also diminishes in accommodating for near objects, from which it may be concluded that during this act that surface also becomes more curved; a simultaneous change in the position of this surface does not seem to occur.[1] Author:Hensen and Author:Völckers found, on the contrary, in the case of dogs, that the posterior surface of the lens moved backward.
Observations in cases of iridectomy and of albinos with transparent irides[2] have shown beyond doubt that there always exists between the ciliary processes and the equator of the lens a free space, in which the zonula is stretched. It is certain that the ciliary muscle in contracting does not compress the equator of the lens. The phenomena to be observed after iridectomy, in the region of the ciliary processes, the zonula, and the equator of the lens, have been thoroughly investigated by Author:Coccius.[3] He established the fact that in accommodating for near objects the points of the ciliary processes move so far forward toward the iris that the processes themselves form an acute angle with the axis of the eye. The circle formed by the ciliary processes becomes smaller. Coccius saw simultaneously a swelling of the ciliary processes and, in agreement with Author:Becker, a widening of the zonular space; according to Coccius, also, the movement of the margin of the lens toward its centre during accommodation may be directly observed.
Hensen and Völckers[4] demonstrated in the case of dogs a forward movement of the choroidea, simultaneous with the contraction of the ciliary muscle. Author:Adamiuk[5] confirmed this, but does not think it true of man, whose ciliary muscle has a different structure from that of the dog. From the accommodation phosphenes, described by himself, Author:Czermak[6] argues that there is a tension of the retina during accommodation.
At all events, the processes to be observed within the lens play
the most important rôle in accommodation, and there is every
- ↑ Helmholtz, Physiologische Optik, § 12.
- ↑ Becker, Wiener medicinische Jahrbücher, 1863 u. 1864.
- ↑ Der Mechanismus der Accommodation, Leipzig, 1868.
- ↑ Hensen und Völckers über den Mechanismus der Accommodation, Kiel, 1868.
- ↑ Centralblatt f. d. med. Wissensch., 1870, No. 19.
- ↑ Archiv für Ophth., vii. 1, 147.
