Tamer Macky, MD (Cairo, Egypt), Dina Helmy, MD (Cairo, Egypt), Nihal El Shazly, MD (Cairo, Egypt)

PURPOSE:

To assess rabbit retinal toxicity to triamcinolone acetonide vehicle, benzyl alcohol, when injected intravitreally.

METHODS:

This prospective comparative experimental study included 24 pigmented rabbits assigned into 2 groups; group 1 (experiment, n=12) received intravitreal 0.1ml of benzyl alcohol (BA), and group 2 (control, n=12) received intravitreal 0.1ml of balanced salt  solution (BSS); all injections were done in the right eyes. Clinical examinations were done on both eyes of all available rabbits before injection, at 1 and 3 hours post injection and together with electroretinograms (ERGs) at 3, 7, 14, 28 and 42 days following injections. Three rabbits from each group were killed at 7, 14, 28 and 42 days and both eyes were sent for either light
or electron microscopic examination.

RESULTS:

Mean amplitudes of ERG a and b waves of the BA-injected eyes were significantly reduced (p<0.01 t-test) at 3 days; 6.42±9.02 μv and 11.18±15.18 μv respectively, (BSS-injected eyes: 30.87±8.22μv and 57.90±13.38μv, respectively); and continued to be significantly reduced in the BA-injected eyes (p<0.01 t-test) at 6 weeks. The mean ganglion cell count was significantly reduced  (p<0.005 t-test) in the BA-injected eyes 8.42±2.4 (BSS-injected eyes: 16.42±3.9). The mean inner nuclear layer (INL) and outer nuclear layer (ONL) thickness were significantly reduced (p<0.005 t-test) in the BA-injected eyes 3.78±0.96μm
and11.77±1.29μm, respectively, (BSS-injected eyes: 6.1±0.92μm and 21.82±0.95μm, respectively). Electron microscopy showed intracellular irreversible changes in all layers at 6 weeks.

CONCLUSION:

Triamcinolone Acetonide’s Vehicle, benzyl alcohol, produced severe irreversible ERG and structural damage to rabbit neurosensory retinal following intravitreal injection.