The crystalline lens system : its embryology, anatomy, physiological chemistry, physiology, pathology, diseases, treatment, operations and after-changes ; with a consideration of aphakia / by Louis Stricker.

  • Stricker, Louis, 1863-
Date:
1899
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Licence: Public Domain Mark

Credit: The crystalline lens system : its embryology, anatomy, physiological chemistry, physiology, pathology, diseases, treatment, operations and after-changes ; with a consideration of aphakia / by Louis Stricker. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    chamber is practically reduced to a narrow space rest ricted to the periphery. In these cases the Cornea is very flat. Water, Cornea and Aqueous have the same index of refraction. Hence in animals which live exclusively in the water, we find that the refraction of light is mainly dependent on the lens, in contradistinction to animals which live in the air. And in accordance with this fact, the lens is found to he almost globular. Here, then, conditions purpose, effect and result mutually equalize each other. In the new-horn in- fant ocular inspection is often sufficient to demonstrate that there is scarcely an anterior chamber. Owing to the gradual accumulation of the aqueous, the lensisnotonly pressed backward, but its general contour is changed. This in- creased filling out of the anterior chamber has likewise a lateral extension, especially toward the less resistant posterior chamber. By this means the Zonula is drawn tense, and the lens is compressed in a saggital direction.7 From now on, contraction of the Ciliary Muscle causes relaxation of the Zonula, and as a result the lens returns to its more globular form, as it ex- isted during foetal life. At birth the lens assumes various changes in its shape, dependent on 'accommodative effort. These changes can not be entirely set aside, even in foetal life, since aside from the changes in the Electrical Conditions of the Oculo-Motorius, which must be followed by contraction of the Ciliary- Muscle, the converging movements of the eyes are associated with accom- modative efforts, even in utero. Though, as far as we know, accommo- dative efforts do not take place during the first few days or even weeks of extrauterine life, nevertheless the action of light on the retina must lead to a contraction of the ciliary muscle. As regards the length of lens fibres, there appears to be a very material difference between this and the foregoing period of growth. In all that has previously been said; in the foetal lens, all the individual fibres of each concentric lamella were of equal length. In each succeeding lamella the individual fibres must be longer than in the preceding, if the rays of the lens star increase in length and each fibre occupies relatively the same position, as its corresponding fibre in the layer beneath. This gradual in- crease in length extends to the close of the first period of growth, as long as the simple tri-star figure continues. Eobinsky8 has beautifully described this condition. He estimates that a fibre which starts exactly at the pole anteriorly, attaches itself posteriorly exactly at a point where the anterior 7 For a different explanation see Collin's Theory, p, 30. 8 Untersuchungen zur Kentniss der Laage und Anordnung der Augen linsen- fasren. Centrab. f. d. med. Wiss, 1882, No. 27.