Skiascopy and its practical application to the study of refraction . hat point is departed from, and constitutes ameasure of the degree of ametropia remaining uncorrected. Form of the Light Area.—The real form of the lightarea on the retina, except under certain conditions in astig-matic eyes, will be circular. If the light be perfectlyfocused on the retina it is circular, because that is the formof the source of light employed (see Chapter III). If thelight be not perfectly focused on the retina, the circularpupil gives its form to the resulting area of diffusion. The influence of regular ast
Skiascopy and its practical application to the study of refraction . hat point is departed from, and constitutes ameasure of the degree of ametropia remaining uncorrected. Form of the Light Area.—The real form of the lightarea on the retina, except under certain conditions in astig-matic eyes, will be circular. If the light be perfectlyfocused on the retina it is circular, because that is the formof the source of light employed (see Chapter III). If thelight be not perfectly focused on the retina, the circularpupil gives its form to the resulting area of diffusion. The influence of regular astigmatism on the apparentform of the light area as seen in the pupil will be discussedin Chapter IV ; and the influences of irregular astigmatismand aberration in Chapter V. These influences, especiallythe latter, are really dominant, and of the greatest practical FORM OF THE LIGHT AREA. 31 importance in nearly all eyes. But in eyes free from suchdefects the form varies with the departure of the observerseye from the point of reversal. If the magnification of the.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectretinos, bookyear1896
