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

Assessment of corneal vessels activity through the 'Barcode sign' of corneal OCT

BACKGROUND/OBJECTIVES

Anterior segment optical Coherence Tomography (AS-OCT) is used extensively in imaging the cornea in health and disease. Our objective was to analyse and monitor corneal vascularisation (CVas) through the corresponding back-shadows visible on AS-OCT.

SUBJECTS/METHODS

AS-OCT scans were obtained from 26 consecutive patients (eyes) with CVas of different aetiologies. AS-OCT horizontal line scans showing the back shadows cast by the vessels were analysed and correlated with findings seen on slit lamp examination. Vessels were graded clinically as active, partially regressed, and regressed. The density of back shadow in the patient samples before and after treatment was analysed using Image-J software.

RESULTS

AS-OCT demonstrated a dense back shadow in all the 26 active vessels studied. When multiple vessels were present, the barcode sign was apparent. The back shadows absent in 22 (84.62%) at the regressed (healed) stage. The intensity of the backshadow had reduced in regressing vessels 4 (15.38%). The integrated density of the backshadow on AS-OCT in the active stage (pre-treatment) and corresponding healed (post-treatment, partially regressed or ghost vessels) scans was statistically significantly different (P < 0.0001).

CONCLUSION

This study demonstrates that AS-OCT provides additional important information in patients with CVas enabling distinction between active and regressing/regressed vessels. Semiquantitative assessment can be made by measuring the integrated density of the back shadows produced by the vessels.

Corneal stromal changes following simple limbal epithelial transplantation on Scheimpflug densitometry: Early results

CONTEXT

Chemical injury to eyes causes limbal stem cell deficiency (LSCD), which leads to conjunctival epithelium and underlying stromal changes. Simple limbal epithelial transplant helps to restore corneal epithelium and corneal stromal clarity. These changes are documented in this prospective eye study.

PURPOSE

To report the changes in epithelial/stromal (E/S) reflectivity ratio and corneal stromal densitometry following simple limbal epithelial transplantation (SLET) in patients with unilateral chemical burn-induced LSCD.

METHODS AND MATERIAL

It is a prospective imaging study of cornea before and after SLET. Corneal densitometry with Pentacam and epithelial and stromal reflectivity on anterior segment optical coherence tomography were analyzed for five patients (n = 5 eyes), who underwent autologous SLET for unilateral chemical burn-induced LSCD.

STATISTICAL ANALYSIS USED

Mann-Whitney U-test and Pearson correlation.

RESULTS

A significant improvement in E/S reflectivity was noted at 1 month ( P < 0.05) after SLET, and this was maintained until the end of 6 months. The densitometry measurements decreased in the entire cornea at every level, that is, anterior, central, and posterior cornea. However, the values did not normalize till the last follow-up at 6 months.

CONCLUSIONS

A trend of normal corneal epithelization exists in eyes undergoing SLET. Densitometry at all the levels, the anterior, central, and posterior cornea, also decreases after SLET. SLET improves visual outcomes in LSCD eyes not only by epithelization but also by reducing stromal scarring.

Focus on limbal stem cell deficiency and limbal cell transplantation

Limbal stem cell deficiency (LSCD) causes severe vision impairment and can lead to blindness, representing one of the most challenging ocular surface disorders. Stem cell deficiency can be congenital or, more often, acquired. The categorization of ocular surface transplantation techniques is crucial to achieving treatment homogeneity and quality of care, according to the anatomic source of the tissue being transplanted, genetic source, autologous or allogenic transplantation (to reflect histocompatibility in the latter group), and cell culture and tissue engineering techniques. The aim of this minireview is to provide a summary of the management of LSCD, from clinical characteristics and therapeutic outcomes to the development of novel therapeutic approaches. The manuscript also briefly summarizes recent findings in the current literature and outlines the future challenges to overcome in the management of the major types of ocular surface failure.

A Review of Contact Lens-Induced Limbal Stem Cell Deficiency

Limbal stem cell deficiency (LSCD) is a pathologic condition caused by the dysfunction and destruction of stem cells, stem cell precursors and limbal cell niche in the corneal epithelium, leading to severe conjunctivalization of the cornea. Etiologies for LSCD span from congenital (aniridia), traumatic (chemical or thermal injuries), autoimmune (Stevens-Johnson syndrome) and iatrogenic disease to contact lens (CL) wear. Of these, CL wear is the least understood and is often a subclinical cause of LSCD. Even with recent advances in LSCD research, limitations persist in establishing the pathogenesis and treatment guidelines for CL-induced LSCD. A literature search was conducted to include original articles containing patients with CL-induced LSCD. This review will critically discuss the complex pathophysiology behind CL-induced LSCD, the underlying risk factors and epidemiology of the disease as well as methods to obtain a diagnosis. Various treatment options will be reviewed based on proposed treatment strategies.

Current clinical applications of anterior segment optical coherence tomography angiography: a review

Optical coherence tomography (OCT) is a revolutionary in vivo imaging technology that presents real-time information on ocular structures. Angiography based on OCT, known as optical coherence tomography angiography (OCTA), is a noninvasive and time-saving technique originally utilized for visualizing retinal vasculature. As devices and built-in systems have evolved, high-resolution images with depth-resolved analysis have assisted ophthalmologists in accurately localizing pathology and monitoring disease progression. With the aforementioned advantages, application of OCTA has extended from the posterior to anterior segment. This nascent adaptation showed good delineation of the vasculature in the cornea, conjunctiva, sclera, and iris. Thus, neovascularization of the avascular cornea and hyperemia or ischemic changes involving the conjunctiva, sclera, and iris has become prospective applications for AS-OCTA. Although traditional dye-based angiography is regarded as the gold standard in demonstrating vasculature in the anterior segment, AS-OCTA is expected to be a comparable but more patient-friendly alternative. In its initial stage, AS-OCTA has exhibited great potential in pathology diagnosis, therapeutic evaluation, presurgical planning, and prognosis assessments in anterior segment disorders. In this review of AS-OCTA, we aim to summarize scanning protocols, relevant parameters, and clinical applications as well as limitations and future directions. We are sanguine about its wide application in the future with the development of technology and refinement in built-in systems.

Role of anterior segment optical coherence tomography in scleral diseases: A review

BACKGROUND

Scleritis and episcleritis are an overlapping spectrum of diseases and accurate diagnosis is of utmost importance as the treatment and prognosis are vastly different. Predominantly a clinical diagnosis, the challenge lies in those cases with equivocal clinical features. Furthermore, clinical grading of scleritis is subjective and hence is neither very reliable nor reproducible. Existing modalities such as slit lamp examination and clinical photographs in scleritis describe macroanatomy but do not provide details on the microanatomy of the sclera. A recent adjusted algorithm for anterior segment optical coherence tomography (AS-OCT) imaging has improved the ability of this device to aid in the diagnosis of all the major forms of scleritis.

PURPOSE

To highlight the role of AS-OCT in delineating various anatomical forms of episcleritis and scleritis and explore this tool in monitoring disease course and response to therapy.

METHODS

A comprehensive literature search was carried out in various medical databases using keywords AS-OCT and scleritis; AS-OCT and episcleritis; anterior segment imaging in scleritis; scleritis and episcleritis; Recent advances in anterior segment imaging. Original articles and novel reports describing the potential role of AS-OCT in the diagnosis and management of scleritis and episcleritis were included.

RESULTS

After a thorough assessment, it was clear that published literature lacks guidelines for uniform interpretation and also for classification and follow-up in scleritis. We describe a uniform protocol for AS-OCT image acquisition, interpretation of images and list the advantages and limitations.

CONCLUSIONS

AS-OCT can be used to localize the level of scleral inflammation thus helping in the diagnosis of scleral inflammatory disease. It can be a valuable tool in studying progression.

Epidemiological features and management of eye burn patients in Wuxi, China

Background

The current study aimed to analyse epidemiological data on eye burns in Wuxi, China, for the years 2015–2021, and to provide insight into the development of appropriate prevention strategies.

Methods

A retrospective study was conducted on 151 hospitalised patients with eye burns. Data collected included gender, age, the monthly distribution of incidence, cause of eye burn, the site of eye burn, the type of surgery, visual outcome, the length of hospital stay and the cost of hospital admission. Statistical analysis was performed using SPSS V.19.0 and Graph Pad Prism V.9.0.

Results

In a total of 151 eye burn patients, 130 were males (86.09%) and 21 were females (13.91%). The proportion of patients classified as grade III was the greatest (46.36%). The average age of our hospitalised patients with eye burns was 43.72 years and the average length of hospital stay was 17 days. The number of injuries was highest in September (14.6%). Among eye burn patients, workers and farmers became the most common occupations (62.91%, 12.58%). The most frequent cause of burns was alkali burns (19.21%), followed by acid burns (16.56%). When admitted to the hospital, patients’ average vision was 0.06, and 49% of them had a poor vision (<0.3, ≥0.05).

Conclusion

With an investigation of 7-year hospitalisation data, the current study provided a fundamental reference for epidemiological features and management of eye burns in Wuxi, China, which could contribute to the development of treatment and prevention strategies.

[Methods of diagnosis and treatment of corneal neovascularization]

Corneal neovascularization is one of the most common causes of decreased visual acuity and disability for vision loss, increase in the risk of corneal graft rejection, and appearance of opacifications on the cornea. This article reviews literature on etiological factors of the development of corneal neovascularization, as well as modern methods of diagnosis, conservative and surgical treatment of this pathology.

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.

Role of AS-OCT in Managing Corneal Disorders

Optical coherence tomography (OCT) is analogous to ultrasound biometry in the cross sectional imaging of ocular tissues. Development of current devices with deeper penetration and higher resolution has made it popular tool in clinics for visualization of anterior segment structures. In this review, the authors discussed the application of AS-OCT for diagnosis and management of various corneal and ocular surface disorders. Further, recent developments in the application of the device for pediatric corneal disorders and extending the application of OCT angiography for anterior segment are introduced.

Role of Anterior Segment-Optical Coherence Tomography Angiography in Acute Ocular Burns

Acute ocular burns have varied manifestations which require prompt diagnosis and management to prevent chronic sequelae. Of these, the detection of limbal ischemia poses a challenge because of the subjective nature of its clinical signs. Anterior segment optical coherence tomography angiography (AS-OCTA) offers an objective method of assessing ischemia in these eyes. This review provides an overview of the technology of AS-OCTA and its applications in acute burns. AS-OCTA generates images by isolating the movement of erythrocytes within blood vessels from sequentially obtained b-scans. Limbal ischemia manifests in these scans as absent vasculature and the extent of ischemia can be quantified using different vessel-related parameters. Of these, the density of vessels is most commonly used and correlates with the severity of the injury. Incorporation of the degree of ischemia in the classification of acute burns has been attempted in animal studies and its extension to human trials may provide an added dimension in determining the final prognosis of these eyes. Thus, AS-OCTA is a promising device that can objectively evaluate limbal ischemia. This will facilitate the identification of patients who will benefit from revascularization therapies and stem cell transplants in acute and chronic ocular burns, respectively.

Advances and Current Clinical Applications of Anterior Segment Optical Coherence Tomography Angiography

Optical coherence tomography angiography (OCTA) is the most relevant evolution based on optical coherence tomography (OCT). OCTA can present ocular vasculature, show detailed morphology for assessment, and quantify vessel parameters without intravenous dye agent. Research on the anterior segment OCTA (AS-OCTA) is only in its initial phase, and its advances in clinical diagnosis and treatment efficacy evaluations require a detailed comparison to traditional imaging methods. In this review of AS-OCTA, we summarize its technical features, imaging advances, current clinical applications in various eye diseases, as well as its limitations and potential future directions. AS-OCTA offers potential advantages in ophthalmic imaging, and with further development it could become a common tool in the near future.

Longitudinal Changes in Corneal Epithelial Thickness and Reflectivity following Simple Limbal Epithelial Transplantation: An Optical Coherence Tomography-Based Study

PURPOSE

To describe the changes in corneal epithelial thickness and reflectivity following simple limbal epithelial transplantation (SLET) using anterior segment optical coherence tomography (ASOCT).

METHODS

This was a prospective imaging study of 31 eyes of 29 patients who had undergone autologous or allogeneic SLET for limbal stem cell deficiency and had stable, avascular surfaces postoperatively. ASOCT scans of all four quadrants were taken preoperatively and at 1-week, 1-month, 3-month, 6-month, and 1-year postoperative time points in the eyes undergoing SLET. Baseline scans were also taken from the normal eye in unilateral cases. The following parameters were obtained from the scans: (i) epithelial thickness (ET), (ii) stromal thickness, (iii) total corneal thickness, (iv) epithelial reflectivity (ER), (v) stromal reflectivity, and (vi) epithelial/stromal (ES) reflectivity ratio.

RESULTS

Chemical injury (24 eyes, 77.4%) was the most common indication for surgery. There was a significant improvement in the ET (184.8 ± 117.1 vs 60.3 ± 10 µm, p < .0001) and ER (144.5 ± 26.4 vs 120.9 ± 28.9, p < .0001) within the initial postoperative period following SLET, which remained stable at the end of 1 year follow-up. There was no difference in the ET of the post-SLET and normal eyes after the 3-month timepoint and this normalization was maintained until the end of the first year. A significant normalization was also noted in the ES reflectivity ratio at the end of 1 year (2.1 ± 0.8 vs 1 ± 0.2, p < .001). A significant correlation was found between the final visual acuity and the total corneal thickness (r = 0.942, p = .005).

CONCLUSION

There is a significant improvement in the epithelial thickness and reflectivity of the cornea in eyes undergoing SLET. ASOCT provides a reliable objective measure of these changes and can be used to monitor the outcomes in these eyes postoperatively.