Optical coherence tomography (OCT) is a method of optical imaging. It can be used in clinical situations to aid with the diagnosis of diseases in many organs such as the retina, cardiovascular system, gastrointestinal tract, urinary tract, or gynecologic organs.
OCT is a high-resolution optical imaging technique that can produce a cross-section image of an object. The image can be produced in real time, allowing this technique to have many applications. There are two methods of OCT: time domain and spectral domain. Within these categories, each one can be performed in different ways. Which one is used depends on the sample being investigated and the advantages and disadvantages of each method.
Applications of Optical Coherence Tomography
Retina
Time domain (TD)-OCT images an object by directly obtaining time-encoded signals. TD-OCT imaging is used to assess the retina to give information regarding retinal thickness and the inner retinal complex (IRC), which is composed of a retinal ganglion cell layer, inner plexiform layer, and inner nuclear layer.
The most common scan patterns of the retina using TD-OCT involves imaging via a 3.4 mm scan around the optic nerve head and six equally spaced radial scans through the macula and optic nerve. This is known as the macular scan pattern. 3D OCT imaging of the retina provides more detailed information than the macular pattern, which can be useful when planning or evaluating the outcome of surgeries. 3D OCT also visualizes the vitreomacular interface in subjects undergoing surgery for epiretinal membrane (a thin sheet of tissue that develops over the macular area, which disturbs vision).
SD-OCT can be used to measure the thickness of the retina and to evaluate the effects of certain diseases on this tissue. The decline in visual acuity seen in diabetic macular edema is caused by retinal thickening. There are many other parameters within the retina that can be measured using OCT such as changes in drusen volume, macular holes, subretinal fluid, and pigment epithelium detachment.
