[Contrast sensitivity in navigating seamen]

Visual acuity measurement is the ophthalmological test used for determining the majority of professional aptitude thresholds. In the case of ship pilotage however, the necessity to detect physical information of size and variable contrast can only be partly assessed by this parameter.

A test considered to be more ergonomic for the visual capacity evaluation of seamen, and for the early diagnosis of ocular abnormalities, was evaluated.

At the time of their statutory aptitude visit, 159 professional seamen underwent a test for morphoscopic sense at variable contrast and luminance, gradual.

Twenty-seven ametropias of -0.75 to +3.00 diopters, 2 hypertensive retinopathies and 2 optical neuropathies were detected. Despite their low visual acuity, the myopic subjects were able to preserve normal visual efficiency in low contrast, without correction. Inversely, in spite of the correction, a deficiency was noted at medium and low contrasts, with a special increase at low luminance. The 7 patients operated on for radial keratotomy, although their visual acuity reached 10/10, presented a morphoscopic discrimination deficiency at low and medium contrasts.

The test used in this study is designed for morphoscopic discrimination testing in which contrast and luminance are variable. This determination of luminance contrast sensibility seems to be an informative, sensitive and reliable means of detecting uncorrected ametropia and diverse organic pathologies at their inset.