Spectral Analysis of Porcine Retinal Vessels in vivo Using Subretinally Implanted Spectralon

Abstract

Abstract: : Purpose: To measure the spectral reflectance of the porcine fundus and the spectral transmittance of retinal vessels in vivo using the technique of intravitreal illumination and the surgical insertion of a small piece of Spectralon subretinally. Methods: Four adult female swine are anesthetized and are ventilated with 100% oxygen. Each eye is illuminated with a scanning monochromator coupled into a fiber optic probe placed into the eye through the pars plana. The illuminated fundus is imaged with a modified fundus camera and spectral images are obtained at 10 nm increment wavelengths in the 420 nm to 700nm spectral range. A standard 3 port pars plana vitrectomy is performed and the same regions of the fundus are imaged again at the same bandwidth and range. The field of view includes adjacent vein/artery pairs and regions of the fundus that are free of large vessels. A small Spectralon chip is then inserted subretinally and the retinal vessels are re–imaged at the same bandwidth and range. The retina is surgically removed and the spectral reflectance RPE/choroid/sclera is measured. Results: The in vivo spectral transmittance of retinal veins and arteries are measured for the intact porcine swine eye and the porcine eye with Spectralon inserted subretinally. The spectral reflectance of the RPE/Choroid/Sclera is estimated from the spectral data and compared to spectral reflectance of the RPE/choroid/sclera measured directly. Conclusions: Isolation of the blood vessels from the influence of the RPE/choroid/sclera layers resulted in spectra that resembled the spectra obtained from hemolyzed blood. The calculated and measured RPE/choroid/sclera spectra were in good agreement.

Keywords: retina • blood supply • vitreoretinal surgery