Ciliary Body Blood Perfusion After Cyclophotocoagulation Using High Frequency Ultrasound Imaging

Abstract

Abstract: : Purpose: Laser diode cyclophotocoagulation (CPC) is not a first-line surgical treatment option in glaucoma management because its effects on intraocular pressure (IOP) are difficult to titrate. Microvascular casts from rabbit ciliary body after CPC suggest an alteration in blood flow. We use high frequency ultrasound imaging in conjunction with an intravenous ultrasound contrast agent to measure ciliary body (CB) blood perfusion after CPC. An understanding of blood flow alteration may help us improve CPC treatment outcome.Methods: A novel method of high frequency ultrasound imaging with IV contrast agent was used to measure CB blood perfusion in 2 anesthetized Dutch-belted rabbits before, immediately after and 1 week after laser diode CPC (Oculight SLx diode laser, Iridex Corp., Moutain View, CA). IOP of the treated eye was measured at each time point using the Tonopen XL (Mentor Ophthalmics, Norwell, MA). To measure blood perfusion, the mean power-per-pixel (MPPP) from images of the ciliary processes was calculated by dividing the total flow power in the region of interest by the tissue area in pixels. All time points were normalized by the averaged peak Doppler power imaged in the femoral artery using a commercial ultrasound scanner. A paired t-test was performed to test the significance of the changes in MPPP at different time points relative to the pre-treatment measurement.Results: Blood flow power map images of the CB show an 11 dB enhancement of MPPP with IV contrast. After CPC, the CB shrinks in size and areas of blood flow are markedly diminished. Table 1 summarizes MPPP measured at each time point and shows a significant decline in both blood perfusion and IOP after CPC.Conclusion: Blood perfusion of the ciliary body diminishes after laser CPC treatment in conjunction with a decline in IOP. Measurement of CB blood perfusion is an initial step in understanding the fundamental characteristics of ocular microcirculation. Table 1  

Keywords: ciliary body • blood supply • imaging methods (CT, FA, ICG, MRI, OCT, RTA, S