Hyperspectral Imaging of the Retina: A Review

Hyperspectral imaging (HSI) is a form of spectral imaging pioneered for remote sensing satellite imaging in agriculture and water control (Fig. 1).1 HSI collects data from across the electromagnetic spectrum by obtaining a contiguous spectrum of wavelengths for every pixel in an image. A 3-dimensional data set called a hypercube is formed, which is comprised of 2 spatial dimensions (x and y) and 1 spectral dimension (λ), where the spatial dimension images are stacked by emission wavelength to form the hypercube (Fig. 2).2 By acquiring a contiguous spectrum, HSI provides a higher spectral resolution compared with multispectral imaging that captures only specific wavelengths such as red, green, and blue (Fig. 3). This enables more precise analysis that can capture subtle spectral differences. There are several different types of HSI techniques, however, most HSI systems include a light source that illuminates the desired image, several wavelength dispersion devices, and area detectors (Fig. 4). Broadly speaking, the goal of this spatially resolved spectral imaging that provides 2-dimensional images across a range of the electromagnetic spectrum, is to enable identification of distinct objects or processes in the image. HSI is now widely used in a variety of fields including food processing,3,4 archeology and art conservation,5 water resource control,6,7 and forensics.8,9 More recently, it has emerged as a useful imaging modality for noninvasive disease diagnosis and image-guided surgery in a variety of medical fields, including ophthalmology.10–12 In recent years, advances in HSI cameras and technology have opened the door for many new applications within ophthalmology. HSI has been used to analyze retinal vascular oxygenation and tissue perfusion as they relate to diabetic retinopathy, retinal vein