Preservation of structure and immunoreactivity at the vitreoretinal interface of the rabbit eye.

BACKGROUND: The vitreous body is implicated in the etiology and pathology of a variety of retinal conditions. Many such conditions are treated surgically to remove the posterior vitreous from the inner limiting lamina (ILL) of the retina, and there is current interest in the adjunct use of enzymes for this purpose. To evaluate the efficacy of these agents in future preclinical studies, improved preservation and assessment methods were developed to establish a baseline histological profile of the vitreous and retina of the rabbit, to identify and distinguish artifactual vitreoretinal separation from authentic posterior vitreous detachment, and to preserve structural integrity while maintaining antigenicity for immunohistochemical analysis. METHODS: Two pigmented rabbits each underwent perfusion with one of three fixatives, either: (1) 10% neutral buffered formalin + cetylpyridinium chloride (NBF/CPC), (2) acid-ethanolic formalin + CPC (AEF/CPC), or (3) formaldehyde-glutaraldehyde + CPC (FG/CPC). An eye fixed in NBF/CPC by immersion, from an additional rabbit, was also included for comparison. Eyes were processed whole through paraffin infiltration. Treatments were assessed by immunohistochemical labeling for retinal and cortical vitreous (CV) markers. RESULTS: In contrast to immersion fixation, perfusion with either NBF/CPC or AEF/CPC maintained vitreous adherence to the ILL during histological processing. NBF/CPC proved best for highlighting intralaminar structure and for labeling type II collagen in the CV, particularly with antigen retrieval. AEF/CPC caused condensation of fibrillar elements in the CV. Collagen XVIII in the ILL was observed with AEF/CPC exclusively. Only retinal vessels near the optic nerve head were labeled for type IV collagen. The labeling of glia was useful for distinguishing between cellular and extracellular elements. GF/CPC hindered detection of collagen II and disrupted posterior segment structure. Expression of type II collagen extended from the ONH directly to CV affiliated with the central canal of Cloquet, a feature characteristic of rabbit eyes. DISCUSSION: Careful tissue preservation and processing techniques minimize artifactual separation of the CV from the ILL. By optimizing the tissue architecture and antigenicity of the vitreoretinal complex, CV may be distinguished from the ILL immunohistochemically. The techniques described may be used to evaluate more effectively the utility of pharmacologic vitreolysis, using experimental animal models.

Feasibility of an antiviral clinical trial requiring cross-country shipment of conjunctival adenovirus cultures and recovery of infectious virus.

PURPOSE: Accurate and timely laboratory diagnosis of adenovirus from conjunctival cultures is essential to ensure appropriate enrollment, and detection of residual infectious virus is essential to evaluate antiviral efficacy in any multicenter national clinical trial. As part of a feasibility study, we investigated those variables that might affect the successful recovery of infectious adenovirus from patient conjunctival cultures after cross-country shipment. MATERIALS AND METHODS: Simulated adenovirus conjunctival cultures were prepared in viral transport media to evaluate the effect of four variables (adenovirus serotype, initial concentration, initial storage temperature [-20 degrees C, 0 degrees C, 20 degrees C], and preshipment storage times [1-5 days]) on the recovery of infectious adenovirus by a central laboratory in St. Paul, MN, following air shipment from Pittsburgh, PA. Upon arrival, the internal temperatures of the containers were recorded, and the samples were cultured on A549 cells using standard tube and/or shell vial culture. RESULTS: Overall, adenovirus was recovered in 352/354 (99.4%) of the samples when the initial titer was greater than 1.0 PFU/ml. Adenovirus serotype, initial storage temperature, and preshipment storage times had no adverse effect on virus recovery. CONCLUSIONS: Simulated conjunctival samples could successfully be shipped cross-country at ambient temperatures to a commercial laboratory for adenovirus isolation by culture. Having demonstrated feasibility, a clinical trial was subsequently carried out that confirmed the ease of shipment and recovery of infectious adenovirus from conjunctival cultures.

A randomized, double-masked, placebo-controlled, multicenter comparison of loteprednol etabonate ophthalmic suspension, 0.5%, and placebo for treatment of keratoconjunctivitis sicca in patients with delayed tear clearance.

PURPOSE: To evaluate loteprednol etabonate ophthalmic 0.5% suspension, versus placebo for treatment of the inflammatory component of keratoconjunctivitis sicca in patients with delayed tear clearance. DESIGN: Randomized, double-masked, placebo-controlled clinical trial. METHODS: Sixty-four patients with keratoconjunctivitis sicca and delayed tear clearance were randomly assigned to receive either loteprednol or vehicle 4 times a day for 4 weeks. Patients were evaluated at weeks 2 and 4 of treatment and 2 weeks after treatment was discontinued. Symptoms were scored using a visual analog scale (VAS) of 1 to 100. Corneal fluorescein staining was scored 0 to 4 in five areas. Conjunctival injection was graded 0 to 3 in the inferior bulbar, nasal bulbar, and inferior tarsal areas. Lid margin injection was graded 0 to 3. Safety was assessed by funduscopy, lens examination, biomicroscopy, visual acuity, and Goldmann tonometry, and by monitoring adverse events and changes in symptoms. RESULTS: In subsets of patients with at least moderate clinical inflammation, there was a significant difference between the loteprednol-treated group and vehicle-treated group after 2 weeks of therapy. The differences did not reach statistical significance at 4 weeks, although the loteprednol-treated patients retained their improvement compared with the vehicle-treated group. Safety evaluations showed both treatments to be well tolerated and similar in the frequency and type of adverse event reported. CONCLUSION: The use of topical loteprednol etabonate 0.5% 4 times a day may be beneficial in patients who have keratoconjunctivitis sicca with at least a moderate inflammatory component.