Biomedical Engineering Reference
In-Depth Information
preloaded ophthalmic terms for organ location (cornea, lens, iris,
etc.), clinical signs/diagnosis (opacity, coloboma, degeneration,
hemorrhage, etc.), specific location (cortex, nucleus, tapetal, ante-
rior, posterior, etc.), and severity (slight, moderate, severe). Other
CROs may have their own in-house online or hand recording sys-
tem. The ophthalmologist should be familiar with each laboratory's
recording system and terminology to be consistent both within and
between studies. When an abnormality is observed, correlation
between dose groups is important when evaluating the incidence
and severity of lesions so that any association with the test article can
be assessed [
1
]. While it would be best if animals were examined out
of dosing order so as to mask the ophthalmologist with respect to
dose group being examined, this is often not possible given the way
animals are housed and entered into the data collection system.
The ophthalmologist should also have a standardized scoring
or grading scheme to assign a severity to any abnormalities seen. In
general, a grading scheme of slight, moderate, and severe/marked
is most common. When using this grading scheme for the transpar-
ent media (cornea, aqueous, lens, and vitreous) a grading of slight
would imply a lesion that does not obstruct visualization of the
deeper tissues past the lesion, a moderate grade implies a lesion that
interferes with but does not fully obstruct the view of the tissues
deep to the lesion, and a severe/marked lesion fully obstructs the
view of structures deep to the lesion (Table
1
). This is analogous to
the terms incipient, immature, and mature when applied to a
cataract. Lesions may also be characterized with respect to the
Table 1
Biomicroscopy grading criteria for cornea, aqueous, lens, and vitreous
opacities
Grade Definition
0
No observable lesion.
1+
Some loss of transparency. The underlying structures are clearly
visible with diffuse illumination.
2+
Moderate loss of transparency. With diffuse illumination the
underlying structures are barely visible, but can still be examined
and graded.
3+ Severe loss of transparency. With diffuse illumination the underlying
structures are not visible when viewed through the lesion and
evaluation of them is impaired.
This grading system is based on the modified Hackett-McDonald scoring system
Grade 1—Slight or mild
Grade 2—Moderate
Grade 3—Marked, excessive, or severe
