A Model for the Effect of Disturbances in the Optical Media on the OCT Image Quality

¹ Ophthalmology, Academic Medical Center, Meibergdreef 9, Amsterdam, 1105AZ, Netherlands
² Ophthalmology, Academic Medical Center, Amsterdam, Netherlands
³ Ocular Signal Transduction, Netherlands Institute for Neuroscience, Royal academy of the Netherlands, Amsterdam, Netherlands
⁴ Ophthalmology, Academic Medical Center, Amsterdam, Netherlands; Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, Netherlands

^* To whom correspondence should be addressed. E-mail: p.h.kok{at}amc.nl.

	Abstract

PURPOSE. The loss of quality of Optical Coherence Tomography (OCT) images resulting from disturbances in the optical media has been modeled. METHODS. OCT measurements were performed in two healthy volunteers using the StratusOCT. Optical disturbances were approached in three ways simulated with filters. The studied effects were: light attenuation (absorptive and reflective filters), refractive aberrations (defocusing lenses) and light scattering/straylight (scattering filters). The same examiner scanned the subjects with the filters placed in front of the eye. The signal strength (SS) values of the scans were then collected. The strength of the filters were expressed in Optical Density, determined for the 830 nm central wavelength of the OCT, (OD=830). RESULTS. A linear relationship has been found between the OD=830, of the absorptive and reflective filters and the SS of the corresponding OCT images. Assuming that reduction of light from the OCT scanning spot on the retina is the critical factor, this light loss was determined for the scattering filters and the defocusing lenses. A comparable linear relationship was found between the SS value and the OD= 830 of these filters. CONCLUSION. The presented model indicates that the loss of OCT image quality in patients with disturbances in the optical media is explained by attenuation of the light in the OCT scanning spot on the retina. A linear relationship between the SS and the single pass logarithmic attenuation of the OCT signal is shown, according to SS = constant -(9.9 (-9.4 to -10.6) ·OD= 830).

Key Words: optical coherence tomography, cataract models, lens opacity

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