25 Corneal foreign body
CLINICAL EXAMINATION
It will be clear from this description that it is important to assess the location of the foreign body within the cornea. This can be divided into surface, penetrating and perforating, in increasing order of seriousness (Figure 25.2). As the name suggests, a surface foreign body will sit on or in the epithelium. The eye is likely to be uncomfortable, rather than very painful, and only mild intraocular signs (such as slight miosis from a reflex uveitis) will be present. Penetrating foreign matter will be embedded within the stroma of the cornea. Some ulceration is likely around the entry site (check with fluorescein dye). If the foreign matter has broken off flush with the corneal surface, or is small and smooth in outline, the patient might be remarkably comfortable. Intraocular involvement will again be minimal.
CASE WORK-UP
Most foreign bodies are of plant matter – other items include paint flecks, metal filings and so on. Since plant matter can be a site of pathological bacterial (or even fungal) contamination, it is sensible to consider sampling for bacterial (± fungal) isolation and sensitivity testing. Doing this at the outset might result in a quicker resolution for the patient.