Tamer A Macky1, Dina Helmy, Nihal El Shazly. 1. Department of Ophthalmology, Kasr El Aini Hospital, Cairo University, El-Manial, Cairo, Egypt. macky@www.com
Abstract
PURPOSE: To assess retinal toxicity of the vehicle of triamcinolone, benzyl alcohol (BA), when injected into the vitreous cavity of rabbits. METHODS: This prospective comparative experimental study included 24 pigmented rabbits assigned into two groups: group 1 (experimental, n = 12) received intravitreal 0.1 ml of BA, and group 2 (control, n = 12) received intravitreal 0.1 ml of balanced salt solution (BSS); all injections were done in the right eyes. Clinical examinations [slit lamp biomicroscopy, indirect ophthalmoloscopy, and three intraocular pressure (IOP) measurements] were done on both eyes before injection, at 1 and 3 h post injection, together with electroretinograms (ERGs) at 3 days, 1, 2, 4, and 6 weeks following injections. Three rabbits from each group were euthanased at 1, 2, 4, or 6 weeks and eyes were sent for light and electron microscopic examination for quantitative morphometric measurements. RESULTS: The mean amplitudes of the a and b waves of the BA-injected eyes were 6.42 +/- 9.02 microv and 11.18 +/- 15.18 microv at 3 days, respectively, which were significantly reduced compared with the BSS-injected eyes (30.87 +/- 8.22 microv and 57.90 +/- 13.38 microv, respectively; P < 0.01 t-test) and the non-injected contralateral eyes (36.20 +/- 7.85 microv and 64.10 +/- 9.36 microv, respectively; P < 0.01 t-test). These ERG responses continued to be significantly reduced in the BA-injected eyes (P < 0.01 t-test) throughout the study period. The mean ganglion cell count was significantly reduced (P < 0.005 t-test) in the BA-injected eyes (8.42 +/- 2.4) compared with the BSS- and non-injected eyes (16.42 +/- 3.9 and 16.5 +/- 4.2, respectively). The mean thicknesses of the inner nuclear layer (INL) and outer nuclear layer (ONL) were significantly reduced (P < 0.005 t-test) in the BA-injected eyes (3.78 +/- 0.96 microm and 11.77 +/- 1.29 microm, respectively) compared with the BSS- (6.1 +/- 0.92 microm and 21.82 +/- 0.95 microm, respectively) and non-injected eyes (7.05 +/- 1.9 microm and 22.49 +/- 1.01 microm, respectively). Electron microscopy showed moderate to severe intracellular changes in the ganglion cell layer, INL, ONL, and photoreceptor layer at 6 weeks in BA-injected eyes, with no significant changes in BSS-injected eye. There was no significant rise in the IOP or clinical evidence of increased lens density during the study period in any of the eyes. CONCLUSIONS: Triamcinolone acetonide's vehicle, BA, produced severe ERG and structural damage to the retina when injected intravitreally.
PURPOSE: To assess retinal toxicity of the vehicle of triamcinolone, benzyl alcohol (BA), when injected into the vitreous cavity of rabbits. METHODS: This prospective comparative experimental study included 24 pigmented rabbits assigned into two groups: group 1 (experimental, n = 12) received intravitreal 0.1 ml of BA, and group 2 (control, n = 12) received intravitreal 0.1 ml of balanced salt solution (BSS); all injections were done in the right eyes. Clinical examinations [slit lamp biomicroscopy, indirect ophthalmoloscopy, and three intraocular pressure (IOP) measurements] were done on both eyes before injection, at 1 and 3 h post injection, together with electroretinograms (ERGs) at 3 days, 1, 2, 4, and 6 weeks following injections. Three rabbits from each group were euthanased at 1, 2, 4, or 6 weeks and eyes were sent for light and electron microscopic examination for quantitative morphometric measurements. RESULTS: The mean amplitudes of the a and b waves of the BA-injected eyes were 6.42 +/- 9.02 microv and 11.18 +/- 15.18 microv at 3 days, respectively, which were significantly reduced compared with the BSS-injected eyes (30.87 +/- 8.22 microv and 57.90 +/- 13.38 microv, respectively; P < 0.01 t-test) and the non-injected contralateral eyes (36.20 +/- 7.85 microv and 64.10 +/- 9.36 microv, respectively; P < 0.01 t-test). These ERG responses continued to be significantly reduced in the BA-injected eyes (P < 0.01 t-test) throughout the study period. The mean ganglion cell count was significantly reduced (P < 0.005 t-test) in the BA-injected eyes (8.42 +/- 2.4) compared with the BSS- and non-injected eyes (16.42 +/- 3.9 and 16.5 +/- 4.2, respectively). The mean thicknesses of the inner nuclear layer (INL) and outer nuclear layer (ONL) were significantly reduced (P < 0.005 t-test) in the BA-injected eyes (3.78 +/- 0.96 microm and 11.77 +/- 1.29 microm, respectively) compared with the BSS- (6.1 +/- 0.92 microm and 21.82 +/- 0.95 microm, respectively) and non-injected eyes (7.05 +/- 1.9 microm and 22.49 +/- 1.01 microm, respectively). Electron microscopy showed moderate to severe intracellular changes in the ganglion cell layer, INL, ONL, and photoreceptor layer at 6 weeks in BA-injected eyes, with no significant changes in BSS-injected eye. There was no significant rise in the IOP or clinical evidence of increased lens density during the study period in any of the eyes. CONCLUSIONS: Triamcinolone acetonide's vehicle, BA, produced severe ERG and structural damage to the retina when injected intravitreally.