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Mustard gas keratopathy a reminder of the dangers of chemical warfare
With the threat of biological terror in recent news, a case from last century gives a glimpse of earlier chemical warfare casualties.
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A case of advanced mustard gas keratopathy is pictured following penetrating keratoplasty. The episcleral tissues possess a porcelain appearance, and conjunctival vascular anomalies are present.With the advent of biological terror in these troubled times, concern has been expressed about the possible onset of chemical warfare. Mustard gas has been used in the past for this purpose. It is a chemical that can be relatively easily produced by any country possessing a capacity for oil production.
Following animal experiments in the late 19th century, the Wehrmacht decided to add this chemical weapon to its arsenal. Mustard gas (dichlorodiethyl sulfide or yperite) is a vesicant poisonous gas that was first released by the German Army on a battlefield at Ypres in April 1915 during World War I.
Due to unfortunate circumstances, the poison gas was able to persist for 3 days in certain sectors of the Allied line. This resulted in serious ocular and respiratory tract pathology secondary to its alkylation reaction with tissues. In these cases, after several hours, lacrimation photophobia and ocular irritation occurs, accompanied by edema of the cornea involving both epithelial and deep layers and swelling of the eyelids associated with formation of blisters. Nearby superficial vessels undergo thrombosis, and later vascular proliferation occurs which can extend onto the cornea.
The vascular injury can enter a hemorrhagic phase in the body, especially at pressure points. Before the entry of the United States into World War I, the government arranged for neurologist Harvey Cushing to visit France to study wartime casualties in case of the likelihood of an outbreak of hostilities. While there, Dr. Cushing observed in patients the graphic outline of hemorrhagic sites on the skin caused by the soldiers’ webbing and belts.
Long-term complications
In mild cases of mustard gas exposure, complete recovery occurs. Long-term complications, however, develop over the years in the case of severe burns secondary to the recurrence of keratitis. The cornea becomes scarred and irregular, and cholesterol and calcium are deposited in its tissues, resulting in progressive impairment of vision. Slit-lamp examination reveals that the episcleral tissues display a characteristic underglaze. White porcelain appearance and unusual vascular anomalies are common. These appear as enlarged, distorted vessels, sometimes with an ampulliform outline accompanied by varicosities and sausage-like vessels. With the passage of time, dense opacification of the cornea results, being most evident in the central and lower sections, as the upper portion has been protected by the overhanging eyelid. The surgeon takes this into account when planning surgery.
In these advanced cases of corneal disease, surgery is indicated and penetrating keratoplasty can produce a satisfactory outcome, as illustrated (see figure) in a veteran operated on some years ago. An earlier generation of ophthalmologists found that lamellar keratoplasty can also be successfully employed for this condition when the scar formation is superficial. In some countries, conjunctival grafts have been employed for treatment of ulcerated areas, but we have had no experience with this maneuver.
For Your Information:
- Frank P. English, FRCS, and William J. Glasson, FRACS, can be reached at 113 Wickham Terrace, Brisbane 4000, Australia; (61) 7-3832-4401; fax: (61) 7-3839-6638.