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MA Choma, K Rao, M Czajka, H Rashed, KP Winter, CA Toth, JA Izatt; Real-Time OCT Imaging of the Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4372.
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Purpose: Optical coherence tomography (OCT) is a new imaging technology whose full utility in the practice of ophthalmology is still being fully realized. Until now, OCT retinal imaging has been constrained by frame rates well below real-time. Slow imaging rates lead to significant motion artifact, which in turn leads to effective resolutions coarser than those determined by the specifications of the system. It also imposes significant limitations on the use of OCT to assess ophthalmic structures during ophthalmic treatment or with eye movement. Methods: Here we demonstrate a prototype for OCT retinal imaging at 8 frames per second using a pulse-stretched Ti:Sapphire femtosecond laser source and a rapid scanning optical delay line. OCT images were acquired through a modified slit lamp under direct observation with video documentation. The optical power used to obtain these images at high speeds exceeded ANSI exposure limits by a factor of approximately 7. We imaged ex vivum porcine eyes in two groups. Group A was untreated and examined with the new OCT system. Group B had intraocular ophthalmic treatments and was imaged with the new OCT system during intra- and extraocular manipulation. Results: Clinically useful quality images of the retina were obtained in real-time. We identified characteristic layers of the retina (RNFL, RPE, and photoreceptor layer), the choriocapillaris, retinal blood vessels, and retinal detachments that were surgically induced post mortem in the porcine eyes. We also were able to observe and induce changes in these structures as visualized by OCT during ophthalmic manipulation and treatment. Real-time imaging was useful in the interactive positing of surgical instrumentation. Additionally, the high rate of image acquisition allowed for precise capturing of artifact-free still-frame images and movies of the retina. Conclusion: In ex vivum testing we have shown that high speed (8 fps) OCT imaging linked to the slit-lamp can be utilized for simple intraocular maneuvers at the slit-lamp. By trading off SNR for lower exposure levels and by optimizing signal processing, we are building an ANSI-compliant system for real-time OCT imaging of the living human retina.
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