OBJECTIVE The aim of this study was to evaluate by serial measurements, pupil mydriasis produced by topical application of tropicamide 1% using a spray in a closed eye or instillation in an open eye in adult and elderly populations. METHODS The research was done from February to April of 2011 in the Policlinica Ronaldo Gazolla, located in the Arcos da Lapa Campus of Estacio de Sá University, RJ- Brazil. It was a clinical trial, controlled and randomized, made in a series of 50 patients that were being prepared for ophthalmoscopy examination. They were submitted to eye drop administration of 1% tropicamide in an open eye and to eyelid margin vaporization in a closed eye. The eyes were chosen for the administration of drops or spray according to a pseudo-random numbers table from Excel (2007) before application. The pupil diameter was measured before instillation and after 10, 20, and 30 min in both eyes, with a millimeter ruler. Biostat 5.0 software was used for statistical calculations. RESULTS Tropicamide 1% was vaporized in a group that presented the following average pupil diameters: 3 mm before the application; 4.16 mm in 10 min; 5 mm in 20 min; and 5.35 mm in 30 min. The group in which tropicamide 1% was instilled presented 2.96 mm of average pupil diameter before the application; 4.22 mm at 10 min; 5.02 mm at 20 min; and 5.44 at 30 min. The two way analysis of variance showed P<0.0001, and the Tukey test performed for comparisons among the groups showed statistical significant differences among all groups except when the measurements were done at the same time. CONCLUSIONS The vaporized tropicamide 1% mydriatic effect in closed eyes was clinically equivalent to the instillation effect of eye drop in open eyes. Other mydriatic drugs sprayed in closed eyes may not have the same effect.