Role of optical coherence tomography angiography in the characterization of vascular network patterns of ocular surface squamous neoplasia

Novel automated non-invasive detection of ocular surface squamous neoplasia using artificial intelligence

Ocular surface squamous neoplasia (OSSN) is a common eye surface tumour, characterized by the growth of abnormal cells on the ocular surface. OSSN includes invasive squamous cell carcinoma (SCC), in which tumour cells penetrate the basement membrane and infiltrate the stroma, as well as non-invasive conjunctival intraepithelial neoplasia, dysplasia, and SCC in-situ thereby presenting a challenge in early detection and diagnosis. Early identification and precise demarcation of the OSSN border leads to straightforward and curative treatments, such as topical medicines, whereas advanced invasive lesions may need orbital exenteration, which carries a risk of death. Artificial intelligence (AI) has emerged as a promising tool in the field of eye care and holds potential for its application in OSSN management. AI algorithms trained on large datasets can analyze ocular surface images to identify suspicious lesions associated with OSSN, aiding ophthalmologists in early detection and diagnosis. AI can also track and monitor lesion progression over time, providing objective measurements to guide treatment decisions. Furthermore, AI can assist in treatment planning by offering personalized recommendations based on patient data and predicting the treatment response. This manuscript highlights the role of AI in OSSN, specifically focusing on its contributions in early detection and diagnosis, assessment of lesion progression, treatment planning, telemedicine and remote monitoring, and research and data analysis.

Decreased retinal capillary density as a beneficial response to 24-week high-speed circuit resistant training in healthy older adults

PURPOSE

To determine the changes in retinal microvascular density after a 24-week high-speed circuit resistance training program (HSCT) in healthy older adults.

METHODS

Thirty healthy older adults were recruited and randomly assigned to either a training group (HSCT) or a non-training (CON) group. Fifteen subjects (age 73.3 ± 7.76 yrs) in the HSCT group exercised three times per week on non-consecutive days for 24 weeks. Fifteen subjects in the CON group (age 72.2 ± 6.04 yrs) did not have formal physical training. Both eyes of each subject were imaged using optical coherence tomography angiography (OCTA) at baseline and at the 24-week follow-up. The vessel densities of the retinal vascular network (RVN), superficial vascular plexus (SVP), and deep vascular plexus (DVP) were measured.

RESULTS

There were no demographic differences between the study groups. There were significant decreases in the retinal vessel densities of RVN, SVP and DVP in the HSCT group (P < 0.05). However, there were no significant changes in all three vascular measurements in the CON group (P > 0.05), although the changes showed a decreasing trend. The decreased vessel densities were doubled in the HSCT group in comparison to the CON group. However, the differences between groups did not reach a significant level (P > 0.05).

CONCLUSIONS

This is the first study to reveal the decreased retinal vessel densities as a possible imaging marker for the beneficial effects of the 24-week HSCT program in older adults.

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.

Automated Image Threshold Method Comparison for Conjunctival Vessel Quantification on Optical Coherence Tomography Angiography

Purpose

To determine the impact of image binarization and the best thresholding method for conjunctival optical coherence tomography angiography (OCTA).

Methods

Vessel density (VD) of 14 OCTA conjunctival images (nine nasal and five temporal conjunctivas, and eight right and six left eyes) from normal subjects was analyzed. The binarization of gold-standard images, created by removing pixels that do not represent vessels on ImageJ software, was assessed by three masked graders to determine consistency of VD for images. Various thresholding methods on ImageJ, including manual, 1-, 2- and 3-step processes, were performed on unprocessed images for comparison. Interclass correlation coefficient (ICC) ≥0.750 were classified as good reliability and selected for calculation of the performance of the pixel location in the binarized images of each method.

Results

Analysis of the gold-standard threshold method achieved an ICC of 0.816 with excellent agreement (R² = 0.965, P < 0.001). From a total 28 different methods and variations performed, only nine methods performed with good reliability, including two 1-step thresholds, six 2-step thresholds, and one 3-step threshold method. Overall, 2-step threshold methods were more reliable than 3-step threshold methods. The 2-step method of Bandpass filter + Phansalkar local threshold (LT) showed the best performance with mean pixel accuracy of 86.9% ± 6.8%, area under the curve of 0.826, sensitivity of 79.0%, and specificity 86.1%.

Conclusions

Bandpass filter + Phansalkar LT was the best method for VD measurement in conjunctival OCTA. Most commonly reported threshold methods showed unsatisfactory agreement. There is a need in the OCTA field for a standardized method to allow comparison between different studies.

Translational Relevance

The proposed threshold method using a widely accessible and commonly used software provides an accurate VD measurement for future OCTA studies.

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.

The use of high resolution optical coherence tomography (HR-OCT) in the diagnosis of ocular surface masqueraders

INTRODUCTION

Ocular surface masqueraders encompass any ocular surface lesion masquerading as another ocular surface lesion. High resolution optical coherence tomography (HR-OCT) has emerged as an adjunctive tool to clinical acumen. This study's purpose is to evaluate the utility of HR-OCT images in guiding the diagnosis and management of those lesions.

MATERIAL AND METHODS

22 individuals with a clinically ambiguous ocular surface lesion with slit lamp photographs (SLP), HR-OCT images, and histopathological examination were included in the study. The presumptive clinical diagnosis based on SLP was compared to the diagnosis suggested by HR-OCT findings and to definitive diagnosis by histopathology. The main outcome of this study was the frequency in which HR-OCT findings guided the clinician to the correct diagnosis.

RESULTS

7 lesions were epithelial, 3 had an epithelial and a subepithelial component, and 12 were subepithelial. HR-OCT was most effective in discerning lesion location, successfully identifying the location in 100% of cases. Classic HR-OCT findings were detected in 68.2% of cases while suggestive features were detected in 31.8% of cases. The epithelial lesions' mean epithelial thickness was 265.4 ± 140.6 μm, the subepithelial lesions' mean was 58.0 ± 25.0 μm, and the combined lesions' mean was 140.0 ± 70.0 μm. The epithelium was significantly thicker in epithelial lesions compared to subepithelial and combined lesions. By ROC analysis we identified that using a cut off of 156 μm, the sensitivity was 86% and the specificity was 93%.

DISCUSSION

HR-OCT can be a valuable diagnostic tool, assisting in the differentiation of ambiguous ocular surface pathologies by providing a cross-sectional, morphological image of the lesion.

Update on the Management of Ocular Surface Squamous Neoplasia

Purpose of review

To review and update the latest findings in diagnosis and management of ocular surface squamous neoplasia (OSSN).

Recent findings

OSSN is the most common anterior segment neoplastic disease process. Several ocular surface imaging techniques have been developed for the early diagnosis and management of clinical and subclinical ocular surface squamous neoplasia, including high-resolution optical coherence tomography (HR-OCT), in vivo confocal microscopy, and ultrasound biomicroscopy. Treatment modalities include both surgical and medical management, with a recent trend towards primary and adjunctive pharmacotherapy.

Summary

There is increasing use of HR-OCT for the diagnosis and monitoring of clinical and subclinical OSSN lesions. Topical pharmacotherapy agents, including interferon α-2b, 5-fluorouracil, and mitomycin C, have demonstrable efficacy in the treatment of OSSN and their use may be dictated based upon tumor factors, patient factors, cost, and side effect profile. Both surgical excision and adjunctive topical medications have excellent success, with the favored treatment method trending towards topical pharmacotherapy as primary therapy.

Imaging depth adaptive resolution enhancement for optical coherence tomography via deep neural network with external attention

Optical coherence tomography (OCT) is a promising non-invasive imaging technique that owns many biomedical applications. In this paper, a deep neural network is proposed for enhancing the spatial resolution of OCTen faceimages. Different from the previous reports, the proposed can recover high-resolutionen faceimages from low-resolutionen faceimages at arbitrary imaging depth. This kind of imaging depth adaptive resolution enhancement is achieved through an external attention mechanism, which takes advantage of morphological similarity between the arbitrary-depth and full-depthen faceimages. Firstly, the deep feature maps are extracted by a feature extraction network from the arbitrary-depth and full-depthen faceimages. Secondly, the morphological similarity between the deep feature maps is extracted and utilized to emphasize the features strongly correlated to the vessel structures by using the external attention network. Finally, the SR image is recovered from the enhanced feature map through an up-sampling network. The proposed network is tested on a clinical skin OCT data set and an open-access retinal OCT dataset. The results show that the proposed external attention mechanism can suppress invalid features and enhance significant features in our tasks. For all tests, the proposed SR network outperformed the traditional image interpolation method, e.g. bi-cubic method, and the state-of-the-art image super-resolution networks, e.g. enhanced deep super-resolution network, residual channel attention network, and second-order attention network. The proposed method may increase the quantitative clinical assessment of micro-vascular diseases which is limited by OCT imaging device resolution.

Ocular surface angiography: from neovessels to neoplasia

The ocular surface vascular system plays a key role in corneal and conjunctival inflammatory, infectious and neoplastic pathology. Angiographic vessel analysis using intravenous dyes and optical coherence tomography technology allow both the quantitative and functional assessment of conjunctival vasculature and corneal neovessels. Based on a thorough understanding of vascular alterations in ocular surface disease, angiographic assessment facilitates the clinical management of corneal neovascularisation, the grading of ocular surface inflammation and the identification of tumour angiogenesis in dysplastic or malignant lesions. This review summarises key aspects of the clinical application of corneal and conjunctival angiography as presented at the 2021 virtual Bowman Club meeting.

The role of imaging technologies for ocular surface tumors

PURPOSE OF REVIEW

This review will discuss the utility of high-resolution anterior segment optical coherence tomography (HR-OCT), in-vivo confocal microscopy (IVCM) and ultrasound biomicroscopy (UBM) in characterizing and diagnosing various ocular surface tumors, namely ocular surface squamous neoplasia (OSSN), conjunctival lymphoma and conjunctival melanoma. The strengths and limitations of each imaging modality will be discussed along with the characteristics findings of each lesion on each imaging platform.

RECENT FINDINGS

HR-OCT can consistently be utilized in the clinic setting to distinguish between epithelial ocular surface tumors such as OSSN as compared with subepithelial tumors such as conjunctival lymphoma and conjunctival melanoma given their distinctive findings. IVCM can be used as an adjunct to HR-OCT to obtain cellular and surface characteristics, whereas UBM can be used to assess tumor depth and thickness for larger and highly pigmented lesions as well as to detect intraocular invasion.

SUMMARY

HR-OCT, IVCM and UBM are all helpful imaging modalities to diagnose and characterize various ocular surface tumors and can serve as valuable adjuncts to monitor treatment response and assess for recurrence ocular surface tumors.

Update on imaging modalities for ocular surface pathologies

Purpose of review

To discuss recent studies of imaging modalities for ocular surface pathologies.

Recent findings

Novel micro-ocular coherence tomography technology can produce high-resolution images of corneal cellular and nervous structures. Ocular coherence tomography angiography can aid in detecting early stage limbal stem cell deficiency. Several studies used in vivo confocal microscopy to evaluate corneal nerve metrics and morphology.

Summary

The applications of anterior segment optical coherence tomography, anterior segment optical coherence tomography angiography, ultrasound biomicroscopy, and in vivo confocal microscopy are useful technologies for imaging the ocular surface. Several studies have used artificial intelligence in combination with imaging technologies to create reliable and effective systems to detect and visualize ocular surface pathologies. AS OCT continues to be a key imaging tool and future development of μOCT technology may further enhance its utility.

Imaging of vascular abnormalities in ocular surface disease

The vascular system of the ocular surface plays a central role in infectious, autoimmune, inflammatory, traumatic and neoplastic diseases. The development, application, and monitoring of treatments for vascular abnormalities depends on the in vivo analysis of the ocular surface vasculature. Until recently, ocular surface vascular imaging was confined to biomicroscopic and color photographic assessment, both limited by poor reproducibility and the inability to image lymphatic vasculature in vivo. The evolvement and clinical implementation of innovative imaging modalities including confocal microscopy, intravenous, and optical coherence tomography-based angiography now allows standardized quantitative and functional vascular assessment with potential applicability to automated analysis algorithms and diagnostics.

Anterior Segment OCTA of Melanocytic Lesions of the Conjunctiva and Iris

PURPOSE

To study the feasibility and diagnostic value of vascular imaging using optical coherence tomography (OCT)-angiography (OCTA) of melanocytic lesions of the conjunctiva and iris.

DESIGN

Cross-sectional study.

METHODS

Twenty-five patients with an untreated conjunctival lesion (5 melanoma, 13 nevus, 7 primary acquired melanosis [PAM]) and 52 patients with an untreated iris lesion (10 melanoma, 42 nevus) were included. Patients were imaged using a commercially available OCTA device, with the addition of an anterior segment lens and manual focussing. Tumor vessel presence, vascular patterns and vascular density were assessed.

RESULTS

Good OCTA images were obtained in 18 of 25 conjunctival lesions and 42 of 52 iris lesions. Failure was caused by lack of patient cooperation, an unfavorable location, or mydriasis. In all imaged conjunctival lesions and 77% of iris lesions, vascular structures were detected. Conjunctival melanoma and nevi demonstrated the same intralesional tortuous patterns, whereas vasculature in eyes with PAM was similar to normal conjunctiva. Both iris melanoma and nevi demonstrated tortuous patterns, distinct from the radially oriented normal iris vasculature.

CONCLUSIONS

Optical coherence tomography angiography (OCTA) allows for noninvasive imaging of the vasculature in melanocytic lesions of the conjunctiva and iris. Good image quality depends highly on patient cooperation and lesion characteristics. Differentiation of benign and malignant lesions was not possible. New software is called for to improve image acquisition and analysis.

Long-Term Efficacy and Safety of Subconjunctival/Perilesional 5-Fluorouracil Injections for Ocular Surface Squamous Neoplasia

Purpose

To investigate the effectiveness and safety of subconjunctival/perilesional 5-fluorouracil injections on ocular surface squamous neoplasia (OSSN) during a 3-year follow-up period.

Patients and Methods

We followed up six patients with intraepithelial OSSN (in one eye each) that had regressed after subconjunctival/perilesional 5-fluorouracil injections. Conjunctival fluorescein angiography (FA) and indocyanine green angiography (ICGA), as well as anterior segment optical coherence tomography (AS-OCT), were performed to evaluate the OSSN status 3 years after initiation of treatment.

Results

The mean age of patients (five males, one female) at baseline was 62.3±11.6 years. The mean number of 5-fluorouracil injections was 17.0±8.6, with a mean treatment duration of 13.0±7.4 weeks. At the final visit, both intratumoral and conjunctival feeding vessels had disappeared on ICGA and FA, with no neovascularization-related leakage, in accordance with the results of AS-OCT. The period from complete tumor regression to final visit according to AS-OCT was 32.5±4.2 months, which was longer than that according to ICGA (31.3±3.2 months, p=0.034). The final best-corrected visual acuity was similar to that at baseline (p=0.128). No side effects were observed in any of the eyes.

Conclusion

Subconjunctival/perilesional 5-fluorouracil injections are an effective and safe treatment for OSSN. Future studies with a larger sample size are warranted for confirmation of our findings, as well as investigation into the reasons for residual areas of non-perfusion in the conjunctiva.

Diagnosis and staging of ocular surface squamous neoplasia

Background: Ocular surface squamous neoplasia (OSSN) is the most common ocular tumour. The diagnosis of OSSN is based on clinical suspicion and confirmed by various diagnostic modalities, of which histology is the gold standard. With the move to less invasive management options such as topical chemo- or immunotherapy, less invasive diagnostic options have come to the fore.Aim: The purpose of this article was to review the current staging and diagnostic modalities for OSSN with a focus on less invasive modalities.Method: A literature review was performed for publications on ocular surface neoplasia and diagnostic modalities.Results: Histology is the gold standard for diagnosing OSSN. Cytology has been shown to be a simple, repeatable and minimally invasive diagnostic modality, which also allows for additional testing such as polymerase chain reaction. Anterior segment optical coherence tomography provides a non-contact method of evaluating the ocular surface, with OSSN showing a thickened hyper-reflective epithelium, abrupt transition zone and demarcation line. Vital dyes are used less commonly with high sensitivity, but lower specificity for OSSN. Finally, confocal microscopy provides en-face images of the ocular surface, with OSSN showing a classic ‘starry night’ appearance.Conclusion: Histology remains the gold standard for diagnosis; however, with the increasing use of topical therapy for OSSN, there has been an increase in the uptake of less invasive diagnostic modalities.

Comparison of ocular surface squamous neoplasia and pterygium using anterior segment optical coherence tomography angiography

Purpose

To compare ocular surface squamous neoplasia (OSSN) and pterygium using anterior segment optical coherence tomography angiography (AS-OCTA).

Observations

Flow patterns of conjunctival vessels in patients with OSSN and pterygium were investigated using AS-OCTA. In case 1, slit-lamp examination of a 72-year-old woman revealed an elevated lesion with increased permeability of fluorescein in the inferior nasal conjunctiva of her left eye. AS-OCTA showed markedly meandering large blood vessels in both the superficial and deep layers. Histopathological evaluation of the conjunctival biopsy indicated conjunctival intraepithelial neoplasia. Case 2 was that of a 79-year-old man with a history of three conjunctival tumor excisions. Slit-lamp examination showed an elevated lesion with hyperpermeability of fluorescein in the nasal conjunctiva of his left eye. AS-OCTA revealed increased meandering vasculature in both the superficial and deep layers. Histopathological investigation concluded that the diagnosis was squamous cell carcinoma. Case 3 involved a 61-year-old man with a pterygium. Slit-lamp examination showed typical findings of an elevated nasal lesion accompanied by a head that appeared triangular with a blunt apex. AS-OCTA revealed increased straight vasculature in the superficial layer and an avascular area in the deep layer of the pterygium head.

Conclusions and importance

AS-OCTA revealed abnormal “zigzag vessel patterns” in both the superficial and deep layers denoting meandering vessels in the patients with OSSN. In the patient with the pterygium, it showed “straight vessel patterns” signifying unbending stretched vessels in the superficial layer and an avascular zone in the deep layer of the pterygium head. These findings may be useful for the differential diagnosis of OSSN and pterygium.