. On the anomalies of accommodation and refraction of the eye, witha preliminary essay on physiological dioptrics. -692 behind the cornea. On their way lies system B, and of it theymeet ft at .3-7073 behind the cornea, that is, while they converge to a pointsituated 31*692 — 5-7073 = 25*9847 behind ft. Calculated from h, F ofsystem B is = 43-707.—We therefore find (according to form. 3 d) the pos-terior focus <p of system Cat ^^j- * |fi22 = 16*296 behind hofB, and consequently 10-296 + 5-936 = 22-23 behind the cornea,that is, 22-231 — 2-3563 = 19875 mm. behind h, of system C. The pos-terior
. On the anomalies of accommodation and refraction of the eye, witha preliminary essay on physiological dioptrics. -692 behind the cornea. On their way lies system B, and of it theymeet ft at .3-7073 behind the cornea, that is, while they converge to a pointsituated 31*692 — 5-7073 = 25*9847 behind ft. Calculated from h, F ofsystem B is = 43-707.—We therefore find (according to form. 3 d) the pos-terior focus <p of system Cat ^^j- * |fi22 = 16*296 behind hofB, and consequently 10-296 + 5-936 = 22-23 behind the cornea,that is, 22-231 — 2-3563 = 19875 mm. behind h, of system C. The pos-terior principal focal distance F of the eye therefore amounts to 19-875 mm. 66 DIOPTRICS OF THE EYE. To calculate the anterior focal distance, we start from rays parallel inthe vitreous humour. Refracted by the lens, these converge at 43*707 be-fore h of system B ; consequent^7 they arrive at the anterior surface of thecornea at 43*707 — 5-7073 = 37*9997, and are there refracted at23-692 x 37-999731-692 + 37-9997before the cornea, that is, 12-918 -f 1-9403 = 14-8583 before *, of Syst. C. Fiar. 43. = 12-918. POSITION OF THE CARDINAL POINTS. 07 The anterior principal focal distance F of the eye therefore amounts to14-8583 mm. A similar separate calculation is not, strictly speaking, necessary for F,because we may apply the formula 5 d. XXIV.—Review of the position of the cardinal points in the eye. We are now enabled to combine in a table the positions of the car-dinal points, first separately of the two component systems of the eye,system A, the cornea, system B, the lens; and subsequently of the com-pound system C, the eye itself. We have prefixed the computed position andcurvature of the refracting surfaces, and represented the values found, intheir true magnitude for each system in a diagram (Fig. 43). Above system I)is placed a schema of the form of the lens and of the position of the cardinalpoints in the eye accommodated for near objects. The line C C representsthe po
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