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

Highlights

• Malignant lesions showed greater peri-lesional vessel depth and vessel diameter.

• AS-OCTA can identify feeder vessels in malignant conjunctival lesions.

• AS-OCTA provided novel vascular parameters for ocular surface lesion assessment.

• AS-OCTA is a promising non-invasive objective tool to assess ocular surface lesions.

Abstract

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.

Introduction

Benign or malignant conjunctival tumors, or ocular surface lesions, are generally classified as melanocytic and non-melanocytic [1]. The latter can be further sub-categorized into epithelial, lymphoid, vascular, lipomatous, fibrous, myogenic, histiocytic, neural, metastatic and secondary tumors [[1], [2], [3]]. These lesions are generally diagnosed through their clinical features, history, risk factors, evolution, location, and confirmed through histopathology [1,4,5]. Morphological lesion characteristics on slit-lamp examination, such as anatomical location, basal diameter, pigmentation, presence of cysts or feeder vessels, have been used to distinguish benign from malignant tumors [6].

The benefits of complimentary diagnostic imaging have been demonstrated for the assessment of these lesions. Ultrasound bio-microscopy, for example, is commonly used to determine the intraocular tumor invasion depth and metastasis, showing limited image resolution with good tissue penetration for the anterior segment [[7], [8], [9]]. Its main disadvantages are the axial resolution, limited accessibility to this imaging technique, the need for submersion and contact under topical anesthesia, and experienced operator for image acquisition [10,11]. The study of the vasculature pattern in ocular tumors may provide additional insight into diagnosis and prognosis of tumors [12]. Although this concept is well established in chorioretinal tumors, studies on anterior segment tumors are scarce [13]. Brunner et al. have recently described the vascular characteristics of ocular surface neoplasia as assessed by indocyanine green angiography (ICGA) [14]. They analyzed epithelial and pigmented lesions, and provided measurements, such as mean vessel diameter, lesion filling times, and quantification of afferent and efferent vessels, with a significantly decreased lesion filling time in malignant lesions, compared to benign lesions.

Anterior segment-optical coherence tomography (AS-OCT) is a non-invasive and non-contact device that can generate high-resolution cross-sectional B-scans of the ocular surface, using near-infrared light with an approximately 5 μm axial resolution [15]. In ocular surface squamous neoplasia (OSSN), it has previously been used to assess the lesion thickness and epithelial thickness [11,16]. The limitation of AS-OCT, however, is the inability to provide functional parameters, such as blood flow. Furthermore, the novel AS-OCT angiography (AS-OCTA) is capable of detecting blood vessel flow (by calculating decorrelation signals) from the red blood cell movement within the vessels through sequential en face scans at the same location. This modality is now widely used in retinal vascular diseases [17] and recently for intraocular tumors [18,19]. The main disadvantages of OCTA, unlike other angiography techniques with dye injection, are the inability to accurately determine venous from arterial and to detect vessel leakage.

The application of AS-OCTA has shown promising results in corneal neovascularization and other ocular surface diseases [20,21]. However, the utility of AS-OCTA in ocular surface tumors remains underexplored. We hypothesize that this novel feature can provide qualitative and quantitative vascular parameters that can aid in the assessment of ocular surface lesions. The aim of this study is to investigate vascular depth and diameter as assessed by AS-OCTA in ocular surface lesions, and to explore if these parameters demonstrate significant differences between malignant and benign lesions. Herein, we describe the preliminary utility of this technology in the setting of ocular surface tumors.