Dear Sir,
We read with interest your recent article entitled “The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic and Transfusion Medicine: reflections from Italy”1. We would like to discuss another blood-derived source at potential risk for SARS-CoV-2 transmission that is represented by homologous products applied as eye drops for the treatment of severe corneal diseases. Since the use of these products in ophthalmic practice is increasing, and the duration of the pandemic is currently unpredictable, we believe this issue is worthy of consideration.
The idea of using blood-derived products to treat ocular diseases was first described over 40 years ago by Ralph et al.2 who developed a mobile perfusion pump to deliver autologous serum (AS) to the ocular surfaces of patients with chemical burns. Since then, AS has been used for decades showing good profiles of both safety and efficacy. Recently, the use of products obtained from donors (allogeneic peripheral blood serum and umbilical cord blood serum, among others) has been proposed as a viable alternative to AS in order to overcome its main drawbacks. These are, firstly, AS may be unavailable in patients with poor venous access or co-existing systemic diseases. Secondly, AS collected from patients with Sjögren’s syndrome and graft-versus-host disease (two underlying diseases frequently complicated by corneal ulcers) contains high levels of pro-inflammatory mediators that would damage the cornea if supplied as eyedrops3.
Further advantages of homologous products include the availability of large quantities of “off-the- shelf” eye drops produced under quality/microbiological control from blood banks, where a supply may be kept and stored in advance to be readily dispensed, thus improving the logistics of the treatment. In addition, the composition of growth factors and cytokines contained in the eye drops can be screened in order to improve the efficacy of the final product4.
Evidence on SARS-CoV-2 transmission through conjunctiva, as well as potential risks of donor-to-host viral transmission through blood-derived products, are a subject of ongoing debate5,6. Many patients attending ophthalmology clinics for various corneal diseases are currently being treated with homologous sera. They will come back for their monthly check-up and ask for a new prescription. In the current situation, ophthalmologists are facing too many unknowns, and new information is needed in the coming months to reach evidence-based decisions. In the meantime, we believe that the use of autologous eye drops should be encouraged, when possible.
Footnotes
The Authors declare no conflicts of interest.
REFERENCES
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