Optical Coherence Tomography in the Diagnosis and Monitoring of Retinal Diseases

Optical coherence tomography (OCT) allows the visualization of the retinal microarchitecture as cross-sectional or tomographic volumetric data. The usefulness of OCT in the management of various retinal diseases is validated by the possibility to allow early diagnosis and to help in the decision-making process. OCT is applied by two main methods: time domain (TD-OCT) and spectral domain (SD-OCT). The advantages of SD-OCT over TD-OCT are significant improvement of the image axial resolution, decreased acquisition times, reduction of motion artifacts, increased area of retinal sampling, and the possibility to create topographic maps by the three-dimensional evaluation of tissues. OCT is the most precise method to measure the central macular thickness (which is the most important practical parameter) in vivo. It has been demonstrated that there are differences in the retinal thickness measurements between OCT models, explained by the higher axial and transverse resolutions of the newer devices. Further research has led to significant improvements in OCT technology represented by ultrahigh resolution OCT (UHR-OCT), swept source OCT (SS-OCT), enhanced depth imaging OCT (EDI-OCT), and adaptive optics. Technological progress in OCT imaging offered new perspectives for better understanding the retinal diseases, opening new avenues for the fundamental and clinical research. This is a review of the data in the literature concerning the evolution of OCT technology in the field of retinal imaging. 1. Introduction The progress of the retinal imaging was determined by three major inventions: the direct ophthalmoscope, the fluorescein angiography, and the optical coherence tomography (OCT). The direct ophthalmoscope was invented by Hermann von Helmholtz in 1851 and gave access to the direct, in vivo visualization of the retina. In 1961 Novotny and Davis injected fluorescein dye intravenously in order to visualize the retinal circulation; thus, the technique named fluorescein angiography was born. In the 1990s OCT was invented which revolutionized the way we see the retina, by being able to visualize precisely the retinal layers—something done before only on pathology slides. Because of its simplicity, noninvasiveness, and richness of information, OCT became soon a crucial investigative tool in most of the retina practices [1]. Retinal diseases such as age-related macular degeneration (AMD), central serous chorioretinopathy, macular hole, vitreomacular interface syndrome, and diabetic maculopathy have taken advantage from the introduction of OCT in the clinical