Covering the gap in depth resolution between OCT and SLO in imaging the retina

Abstract

Two instruments are now available for high depth resolution imaging of the retina. A scanning laser ophthalmoscope is a confocal instruments which can achieve no more than 0.3 mm depth resolution. A longitudinal OCT instrument uses a superluminescent diode which determines a depth resolution better than 20 microns. There is a gap in depth resolution between the two technologies. Therefore, different OCT configurations and low coherence sources are investigated to produce a choice of depth resolutions, and to cover the gap between the old confocal technology and the new OCT imaging method. We show that an instrument with adjustable depth resolution is especially useful for the en-face OCT technology. Such an instrument can bring additional benefits to the investigation process, where different requirements must be met. For instance, a poor depth resolution is required in the process of positioning the patient's eye prior to investigation. A good depth resolution is however necessary when imaging small details inside the eye. The utility of the OCT en-face imaging with adjustable coherence length for diagnostic is illustrated by images taken from the eye of a volunteer. Images with a similar aspect to those produced by a scanning laser ophthalmoscope can now be obtained in real time using the OCT principle.