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Figure 1-4, Fiber-optic interferometer OCT system. The optical interferometer shown in Fig. 1-3 can be built using fiber optic components to contstruct a compact and modular system. The light source used in most OCT systems is a low-coherence, superluminescent diode which is directly coupled into an optical fiber The interferometer is built using an optical fiber coupler (splitter) where one fiber forms the measurement path of the interferometer and the other the fiber forms the reference path of the interferometer i he fiber in the measurement path is engineered as a remote probe which may be interfaced to a variety of ophthalmic instruments.

within the instrument, while the optical fiber in the second arm of the interferometer is connected to the OCT ophthalmic instrument resembling a slit-lamp biomicroscope or fundus camera. In other applications, the fiber optic probe can be interfaced with endoscopes or catheters for measurement of images at distal points, I he technological base for the instrument is well developed because of its widespread use in fiber-optic communications networks. Thus, its inherent reliability and robustness is exceedingly high. In addition, the use of a fiber-optic technology is well suited for interfacing to different instruments for clinical imaging.

Axial Range, Distance, and Thickness

The simplest type of measurement that can be performed by OCT is a measurement of axial range analogous to ultrasound A-mode ranging. Range information and tissue distances or thicknesses are determined by electronically measuring the signal from the light sensitive detector and then processing the signal electronically and displaying it by computer Figure 1-5 shows an example of axial range measurements performed in the anterior chamber [17-20], The graph shows the intensity of the reflected light from different structures within the anterior eye as a function of

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