Biomedical Engineering Reference
In-Depth Information
enucleation, at the time of trimming the globe and ocular tissue,
and at the time of microscopic section evaluation. To discover
microscopic findings, one must choose methods, which will prepare
the ocular tissue for the various types of microscopic examinations.
There are various ways of obtaining pristine ocular sections for
evaluation. What works for one laboratory may not work for
another laboratory. Therefore, if a histotechnology laboratory is
performing a technique for the first time, it is best if a method
development study is performed first. This study will help to deter-
mine if the laboratory personnel will have some difficulties with
obtaining acceptable ocular sections. Results often are better when
there are fewer technical staff handling the ocular tissue, but
regardless, good results depend on good communication among
the study director, study pathologist, study ophthalmologist, and
pathology laboratory personnel.
Ocular studies may involve ocular medical devices, including
those that are used for drug delivery [
1
-
4
]. An ocular medical
device is a device that comes in contact with the exterior of the
eye (e.g., contact lens and nasal canalicular plug) and those devices
that are implanted within the structures of the globe (e.g., sub-
conjunctiva, sclera, suprachoroid, vitreous, and lens). These devices
are tested for evidence of biocompatibility (i.e., an absence of
localized tissue irritation or toxicity) by following established inter-
national standards [
5
-
8
]. The in-life phase of these studies involves
the use of standard methods such as the Draize scale for scoring
ocular findings. This includes biomicroscope slit-lamp examination
in accordance with criteria established by McDonald et al. [
9
].
These findings are used in an attempt to determine microscopic
correlates.
For standard systemic toxicity studies, there is generally a
fairly standard approach used to examine the globe, which is
designed to detect ocular findings associated with systemic toxic-
ity [
10
]. This approach is generally used for studies which involve
ophthalmic examinations consisting of direct ophthalmoscopy,
slit-lamp biomicroscopy, and fundoscopy, and studies which
have no clinical ophthalmic findings. The test article would be a
systemically administered small molecule or biologic entity and
the approach involves examination of paraffin-embedded, midsag-
ittal sections of globes that are a few microns in thickness and
stained with hematoxylin and eosin (H&E) [
10
-
14
]. If the test
article is applied topically, injected or implanted, then the standard
approach needs to be modified to look for localized effects, as well
as, systemic effects.
