Microdialysis Measurement of Ascorbic Acid in Rabbit Vitreous After Vitreous Surgery

Abstract

Abstract: : Purpose: A method for long–term intravitreous microdialysis was used to measure endogenous reduced ascorbic acid (AA) in the vitreous of rabbits by HPLC–ECD before and after the vitreous surgery. Methods: Cellulose microdialysis probes were implanted into the vitreous humor of each eye and after stabilization AA measurements were recorded over a 10 day period. Two–third of the vitreous was removed through sclerotomies in the pars plana. The effect of the triamcinolone acetonide (TA) injection was also evaluated dividing into four groups; group 1, sub–tenon TA (20mg) injection alone, group2, intravitreous TA (4mg) injection alone, group 3, both sub–tenon TA (20mg) injection and vitrectomy, group 4, intravitreous TA (4mg) injection just after the virectomy. Results: The AA concentration after the vitrectomy significantly decreased from day 2 and continued over a period of 7 days and the maximal reduction was 53%(P<0.01). Although the AA concentration increased by day 10, it did not return to control levels. Although no remarkable change of AA level was observed in group 1 and 2, a mild rescue of AA concentration reduction and recovery of AA concentration after vitrectomy was recognized in group 3. Conclusions: A high rescue of AA concentration reduction was observed in group 4. The protective role of ascorbic acid in the vitreous humor against vitreous surgery is suggested and that is markedly improved by the intravitreous TA injection.

Keywords: vitreoretinal surgery