Objective: To compare the pupillary response to a single drop and three drops of a combination of eye drops (0.2% cyclopentolate and 1.0% phenylephrine) in preterm infants.
Design: Prospective comparative study.
Material and method: Preterm infants scheduled to undergo their first retinopathy of prematurity (ROP) screening in the Neonatal Intensive Care Unit, Songklanagarind Hospital, between 1 August 2007 and 30 August 2008, were enrolled in the present study. An eyelid speculum was placed after the topical anesthetic, 0.5% tetracaine, application to measure the baseline horizontal pupil diameter with a Vernier caliper. Then each eye was randomized to either receive a drop of mixture of 0.2% cyclopentolate and 1.0% phenylephrine single dose for group A, or triple doses of 10-minute interval for group B. The pupil diameter was measured at 45 and 60 minutes after instillation and a fundus examination was performed afterward.
Results: Seventy preterm infants, 45 males and 25 females, were included in the present study. The mean gestational age was 30.49 +/- 2.34 weeks (range of 24-36 weeks) and the mean birth weight was 1,368.00 +/- 438.99 grams (range of 640-2,850 grams). At baseline, the mean pupil diameter was 2.18 +/- 0.44 mm in group A and 2.19 +/- 0.44 mm in group B (p = 0.90). The mean pupil diameter at 45 minutes after instillation was 5.50 +/- 0.80 mm in group A and 6.02 +/- 0.56 mm in group B (p < 0.01). At 60 minutes after instillation, the mean pupil diameter was 6.13 +/- 0.82 mm in group A and 6.77 +/- 0.41 mm in group B (p < 0.01).
Conclusion: The pupil size of preterm infants was significantly larger after three drops of the eye drop mixture (0.2% cyclopentolate and 1.0% phenylephrine) than after a single drop. However, a dilated pupil diameter > or = 6 mm was adequate for the peripheral retina examination.