Subconjunctival Exposure to Carbopol Causes Chronic Histiocytic Inflammatory Response in Rabbits

We recently reported a clinical association between surgical exposure to the ophthalmic lubricant GenTeal gel and postoperative subconjunctival necrotizing granulomatous inflammation. We used a rabbit model to test our hypothesis that subconjunctival exposure to the carbopol 980 component is responsible for inciting chronic inflammation.

Of eight adult wild-type Dutch belted rabbits, 16 eyes received subconjunctival injections of the following: hydroxypropyl methylcellulose (HPMC) 0.3% with carbopol 980 (GenTeal gel, n = 4), HPMC 0.3% (GenTeal tears, n = 3), 0.1% carbopol 980 in sterile water (n = 3), HPMC 1.7% (ImproVue, n = 3), and balanced salt solution (BSS, negative control, n = 3). Rabbits were examined weekly for clinical evidence of inflammation, and biopsies were taken for final pathology 10 weeks postinjection.

All seven eyes exposed to subconjunctival carbopol 980 (HPMC 0.3% with carbopol 980 or 0.1% carbopol 980) demonstrated conjunctival injection and edema at 4 weeks followed by yellow subconjunctival lesions with scattered pigmentation at 10 weeks. Each of these eyes demonstrated chronic histiocytic inflammation on pathology. No eyes treated with HPMC 0.3%, HPMC 1.7%, or BSS (noncarbopol-containing agents) developed clinical abnormalities or histiocytic inflammation (Fisher's exact test P < 0.0001).

Subconjunctival exposure to ophthalmic lubricants containing carbopol 980 stimulates a chronic histiocytic inflammatory response. HPMC-based lubricants lacking carbopol 980 are well tolerated in the subconjunctival space.

Ophthalmic lubricants containing carbopol polymers should be avoided during surgical procedures that may result in subconjunctival exposure. Caution should be exercised when considering surgical use of biomedical products containing highly cross linked, high molecular weight acrylic acid polymers.