Biomedical Engineering Reference
In-Depth Information
Fig. 2 Routes of drug administration to the eye
retrobulbar, and posterior juxtascleral) and intravitreal route
(Fig.
2
). The most commonly employed and recommended routes
for treating ocular diseases include topical drops for anterior cham-
ber and intraocular injections/devices (implants) for posterior cham-
ber. These routes of drug administration are discussed in the
following sections. Readers are directed to Chapter
7
for intravitreal
implants/devices.
Topical eye drops may be solution, emulsion, or suspension con-
sisting of water, active pharmaceutical ingredient, excipients, and
preservatives. Advantages of topical drop administration to eye
include patient convenience, self-administrable, efficacious, and
cost-effective treatment strategy. It is noninvasive, avoids first-pass
metabolism, and allows selective delivery of drugs to anterior ocular
tissues. Therefore, topical eye drops remain the mainstay for the
treatment of anterior ocular pathologies. Ophthalmic solutions are
prepared in glass/LDP plastic container for single- or multi-dose
administrations (Fig.
3
). These devices are specially designed and
fitted with different types of dropper tips such that a defined
volume of drug solution is dispensed with each application. Com-
mercially available topical medications dispense a range from 25.1
to 70
2.1
Topical Route
L with an average drop size of 39
L[
3
,
4
]. In a healthy
μ
μ
human, the tear volume is 7-9
L with a turnover rate of
μ
0.5-2.2
L/min. Topical formulations are intended for instillation
as a drop into the lower conjunctival sac (cul-de-sac) [
5
]. Topical
drops may be administered by lowering the eyelid or by pinching
μ
