Comparison of Manual Versus Automated Choroidal Thickness Measurements Using Swept-source Anterior Segment Optical Coherence Tomography

The choroid, which is located between the retina and the sclera, is a connective tissue layer that is densely packed with blood vessels and is responsible for supplying oxygen and nutrients to the retina's periphery. One of the primary functions of the choroid is to support the metabolism of the retinal pigment epithelium (RPE). It is implicated in the pathogenesis of a variety of retinal disorders, including age-related macular degeneration, polypoidal choroidal vasculopathy, central serous chorioretinopathy, and high myopia-associated chorio retinal atrophies. Because choroidal alteration has a fundamental role in the development and progression of these diseases, choroidal thickness provides comprehensive information to physicians.

For the study of the choroid, researchers have used ultrasound, magnetic resonance imaging MRI, and Doppler laser, but these methods have limited utility due to a lack of resolution. Contrary to this, indocyanine green (ICG) angiography provides valuable clinical information but does not provide cross-sectional images of the choroid for in vivo research studies.

Optical coherence tomography (OCT) has gained in popularity in clinical and experimental ophthalmology over the last decade as a way to acquire detailed, three-dimensional images of the retina . Imaging the entire choroid, on the other hand, has proven to be more difficult due to the significant decline in signal strength beyond the RPE prompted by the pigment in the RPE and choroid and light scattering in the vasculature. The development of improved depth imaging (EDI) by Spaide et al. opened the door to quantitative choroid assessment. Choroid imaging is currently possible using one of two optical coherence tomography (OCT) techniques: (1) spectral-domain (SD) OCT utilizing standard light sources using EDI, and (2) swept-source (SS) OCT using a long wavelength light .A 1 m-band light source is used in SS-OCT, which penetrates deeper into the retino choroidal tissues and so optimizes the resolution. To better visualize retinal and choroidal changes, SS-OCT can concurrently display a focused image of both the retina and the choroid. This renders it an accurate technology for assessing choroidal thickness.

Such findings of choroidal thickness changes revealed that the choroid and choroidal thickness may be important attributes in the evaluation of ocular pathology. To properly understand the scientific value of these potential choroidal thickness variations, it would appear that comprehensive and systematic normative values for choroidal thickness are fundamental.