqueous humour outflow. Additional PGA-induced modifications can be recognized in the cornea, corneo-scleral limbus, conjunctival stroma and, conjunctiva-associated lymphoid tissue, mainly appearing as inflammatory changes. OS epithelia desquamation, chemosis, apoptosis, dendritic cell activation, conjunctival or episcleral vasodilation, and sub-basal nerve plexus disruption were also described in patients receiving preserved PGAs.

CONCLUSION

PGAs induce several modifications of the OS structures and adnexa; nonetheless, none of them significantly reduces the local safety profile of this class of drugs. Moreover, the OS changes do not affect the IOP lowering efficacy of PGAs. On these bases, local SEs of PGAs should not discourage clinicians in using this class of medications because of their efficacy, the systemic safety profile, and the better adherence.

The diagnosis of limbal stem cell deficiency

Limbal stem cells (LSCs) maintain the normal homeostasis and wound healing of corneal epithelium. Limbal stem cell deficiency (LSCD) is a pathologic condition that results from the dysfunction and/or an insufficient quantity of LSCs. The diagnosis of LSCD has been made mainly based on medical history and clinical signs, which often are not specific to LSCD. Methods to stage the severity of LSCD have been lacking. With the application of newly developed ocular imaging modalities and molecular methods as diagnostic tools, standardized quantitative criteria for the staging of LSCD can be established. Because of these recent advancements, effective patient-specific therapy for different stages of LSCD may be feasible.

In vivo imaging of palisades of Vogt in dry eye versus normal subjects using en-face spectral-domain optical coherence tomography

PURPOSE

To evaluate a possible clinical application of spectral-domain optical coherence tomography (SD-OCT) using en-face module for the imaging of the corneoscleral limbus in normal subjects and dry eye patients.

PATIENTS AND METHODS

Seventy-six subjects were included in this study. Seventy eyes of 35 consecutive patients with dry eye disease and 82 eyes of 41 healthy control subjects were investigated. All subjects were examined with the Avanti RTVue® anterior segment OCT. En-face OCT images of the corneoscleral limbus were acquired in four quadrants (inferior, superior, nasal and temporal) and then were analyzed semi-quantitatively according to whether or not palisades of Vogt (POV) were visible. En-face OCT images were then compared to in vivo confocal microscopy (IVCM) in eleven eyes of 7 healthy and dry eye patients.

RESULTS

En-face SD-OCT showed POV as a radially oriented network, located in superficial corneoscleral limbus, with a good correlation with IVCM features. It provided an easy and reproducible identification of POV without any special preparation or any direct contact, with a grading scale from 0 (no visualization) to 3 (high visualization). The POV were found predominantly in superior (P<0.001) and inferior (P<0.001) quadrants when compared to the nasal and temporal quadrants for all subjects examined. The visibility score decreased with age (P<0.001) and was lower in dry eye patients (P<0.01). In addition, the score decreased in accordance with the severity of dry eye disease (P<0.001).

CONCLUSION

En-face SD-OCT is a non-contact imaging technique that can be used to evaluate the POV, thus providing valuable information about differences in the limbal anatomy of dry eye patients as compared to healthy patients.

Characterization of the Corneal Subbasal Nerve Plexus in Limbal Stem Cell Deficiency

PURPOSE

To quantify the changes in the subbasal nerve plexus in patients with limbal stem cell deficiency (LSCD) using in vivo laser scanning confocal microscopy.

METHODS

In this retrospective cross-sectional comparative study, confocal images of 51 eyes of 37 patients with LSCD collected between 2010 and 2015 by the Heidelberg Retina Tomograph III Rostock Corneal Module Confocal Microscope were analyzed. Two independent observers evaluated the scans of the central cornea. Seventeen normal eyes of 13 subjects served as controls. Total subbasal nerve density (SND), density of long nerves (ie, nerves 200 μm or longer), and the degree of tortuosity were quantified.

RESULTS

The mean (±SD) total SND and long nerve density were 48.0 ± 34.2 and 9.7 ± 10.9 nerves/mm, respectively, in all eyes with LSCD and 97.3 ± 29.9 and 35.3 ± 25.3 nerves/mm, respectively, in eyes of the control group (P < 0.001 for both comparisons). Compared with SND in control subjects, SND was reduced by 34.9% in the early stage, 54.0% in the intermediate stage, and 73.5% in the late stage of LSCD. The degrees of nerve tortuosity were significantly greater in patients with LSCD than in control subjects and differed among the early, intermediate, and late stages of LSCD. Reductions in total SND and long nerve density were positively correlated with the severity of LSCD.

CONCLUSIONS

Reductions in total SND and long nerve density were accompanied by increases in nerve tortuosity in eyes with LSCD. These parameters could be used as quantifiable measures of LSCD severity.

Clinical and morphological manifestations of aniridia-associated keratopathy on anterior segment optical coherence tomography and in vivo confocal microscopy

PURPOSE

The study aimed to evaluate clinical and morphological changes in the limbal palisades of Vogt (POV) at different stages of aniridia-associated keratopathy (AAK) and to assess possible utility of anterior segment optical coherence tomography (AS-OCT) for the visualization of limbal progenitor structures as it correlates to laser scanning confocal microscopy (LSCM) data.

METHODS

The study involved 32 patients (59 eyes) with congenital aniridia. AAK stage was defined based on biomicroscopy. Assessment of limbal zone and detection of POVs in identical areas was performed by LSCM (HRT3) and AS-OCT (RTVue XR Avanti) using 3D Cornea (En Face mode) and Cornea Cross Line protocols.

RESULTS

Intact and changed POVs were found in 8/8 stage 0 eyes, in 1/21 stage I and 2/13 stage II eyes. Spearman's correlation coefficient in assessing the consistency of the POV diagnostic results by LSCM and AS-OCT for the inferior limbus was r_S = 0.85 (P < 0.05), for the superior limbus - r_S = 0.53 (P < 0.05). AS-OCT was less sensitive for detection of partially present POVs in superior limbus. The negative correlation between AAK stage and POV preservation was determined (r_S = -0.5, P < 0.05). There was no correlation between AAK stage and patient age (r_S = 0.235, P = 0.209). Three patients with PAX6 3' deletion showed stage 0 AAK with intact or slightly disturbed POVs morphology and transparent cornea.

CONCLUSION

AS-OCT may be an additional diagnostic tool for POV visualization in vivo in aniridic patients. Its diagnostic accuracy is subject to selection of anatomic region, nystagmus and the degree of POV degradation.

Existence of Normal Limbal Epithelium in Eyes With Clinical Signs of Total Limbal Stem Cell Deficiency

PURPOSE

To report the presence of normal limbal epithelium detected by in vivo confocal laser scanning microscopy (IVCM) in 3 cases of clinically diagnosed total limbal stem cell deficiency (LSCD).

METHODS

This is a retrospective case report consisting of 3 patients who were diagnosed with total LSCD based on clinical examination and/or impression cytology. Clinical data including ocular history, presentation, slit-lamp examination, IVCM, and impression cytology were reviewed.

RESULTS

The etiology was chemical burn in 3 cases. One patient had 2 failed penetrating keratoplasties. Another had allogeneic keratolimbal transplantation, but the graft failed 1 year after surgery. The third patient had failed amniotic membrane transplantation. These 3 patients presented with signs of total LSCD including the absence of normal Vogt palisades, complete superficial vascularization of the peripheral cornea, nonhealing epithelial defects, and corneal scarring. Impression cytology was performed in 2 cases to confirm the presence of goblet cells. However, each patient still had distinct areas of corneal and/or limbal epithelial cells detected by IVCM.

CONCLUSIONS

Residual normal limbal epithelial cells could be present in eyes with clinical features of total LSCD. IVCM seems to be a more accurate method to evaluate the degree of LSCD.

Amnion-assisted conjunctival epithelial redirection in limbal stem cell grafting

AIMS

To develop a technique using amniotic membrane (AM) to prevent admixture of conjunctival epithelial cells and limbal explant-derived corneal epithelial cells in patients undergoing limbal stem cell transplantation. To compare this technique with the current method of 'sequential sector conjunctival epitheliectomy' (SSCE).

METHODS

26 patients with total limbal stem cell deficiency who underwent ocular surface reconstruction with limbal stem cells transplantation were retrospectively studied. Patients were categorised into group A (11) in which AM was used to direct the conjunctival epithelial cells away from the corneal surface so that the latter could be covered by the limbal explant-derived epithelial cells-the procedure was termed 'amnion-assisted conjunctival epithelial redirection' (ACER)-and group B (15) in which the conjunctival epithelium was prevented from migrating on to the corneal surface by SSCE.

RESULTS

In nine eyes of group A, the conjunctival epithelium was successfully directed on to the AM, preventing admixture with limbal explant-derived corneal epithelial cells. The AM was removed or it came off spontaneously within 1-4 weeks. Patients treated with SSCE (group B) underwent two to four interventions until complete re-epithelialisation. 12 patients had pain or discomfort. 11 patients had conjunctival haemorrhage during SSCE. The cornea was epithelised from the limbal explant-derived epithelium in all patients.

CONCLUSIONS

ACER is a viable option in limbal transplantation that reduces multiple patient visits, bleeding and pain that can be associated with SSCE.

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.

Correlation between the existence of the palisades of Vogt and limbal epithelial thickness in limbal stem cell deficiency

BACKGROUND

The aims of the study were to investigate limbal epithelial thickness in subjects with limbal stem cell deficiency and to evaluate the correlation between the palisades of Vogt and limbal epithelial thickness.

DESIGN

Cross-sectional observational study.

PARTICIPANTS

Twenty-four subjects (39 eyes) with limbal stem cell deficiency and 20 normal controls (20 eyes).

METHODS

Anterior segment optical coherence tomography and laser scanning confocal microscopy were performed to assess each quadrant of the limbus.

MAIN OUTCOME MEASURES

Limbal epithelial thickness and palisades of Vogt morphology in each quadrant were characterized. The correlation between limbal epithelial thickness and palisades of Vogt was analysed.

RESULTS

The average limbal epithelial thicknesses in eyes with limbal stem cell deficiency were 19.9%, 23.4%, 13.8% and 13.5% less than normal controls at superior, inferior, nasal and temporal limbus (P = 0.008, 0.006, 0.014 and 0.011, respectively). Limbal epithelial thicknesses within limbal quadrants with palisades of Vogt were similar to those measured in the same quadrants in normal controls, whereas limbal epithelial thicknesses in the superior, inferior, nasal and temporal quadrants without palisades of Vogt were 27.8%, 29.8%, 14.7% and 15.6% less than the limbal epithelial thickness in corresponding regions of normal eyes (superior and inferior: P < 0.001; nasal and temporal: P = 0.005). Limbal epithelial thickness in the nasal and temporal quadrants was significantly less than that in the superior and inferior quadrants, both in normal controls and in limbal stem cell deficiency subjects(P < 0.001 and P = 0.019). Regression analysis showed that limbal epithelial thickness had a significant correlation with the presence of palisades of Vogt in each quadrant (superior, P = 0.002; inferior, P = 0.001; nasal, P = 0.047; temporal, P = 0.030).

CONCLUSIONS

A significant correlation was found between limbal epithelial thickness and the presence of palisades of Vogt. Limbal epithelial thinning as observed with anterior segment optical coherence tomography is a sign of limbal stem cell deficiency.