INTRODUCTION:
The cornea is the clear transparent dome shaped anterior-most part of the eyeball that serves as the major refracting surface for focusing of images on the retina.
Infectious keratitis, or suppurative corneal ulcer, is characterized by a corneal epithelial defect with underlying stromal inflammation and destruction caused by multiplying organisms and their toxins. Associated uveal tissue and anterior chamber inflammation also occur.
Collagen cross-linking (CXL), a procedure routinely used for control of progression of keratoconus, has been found to have beneficial effects on many types of corneal ulcers. An observational pilot study in our institution in 2013-2014, demonstrated a beneficial effect of CXL in suppurative corneal ulcers.
OBJECTIVES:
Primary objective:
To determine the benefit of adjunctive collagen cross linking (cxl) in reduction of the “time to healing” of suppurative corneal ulcer.
Secondary objectives:
1. To determine any difference in treatment failure rate (rates of perforation/keratoplasty/evisceration) of corneal ulcers treated with cxl as compared to the control group.
2. To assess the effect of risk factors (size of ulcer/diabetic status/type of organism)in outcome of corneal ulcer treatment with cxl compared to controls.
METHODS:
Study Design:
Single-Blinded, Randomized, Controlled Clinical Trial conducted at Department of Ophthalmology, Christian Medical College, Schell Campus, Vellore.
The study had two arms:
Interventional group:
Patients with infective corneal ulcer who satisfy the inclusion and exclusion criteria on standard medical therapy randomized to adjunctive COLLAGEN CROSS-LINKING (CXL)
Comparative group:
Patients with infective corneal ulcer who satisfy the inclusion and exclusion criteria on standard medical therapy randomized to SHAM CXL.
Patients with suppurative corneal ulcers were admitted after routine microbiological analysis (scraping for smear and culture), and assessed on a daily basis to determine response to treatment. All patients who fit the inclusion and exclusion criteria and were randomized tointerventional and control group.
Inclusion Criteria:
1. Adults greater than 18 years of age.
2. Corneal ulcer size of 2mm to 6mm.
3. Ulcer infiltrate depth upto 2/3 of the corneal thickness.
4. Smear and/or culture positive for fungus or bacteria.
5. Patients who are willing for inpatient care.
Exclusion Criteria:
1. Suspected viral keratitis.
2. Suspected acanthamoeba keratitis.
3. Corneal thinning greater than 50% on clinical assessment at presentation.
4. Any pre-existing corneal pathology.
5. History of previous collagen cross-linking.
6. Patients who are unable or unwilling to give consent.
RESULTS:
Our pilot study conducted in 2014 showed clinically significant reduction in duration of healing post adjunctive treatment of corneal ulcers with CXL. The present study is a randomized control trial to study the effectiveness of crosslinking as an adjuvant therapy in healing of ulcers. 44 patients were recruited fitting the inclusion criteria and were randomized to an Intervention group and sham cross linking (Control) group. 17 patients in each group completed treatment. All patients received topical antimicrobial therapy. Within 48 hours of enrollment either crosslinking or placebo treatment was started. Each patient in the study group received maximum of three sessions of cross linking. Symptom relief and time of healing were noted. The results were compared between the Intervention group and the Control group. Both groups showed similar healing time of 29.85 days of healing of ulcers, as well as similar success and failure rates.
There was no difference in the time of healing between the two groups. (p value = 0.918).
Hence, this study does not suggest that collagen cross linking adds any benefit to the time taken to for fungal corneal ulcers to heal.
CONCLUSION:
1.Collagen crosslinking has no benefit in reducing the time of healing of ulcers.
2.CXL does not reduce or increase the failure rate of corneal ulcers.
3. There was no correlation between size of ulcer/diabetic status/type of organism and the outcome of corneal ulcer treatment with CXL compared to controls