Should antibiotics be started pre-operatively?

Unfortunately there is no clear answer to this question.  Topical antibiotics prior to cataract surgery is a popular method of prophylaxis in the United States.  The rationale behind this is that antibiotic levels exceeding the minimal inhibitory concentration (MIC) of bacteria in the aqueous humour would prevent infection.

Data from the European Society of Cataract and Refractive Surgeons (ESCRS) group illustrated that the placebo group demonstrated an increased in risk of laboratory confirmed endophthalmitis compared to the group receiving two drops 0.5% levofloxacin 1 hour prior to cataract surgery.  However, this finding was not statistically significant (1,2).

In 2008, Vasavada et al. compared 2 moxifloxacin regimens for pre-operative cataract prophylaxis.  This was a prospective, randomised triple-masked trial evaluating the aqueous concentration of moxifloxacin following 2 dosing regimens pre cataract surgery.  Group A had moxifloxacin instilled 4 times a day 1 day before surgery plus 1 drop 2 hours before surgery and Group B had moxifloxacin instilled 2 hours before surgery and then every 15 minutes for 1 hour.  They concluded that both dosing regimens produced substantially higher aqueous concentrations than the known minimum inhibitory concentration for Staphylococcus epidermidis.  Group B achieved significantly higher aqueous concentrations than Group A (3).   In addition, both regimens were also found to reduce the amount of conjunctival bacterial flora (4).  Unfortunately, this was not correlated to endophthalmitis rates but one can hypothesise that the above regimens would confer a lower endophthalmitis complication rate post-operatively.

Ta et al.  compared the use of Ofloxacin antibiotic treatment 1 hour prior to surgery compared to 3 days of pre-treatment and concluded that the 3 day pre-treatment reduced bacterial conjunctival flora (5).  Chang et al. carried out a survey of American Society of Cataract and Refractive Surgery members. 52% surveyed utilised the latter 3-day pre-treatment method described by Ta, whilst 26% employed a 1-day prior and 22% used a same-day topical antibiotic prophylaxis regimen (6).

In conclusion, it appears that antibiotic pre-treatment probably does confer an advantage at reducing endophthalmitis rates.  It is unclear, however, whether this advantage is negated with the use of other intra-operative prophylaxis treatments including the use of povidone-iodine, subconjunctival and intracameral antibiotics.

 

Mr Adam H. Ross MbChB, MRCOphth.

References.

1.  Barry P,Seal DV,Gettinby G, et al.  ESCRS study of prophylaxis of postoperative endophthalmitis after cataract surgery: preliminary report of principal results from a European multicenter study. J Cataract Refract Surg 2006; 32:407–410.

2.  Seal DV, Barry P, Gettinby G, et al. ESCRS study of prophylaxis of postoperative endophthalmitis after cataract surgery: case for a European multicenter study. J Cataract Refract Surg 2006; 32:396–406.

3.  Vasavada AR, Gajjar D, Raj SM, Vasavada V, Vasavada V.  Comparison of 2 moxifloxacin regimens for preoperative prophylaxis: prospective randomized triple-masked trial. Part 1: aqueous concentration of moxifloxacin. J Cataract Refract Surg. 2008 Aug;34(8):1379-82.

4.  Vasavada AR, Gajjar D, Raj SM, Vasavada V, Vasavada V. Comparison of 2 moxifloxacin regimens for preoperative prophylaxis: prospective randomized triple-masked trial. Part 2: residual conjunctival flora.  J Cataract Refract Surg. 2008 Aug;34(8):1383-8.