The answer is: yes, it can, though thankfully not too often. An open cold sore, however, can lead to an infection of the eyes by way of a smear infection for instance through a hand being wiped across the face. Infection of the retina (the back of the eye) is of a particularly dangerous kind. If the virus invades the eye and infects the retina it could end up destroying it. This, of course can lead to blindness1). Fortunately this is a rare event.
In other infrequent cases it has been observed that the herpes virus can cause paralysis of the facial nerve (Bell’s palsy)2). This means that patients can no longer move the muscles in part of their face, which is a serious condition.
A herpes genitalis infection (HSV2 –different from the facial virus) can be transmitted to a child during the process of birth. The consequences for the newborn child can be severe, as the virus can spread throughout the child's body through its bloodstream. In this situation a newborn child can display widespread symptoms on its skin, in the cavity of the mouth or throat, in other major organs and in particularly severe cases even paralysis may occur3).
These severe diseases are luckily very rare. Even though 85% of the population are infected by one form of this virus (HSV1), aren't aware of it, as they don't suffer from visible symptoms. They don’t suffer from cold sores or other symptoms and live normally without any afflictions. However 33% of the population regularly suffer from cold sores. This can be painful and, is often very unsightly for those affected.
In order to successfully target the infection it is important to take measures to prevent cold sores at an early stage.
1) M. Cordero-Coma et al.: Herpetic retinitis. (Review) In: Herpes Band 14, Nr. 1, 2007, S. 4–10.
2) S. Murakami et al.: Bell’s palsy and herpes simplex virus: Identification of viral DNA in endoneurial fluid and muscle. In:Ann Intern Med Band 124, Nr. 1, 1996, S. 27–30.
3) R. Marre, T. Mertens, M. Trautmann, E. Vanek: Klinische Infektiologie. München Jena 2000 ISBN 3-437-21740-2 S. 802f
E. Anzivino et al.:Herpes simplex virus infection in pregnancy and in neonate: status of art of epidemiology, diagnosis, therapy and prevention. Virol J. (2009) 6:40 (Review)