The absolute threshold of the dark-adapted eye is recorded at different eccentricities for various degrees of defocussing. An ophthalmic lens of variable power is inserted in the optical path to produce a blurred image on the retina, corresponding to that of an uncorrected myopia and hyperopia, while the central vision of the subject is accurately accommodated for 1 m. The depth of focus, defined in terms of the criterion of visibility, as suggested by OGLE, is found to increase with eccentricity. The poor sensitivity to blur of the peripheral retina is presumably a consequence of the overlap of the receptor fields at large off-axis angles. The suggestion is made that the edge detectors, called into play be the obliqueray astigmatism, tend to counteract the deleterious effects.

Keywords:
Scotopic Vision, Peripheral Vision, Eye dioptrics
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© 1975 S. Karger AG, Basel
1975
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