Pupillometry in Chagas disease

We investigated parasympathetic innervation abnormalities of the iris sphincter and ciliary muscles in chronic Chagas disease by measuring pupillary diameter and intraocular pressure.

A group of 80 patients with Chagas disease was compared with 76 healthy individuals without chagasic infection. The following procedures were performed: pupillometry, hypersensitivity test to pilocarpine 0.125%, intraocular pressure measurement (IOP), basal pupil diameter (BPD), absolute pupillary constriction amplitude (ACA), relative pupillary constriction amplitude (RCA) and the presence of anisocoria.

The prevalence of anisocoria was higher in chagasic patients (p<0.01). These patients had mean basal pupillary diameter, mean photopic pupillary diameter and mean value of absolute pupillary constriction amplitude significantly lower than non-chagasic ones (p<0.01, mean difference -0.50mm), (p=0.02, mean difference -0.20mm), (p<0.01, mean difference -0.29mm), respectively. The relative pupillary constriction amplitude did not differ between the two groups (p=0.39, mean difference -1.15%). There was hypersensitivity to dilute pilocarpine in 8 (10%) of the chagasic patients in the right eye and in 2 (2.5%) in the left eye and in 1 (1.25%) in both eyes. The mean value of intraocular pressure had a marginal statistical significance between the two groups (p=0.06, mean difference -0.91mmHg).

Patients with chagasic infection may exhibit ocular parasympathetic dysfunction, demonstrable by pupillometry and the dilute pilocarpine hypersensitivity test.