Exploring the use of millipore filters to prevent post-injection endophthalmitis: A proof-of-concept in-vitro study

Millipore filters are routinely used in vitreous surgeries for loading intraocular gas. This study purports to establish feasibility of in-line Millipore filter as a filtration barrier and rationalize their use during intravitreal antivascular endothelial growth factor (antiVEGF) injection to reduce the risk of endophthalmitis.

Proof-of-concept in-vitro study.

At the Ocular Microbiology section of a tertiary care eye center in North India, bacterial broths of various microorganisms (Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Escherichia coli, Corynebacterium species, Streptococcus species, and a mixture of Staphylococcus aureus and Pseudomonas aeruginosa) of different concentrations (McFarland 0.5 and McFarland 1) were inoculated onto blood, chocolate, and/or MacConkey agar with (Group 1) or without (Group 2) in-line sterile Millipore filter of 0.22-micron pore size (Set GS Mini filter, ARCEOLE, France). The filter was attached to a one-ml syringe with bacterial broth solution at one end and a 30-gauge needle at the other. Culture plates were incubated and observed daily for colony formation with photographic documentation for up to 5 days.

Bacterial broths could be injected across the filter with little resistance. None of the culture media showed growth when filters were used, compared with growth in all culture plates when inoculation of broth was done without the filter. The fluid loss in the filter (dead space volume) ranged from 0.12 to 0.17 ml.

Millipore filter act as an effective filtration barrier and could enhance the safety of intravitreal antiVEGF injection by reducing the risk of endophthalmitis. Further microbiological and toxicology studies are essential before their integration into clinical practice.