Lectures on the parts concerned in the operations on the eye, and on the structure of the retina ... To which are added, a paper on the vitreous humor; and also a few cases of ophthalmic disease / by William Bowman.

Date:
1849
Catalogue details

Licence: Public Domain Mark

Credit: Lectures on the parts concerned in the operations on the eye, and on the structure of the retina ... To which are added, a paper on the vitreous humor; and also a few cases of ophthalmic disease / by William Bowman. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    SIZE AND TENSION OP THE EYEBALL. Size of the eychall.—The size of the adult human eye varies Mathiii certain hmits, as might have been expected. Nevertheless, as it is a part wliichj by reason of its complex mechanism^ and the peculiarity of some of the textures it comprises, attains its complete development, like the interna] ear, before most other organs of the body have reached their adult condition, these limits are very confined, if we except instances amounting to disease. Of many measurements which I have made, the general result is that the diameter of the sclerotica is from seven- eighths of an inch to an inch. The transparent cornea forms by its anterior surface a portion of a sphere, the diameter of which is from -]-| to of an inch (that is, of usually less than two-thirds of an inch), and it often happens that the surface of the globe recedes, or is depressed, very superficially near the line of junction of the sclerotica and cornea. The cornea forms from one-sixth to one-seventh of the horizontal circumference of the ■whole globe. In considering the size of the eye, I should guard you against judging of it in any degree by the size of tlie aperture of the eye- Hds j the latter, indeed, is that which most governs the apparent size of the baU, and is also of much importatice to the practical surgeon, as enabhng him more or less readily to manipulate in his operations on parts within the lids. Moreover, the cornea is often apparently smaller than it really is, in consequence of the formation of a ring of opacity close to its border in the declining stages of life. Tension in health and disease.—The eyeball has naturally a certai]! tension, arising from the due repletion of the outer case with the tissues contained witliin. It gives a tight or resisting feel to the finger applied upon it, and the exact degree of this tension belonging to the healthy state it is essential for you to know, both that you may be aware of the resistance your instruments will encounter, and also that you may be able rightly to appreciate? by the touch the departures from the healthy standard of tension which occur in the course of several diseases. When disorganizing processes have occurred in the interior, the eyeball frequently becomes soft, at other times hard, although, perhaps, the finger alone can inform you of these evidences of the impaired nutrition of the organ. Again, in inflammations of an acute kind attacking the globe, an unnatural hardness is perceptible on pressure, usually accompanied by that duU sickening pain which attends distension of the fibrous tissues, and referrible in this case, I