Intraocular drug delivery into silicone oil-filled eyes: Experience with cidofovir (HPMPC)

Purpose. The management of vitreoretinal diseases, such as CMV retinitis, with local pharmacologic therapy is complicated in the setting of silicone oil vitreous substitute. We have previously shown that intravitreal cidofovir is effective in the treatment of CMV retinitis and undertook this pilot study to evaluate the feasibility and efficacy of these injections in eyes filled with silicone oil. Methods. We performed 12 intraocular injections of 10ug of cidofovir in seven oil-filled eyes of six patients with CMV retinitis. The 10ug dose (half the dose previously used) was chosen because of the small volume of ocular fluid in silicone filled eyes. Injections were performed through the pars plana into the middle of the silicone oil bubble. The spherical aqueous bubble could immediately be visualized within the oil using indirect ophthalmoscopy. Eyes were examined every two weeks. None of the patients were on any other type of systemic anti-CMV therapy during the entire study period. Results. Of the eight injections (in four eyes) which had adequate follow-up, seven (87.5%) resulted hi healing of the retinitis. Median time to progression after a single injection in eyes with active retinitis was 56 days. There were no cases of iritis, hypotony, or retinal redetachment with the 10ug dose. One eye had the aqueous bubble of cidofovir still undissolved in the silicone oil at the initial follow-up visit, at which time the retinitis remained active. The bubble was mechanically moved into the aqueous phase with a 27g needle and the retinitis then went on to heal without additional treatment. Conclusions. Intraocular injections directly into a silicone oil bubble can be easily and safely performed. Treatment of CMV retinitis by injecting lower-dose cidofovir with this technique appears to be safe and effective. These findings may have implications for the treatment of other vitreoretinal diseases in the presence of non-aqueous tamponading agents, including proliferative vitreoretinopathy.