Intracameral medication: is it worth the risk?

The familiar dictum ‘‘First, do no harm’’ is particularly applicable in the setting of intracameral medications in cataract and anterior segment surgery. Intracameral medication has multiple potential uses in these surgical procedures, including pupil dilation, anesthesia, and prevention of endophthalmitis/inflammation. Its advantages and disadvantages were highlighted in the ‘‘Spotlight on Cataract’’ session at the November 2007 American Academy of Ophthalmology meeting. One primary advantage is the ease of delivery. Multiple applications of topical drops are unnecessary when medication is delivered into the anterior chamber. This has the additional advantage of eliminating toxicity from topical medications, especially those with preservatives such as benzalkonium chloride (BAK), since intracameral medications are mostly preservative free. Another possible advantage is enhanced efficacy as the theoretically higher dose is at the site where the medication’s action will take place. Finally, intracameral medications eliminate issues of patient compliance, including difficulties in obtaining and using postoperative drops properly. Of the potential disadvantages or complications associated with the use of intracameral medications, one of themost worrisome is the potential for toxic anterior segment syndrome (TASS). This acute, sterile postoperative inflammation is often secondary to anterior segment toxicity from medications or solutions placed in the anterior chamber during or immediately following cataract surgery. Corneal endothelial cells are very sensitive to any form of toxic exposure, and one of the earliest outbreaks of a TASS-like entity was the toxic endothelial cell destruction syndrome (TECDS). An important issue with intracameral medications is the proper concentration or dose of the medication. If the concentration is too high, there is potential toxicity. Examples of this toxicity are a concentration of 2% or greater in the case of lidocaine or 0.5% or greater in the case of bupivacaine, both of which can cause endothelial damage. Dilution errors in mixing antibiotic agents can be important. Some agents such as gentamicin have a very small therapeutic range and a high concentration can cause toxicity. In addition to issues of concentration or dose, medications that are custom mixed must have the proper pH. Custom-mixed medications must often be buffered to obtain a physiologic pH. When used intracamerally, an antibiotic agent such as vancomycin can be acidic if it is notproperlybufferedandmixedwithabalanced saline solution. Osmolarity is also a potential