Biomedical Engineering Reference
In-Depth Information
ISO 10993-1 [
1
] defines three broad types of body contact: (1)
surface contacting, (2) externally communicating, or (3) implant.
Within each of these major categories there are subcategories.
Surface contacting includes the skin, mucous membranes, and
skin or mucous membranes where the surface is breached or dam-
aged. Contact lenses and lens solutions would be considered exam-
ples of devices in the surface contacting, mucous membranes
category. Externally communicating includes devices with indirect
blood path, tissue/bone/dentin, and circulating blood exposure.
Ocular devices in this category could include ophthalmic instru-
ments and fluid sets used during cataract surgery, i.e., an item with
contact inside the eye but a portion that remains outside the eye.
The final category is implant devices and this is subdivided into
those with tissue/bone contact and those with blood contact. An
IOL or aqueous shunt would fall into this category.
Devices are categorized based on their duration of tissue/body
contact. The three durations are (1) limited exposure (
1.2 General Testing
Requirements Based
on Contact and
Duration
24 h), (2)
prolonged exposure (
>
24 h to
30 days), and (3) permanent
contact (
30 days). These contact durations are based on single,
multiple, or repeated exposure. So for a device such as a contact
lens, it may be worn for 12-16 h a day (limited exposure), but
because of multiple exposures, it is considered to be in a prolonged
exposure category.
The combination of type of body contact and contact duration
determines the types of biological effects that must be considered
for a device. In general, surface contacting, limited exposure
devices require assessment of the fewest biological effects. As the
body contact becomes more invasive and/or the duration of con-
tact increases, the potential for adverse biological effects increases,
prompting the need to evaluate more biological effects.
>
ISO 10993-1 defines the biological effects that must be considered
for a device. These effects include cytotoxicity, irritation/intracuta-
neous reactivity, sensitization, acute systemic toxicity, subacute/
subchronic toxicity, genotoxicity, implantation, and hemocompat-
ibility. These biological effects for consideration are common to all
medical devices. Depending on the nature of the device, additional
biological effects may require evaluation such as chronic toxicity,
biodegradation, toxicokinetics, immunotoxicity, and organ-specific
toxicities. ISO 10993-1 requires that you consider what is known
about the biomaterials composing the device, the history of use of
the material, and the nature and quantity of leachable chemicals/
substances that could have biological exposure during use. Based
on the information, a determination is made as to whether
sufficient data are available to address the biological effects appro-
priate for the tissue contact and duration of exposure for the device.
If sufficient data are not available, testing must be conducted to
assure the material does not cause an adverse effect. The following
1.3 Biological Effects
to Consider
