DISCUSSION
The results of experiment 1 confirmed the substantial mydriatic effect of the study drug. This
effect is actually very considerable, sets in early, lasts for approximately 2 hr and is not accompanied
by any refractive effect. Consequently, it does not lead to visual function abnormalities worthy of
note. However, though we did not specifically study this aspect, on the basis of the normal subjects’
and glaucoma patients’ comments, we can conclude that they found an increased sensitivity to light
during the ibopamine effect. This is due exclusively to dilation of the pupil, there being no accom-
modation effects. It should be noted, however, that the use of ibopamine is typically limited in the
course of time.
The ibopamine-induced mydriasis appears to be due exclusively to activation of alpha1-adrener-
gic receptors, as clearly demonstrated by the fact that it is completely inhibited by pretreatment with
dapiprazole, a drug known for its ability to block such receptors (16). This finding is in good agree-
ment with the data reported for the use of another alpha-blocker, thymoxamine (8). Of particular in-
terest is the fact that even stable mydriasis induced by ibopamine is rapidly and completely reversed
by subsequent dapiprazole treatment. This means that there is good reason to postulate the use of
ibopamine to obtain rapid, well tolerated, easily reversible, risk-free diagnostic mydriasis along the
lines of the proposals made by Mapstone in relation to the consecutive use of phenylephrine and thy-
moxamine (17).
Our results also confirm that the instillation of ibopamine does not induce any appreciable ef-
fects on IOP in normal eyes, whereas, in eyes affected by initial glaucoma, it causes a significant,
though not striking, increase in IOP.
In any event, the innocuous nature of the possible diagnostic use of ibopamine instillation is con-
firmed by the fact that it does not give rise to changes in any of the biometric variables regarded as
important indices in determining the risk of angle closure.
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