To Study and Determine the Role of Anterior Segment Optical Coherence Tomography and Ultrasound Biomicroscopy in Corneal and Conjunctival Tumors

Anterior segment optical coherence tomography in ocular surface tumours and simulating lesions

This study aims to systematically review the reported literature on the use of anterior segment optical coherence tomography (AS-OCT) in ocular surface tumours and simulating lesions. A systematic literature search was done using PubMed, Scopus, and Web of Science databases between January 2002 and December 2021. On AS-OCT, ocular surface squamous neoplasia typically demonstrate epithelial thickening, epithelial hyperreflectivity, and an abrupt transition between normal and abnormal epithelium. Conjunctival nevi usually show mildly hyperreflective epithelium of normal thickness, internal hyperreflectivity, and intralesional cysts which is the hallmark of this tumour. Primary acquired melanosis presents with normal thickness epithelium, basal epithelial hyperreflectivity, and absence of cysts. Conjunctival melanoma demonstrates hyperreflective normal/thickened epithelium, hyperreflective basal epithelium, internal hyperreflectivity, and absence of intralesional cysts. Conjunctival lymphoma shows homogenous, low-medium reflective subepithelial lesions with smooth borders, and dot-like infiltrates. Benign reactive lymphoid hyperplasia findings are similar to lymphoma but the infiltrates are more hyperreflective compared to lymphoma. Pterygium shows thickened conjunctival epithelium, epithelial hyperreflectivity, and subepithelial wedge-shaped hyperreflective tissue separated from the overlying epithelium by a cleavage plane. Pinguecula demonstrates mildly thickened epithelium and similar findings with pterygium but does not extend beyond the corneal limbus. This review shows that AS-OCT, as a noninvasive tool, has potential uses in the differential diagnosis of ocular surface tumours and simulating lesions. Major limitations of AS-OCT include limited visualization of the posterior border of thick, keratinized, and pigmented tumours and lack of assessment of large conjunctival tumours in a single cut.

Deep Learning-Based Retinal Nerve Fiber Layer Thickness Measurement of Murine Eyes

Purpose

To design a robust and automated estimation method for measuring the retinal nerve fiber layer (RNFL) thickness using spectral domain optical coherence tomography (SD-OCT).

Methods

We developed a deep learning-based image segmentation network for automated segmentation of the RNFL in SD-OCT B-scans of mouse eyes. In total, 5500 SD-OCT B-scans (5200 B-scans were used as training data with the remaining 300 B-scans used as testing data) were used to develop this segmentation network. Postprocessing operations were then applied on the segmentation results to fill any discontinuities or remove any speckles in the RNFL. Subsequently, a three-dimensional retina thickness map was generated by z-stacking 100 segmentation processed thickness B-scan images together. Finally, the average absolute difference between algorithm predicted RNFL thickness compared to the ground truth manual human segmentation was calculated.

Results

The proposed method achieves an average dice similarity coefficient of 0.929 in the SD-OCT segmentation task and an average absolute difference of 0.0009 mm in thickness estimation task on the basis of the testing dataset. We also evaluated our segmentation algorithm on another biological dataset with SD-OCT volumes for RNFL thickness after the optic nerve crush injury. Results were shown to be comparable between the predicted and manually measured retina thickness values.

Conclusions

Experimental results demonstrate that our automated segmentation algorithm reliably predicts the RNFL thickness in SD-OCT volumes of mouse eyes compared to laborious and more subjective manual SD-OCT RNFL segmentation.

Translational Relevance

Automated segmentation using a deep learning-based algorithm for murine eye OCT effectively and rapidly produced nerve fiber layer thicknesses comparable to manual segmentation.

Anterior segment optical coherence tomography angiography in the assessment of ocular surface lesions

PURPOSE

Describe the utility of anterior segment optical coherence tomography angiography (AS-OCTA) to assess ocular surface lesions.

METHODS

Retrospective, case-control study of 10 eyes of 9 patients with malignant lesions and 23 eyes of 22 patients with benign lesions. Lesions included 13 epithelial, 10 pigmented and 10 lymphoid lesions. Graders performed an average of 3 depth and diameter measurements of peri-lesional vessels entering each lesion on AS-OCTA. Statistical models to assess differences between groups accounted for bilateral eye inclusion and lesion thickness (on AS-OCT). Receiver operating characteristic (ROC) curve and area under the curve (AUC) were performed for each parameter.

RESULTS

In the benign and malignant groups, age was 49.5 ± 22.4 and 64.3 ± 10.6 years (p = 0.145) with 45% males and 55% males (p = 0.458), in their respective groups. AS-OCTA showed greater peri-lesional vessel depth and diameter in malignant lesions (315.2 ± 73.0 μm, p < 0.001 and 76.4 ± 18.2 μm, p < 0.001; respectively) compared to benign lesions (199.4 ± 34.1 μm and 44.0 ± 9.4 μm, respectively). Malignant lesions showed deep and dilated peri-lesional vessels, which may represent feeder vessels. Vessel depth showed AUC = 0.980, 90.9% sensitivity and 100.0% specificity with a 236.5 μm cutoff. Vessel diameter showed AUC = 0.960, 100.0% sensitivity and 88.9% specificity with a 53.9 μm cutoff.

CONCLUSION

AS-OCTA shows greater peri-lesional vessel depth and diameter of malignant lesions compared to benign lesions. This imaging modality provides novel and non-invasive functional vascular parameters that can potentially aid the assessment of ocular surface lesions.

Spectrum of AS-OCT features of ocular surface tumors and correlation of clinico-tomographic features with histopathology: a study of 70 lesions

PURPOSE

To assess the correlation between clinical and anterior segment optical coherence tomographic (AS-OCT) details and histopathological changes in various ocular surface lesions.

METHODS

Prospective case series of 70 lesions in 65 patients.

RESULTS

AS-OCT revealed epithelial changes in OSSN (n = 19; 44%), squamous papilloma (n = 3; 60%), nevus (n = 1; 33%), epithelial hyperplasia (n = 1; 33%), granular dystrophy (n = 1; 100%) and granulation tissue (n = 1; 100%); subepithelial changes in chronic inflammation (n = 4, 100%), lymphoma (n = 3; 100%) and arteriovenous malformation (n = 1; 100%); combined epithelial and subepithelial changes in OSSN (n = 24; 56%), squamous papilloma (n = 2; 40%), PEH (n = 3; 100%), nevus (n = 2; 67%), epithelial hyperplasia (n = 2; 67%), solar elastosis (n = 1; 100%), lobular capillary hemangioma (n = 1; 100%) and sebaceous carcinoma (n = 1; 100%). Epithelial involvement on AS-OCT paralleled the histopathological findings in 98% (n = 69) and subepithelial involvement in 83% (n = 58). The correlation of clinico-tomographic diagnosis with histopathology diagnosis was seen in 77% (n = 54) lesions. Sensitivity and specificity of AS-OCT as a diagnostic tool for detection of epithelial involvement were 100% and 92% and for subepithelial involvement was 98% and 100%, respectively.

CONCLUSION

The correlation between AS-OCT and histopathology features determining epithelial and subepithelial involvement is excellent. It is a useful adjunctive tool for the diagnosis of ocular surface lesions.

Incidentally detected primary corneal squamous neoplasia in an elderly man presenting with cataract

Primary corneal neoplasia (PCN) is a rare cancerous lesion of cornea usually encountered in elderly. The clinical symptoms are generally non-specific, with ocular irritation, redness, cosmetic disfigurement and varying degrees of visual disturbances depending on visual axis involvement. Corneal neoplasia is usually associated with surrounding conjunctival lesions and incidentally detected PCN is rarely encountered in clinical practice. Presently, we report a case of isolated unilateral PCN diagnosed incidentally in an elderly man presenting with cataract. In vivo confocal microscopy aided in its diagnosis after impression cytology was repeatedly negative. Cataract surgery was deferred and the patient was administered three cycles of mitomycin C 0.04% 4 times/day. The tumour margins receded as evident on clinical examination and on anterior segment optical coherence tomography. We discuss the role of various corneal imaging modalities in diagnosis and management of PCN besides highlighting importance of comprehensive slit-lamp examination in patients planned for cataract surgery.

The Effectiveness of Ultrasound Biomicroscopic and Anterior Segment Optical Coherence Tomography in the Assessment of Anterior Segment Tumors: Long-Term Follow-Up

Background

Differential diagnosis and follow-up of small anterior segment tumors constitute a particular challenge because they determine further treatment procedures. The aim of this study was to evaluate the efficacy of the UBM (ultrasound biomicroscopy) and AS-OCT (anterior segment optical coherent tomography) in distinguishing different types of anterior segment lesions.

Methods

It was a retrospective, noncomparative study of case series of 89 patients with the suspicion of anterior segment tumor referred to the Ophthalmology Clinic, Medical University of Białystok, Poland, between 2016 and 2020. UBM was used to assess tumor morphology including height, location, and internal and external features. In cases in which UBM did not provide enough data, the AS-OCT images were analyzed. The data on demographics, best corrected visual acuity (BCVA), intraocular pressure (IOP), and rate of complications were also collected. Patients were followed up from 1 to 48 months.

Results

The mean observation period was 26.61 ± 16.13 months. Among the patients, there were 62 women and 27 men at a mean age of 55.59 ± 19.48 (range: from 20 to 89 years.) The types of tumors were cysts (41%), solid iris tumors (37.1%), ciliary body tumors (7.9%), peripheral anterior synechiae (PAS 3.4%), corneal tumors (4.5%), and others (5.6%). Patients with cysts were younger than patients with solid iris tumor (p=0.002). Women had a cyst as well as solid iris tumor more frequently than men, but less often a ciliary body tumor (p < 0.05). The horizontal size of tumor was positively correlated with patients' age (r_s = 0.38 and p=0.003) and negatively correlated with visual acuity (r_s = −0.42 and p=0.014). During the 4 years of diagnosis, only 2.2% of lesions exhibited growth (growth rate of 0.02 mm per year). Among 15 cases in which visualization with UBM was not satisfactory (mostly iris nevi), AS-OCT was helpful in diagnosis of 13 patients.

Conclusions

Both UBM and AS-OCT are effective methods in detection and diagnosis of tumors of the anterior eye segment, but in some cases, AS-OCT adds additional value to the diagnosis. Many lesions can be managed conservatively because they did not demonstrate growth during 4 years of the follow-up period.

AS-OCT Guided Treatment Of Diffuse Conjunctival Squamous Cell Carcinoma With Resection, Amniotic Membrane Graft And Topical Mitomycin C

Purpose

To evaluate the efficacy of combined limited surgical resection, amniotic membrane graft and topical mitomycin C in treatment of diffuse conjunctival squamous cell carcinoma (CSCC) diagnosed and followed up by anterior segment optical coherence tomography (AS-OCT).

Subjects and methods

A prospective study was performed on 24 eyes with diffuse CSCC. Fifteen eyes underwent lesion limited resection followed by postoperative topical mitomycin C 0.04% eye drop (MMC group) while nine eyes underwent complete excision and cryotherapy (no MMC group). Amniotic membrane graft was applied in all cases. The diagnosis was based on clinical and AS-OCT specific criteria of CSCC and was confirmed by histopathological results.

Results

The study population was similar between the two groups. Mean postoperative follow-up was 27.1±4.1 months. The mean extent of the limbal involvement was 7.0±0.7 and 7.25±0.6 clock hours in MMC and no MMC groups, respectively. The mean size of conjunctival defect after tumor excision in MMC group (60.8±9.2 mm²) was significantly lower than in no MMC group (92.4±17.3 mm²). Histopathological diagnosis revealed invasive SCC in all specimens. The mean preoperative conjunctival epithelial thickness decreased significantly in both groups at 2-year follow-up. It decreased from 267±24.2 and 256±19.1 μm preoperatively to 56.7±11.6 and 60.4±9.6 μm at 2-year follow-up in MMC and no MMC groups, respectively. The mean number of MMC treatment cycles was 2.1±0.85 cycles. Recurrence was recorded in zero (0%) and 1 (11%) patients at 2-year follow-up in MMC and no MMC groups, respectively. Histopathological diagnosis revealed invasive SCC in all specimens. The mean preoperative conjunctival epithelial thickness decreased significantly in both groups at 2-year follow-up. It decreased from 267±24.2 and 256±19.1 μm preoperatively to 56.7±11.6 and 60.4±9.6 μm at 2-year follow-up in MMC and no MMC groups, respectively. The mean number of MMC treatment cycles was 2.1±0.85 cycles. Recurrence was recorded in zero (0%) and 1 (11%) patients at 2-year follow-up in MMC and no MMC groups, respectively.

Conclusion

The treatment of diffuse CSCC with AS-OCT guided combined therapy includes limited surgical resection, AMG, and postoperative topical MMC, achieves a complete tumor resolution and good functional and cosmetic outcomes minimizing the burden of surgery, and improves postoperative patient comfort in our study cohort.

Assessment of Anterior Chamber by Ultrasound Biomicroscopy and Anterior Segment Optical Coherence Tomography in Patients with Inflammatory Glaucoma

Objective

To investigate the clinical indications of ultrasound biomicroscopy (UBM) and anterior segment optical coherence tomography (AS-OCT) in eyes with inflammatory glaucoma.

Methods

Sixteen patients (16 eyes) with inflammatory glaucoma were analysed retrospectively. All of the subjects underwent UBM and AS-OCT scans, measuring the following parameters: central corneal thickness (CCT), central anterior chamber depth (ACD), angle-opening distance (AOD500), and trabecular-iris angle (TIA500) in four quadrants.

Results

Both the UBM and AS-OCT generated detailed, high-resolution images of the anterior segments of the eyes with inflammatory glaucoma. Moreover, the UBM and AS-OCT exhibited statistically similar measurement results for all of the indices. A Bland–Altman analysis showed a high level of agreement between the two imaging techniques. Additionally, the UBM was able to visualize the ciliary body and pars plana, while the cells and the flare in the anterior chamber appeared more pronounced in the UBM images.

Conclusions

Both the UBM and AS-OCT are useful tools for anterior segment imaging and taking measurements needed for evaluating inflammatory glaucoma. The AS-OCT has the advantages of being noninvasive and fast, whereas the UBM is presently unparalleled in the visualization of the ciliary body and pars plana.

Freeform optical design for a nonscanning corneal imaging system with a convexly curved image

Most existing techniques that are typically used by specialists to image the cornea are based on point, slit, or annular scanning due to a narrow field of view. The difficulty in achieving a larger field of view comes from the convex shape of the human eyeball. Field curvature for a refractive imaging system with positive power is typically negative and thus a concave image surface. In order to view the full cornea and sclera with snapshot imaging, we calculate qualified two- and three-mirror solutions from Seidel aberration theory. A three-mirror solution is further optimized as a high-resolution off-axis imaging system using freeform surfaces, which can obtain a full-field tailored image shell without scanning. The lateral resolution on the cornea is about 10 μm with good modulation transfer function (MTF) and spot performance. To ease the assembly, a monolithic design is achieved with slightly lower resolution, leading to a potential mass production solution.