Clinicians have several tools available to diagnose corneal neovascularization (NV), but they all have their shortcomings. Traditional methods such as slit lamp biomicroscopy, color photography and videography can result in imprecise imaging that lack quantification, and even more precise tools such as fluorescein and indocyanine green angiography are invasive and can be time sensitive. A research team from the United States and Germany suggests another option: OCT angiography (OCT-A) as an effective and noninvasive approach in detecting corneal NV.

Their study included 12 eyes of 12 patients with corneal NV who were tested with both an 840nm spectral domain OCT-A and a 1,050nm swept-source OCT-A. Of the 12 cases, five patients had interstitial keratitis, two had limbal stem cell deficiency, three had corneal transplant rejection and one patient each had pterygium or neurotrophic ulcers.

The study then compared the OCT-A results with clinical slit-lamp estimations of NV depth.

The researchers found OCT-A was able to map corneal NV in 3D and measure vessel depth and density. The investigators also noted the depth of corneal NV varied between different pathologies in a manner consistent with previous studies.

When looking at severity levels, the researchers found four patients had superficial corneal NV, four had midstromal NV and four others had deep NV. The superficial, midstromal and deep NV cases had an average vessel depth of 23%, 39% and 66% on 1,050nm OCT-A, respectively.

Additionally, eight cases showed excellent agreement in the mean vessel depth between the two systems. However, the average vessel density measured by the 840nm OCT-A was higher—about 1.6-fold—compared with the 1050nm OCT-A.

The investigators also noted the measured vessel density appeared to be affected by the interscan time, which impacted blood flow velocity sensitivity and the wavelength and thus the ability to penetrate through opacity.

“This study represents the first application of corneal OCT-A to quantify the depth of corneal NV. The results demonstrate that OCT-A is capable of differentiating vessel depth in corneal NV and can provide an estimated average vessel depth, which corresponded well with the clinical examination,” the researchers wrote in their paper.

Nanji A, Redd T, Chamberlain W, et al. Application of corneal optical coherence tomography angiography for assessment of vessel depth in corneal neovascularization. Cornea. December 20, 2019. [Epub ahead of print].