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Editor,—Medications used to treat glaucoma can cause side effects such as irritation, redness, foreign body sensation, and pain in the eye.1 There are reports that latanoprost has almost no serious side effects.
We present two patients treated with latanoprost for primary open angle glaucoma who developed herpes keratitis.
CASE REPORTS Case 1
A 68 year old female patient presented to the cornea department of the eye clinic, University of Athens, in January 1997. She was being treated for primary open angle glaucoma with latanoprost drops once daily for the past 3 months. Visual acuity in the right eye was 20/40 and in the left 20/20. The intraocular pressure of the left eye was 16 mm Hg. Examination with a slit lamp demonstrated a dendritic ulcer in the right eye (Fig 1). Immunofluorescence studies of the cornea epithelium from the ulcer demonstrated the presence of herpes simplex virus. Latanoprost treatment was discontinued and the patient was placed on antiviral treatment. Two weeks later the keratitis had resolved. The patient was treated again with latanoprost drops once daily in the right eye. Three months later she developed the same problems in the right eye. Latanoprost treatment was discontinued again and antiviral treatment with aciclovir ointments was recommended. There has been no recurrence of the herpetic infection.
A 65 year old female presented to the cornea department of the eye clinic, University of Athens, in March 1997. Examination detected epithelial lesions in the centre of the cornea in the right eye (Fig 2) and at 11 clock hours in the periphery of the left eye.2The patient had had treatment with latanoprost once daily for primary open angle glaucoma during the past 2 months. There was no history of herpes keratitis. Latanoprost treatment was discontinued. The samples of the corneal epithelium from the ulcerated area of both eyes demonstrated the presence of herpes simplex virus, using immunofluorescence. After antiviral treatment, trabeculectomy was carried out in the right eye, when latanoprost treatment was continued in the left eye. After a small period of time, in the right eye—without latanoprost treatment—there was no herpetic infection, while in the left eye—with latanoprost treatment—herpetic infection presented again.
Both patients presented with herpes keratitis during latanoprost treatment. After discontinuing the latanoprost treatment, there was no recurrence of the keratitis.
Latanoprost is a prostaglandin analogue.34 It is an esterified predrug inactivate until its enzymatic hydrolysis in the cornea, where it becomes a biologically active acid.5Owing to the biochemical disturbance in the cornea, and the keratopathy confirmed with staining, we can suppose that the presence of latanoprost predisposes the appearance of herpes keratitis.
More cases must be studied before we can reach more specific conclusions.