The Prognosis of Incipient Senile Cataract
Boston Medical and Surgical Journal
To the lay mind the diagnosis of cataract is equivalent to a sentence of certain blindness at no very distant date. Unfortunately this opinion prevails with many medical men who have not given special attention to the eye. It is the purpose of this paper to show that a much more optimistic prognosis is justifiable. The importance of correcting this misconception can hardly be over-estimated. The definition of the word in the Standard Dictionary is "an opacity of the crystalline lens of the eye
... ne lens of the eye or its enclosing capsule resulting in complete or partial blindness. ' ' This is certainly a terrible doom to contemplate, and in many instances has induced great despondency and even melancholia. While the definition is true of the progressive type it is not true of a very large percentage of cases, the Fio. 1. (Landolt.) Schematic eye. o' Anterior or flint principal focus; a, anterior surface of the cornea ; //' and //v principal point« ; K' and K" nodal point* ; o" posterior or second principal focus ; P.c., fovea cent ral is; o'o"ß optic axis. non-progressive type, for whom this is a most cruel misconception. The eye is a most highly differentiated sense organ and the lens unlike any other tissue. It is double convex in form, 5 mm. in thickness and 9 mm. in diameter, situated just posterior to the iris, resting upon a concavity of the vitreous body. The posterior surface is slightly more curved than the anterior, but this latter has the property of increasing its convexity by the contraction of the ciliary muscle. This process is known as accommodation, and by it the eye is focused for objects at different distances. Embryology teaches us that it is entirely of epithelial origin. The anterior capsule is lined with a single layer of cubical cells which by a process of elongation grow into fibres which extend from the anterior to the posterior capsule. In other epithelial structures the worn out cells are exfoliated; but here, as new cells are formed, the older ones are squeezed together in the centre, gradually forming a nucleus, which increases as age advances, finally forming a hard centre. The enveloping substance is called the cortex. There is no definite line of separation Fio. 2 (Landolt.) Anterior portion and ciliary region of the eye. Cof the ciliary muscle; z, zone of Zinn. The full lines indicate the crystalline lens, iris, and ciliary body in a state of rest; the dotted lines show the same in a state of Hciommodation. between the two, but a gradual increase in density from without inward. In elderly people the refraction of the centre is often quite different from the periphery. Fio. 3. (Henderson.) Showing growth of lens fibres from epithelial cells lining anterior capsule, the nuclei accumulated in the equatorial zone, and lines formed by union of ends of fibres. The lens has no blood vessels, its nutrition being secured by absorption of lymph from the ciliary processes. The metabolism is, therefore, extremely slow. A complete enumeration of the varieties of cataract would transcend the limits of this pa*per, but a few must be mentioned, with no further explanation than the names imply. Congenital and acquired. Primary and secondary. Hard and soft.