Increased depth of one portion of the anterior chamber may he accompanied v increased shallowness of another, from tiltin;j forward of some portion of the lens against the iris and ciliary body: a relation which may result in setting 111) a condition of glaucomatous tension and form a very important factor in the prog ress of the case.
By employing focal illumination the edge of the lens can be seen in the pupil, which, however, usually requires to be dilated for this purpose. The lens itself will appear as a delicate gray compared with the pure black of the aphakic por tion of the pupil, and its edge will ap pear luminous on account of the total reflection which the rays of light enter ing. the marc.r,inal portions of the lens from the front undergo at its posterior surface; for at the edge of the lens they strike this posterior surface very obliquely.
With the ophthahnoscope, on the other hand. the edge of the lens appears black, for the same reason, the light coming into this portion of the lens from the fundus being reflected back into the eye.
When there is complete dislocation of the lens there will be an absence of the catoptric lenticular images. The lens itself when opaque may be visible through the pupil with the naked eye. As a rule, however, examination with the ophthalmoscope is necessary for its detection. It may be connected with the funclus or freely movable in the fluid vitreous (cataracta natans).
There is now more marked and general tremulousness of the whole area of the iris on quick movements of the eyes and head, with an abnormally, but uniformly, deep anterior chamber.
\Viten once seen there is no difficulty in determining the nature of the floating body, on account of its shape and size and the fact that no other condition occurs with which it is possible to con found it.
When the lens is displaced into the an terior chamber its appearance is charac teristic, its margin having a golden luster due to total reflection of light, making it look like a large drop of oil in the an terior chamber, which is much deepened, especially at its lower part. The lens assumes, moreover, a more spherical form than when in situ, on account of the loss of the compressing influence of the fibres of the suspensory ligament and choroicl, etc. The irritation it sets up often causes a contraction of the pupil behind it.
In ease of old, traumatic, dislocated, cataractous lens the central half of the pupillary quarter of the iris was altered in color and in brilliancy, while the oph thalmoscope revealed an alternate free transmission of the choroidal reflex and intercepting radial lines of iris-stroma.
This latter points to a previously-existing radial muscular mechanism in the once healthy iris. Symon (Australasian Med.
Gaz., July 15, '92).
Condition of Vision.—Sight is always impaired to a greater or less extent. In partial dislocation, vision is affected, be cause rupture of the fibres of the sus pensory ligament destroys the power of accommodation, and, at the sante time, by permitting increase in the convexity of the lens, makes the eye highly myopic. Moreover, the tilting of the lens on its axis induces a variable amount of astig matism, regular and irregular, lateral displacement having a similar effect.
In higher degrees of displacement, where the edge of the lens lies across the area of the pupil, not only is there a higher degree of visual failure, but there is also diplopia, two blurred images being seen. This is due to the fact that the edge of the lens acts as a prism, and causes the rays of light entering the eye through it to be deviated in the direction of the dislocation, while those entering tbe aphakic portion of the pnpil are un changed in direction except in so far as they are made to converge and form an indistinct image on the retina.
Case of double dislocation, one upward, the other downward, with atrophy of the zonula. There was so-called monocular triplopia from a double image formed by the displaced lens, joined to a third image made by the media without the lens. Heddaeus (Zehender's klin. Monats. f. Augenh., May, '88).
Considered, therefore, with regard to that portion of the pnpil still occupied by the lens, the eye is myopic, and the image formed by the light-rays passing through it can be cleared to a greater or less extent by concave sphero-cylindrical lenses. With regard to that part from which the lens is absent, the eye is highly hypermetropic, and its image can be made clear by the aid of a convex spher ical glass, and such a cylinder as is neces sary to correct the corneal astigmatism. In a later stage vision may be further impaired by the development of opacities in the lens.