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R. Dale, D. Choi, D. Gattey; Colvard Pupillometer Measurement of Routine Dilation in Adult Eyes: Tropicamide and Phenylephrine versus Tropicamide Alone . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5636.
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The purpose of this study is to use the Colvard infrared pupillometer to accurately compare the dilation effect of two different eye drop regimens: tropicamide 1% plus phenylephrine 2.5% versus tropicamide 1% alone. We hypothesize that when used for routine clinical exams tropicamide alone is clinically equivalent to tropicamide and phenylephrine together.
To test this hypothesis, we recruited study subjects aged 19 to 65 years who were scheduled for a routine examination in a general ophthalmology clinic. Patients were interviewed to obtain informed consent and to collect data about possible confounding factors such as age, gender, ethnic background, current eye medications and medical history. Each patient's eye color was graded against a photographic standard. A baseline scotopic pupil measurement was obtained using the Colvard pupillometer. Following this, every patient received a drop of benoxinate and fluorescein and had applanation tonometry performed. In all patients, one eye was randomized to serve as the control eye and received both phenylephrine and tropicamide. The fellow eye served as the experimental eye and received tropicamide alone. A blinded examiner repeated Colvard pupillometer scotopic pupil measurements at 15 and 30 minutes following drop instillation. Clinical equivalence for a routine exam was defined as a dilation difference no greater than one millimeter between the control and study eyes.
Fifty–seven patients participated in the study. At thirty minutes, the control eyes measured an average pupil diameter of 7.51 mm with a 95% confidence interval (CI) of 7.27 to 7.74 mm. The experimental eyes measured 6.96 mm (95% CI 6.72 to 7.20 mm). The difference of the average change from time zero to time 30 minutes comparing the control and study groups was 0.62 mm (95% CI 0.45 to 0.80 mm). This difference did not meet our previously determined definition of a clinically significant difference.
In routine examinations of adults similar to this study population, use of phenylephrine in addition to tropicamide does not provide a clinically significant increase in the magnitude of pupil dilation. Phenylephrine may lessen clinical signs of conjunctival injection and ptosis, and may pose a small increased risk of harm in patients who cannot withstand mild increases in heart rate and blood pressure. The findings of this study suggest that use of phenylephrine for routine dilated eye examination of adults is unnecessary.
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