Structural Changes in Thin Keratoconic Corneas Following Crosslinking with Hypotonic Riboflavin: Findings on In Vivo Confocal Microscopy

Purpose: To report structural changes observable in in vivo confocal microscopy (IVCM) in keratoconic corneas <400 μm treated with hypotonic riboflavin and collagen crosslinking (CXL). Method: Ten eyes of ten patients with progressive keratoconus and corneal thickness between 350 and 399 μm underwent CXL with hypotonic riboflavin. IVCM was performed preoperatively and at one month, three months, and six months after the procedure. Results: IVCM analysis one month postoperatively showed complete absence of the subepithelial nerve plexus with gradual regeneration over six months in 8 of the 10 eyes, and poor regeneration in the remaining 2 eyes. The anterior stroma showed extracellular lacunae and hyper-reflective cytoplasm in a honeycomb appearance signifying edema at one month which gradually decreased over six months post CXL. Stromal keratocyte apoptosis was evident in the anterior stroma in all cases and extended to the posterior stroma in four eyes with gradual regeneration evident at three and six months. The specular endothelial count decreased by 8% (P = 0.005) post-CXL, but no corneas developed clinical signs of endothelial trauma. Conclusion: IVCM analysis of thin corneas after hypotonic CXL showed posterior corneal structural changes. Posterior stromal changes were accompanied by a decrease in the endothelial cell count. This case series was a preliminary feasibility study that might necessitate conducting a well-designed controlled study

Exploratory use of fluorescent SmartProbes for the rapid detection of microbial isolates causing corneal ulcer

PURPOSE:To explore the use of optical SmartProbes for the rapid evaluation of corneal scrapes from patients with suspected microbial keratitis, as a clinical alternative to Gram stain. DESIGN:Experimental study with evaluation of a diagnostic technology. METHODS:Corneal scrapes were collected from 267 patients presenting with microbial keratitis at a referral cornea clinic in South India. Corneal scrapes were flooded with SmartProbes (BAC One or BAC Two) and evaluated by fluorescence microscopy (without the need for sample washing or further processing). The SmartProbe labelled samples were scored as bacteria/fungi/none (BAC One) or gram-negative bacteria/none (BAC Two) and compared to Gram stain results. RESULTS:Compared to Gram stain, BAC One demonstrated sensitivity and specificity of 80.0 and 87.5 percent respectively, positive and negative predictive values (PPV, NPV) of 93.8 and 65.1 percent, and an accuracy of 82.2. BAC Two demonstrated sensitivity and specificity of 93.3 and 84.8 percent respectively, a NPV of 99.2 percent and an accuracy of 85.6 percent. When the corresponding culture results were compared to the Gram stain result, the sensitivity and specificity were 73.4 and 70.7 percent, the PPV and NPVs were 86.5 and 51.0 percent, and an overall accuracy of 72.6. CONCLUSIONS:Fluorescent SmartProbes offer a comparative method to Gram stain for delineating gram-positive or gram-negative bacteria or fungi within corneal scrapes. We demonstrate equivalent or higher sensitivity, specificity, PPV and NPVs, and accuracy than culture to Gram stain. Our approach has scope for point-of-care clinical application to aid in the diagnosis of microbial keratitis

The Case for Fungal Keratitis to Be Accepted as a Neglected Tropical Disease

Amongst the treatable cause of blindness among young people, fungal keratitis ranks high. There are an estimated 1,051,787 to 1,480,916 eyes affected annually, with 8-11% of patients having to have the eye removed. Diagnosis requires a corneal scraping, direct microscopy and fungal culture with a large number of airborne fungi implicated. Treatment involves the intensive application of antifungal eye drops, preferably natamycin, often combined with surgery. In low-resource settings, inappropriate corticosteroid eye drops, ineffective antibacterial therapy, diagnostic delay or no diagnosis all contribute to poor ocular outcomes with blindness (unilateral or bilateral) common. Modern detailed guidelines on fungal keratitis diagnosis and management are lacking. Here, we argue that fungal keratitis should be included as a neglected tropical disease, which would facilitate greater awareness of the condition, improved diagnostic capability, and access to affordable antifungal eye medicine