Imaging and Clinical Studies of the Choroid

The choroid, as an important nutrient tissue supplying the outer retinal layer and macular region, is primarily vascular in structure. The choroid accounts for approximately 70% of the blood flow to the entire uvea and, as the vascular system supplying the outer layer of the retina and the macula, it accounts for approximately 2/3 of the blood flow to the entire eye. Because of its unique structure and function, the choroid plays a pivotal role in ocular disorders. For a long time, the study of the choroid has been in an exploratory stage due to its deep anatomical location and the limitations of the examination equipment. As research has progressed, it has become increasingly clear that choroid-related changes are a crucial factor in the pathogenesis of many ocular diseases. Qualitative changes in the choroid occur when ocular disorders occur, particularly when blood flow status is altered due to local or systemic disease, resulting in corresponding changes in choroidal blood flow, choroidal thickness, and choroidal volume. It has been shown that choroidal changes precede retinopathy in some eye diseases, for example, diabetic fundopathy: diabetic choroidopathy precedes diabetic retinopathy. In ocular disease, then, changes in choroidal structure and imaging play a prerequisite role in the early detection and treatment of the disease. This article, therefore, reviews the common clinical imaging modalities of the choroid in ophthalmology and the choroidal changes in related ocular diseases.