Near-infrared reflectance imaging of neovascularization in proliferative diabetic retinopathy

Abstract

Background Blood is one of the main absorbers in the near-infrared spectrum and thus retinal vessels appear dark in near-infrared reflectance (NIR) images. Proliferative diabetic retinopathy (PDR) is characterized by abnormal neovascularization which also absorbs light and appears dark against a lighter fundus background. We analyzed neovascularization in PDR using NIR imaging, by observing changes in the neovascular complexes (NVCs) contrast and reflectivity over time. Methods Retrospective case series of 20 eyes of 17 patients with PDR who underwent NIR imaging with optical coherence tomography (OCT) using the Spectralis System. NVCs presence and activity was determined using clinical, tomographic and angiographic criteria. At baseline, all NVCs were qualitatively graded in the NIR image into 3 groups (absent, present and inactive and present and active) and their evolution over time was registered as progression, regression or same status. Results Twenty-seven NVCs were imaged, of which, 52% were neovascularization of the disc (NVD) and 48% were elsewhere (NVE). Consecutive NIR images were obtained from baseline to up to 5 time-points with a mean follow-up of 3.2 ± 1.7 years. All eyes underwent laser treatment and 30% had additional intravitreal therapy. Using NIR imaging, NVCs were classified at baseline as absent, present and inactive and present and active, respectively in 11, 4 and 85% of cases. NIR identified active neovascularization as hyporeflective irregular dark vessels originating from the retinal venules in NVE or from the disc in NVD. In all groups during follow-up, progression was identified as the development of new vascular hyporeflective dark fronds while regression was shown by reduced dark perfusion. Five eyes developed a wolf’s jaw configuration with vascular hyporeflective new vessels and hyperreflective tissue from extensive fibrosis. Fibrosis was more apparent in later images, reaching 86%. In 3 cases (11%), the NVC was no longer seen in NIR, although was still identifiable on OCT over the NVC area. Conclusions NIR is a non-invasive imaging modality commonly performed alongside OCT and frequently overlooked which can be useful to evaluate NVCs in PDR. Changes in NVC contrast and reflectivity due to blood perfusion can help in the detection and monitoring of diabetic proliferative disease and aid clinicians in daily practice.

Diagnostic and Therapeutic Challenges

“…Thus, it is probable that the VEGF produced resulted in the NVD that grew quite large into the vitreous cavity and along the posterior hyaloid face. 5 Although this degree of NVD is unusual, it should not be interpreted as natural retinal vessels. The FA clearly shows the extensive leakage from the NVD that would not be present from terminal segments of nonneovascular retinal vessels.…”

“…Often, this degree of ischemia leads to ocular neovascularization such as neovascularization of the disk (NVD), neovascularization of the epiretina, or neovascularization of the iris. 5 So, where would the reported avulsed network of natural vessels derive? Second, previously published cases describe that natural vessels can avulse.…”

Current status and future possibilities of retinal imaging in diabetic retinopathy care applicable to low- and medium-income countries

“…Neovascularization in the eyes with PDR commonly appears as hyporeflective irregular blood vessels. [ 64 65 ] However, image artifacts are common which can make interpretation challenging.…”

Developments in Non-Invasive Imaging to Guide Diagnosis and Treatment of Proliferative Diabetic Retinopathy: A Systematic Review

“…Exploratory parameters include retinal non-perfusion and retinal nerve fibre layer thinning [73]. In 2020, Vaz-Pereira et al [39] reported high-contrast near infrared reflectance imaging with a field of view of 30 • was able to observe changes in the neovascular complexes at the disc and elsewhere in 20 eyes with PDR.…”