Fundoscopy: to dilate or not to dilate?

Liew et al. highlight the very small risks associated with
precipitating an attack of angle closure glaucoma when dilating a pupil
for the purposes of fundoscopy. We would agree with the authors that this
is indeed because the use of mydriatic drops result in a pupil that is
fully dilated rather than partially dilated and therefore less likely to
cause pupil block. This can be illustrated further by the problems created
by other pharmacological agents and their effects on the eye.

The initiating event in acute angle closure glaucoma is incomplete
mydriasis (pupil dilation) resulting in pupil block and the prevention of
aqueous drainage through the trabecular meshwork. This partial mydriasis
is normally caused by poor ambient lighting conditions but drugs with
adrenergic and anticholinergic properties have also been identified as
causative agents. These drugs include ipratropium1 and the tricyclic
antidepressants2 and more recently the serotonin selective reuptake
inhibitors (SSRIs) such as paroxetine (seroxat)3 and fluoxetine (prozac)4
have been implicated via their anticholinergic properties. The SSRIs have
a lower incidence of anticholinergic effects than tricyclic
antidepressants but some still remain.5

The British National Formulary advises caution with the use of these
drugs in patients with a history of angle closure glaucoma. This is
however misleading, as patients who have had an attack of angle closure
glaucoma will hopefully have been treated with either iridotomies or
trabeculectomies and therefore no longer be at risk. We would therefore
recommend that all patients who are commenced on these drugs (ipratropium,
tricyclics and SSRIs) be warned of the risk of ophthalmic symptoms
(painful red eye, blurring of vision, headache, nausea and vomiting)
especially those that are especially at risk (i.e. elderly, female,
hypermetropic refractive error). This will hopefully result in reduced
ocular morbidity in those patients that are unfortunate enough to develop
this complication.

1 Singh J, O'Brien C, Wright M. Nebulized bronchodilator therapy
causes acute angle closure glaucoma in predisposed individuals. Respir
Med. 1993 Oct;87(7):559-61.

2 Ritch R, Krupin T, Henry C, Kurata F. Oral imipramine and acute
angle closure glaucoma. Arch Ophthalmol. 1994 Jan;112(1):67-8.

3 Browning AC, Reck AC, Chisholm IH, Nischal KK. Acute angle closure
glaucoma presenting in a young patient after administration of paroxetine.
Eye. 2000 Jun;14 ( Pt 3A):406-8.

4 Ahmad S. Fluoxetine and glaucoma. DICP. 1991 Apr;25(4):436

5 Briley M, Moret C. Neurobiological mechanisms involved in
antidepressant therapies. Clin Neuropharmacol. 1993 Oct;16(5):387-400

Competing interests:
None declared