Photographic assessment of intermittent exotropia using a translucent cover

Abstract

Purpose: To evaluate the validity of the photographic assessment with a translucent cover that is clinically available for the evaluation of intermittent exotropia. Methods: Photographs of 270 patients who cooperated for the prism and alternate cover test (PACT) were reviewed. Full-face images were obtained with a digital camera while a translucent cover was placed in front of either eye. The change in distance from the medial canthus to the nasal limbus with occlusion was measured and the photographic angle was estimated by three independent ophthalmologists based on representative photographs. These two measurements were correlated with the angle measured using the PACT, and clinical features related to the discrepancy between the photographic angle and the angle measured with the PACT were determined. Results: Patients with intermittent exotropia of 27.0 ± 6.1 prism diopters (PD) showed a 4.5 ± 3.3 mm exodrift and an estimated angle of 29.0 ± 4.3 PD on the photographs with occlusion. The exodrift distance and photographic angle were positively correlated with the angle of PACT (r = 0.256, P < .001 and r = 0.546, P < .001, respectively). Of the 47 patients with a discrepancy of greater than 8 PD, 38 patients (80.9%) were regarded as having a photographic angle that was larger than the angle of PACT, which was more common in older patients, in those with a small distance angle, and when taking off the spectacles. Conclusions: Photographs with a translucent cover can reveal the latent components of intermittent exotropia. However, the photographic angle might differ from the real angle, particularly in older patients with a small angle and with the spectacles off.