Purpose: To investigate the sterility of non-preserved autologous serum drops in hospitalized patients with persistent corneal epithelial defects.
Methods: Thirty patients with persistent corneal epithelial defects (aged between 28 and 85, mean 67+/-14 years) were treated with autologous serum drops in five different wards of a university eye hospital between October 2001 and March 2002. After centrifugation of freshly collected autologous blood, the serum was stored in sterile drop bottles at refrigerator temperature (7 degrees C) and applied undiluted every 1 or 2 h up to 7 days. Using blood, chocolate, endo, and Sabouraud agar media, we assessed the sterility of autologous serum drops on the day before application and on the 4th and 7th days. Examinations performed on the 1st and 4th days included 40 autologous serum drops each and on the 7th day 120 samples (40 serum drops, 40 bottle tops, and 40 bottle bottoms). The agar media for bacterial examination were read after 48 h of incubation time, and those for fungal examination were read after 21 days. All patients had received topical autologous serum therapy and prophylactic antibiotic drops for at least 7 days.
Results: The time period of autologous serum treatment ranged from 7 to 28 (10+/-5) days. On the 1st and 4th days autologous serum drops were sterile. On the 7th day, 3 of 40 (7.5%) samples were contaminated with Staphylococcus epidermidis. Two of these contaminations were due to a combined serum drop and bottle top contamination (5%). A third case resulted from additional bottle bottom contamination (2.5%). None of the samples examined showed signs of fungal infection. During application of autologous serum as well as during the follow-up period no patient showed any symptoms of ocular infection.
Conclusions: The application of autologous serum has proven to be a practicable therapy in patients with persistent corneal epithelial defects. When the drops are applied by trained personnel, the absence of contamination can be ensured up to the 4th day. By additional application of prophylactic antibiotic drops, infections may be avoided even if refrigerated non-preserved autologous serum is used up to 7 days.