Biomedical Engineering Reference
In-Depth Information
Fig. 5 Autodrop
®
device delivering topical drops into cul-de-sac of the eye
(Owen Mumford Ltd, Woodstock, Oxfordshire, UK) (modified and reproduced
from [
71
]
Example of such holder includes “Autodrop
®
” (Owen Mumford
Ltd, Woodstock, Oxfordshire, UK) (Fig.
5
). These holders help in
directing gaze away from descending drops, hold lower eyelid,
prevent eye blinking, and efficiently deliver topical drop into the
cul-de-sac. Such devices may improve patient compliance and min-
imize drug loss due to blinking while drop application.
During past two decades considerable momentum has been gained
by intravitreal injection. This technique is an invasive method of
drug delivery involving direct administration of drug solutions into
the vitreous humor via pars plana using a 30 gauge needle. High
drug concentrations are achieved in vitreous/retina following
intravitreal injection relative to periocular injections. The proce-
dure for intravitreal injection involves several steps. Initially the
pupil is dilated and the individual is reclined. Topical anesthetics
such as proparacaine 0.5 % and an antibiotic (Zymar
2.2
Intravitreal Route
) (Allergan,
Inc., Irvine, CA) are applied to the eye. The outer ocular skin, eye
lashes, caruncle, and upper and lower eyelids are swabbed with 10 %
povidone-iodine followed by insertion of a lid speculum. A
preservative-free 4 % lidocaine is applied for 30 s with a cotton tip
applicator, followed by two drops of artificial tears (Systane
®
)
(Alcon Laboratories Inc., Fort Worth, TX) to cornea. A drop of
5 % betadine solution is applied in conjunctival cul-de-sac. The
injection site is located at 6-7 o'clock of the right eye or at
5-6 o'clock of the left eye. The injection site is selected at
3.0-3.5 mm posterior to the limbus, inferotemporally, and the
needle is directed towards the center of the vitreous humor to a
depth of 4-6 mm. A volume of ~200
™
L may be administered with a
30 or a 32 gauge needle, over a period of 0.5-2.0 s. Post injection
the needle is slowly retracted and removed. Patients are subjected
to retinal perfusion by indirect ophthalmoscopy followed by
μ
