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Research Optimising the delivery of topical ophthalmic medication in dogs ranges up to 56.4μl. The amount of
Methodology
remaining eye drop after instillation
Two drop methods were compared.
is as high as 30.3μl. This could
The standard Minim (standard
lead to systemic side effects,
tip) was modified by attaching a
such as hypotension, bradycardia,
Gilson tip to the Minim (modified
and tremors after using a local
tip). Both studies were conducted
anaesthetic. A commonly used
in a laboratory at the University
drug, Tropicamide, causes pupil
of Cambridge Veterinary School. Stage 1: Tropicamide 1.0% in a
dilation as its main effect in order to Florence Clark (UPPER Sixth)
E
allow examination of the retina, but
standard and a modified Minim
this can last for many hours, giving
dispenser was dispensed one drop
side effects such as blurred vision,
at a time onto a weighing scales,
ye drops are commonly
meaning for example that patients
recording the weight in milligrams).
used worldwide in both
can’t drive for hours after its use.
Mean and standard deviations were
humans and animals in
Smaller drops may mean a faster
calculated for both sets of data,
healthy and diseased states.
recovery. Therefore, there is a need
and a 2-tailed Student’s t-test was
They are usually administered
to develop a suitable method of
applied to test for the significance
by the patient themselves or
delivering ophthalmic medication at
between the two means.
a carer and are a commonly
an appropriate volume.
used medication.
Stage 2: two healthy adult dogs were studied using three different
Previous studies have tried methods to reduce drop volume,
conditions, sham treatment
but these results in impractical
(n=1), then Tropicamide 1.0% was
such as glaucoma, dry eye, ocular
methods, such as the addition of a
administered by standard (n=3)
inflammation, infection and allergies
steel needle or glass capillary tube
and modified (n=5) tips into one
to name a few. As with all drugs,
to the dropper bottle.
or another eye. Pupil diameter
They deliver ophthalmic drugs for the treatment of various diseases
the dose of the active ingredient is important both for effectiveness
was recorded over 330 minutes.
The aim of my research was to develop a safe and practical
and safety of the patient. The dose
method to administer drops with a
Results
is determined through the volume
small and consistent volume. The
As part of the first stage of
and concentration of the drop, and
hypothesis was that by attaching
the research, n=28 drops were
the number of drops. There is a
a Gilson pipette tip to a Minim
weighed from the standard tip
huge variety of devices used to
dropper (a single-dose eye drop
and n=27 from the modified tip.
administer these drops. Generally,
dispenser), the drop weight (or
The mean drop weight with the
they come in multi- or single-
volume) will be significantly and
standard tip was 31.4mg and for
dose dispensers, with a variety
consistently reduced and associated
the modified tip it was 10.0mg
of different dropper tips which
with an identical Tropicamide
(see Table 1). The t-test showed
can have a substantial effect on
induced maximal pupil dilation, and
that these results were statistically
the volume and hence the dose
earlier recovery compared to a
significantly different, with a
of medication administered. It is
standard Minim dropper.
p value of less than 0.0001.
important manufacturers consider the design of the tips so that doses are administered easily, effectively
Table 1: Comparison of mean and median weights, and standard deviations of drops dispensed from modified (n=27) and standard tips (n=28) (mg weight)
and safely. Mean (mg)
Currently the volume of eye drops dispensed is too large for the eye to hold. The average drop volume from different preparations
Standard deviation (mg)
Median (mg)
Standard tip
31.4
15.1
33.0
Modified tip
10.0
3.42
10.0
11
P value
<0.0001
