ABSTRACT
To assess rabbit retinal toxicity to triamcinolone acetonide vehicle, benzyl alcohol, when injected intravitreally. 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 for quantitative morphometric measurements. Mean amplitudes of ERG a and b waves of the BA-injected eyes were 6.42 +/- 9.02 micro v and 11.18 +/- 15.18 micro v at 3 days respectively, which was significantly reduced compared to the BSS-injected eyes [30.87 +/- 8.22 micro v and 57.90 +/- 13.38 micro v, respectively; p<0.01 t-test] and the non-injected contralateral eyes [36.20 +/- 7.85 micro v and 64.10 +/- 9.36 micro v, respectively; p<0.01 t-test]. These ERG responses continued to be significantly reduced in the BA-injected eyes [p<0.01 t-test] of the unkilled rabbits up to 6 weeks. The mean ganglion cell count [at a magnification of X200 in a standard frame of 4740.32 micro m[2]] were significantly reduced [p<0.005 t-test] in the BA-injected eyes [8.42 +/- 2.4] compared to the BSS- and non-injected eyes [16.42 +/- 3.9 and 16.5 +/- 4.2, respectively]. 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 +/- 0.96 micro m and 11.77 +/- 1.29 micro m, respectively] compared to the BSS- [6.1 +/- 0.92 micro m and 21.82 +/- 0.95 micro m, respectively] and non-injected eyes [7.05 +/- 1.9 micro m and 22.49 +/- 1.0/micro m, respectively]. Electron microscopy showed intracellular irreversible changes in the GCL, INL, ONL, and PRL at 6 weeks in group 1, with no significant changes in group 2. There was no significant rise in the intraocular pressure or clinical evidence of increased lens density during the study period. Triamcinolone Acetonide's Vehicle, benzyl alcohol, produced severe irreversible ERG and structural damage to rabbit neurosensory retinal following intravitreal injection