Purpose
To investigate the morphologic characteristics of choroidal nevi using swept-source optical coherence tomography and compare this with enhanced-depth optical coherence tomography.
Design
Retrospective observational case series.
Methods
One choroidal nevus each from 30 eyes of 30 patients was included and received imaging with swept-source OCT (SS-OCT) and enhanced-depth imaging OCT (EDI-OCT). For SS-OCT, a scan acquisition protocol was used involving 12 mm horizontal and vertical scans in the posterior fundus. The main outcome measures were morphologic features of choroidal nevi obtained with SS-OCT imaging. These features were compared to images obtained with EDI-OCT. A 2-tailed Fisher exact test was the statistical method used.
Results
SS-OCT allowed for an appreciation of intralesional details: Of the 30 nevi imaged, intralesional vessels were apparent in 30 (100%), intralesional cavities in 6 (20%), intralesional granularity in 14 (47%), abnormal choriocapillaris in 25 (83%), and abnormal choriocapillaris confined to the tumor apex in 17 (58%). Distended bordering vessels were identified in 22 nevi (73%) and were significantly associated with the presence of previous or persistent subretinal fluid. Intrinsic hyperreflectivity with hyporeflective shadowing was significantly ( P = .05) more apparent in 14 of 21 melanotic nevi (67%) compared with 2 of 9 amelanotic nevi (22%). Visualization of the complete nevus-scleral interface was significantly ( P = .02) more apparent in 7 of 9 amelanotic nevi (78%) compared with 6 of 21 melanotic nevi (29%), and was not significantly related to tumor thickness (measured by ultrasound) or to tumor configuration. Tumor diameter (but not tumor height) was statistically significantly associated with secondary retinal changes ( P = .05) and configuration ( P = .01). EDI-OCT was equivalent at determining secondary retinal changes ( P = .29), the presence of distended bordering vessels ( P = 1), visualization of the nevus-scleral interface ( P = .6), and hyporeflective gradation at the nevus-scleral interface ( P = .33). However, in melanotic lesions, SS-OCT was significantly superior at visualizing intralesional vessels ( P = .0002), intralesional granularity ( P = .0005), and abnormal choriocapillaris ( P = .0001).
Conclusion
Imaging of choroidal nevi with SS-OCT enables visualization of intralesional details such as vessels (present in 100% of tumors imaged), cavities, and granularity. For melanotic lesions, SS-OCT is significantly better at depicting certain intralesional characteristics compared to EDI-OCT. Distended bordering vessels were recognized in over two thirds of the nevi imaged and were significantly associated with previous or persistent subretinal fluid.
The first reports on optical coherence tomography (OCT) imaging of choroidal nevi described the “limitations” of the technology. In 1998, Schaudig wrote that “the more important information of tumor histology is hidden in diffuse and weak subretinal backscattering.” Time-domain OCT (TD OCT) could provide information on secondary retinal changes and this became the subject of multiple reports from various groups. However, owing to shadowing and lack of signal penetration, TD OCT gave poor imaging details deeper to these retinal changes. Literature on the use of spectral-domain OCT (SD OCT) imaging of choroidal nevi is scarce. Sayanagi and associates showed that SD OCT allows for better identification of secondary retinal changes, but imaging of the tumor “was limited only to the anterior aspect.”
In 2011, the use of enhanced-depth imaging OCT (EDI-OCT), a modification of SD OCT image acquisition, for evaluating choroidal nevi was described. Using EDI-OCT, Torres and associates further expounded upon the influence of pigmentation on image quality and characteristics, and demonstrated that amelanotic nevi had less shadow and a homogenous, medium reflectivity. In the same year, Shah and associates used EDI-OCT to capture images of the anterior tumor sufficient for them to describe that 94% of choroidal nevi had choriocapillaris thinning. However, even with the EDI-OCT technique, pigmented lesions continued to demonstrate shadowing, which compromised visualization beyond the anterior tumor or inner choroid.
Swept-source OCT (SS-OCT) has recently gained momentum, and aspects of this technology would presumably offer improved images of the choroid and pigmented lesions therein. It uses a wavelength-tunable laser and dual-balanced photodetector offering higher imaging speed. Its adaptability to a longer wavelength (on the order of 1 μm) improves the imaging range to include the choroid and penetrates melanin to a greater extent. Besides investigations of vitreous and retinal architecture, SS-OCT has revealed novel findings in choroidal and scleral characteristics in normal eyes and in those with pathologic myopia, in addition to choroidal features of diseases such as chronic central serous chorioretinopathy and reticular pseudodrusen.
However, there are still opportunities to expand the utilization of this novel imaging technology in the analysis of additional choroidal pathology. The aim of this present study is to use this long-wavelength SS-OCT system to image the morphologic characteristics of choroidal nevi.
Methods
The study adhered to the tenets of the Declaration of Helsinki, complied with the Health Insurance Portability and Accountability Act, and was approved by the Institutional Review Board of Memorial Sloan Kettering Cancer Center. Informed consent was obtained from all patients prior to SS-OCT examination. The study included 30 choroidal nevi in 30 eyes of 30 patients (7 male, 23 female) recruited from the institution of Memorial Sloan Kettering Cancer Center, New York between September 1, 2012 and May 31, 2014. Patients with macular choroidal nevi were consecutively included. Of the 40 patients that were approached for inclusion in the study, 10 patients declined participation because of a scheduling conflict. Patients received imaging with the SS-OCT device at the clinical practice of Vitreous Retina Macula Consultants of New York and EDI-OCT imaging at either Vitreous Retina Macula Consultants of New York or Memorial Sloan Kettering Cancer Center.
Examination
All enrolled patients received an ophthalmologic examination complete with best-corrected visual acuity, ultrasonography, intraocular pressure, dilated fundus examination, and fundus photography. Patients were imaged with the DRI OCT-1 Atlantis 3D SS-OCT device (Topcon Medical Systems, Oakland, New Jersey, USA), centered at 1050 nm for enhanced choroidal penetration. The axial resolution was approximately 6 μm with a scan speed of 100 000 A-scans per second. A scan width of 12 mm was used and 5-line cross-scan patterns with 0.25 mm spacing were chosen in both the horizontal and vertical direction. Thirty-two averaging scans were obtained per line. EDI-OCT images were obtained with the Heidelberg Spectralis HRA+OCT (Heidelberg Engineering, Heidelberg, Germany). A scan of 9 mm was used and 13-line cross-scan patterns were chosen in the both the horizontal and vertical direction.
Data Collection
Demographic data were collected on each patient, including sex and age. Clinical features included diameter of the nevus (mm), height (mm) and configuration (plateau, dome, mushroom) of the nevus determined by standard ultrasonography, color (melanotic vs predominantly amelanotic), and retinal changes (retinal pigment epithelial [RPE] changes, drusen, orange pigment, halo, subretinal fluid). SS-OCT features were recorded and included presence of secondary retinal/RPE changes: drusen, RPE alterations, cystoid macular edema, ellipsoid alterations, visualization of Bruch membrane, and orange pigment correlated with fundus autofluorescence. Previous or persistent subretinal fluid was established through historical OCT images and/or the presence of characteristic areas of hyper-autofluorescence detected with autofluorescence imaging. The main outcome measure included tumor characteristics determined by SS-OCT, which included intrinsic hyperreflectivity with hyporeflective shadowing (optical shadowing), visualization of the nevus-scleral interface, presence of hyporeflective line at the nevus-scleral interface, presence of intralesional vessels, cavities or granularity, presence of distended bordering vessels and association with subretinal fluid, and presence of abnormal choriocapillaris and whether confined to the tumor apex. The configuration of the tumor was recorded into 3 groups: plateau (no distention of the retina), dome (distention of retina only), and almond (distention of the retina and sclera).
Secondary retinal changes and tumor characteristics obtained by the SS-OCT technology were compared to EDI-OCT images, which were available for all patients.
Statistical Analysis
Statistical analysis was performed using the 2-tailed Fisher exact test on GraphPad Software, Inc (La Jolla, California, USA). Tumor characteristics were compared between melanotic and amelanotic tumors, and configuration and secondary retinal changes were compared between tumors less than or equal to 3 mm in diameter and those larger than 3 mm; and between tumors less than or equal to 1 mm in height and those larger than 1 mm. Visualization of the nevus-scleral interface was compared between different tumor configurations and tumors less than or equal to 1.4 mm in height and those greater than 1.4 mm in height (1.4 mm was the median height and was therefore selected as the cutoff). The presence of previous or persistent subretinal fluid was compared between nevi with and without distended bordering vessels. Retinal changes and tumor characteristics were compared between EDI-OCT and SS-OCT. A P value less than or equal to .05 was considered statistically significant.
Results
Twenty-one melanotic and 9 amelanotic choroidal nevi were studied with a median height of 1.4 mm (range 0.8–3.2 mm) and diameter of 5 mm (range 1.5–11 mm). The following secondary retinal changes were detected by both SS-OCT and EDI-OCT in the 30 eyes studied: drusen in 22 (73%), RPE alterations in 26 (87%), cystoid retinal edema in 4 (13%), and ellipsoid alterations in 22 (73%). Of 30 eyes, an intact Bruch membrane was visible by SS-OCT in 17 (57%), compared to 12 (40%) by EDI-OCT.
With SS-OCT it was possible to detect intralesional details of both melanotic and amelanotic nevi, including intralesional vessels (appearing equidistant and equal in size), cavities, granularity, distended bordering vessels, and hyporeflective gradation at the nevus-scleral interface, as well as other details such as the presence of intrinsic hyperreflectivity with hyporeflective shadowing, visualization of the nevus-scleral interface, and status of the choriocapillaris ( Table 1 ). Distended bordering vessels were significantly associated with the presence of previous or persistent subretinal fluid ( P = .03): of 22 tumors with distended bordering vessels, 10 had SRF (45%), compared to 0 of 8 tumors without distended bordering vessels (0%).
| OCT Characteristics | Swept-Source Imaging | |||
|---|---|---|---|---|
| All Nevi (n = 30) | Melanotic (n = 21) | Amelanotic (n = 9) | P Value a | |
| Intrinsic hyperreflectivity with hyporeflective shadow | 53% (16) | 67% (14) | 22% (2) | .05 |
| Visualization of nevus-scleral interface | 43% (13) | 29% (6) | 78% (7) | .02 |
| Hyporeflective gradation of nevus-scleral interface | 27% (8) | 19% (4) | 44% (4) | .2 |
| Intratumoral vessels | 100% (30) | 100% (21) | 100% (9) | 1 |
| Intratumoral cavities | 20% (6) | 14% (3) | 33% (3) | .33 |
| Intratumoral granularity | 47% (14) | 48% (10) | 44% (4) | 1 |
| Distended bordering vessels | 73% (22) | 76% (16) | 67% (6) | 1 |
| Abnormal choriocapillaris | 83% (25) | 76% (16) | 100% (9) | .29 |
| Abnormal choriocapillaris at apex only | 58% (17) | 48% (10) | 78% (7) | .23 |
Three distinct anatomic nevi configurations were identified ( Figures 1 and 2 ). These configurations were termed “plateau” (distention into the sclera only), seen in 6 of 30 eyes (20%); “dome” (distention into the retina only), seen in 8 of 30 eyes (27%); and “almond” (distention into both sclera and retina), seen in 10 of 30 eyes (33%). Even in instances where the nevus-scleral interface was not fully visualized along the entire length of the tumor, there was adequate visualization at the sides to determine presence of scleral distention. Six of the 30 nevi (20%) were either dome or almond in configuration, but shadowing prevented exact determination, owing to inadequate visualization of the nevus-scleral interface. Ultrasonography could identify the tumor configuration in 27 of 30 tumors (90%). The remaining 3 tumors were read as plateau on ultrasound, but were determined to be dome shape on SS-OCT.
Visualization of the nevus-scleral interface was statistically more likely in amelanotic vs melanotic nevi ( Table 1 ). However, visualization was not significantly related to tumor thickness when comparing those less than or equal to 1.4 mm and those greater than 1.4 mm: P = .16 for all tumors, P = .18 for melanotic tumors, and P = .44 for amelanotic tumors. Visualization of the nevus-scleral interface was not significantly associated with tumor configuration ( P = .66).
Tumor diameter was significantly associated with secondary retinal changes ( P = .05) and configuration ( P = .01). Of 8 tumors less than 3 mm in diameter, 3 had retinal changes (38%), compared with 21 of 22 tumors greater than 3 mm in diameter (95%). Furthermore, of 22 tumors greater than 3 mm in diameter, 21 had a configuration that distended into the retina (dome or almond) (95%), compared with 4 of 8 tumors less than 3 mm in diameter (50%).
Tumor height (less than vs greater than 1 mm) was not associated with secondary retinal changes ( P = 1) or a configuration that distended into the retina ( P = .3). Of 10 tumors less than 1 mm in height, 9 had retinal changes (85%), comparable to 17 of 20 tumors greater than 3 mm in diameter (95%). Furthermore, of 20 tumors greater than 1 mm in height, 18 had a configuration that distended into the retina (dome or almond) (90%), comparable to 7 of 10 tumors less than 3 mm in diameter (70%).
Visualization of secondary retinal changes and tumor characteristics by EDI-OCT and comparison with SS-OCT is depicted in Table 2 . EDI-OCT was equivalent at determining secondary retinal changes, the presence of distended bordering vessels, visualization of the nevus-scleral interface, and its hyporeflective gradation. However, SS-OCT was significantly superior at visualizing intralesional vessels, intralesional granularity, and abnormal choriocapillaris in melanotic lesions. Furthermore, the morphology of melanotic nevi could be visualized significantly better with SS-OCT compared with EDI-OCT ( P = .0001). Of 21 melanotic tumors, the morphology could be determined in 21 (100%) with SS-OCT, compared to 16 (53%) with EDI-OCT. In amelanotic lesions, visualization of the morphology was equivalent with SS-OCT and EDI-OCT ( P = 1).
