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Kari V Vienola, Ravi Sankar Jonnal, Justin V Migacz, Iwona Gorczynska, Robert Zawadzki; Multi-modal retinal imaging with active retinal tracking and wavefront sensing. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4571.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate a 2nd generation multi-modal retinal imaging system using a tracking scanning laser ophthalmoscope (TSLO) to stabilize the optical coherence tomography angiography (OCTA) acquisition in real-time. Further on, ocular aberrations are recorded with a custom Shack–Hartmann wavefront sensor. Besides the OCTA/TSLO data, the system can be utilized as a screening tool to evaluate the patient’s suitability for adaptive optics (AO) based imaging systems.
The system schematic is shown in Fig. 1. All three sub-systems (OCTA, TSLO and HS-WFS) are optically coupled with a use of dichroic mirrors before entering the eye. The wavefront detection path is then peeled off with a beams splitter as the ophthalmic lens is translated to correct for patient’s refractive error and thus would move the pupil plane. The TSLO uses 840 nm light to image the eye at 30 Hz frame rate with a 5° field-of-view with 960 Hz bandwidth for motion detection. The OCTA uses a 1060 nm swept laser operating at 100 kHz sweep frequency to image the retina and the wavefront sensing is done with 755 nm superluminescent diode. The real-time motion correction from TSLO to the OCTA is done with combining voltage signals controlling the scanning mirrors and the TSLO-generated correction (motion) signal using an analog summing amplifier.
The proposed system’s subassemblies have been individually evaluated (Fig. 2). Data from all three subsystems have been collected from subjects who were later imaged using AO-OCT, and TSLO motion traces have been used to correct motion artifacts in OCTA images in post-processing. Data from the wavefront sensor has been used to exclude some patients from AO-OCT imaging.
Real-time eye tracking provides two-fold benefit for the combined system. As OCT angiograms are generated from the volumes, eye motion produces spurious decorrelation resulting in OCTA artifacts. Real-time eye tracking can potentially remove these artifacts. Besides this, OCTA with motion tracking should improve the angiogram quality after averaging as the OCT volumes can be registered more accurately due to minimal motion error. Secondly, as the wavefront detection and eye motion is acquired simultaneously, dynamic ocular wavefront changes can be observed respect to eye motion and determine if the subject is a good candidate for AO imaging.
This is a 2020 ARVO Annual Meeting abstract.
Schematic of the combined imaging system. Each system can be operated individually.
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