Blood-ocular barrier permeability and electroretinogram after intravitreal silicone oils of varying composition

Silicone oils, used as long-term retinal tamponades, cause retinal toxicity that may be related to certain ingredients. Specific additives, proven to increase corneal endothelial permeability, were added to a purified oil, and placed into the vitreous of rabbits to assess their effects on the retina. Oils were exchanged for vitreous at constant intraocular pressure to 1 ml oil volume. Blood-ocular barrier permeability was measured with fluorophotometry after intravenous dye, and retinal function was measured using dark-adapted electroretinography (ERG). Each parameter was determined at eight week intervals: this periodicity was chosen to allow any toxicity to develop based upon prior data in the literature. The fluorescein concentration in different ocular compartments indicated an increased aqueous humor fluorescein concentration after pure oil (a non-statistically significant 50% increase) or oil plus long chain additive (a significant 240% increase). After oil plus a linear series of compounds both aqueous humor (2000%) and anterior vitreous fluorescence (8000%) was statistically significantly increased, indicating a breakdown of the blood-aqueous barrier. The height of the b-wave of the ERG was unaffected by any oil in the presence or absence of additive. Overt changes were minimal with oil alone, increased with oil containing linear chain additive, and were extensive with oil with long chain additive.