IOLs as drug delivery devices?

It has been speculated that the unacceptable rate of endophthalmitis is a result of the introduction of sutureless clear cornea incision but it also may be a consequence of bacterial resistance to ciprofloxacin that has developed over time. Indeed, a recent study found that 37% of bacteria isolated from clinical cases of endophthalmitis showed resistance to the antibiotic.² The new fourth- generation fluoroquinolones have been suggested as a substitute and a solution to this issue of bacterial resistance, however, most topical administration protocols do not achieve the MIC90 value (minimum inhibitory concentration of drug) required for Staphylococcus epidermidis inhibition.^3,4 We are thus presented with another problem - we have the drugs but we need to find the most effective way of delivering them.

IOLs were presoaked for 24 hours in either gatifloxacin 3 mg/ml (Zymar, Allergan) or moxifloxacin 5 mg/ml (Vigamox, Alcon Laboratories) before being implanted into the evacuated capsular bags of 15 rabbits' eyes. The right eye was randomly assigned to one presoaked IOL; gatifloxacin or moxifloxacin, whilst the left eye received an IOL presoaked with the other antibiotic. The rabbits did not receive any other antibiotic before, during or after the operations, making the IOL the sole source of antibiotic.

Aqueous humour was sampled four, eight or 12 hours after the implantation of the IOL. Each eye was only sampled once for a total of five eyes in each subgroup. The aqueous samples were immediately frozen and sent on dry ice to David Nix, PharmD at the University of Arizona, USA where high-performance liquid chromatography testing was used to determine the concentration of gatifloxacin and moxifloxacin in each sample.