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F. P. Almeida, J. A. S. Ribeiro, R. C. Siqueira, A. Silva-Cunha, J. B. Saliba, R. Jorge, A. Messias; Retinal Toxicity of Cyclosporine Intravitreally Delivered by a Biodegradable Implant in Rabbits. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5584.
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To investigate the toxic effects of an intravitreal poly-lactic-co-glycolic acid (PLGA) biodegradable cyclosporine A (CsA) implant on retinal function in rabbits.
Rabbits have been assigned to receive either an intravitreal implant of PLGA biodegradable system with 350 µg of CsA (n=4), or without the compound as control group (PLGA; n=4). Intensity-response relationship of dark-adapted electroretinography (ERG) responses was evaluated at baseline and 8 weeks after the procedure, by applying 13 increasing luminance white flash (4ms - 0.00003 to 100 cd.s/m²). A hyperbolic model was used to derivate the b-wave saturating amplitude (Vmax) and the luminance for reaching 50% of Vmax (k). Subsequently, light-adapted ERG was recorded after 10 min of light adaptation. In addition, slit lamp examination and intraocular pressure (IOP) measurements were performed weekly.
No effects were observed in respect to a-wave amplitude or Vmax in group PLGA (P>0.05). In contrast, in CsA, although no changes were observed on a-wave: mean ± SE: 164.3 ± 14.9 µV at baseline and 170.3 ± 20.3 µV 8 weeks after implant (P>0.05), a significant reduction on Vmax was observed, Vmax: 182.6 ± 9.9 µV at baseline and 100.0 ± 14.5 µV 8 weeks after implant (P<0.05). Consequently, eyes in CsA group showed negative ERG responses 8 weeks after treatment with b/a ratio reducing from 2.0 ± 0.1 at baseline to 1.1 ± 0.1 8 weeks after implant (P<0.05). No sign of inflammation was noticed on slit lamp examinations and IOP maintained stable during the study period.
The PLGA biodegradable system alone causes no ERG changes, while our data suggest that implants with CsA causes impairment on rod postreceptoral pathway function after 8 weeks follow-up. Further studies are necessary to determine structural changes, and the toxicity profile of CsA for this implant.
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