Nubile and associates recently published an interesting study evaluating the integration of amniotic membrane into the corneal stroma after amniotic membrane transplantation for persistent noninfectious corneal ulcers. The authors investigated the integration patterns of amniotic membrane using laser scanning in vivo confocal microscopy and anterior segment optical coherence tomography. They documented that integration of amniotic membrane into the corneal stroma is preceded by epithelialization over the amniotic membrane covering the ulcer and that the integrated amniotic membrane undergoes progressive modifications characterized by early loss of amniotic epithelial cells, changes in fibrillar structure, and repopulation by corneal stroma-derived cells. Moreover, a stable increase in corneal thickness was achieved in all patients. These findings confirm that stromal integration of amniotic membrane provides corneal biomechanical stability, which is extremely important especially in cases of marked stromal thinning.
However, there is another aspect of stromal integration of amniotic membrane that we would like to highlight. Seitz and associates first showed that amniotic membrane may be integrated in toto into the corneal surface and may be preserved there for months, whereas the same research group investigated the integration patterns of amniotic membrane into the human cornea after amniotic membrane transplantation and documented the intrastromal integration of amniotic membrane. It is well known that persistent corneal epithelial defects often are the clinical expression of herpetic eye disease, which is characterized by a variety of clinical manifestations. The preliminary data of our ongoing study indicate that cryopreserved amniotic membrane can be infected with herpes simplex virus 1 (data under submission). This finding suggests that amniotic membrane transplantation in case of undiagnosed epithelial herpetic keratitis may result in spread of the herpetic infection from the corneal surface into the stroma, thereby potentially deteriorating the clinical outcome.
Nubile and associates included in their study patients with noninfectious corneal ulcers, which is a very reasonable selection of patients. With regard to our findings, we support that in cases of herpetic ulceration or even on suspicion of epithelial herpetic eye disease, amniotic membrane transplantation should be performed with special precaution. In our opinion, an adequate topical and systemic antiherpetic treatment is of paramount importance for preventing the potential spread of the viral infection into the corneal stroma, which may have unfavorable consequences for the clinical outcome.