Diagnosis.—The' search for a foreign body in the cornea should be made by all the following methods: Oblique il lumination, the ophthalmoscope, and with the cyc placed so as to reflect from its surface an area of light, as before a large window. If the foreign body has been imbedded many hours or days there also will be pericorneal redness, most de cided at the part of the corneal margin nearest the foreign body. In using oblique illumination foreign bodies of light color arc rendered evident when the light is strongly concentrated on the cornea and the iris in comparative shadow. Dark particles are rendered dis tinct by concentrating the light on the iris behind, thus furnishing a light back ground. Light foreign bodies are best seen against the black pupil; dark ones against the illuminated iris. It is there fore necessary to vary the oblique illu mination and to look at the cornea from different directions.
With the ophthalmoscope all foreign bodies except particles of glass appear black against the red reflex from the pupil. By turning the eye in different directions, this reflex must be obtained through different parts of the cornea. Sometimes with the ophthalmoscope the appearance of a foreign body is caused by a slight disturbance of the corneal surface; so, that after the position of such a black speck has been ascertained it must be examined by oblique illumina tion.
In young children where nmch diffi eulty is experienced in examining the cornea the child should be laid across the nurse's lap in such a way that its legs are between her body and left arm, her right hand being. free to control the child's hands. The examiner sits op posite with a towel or rubber sheet across his lap and places the child's head between his knees. In this way the child is prevented from kicking. and struggling, and its head is held steady, leaving the examiner's hands free to wparate the lids, make the necessary examination, and apply the proper reme dies. C. A. Wood and T. A. Woodruff ("Med. Standard, Oct., 1901).
The reflection of an area of light, as a large window opening to the sky, or a strongly-illuminated card held close be fore the eye, is uniform from the normal cornea. But when by the presence of a foreign body the corneal surface is rough ened, the irregularity caused in the re flection is very noticeable, and furnishes the most-readily-applicable method of recognizing the presence and location of such an injury or foreign body. If, how
ever, the disturbance of the surface be slight, it is liable to be masked by the layer of mucus which covers the normal cornea; and to avoid this source of error the corneal surface should be dried by touching it with a bit of absorbent cot ton.
Treatment.—In general, foreign bod ies lodged in the cornea should be at once removed. This is usually a very simple operation with the eye placed under the influence of local anwstliesia. A single drop of a 2-per-cent. solution of cocaine, or a 1-per-cent. solution of holocain, placed directly upon the cornea produces the necessary anTsthesia in from three to five minutes. Occasionally a foreign body can be wiped away by a little ab sorbent cotton wrapped closely and firmly around the end of a probe or match-stick. If more firmly imbedded the ordinary spud is to be used by thrust ing it into the wound alongside of the foreign body, and by something of a wedge-like action, pushing the foreign body out.
Foreign bodies of a certain character, as splinters of wood or the beards of grain or grasses, may require to be ex tracted as a splinter is extracted from the skin, by making an incision along it with a needle or cornea-knife, so as to freely expose it, and then lifting it out of its bed. When the foreign body extends somewhat into the anterior chamber, the eye should be kept quiet until the aqueous humor has refilled the chamber. Then a broad needle is to be thrust un derneath the foreign body, and held with its point imbedded in the posterior sur face of the cornea, while the foreign body is extracted.
Occasionally when the condition of the patient, or the lack of proper instru ments, or of a local anmsthesia renders the extraction of the foreign body im possible, it is proper to cleanse the sur face of the eye as thoroughly as possible, and allow it to remain for a few days until the process of suppuration has loos ened it. Then it can be washed or wiped out. But such a process is always at tended with danger of infection of the deeper structures of the eye and serious damage or complete functional loss of the organ.
Bits of iron imbedded in the cornea very quickly give rise to a brown stain, probably due to oxide of iron. This stain may remain after the removal of the foreig,n body, but is always cast off within a few days. It is better to remove it at once by scraping, as it often proves a source of irritation and always ulti mately separates as a slough.