4. _If the eye contain a foreign body._ Usually these are pieces of metal or glass. The following points should be investigated to determine whether the foreign body be in the eye:--
(i) The history of these accidents is usually the same. The patient is chipping with a hammer and chisel, and a piece flies off and strikes the globe. In the case of glass it is usually a mineral-water bottle which bursts.
(ii) The position and nature of the wound in the cornea and sclerotic.
(iii) The condition of the anterior chamber--whether evacuated or not.
(iv) The tension of the eye, which may be lowered.
(vii) Whether the foreign body is visible with the ophthalmoscope or by focal illumination.
(viii) The localization of the foreign body by the X-rays. The latter is the most important factor of all, since the foreign body may pass right through the globe and be embedded in the orbit.
[Illustration: FIG. 124. AUTHOR’S CHAIR FOR THE LOCALIZATION OF FOREIGN BODIES IN THE EYE BY THE X-RAYS. A is a rifle sight for centring the anode, C, on the cross wire, B, behind which the photographic plate is subsequently placed. P is the screw clamping the head-piece on to the patient’s head. Q is the screw for regulating the height of the tube and the distance from the patient. R is the screw for regulating the height of the head-piece. The inset shows the arm carrying the tube more highly magnified. E is the sliding arm carrying the tube for lateral displacement marked for stereoscopic photographs. F is the pointer for marking the position of the anode. D is the screw for clamping when in position.]
=Operative treatment.= If the injury be a recent one and the foreign body a metal of magnetizable properties, it is best removed by an electro-magnet after localization by the X-rays (Fig. 124). Sideroscopes have been used, but are not so satisfactory. If the foreign body be non-magnetizable, such as a piece of copper cap or manganese steel, an attempt may be made to remove it with forceps after localization. If the foreign body be embedded in the lens it is often advisable to extract the lens together with it. If the foreign body be of glass, and it be only small, it is usually best left alone, unless capable of easy removal, _e.g._ if it be situated in the anterior chamber; the eye will often tolerate the presence of glass provided it be aseptic.