Pupillary dilation and its effects on automated perimetry results

The effects of miotic drugs on visual field sensitivity have been well documented, but few studies have reported the effects of active pupillary dilation on visual field sensitivity. Since visual field testing is sometimes performed when a patient is undergoing pupillary dilation for fundus examination, the effects of active pupillary dilation is of concern to today's optometrist.

The effects of active pupillary dilation on automated static threshold perimetry were studied in 23 normal subjects using the Humphrey Field Analyzer and the 30-2, StatPac, and FastPac programs. Baseline automated perimetry was performed on both eyes of each subject with the Humphrey Field Analyzer. On a separate visit, automated perimetry was performed on both eyes of all subjects while each eye was undergoing active pupillary dilation. Baseline and dilated visual field parameters were compared.

A decrease in foveal threshold of 1.95 decibels (p = 0.0081), a mean deviation loss of 1.15 decibels (p = 0.0001), a decrease in short-term fluctuation (SF) of 0.19 decibels (p = 0.0423), and a decrease in the SF2 of 0.56 decibels (p = 0.0374) were found in the dilated fields as compared with the baseline visual fields in the first eye tested. A decrease in foveal threshold of 2.56 decibels (p = 0.0081) and a mean deviation loss of 1.43 decibels (p = 0.0001) were found in the dilated fields as compared with the baseline visual fields in the second eye tested.

These findings indicate that active pupillary dilation in healthy subjects produces statistically significant differences, although these differences may not be clinically significant. To ensure repeatable visual fields, consistent pupil diameter should be controlled during serial visual field testing.