The effect of phenylephrine on pain and flare intensity in eyes with uveitis

To investigate the influence of protein concentration in the anterior chamber, measured by laser flare meter, on pain sensation after phenylephrine instillation in patients with iridocyclitis.

Twenty-five consecutive patients with iridocyclitis were included. Patients with cataract, exfoliation syndrome, diabetes mellitus, glaucoma or any other previous ocular diseases or ocular surgery were excluded. Patients were divided into two groups: Group 1--without fibrinoid reaction (FR) in the anterior chamber (18 patients), and Group 2--with FR (7 patients). Protein concentration in the anterior chamber was measured with laser flare meter (FC 500, Kowa Co., Japan). Pupil size was measured by Alcon Tilo Scale, and pain sensation was estimated by Visual Analogue Scale (VAS, Kabi Pharmacia). All measurements were done before and 1 hour after topical instillation of 10% phenylephrine hydrochloride into the subconjunctival sac of the inflamed eyes.

Eyes with iridocyclitis and fibrinoid reaction (FR) have a higher flare intensity compared to those without FR (p<0.05). Pupil size was significantly increased after phenylephrine instillation in both study groups (Wilcoxon test, p<0.05). The VAS pain and flare intensity were significantly decreased in group without FR after phenylephrine instillation (Group 1) compared to values before treatment (Wilcoxon test, p<0.05). In eyes with FR (Group 2), no significant influence of phenylephrine instillation was found on VAS pain and flare intensity.

After phenylephrine instillation, flare intensity and pain were significantly decreased only in eyes with iridocyclitis and without FR. The decreasing level of flare intensity, and paralysis of the pupil after phenylephrine instillation seem to alleviate pain in those eyes.