Bernard,
I don't think a person's seizure threshold would be "abnormally" low to have photosensitivity. What they have is sensitivity to light, or develop it from repeated exposure. that will trigger reflex seizures. Over time, thinking of the kindling model of epilepsy, this can become a chronic disorder to repeated exposure to the irritant, in this case lighting. The same might hold true for other sensitivies too. Also, keep in mind, that in the kindling model, the initial exposure to an irritant is not harmful and causes no reaction; it is the repetition, the frequency of the repetiion, that leads to the problem developing, the overload. It is possible that Puwono's son's seizures were triggered by photosensitivity. This abstract is from Pub Med:
1: Exp Neurol. 1986 Feb;91(2):343-54.
Lateral geniculate kindling and long-lasting photosensitivity in cats.
Wada Y, Minabe Y, Okuda H, Jibiki I, Yoshida K, Yamaguchi N.
The kindling response of the lateral geniculate body (GL) was compared with that
of the amygdala, using cats. Daily electrical stimulation in the GL group led to
the generalized tonic-clonic convulsion in most subjects and the resulting state
of seizure susceptibility was long-lasting, as in the amygdala group. The
kindling response of the GL differed from that of the amygdala in some respects,
i.e., rapid kindling, short latency for seizure generalization, a different
pattern of behavioral seizure development, and seizure regression during the
course of kindling. The effects of photic stimulation with pentylenetetrazol
administration were also examined before and after kindling in both groups. This
study revealed that the photically induced myoclonus, at times proceeding to the
generalized tonic-clonic convulsion, was provoked repeatedly as a result of GL
kindling, whereas none of the amygdala-kindled cats showed such marked
photosensitivity. These photically induced seizures were invariably observed for
at least 4 weeks after GL kindling. Our results suggest that a neural mechanism
participating in GL kindling is different from that in amygdala kindling, and
that there might be cross-sensitization between seizure susceptibility resulting
from GL kindling and photosensitivity.
PMID: 3943578 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov/sites/entrez