. The refraction of the eye; including a complete treatise on ophthalmometry; . Figs. 96, 97, and 98.—Fig. 96, emmetropic eye; Fig. 97, myopic eye; Fig. 98, hy-permetropic eye. /, nasal side; E, temporal side; n, optic nerve; ga, optic axis;ll\ visual line; d, center of motion; K, nodal point. (After Bonders.) negative; and the farther inward from the posterior pole ofthe eye the macula is situated, the larger the negative anglealpha will be. 2. The length of the eyeball itself influences the size of theangle alpha. In emmetropia, the angle alpha is positive, and averages5°; in hypermetropia,
. The refraction of the eye; including a complete treatise on ophthalmometry; . Figs. 96, 97, and 98.—Fig. 96, emmetropic eye; Fig. 97, myopic eye; Fig. 98, hy-permetropic eye. /, nasal side; E, temporal side; n, optic nerve; ga, optic axis;ll\ visual line; d, center of motion; K, nodal point. (After Bonders.) negative; and the farther inward from the posterior pole ofthe eye the macula is situated, the larger the negative anglealpha will be. 2. The length of the eyeball itself influences the size of theangle alpha. In emmetropia, the angle alpha is positive, and averages5°; in hypermetropia, it is positive, and averages ° in non-squinting eyes; while, in myopia, itis, as a rule, positive, but may be nilor negative, and averages a little lessthan 2°. These are the figures givenby Bonders; and this author explainsthe influence of the length of the eye-ball on the size of the angle alpha^as follows: — The distance, kg (Fig. 98), from the nodal point to theretina is to be taken into account. • It is evident that, if in thehypermetropic eye, wdiere this d
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