Charles A. Wilson

Oxygen kinetics in preretinal perfluorotributylamine

Previous studies have relied on various electrodes or probes to monitor preretinal oxygen tension in an effort to gain insight into retinal oxygenation. In order to corroborate and extend the results of such studies, we developed a relatively non-invasive method of determining preretinal oxygen tension using 19F nuclear magnetic resonance (NMR) spectroscopy. Small liquid perfluorocarbon (LPFC) droplets were injected into the preretinal vitreous space of the rabbit eye. The T1 value obtained from the fluorine nuclide could then be used to determine preretinal oxygen tension (PO2) with a high degree of sensitivity, since the fluorine spin-lattice relaxation rate (T1)-1 in LPFCs is directly proportional to PO2 under conditions of no flow and known temperature. In the present study, we investigated the oxygen uptake and clearance rates from small preretinal droplets of the LPFC perfluorotributylamine (FTBA) in response to step changes in arterial PO2. At all FTBA volumes examined (2, 10 and 100 microliters), the oxygen uptake and clearance curves were well approximated by a simple exponential equation with mean time constants 9.8/15.3, 21.4/19.4 and 77.7/45.3 min (uptake/clearance), respectively. Following return to normoxemic (baseline) conditions, FTBA droplets provided a preretinal PO2 of 39.4 +/- 9.2 mmHg (mean +/- S.D., n = 12). The 19F NMR method provides a measure of steady-state preretinal PO2 that independently verifies and complements information obtained using oxygen-sensitive microelectrodes or probes. However, the long time constants for oxygen uptake and clearance, particularly in FTBA volumes on the order of 10 microliters and greater, may represent a practical limitation of this method for determining rapid oxygen flux in the preretinal vitreous space.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental traction retinal detachment in the cat

AbstractWe developed a reproducible model of traction retinal detachment (TRD) in the cat eye by creating a serous retinal detachment and then injecting 2.5 × 105 kitten dermal fibroblasts into the vitreous cavity at the site of a retinal wound. Serous detachments were produced by exposing an area of retina to focused light after intravenous injection of rose bengal (a photosensitizing dye). TRD developed rapidly within the first 2 weeks after fibroblast injection, accompanied by the formation of vitreoretinal strands and, to a lesser degree, epiretinal and/or subretinal proliferation. Histopathology demonstrated fibroblasts within the vitreous or along the posterior hyaloid face. Focal deposits of fibroblasts were occasionally found on the inner surface of the retina and/or in the subretinal space. Fibroblast proliferation was confirmed by uptake of radiolabeled thymidine. Deposition of collagen was noted at as early as 3 days after fibroblast injection. Neovascularization was not observed. Control eyes that did not receive fibroblasts showed resolution of serous detachment without retinal traction. In all eyes, retinal degeneration and thinning were seen in the area of previous photodynamic treatment. In this model of TRD, anteroposterior traction (due to vitreous strands) predominates, as is observed in experimental posterior penetrating ocular injury induced by intravitreal blood injection, which also results in vitreous strand formation. Our model, however, enables clinical assessment of TRD in the cat without the media opacification produced by vitreous blood.nOffprint requests to: D.L. Hatchell