The Police Department of the Ministry of Internal Affairs and the
Ethical Review Committee of Helsinki University Eye Hospital approved
the research plan, which followed the tenets of the Declaration of
Helsinki. Each subject gave informed consent.
The study was performed in two stages. For the first, five police
officers were used (men, 27–34 years of age). All had been exposed
several times to OC or to diorthochlorobenzyldenemalononitrile (CS):
three officers 3 times, one 5 times, and one 15 times. For the test,
subjects were treated with the OC spray and after first aid, were
queried about symptoms and examined by slit lamp biomicroscopy, corneal
photography, corneal sensitivity testing with a Cochet–Bonnet
esthesiometer, determination of tear fluid NGF levels, and in vivo
confocal microscopy. The group was re-examined 1 day, 1 week, and 1
month after OC exposure. Visual acuity was also measured at these
times. In this group of subjects, prominent changes in corneal
sensitivity were noticed. Therefore, in a second group of five police
officers (four men and one woman, 24–50 years of age), the eyes were
evaluated before and after OC exposure by the same clinical
explorations made in the previous group. Corneal sensitivity was,
however, more extensively explored using a noncontact gas
esthesiometer. Subjects were examined within the first hour, 1 day, and
1 week after OC exposure. Three subjects of this group had never been
exposed before to OC or CS. One had undergone bilateral photorefractive
keratectomy 2 years earlier. The remaining two officers had experienced
two and three previous OC exposures, respectively.