Biomedical Engineering Reference
In-Depth Information
Fig. 45 Slit lamp examination of a rat with buphthalmos noted in pretest
examination
induced in the rat by temperature (cold), dehydration, anoxia, and
specific drugs (opiates, opioids, phenothiazine) [
53
,
57
,
58
].
Buphthalmos and glaucoma have been observed and are typi-
cally congenital (Fig.
45
)[
49
]. Unfortunately, the intraocular pres-
sure is generally not determined in affected animals as this is most
often noted in young rats in a pretest examination and they are
usually eliminated from study without further diagnostics or fol-
low-up.
Retinal dysplasia may be noted in rats and can be unilateral or
bilateral [
27
]. Retinal degeneration may occur spontaneously, be
associated with aging, occur as a result of orbital bleeding techni-
ques, occur secondary to phototoxicity, or be inherited [
27
,
47
,
59
-
66
]. It is reported that the prevalence of senile retinal degener-
ation in the 2-year-old Wistar rat may be as high as 10 % [
60
]. In
addition, retinal degeneration can be a toxicologic effect [
53
]. Care
should be taken to evaluate retinal “blanching” in combination
with the temperament and restraint required to examine a particu-
lar animal. Excessive restraint will result
in apparent
retinal
degeneration.
As rats age, the prevalence of corneal, lenticular, and retinal
abnormalities will increase and in a 2-year chronic study abnorm-
alities may be found in
50 % of the animals examined [
29
,
38
].
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