November 2009

 

OPHTHALMOLOGY NEWS

 

Keratitis & predisposing factors


by Matt Young EyeWorld Contributing Editor

 

Some factors associated with microbial keratitis resulting in eye loss:

• Glaucoma • Persistent epithelial defect • Steroid eye drops • Use of chloramphenicol • Use of long-term corticosteroids • Rheumatoid arthritis • Herpes simplex keratitis Source: Rasik B. Vajpayee, F.R.C.S.

 
Pseudomonas keratitis: two days from first symptoms with epithelial defect and anterior stromal infiltrates Source: Antoni Salvador, M.D.

Evisceration or enucleation are obviously last resorts for patients with serious eye disease; a new study looks at what factors often lead to these drastic measures.

The research focused on a group of patients in Australia, all of whom suffered from microbial keratitis. Investigators looked beyond the diagnosis of microbial keratitis to other associated factors, such as whether or not they had glaucoma, to determine who may be at most risk for losing their infected eyes. The patients often did have glaucoma, as well as persistent epithelial defects, according to the study, which was published online in May 2009 in Graefe’s Archive for Clinical and Experimental Ophthalmology.

Interestingly, these patients frequently suffered from the same systemic disease: rheumatoid arthritis, a factor that was shared more often than in previous studies. By analyzing factors associated with these microbial keratitis cases that resulted in eye loss, investigators may have brought corneal surgeons a step closer to saving more eyes.

Uncovering associated factors

Study co-author Rasik B. Vajpayee, F.R.C.S., Centre for Eye Research Australia, University of Melbourne, Melbourne, Australia, and colleagues analyzed 47 patients with microbial keratitis that underwent evisceration or enucleation. “In our hospital, the most common indications for enucleation and evisceration in this age group were non-resolving severe keratitis … and corneal perforation,” Dr. Vajpayee reported. Thirty patients (64%) had non-resolving severe keratitis and 17 patients (36%) had corneal perforation. The most common factors associated with eye loss included glaucoma (23 patients, 49%), persistent epithelial defect (18 patients, 38%), and usage of steroid eye drops (11 patients, 23%).

“The incidence of associated glaucoma in our study was higher than in the previous studies,” Dr. Vajpayee reported. “Presence of glaucoma can lead to corneal epithelial abnormalities directly, as well as due to the use of anti-glaucoma medications that can further predispose to the development of microbial keratitis.”

John D. Sheppard, M.D., professor of ophthalmology, microbiology, and immunology, Eastern Virginia Medical School, Norfolk, Va., suggested that glaucoma could be associated with eye loss because after glaucoma surgery blebs can get infected, causing scleritis. “If that takes off, it’s horrible,” Dr. Sheppard said. Topical chloramphenicol was not found to be a helpful agent in protecting these patients from bacteria. “At the time of presentation, 36% of the patients were using topical chloramphenicol,” Dr. Vajpayee reported. “This is important, considering the fact that a significant number of bacteria (45%) isolated were resistant to chloramphenicol. This may also explain the high level of resistance against this particular drug. In all these cases, chloramphenicol was started as the first-line therapy by the attending general practitioner before referring these patients to the specialist.”

However, Dr. Sheppard suggested that chloramphenicol still is an excellent antibiotic agent. “Chlor-amphenicol is very safe,” Dr. Sheppard said. It has been banned in the U.S. because of isolated cases of aplastic anemia, a rare, unpredictable, and usually fatal disease, Dr. Sheppard said, but it remains widely used in other areas of the world. The fact that many of these patients also were on long-term corticosteroids did not work in their favor. “The prolonged use of corticosteroids decreases the efficacy of the local immune response, increasing the patient’s susceptibility to microbial keratitis,” Dr. Vajpayee reported. “Steroid use also increases the risk of acquiring an infection or worsening the existing infection in these patients, by increasing the virulence of infective organisms.”

Dr. Sheppard agreed that steroids can exacerbate ocular infections. “Using steroids is an ideal way to grow fungus; steroids make viruses, funguses, and protozoans worse,” Dr. Sheppard said. Rheumatoid arthritis also tied in heavily to these patients’ poor outcome. “Cases with rheumatoid arthritis have associated dry eyes which predispose these patients to the development of microbial keratitis,” Dr. Vajpayee reported. “In the context of rheumatoid arthritis, corneal melting and perforation are more likely to occur in the presence of microbial keratitis and dry eyes.”

Patients with rheumatoid arthritis may also not be able to apply drops effectively, which may exacerbate their ocular situation, Dr. Vajpayee noted. Importantly, although these associated factors may have contributed to the poor outcomes of these patients, Dr. Vajpayee noted that they also delayed treatment for a significant period of time. Symptoms lasted, on average, 18 days before treatment. “This delay was probably an important risk factor in spreading the infection inside the eye, thereby leading to a poor visual outcome,” Dr. Vajpayee reported.

Editors’ note: Dr. Vajpayee has no financial interests related to this study. Dr. Sheppard has no financial interests related to his comments.

Contact information

Sheppard: 757-622-2200, docshep@hotmail.com
Vajpayee: rasikv@unimelb.edu.au

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