Comparison of the efficacy of various concentrations and combinations of serum, ethylenediaminetetraacetic acid, tetracycline, doxycycline, minocycline, and N-acetylcysteine for inhibition of collagenase activity in an in vitro corneal degradation model.

OBJECTIVE To compare the efficacy of various concentrations and combinations of serum, EDTA, 3 tetracyclines, and N-acetylcysteine (NAC) for collagenase inhibition in an in vitro corneal degradation model. SAMPLE Grossly normal corneas from recently euthanized dogs and horses and fresh serum from healthy dogs and horses. PROCEDURES Serum was pooled by species for in vitro use. For each species, sections of cornea were dried, weighed, and incubated with clostridial collagenase (800 U/mL) in 5 mL of a 5mM calcium chloride-saline (0.9% NaCl) incubation solution and 500 µL of 1 of 19 treatments (homologous serum; 0.3%, 1.0%, or 2% EDTA; 0.1%, 0.5%, or 1.0% tetracycline, doxycycline, or minocycline; 0.5%, 1.0%, or 5.0% NAC; serum with 0.5% tetracycline; serum with 1.0% EDTA; or 1.0% EDTA with 0.5% tetracycline). Positive and negative control specimens were incubated with 5 mL of incubation solution with and without collagenase, respectively. Each control and treatment was replicated 4 times for each species. Following incubation, corneal specimens were dried and reweighed. The percentage corneal degradation was calculated and compared among treatments within each species. RESULTS Treatments with tetracyclines at concentrations ≥ 0.5%, with EDTA at concentrations ≥ 0.3%, and with NAC at concentrations ≥ 0.5% were more effective at preventing corneal degradation than serum in both species. The efficacy of each combination treatment was equal to or less than that of its components. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested EDTA, tetracyclines, and NAC may be beneficial for topical treatment of keratomalacia, but in vivo studies are required.

Eye examination in the cat: Step-by-step approach and common findings.

PRACTICAL RELEVANCE: The ability to perform a complete eye examination in the cat is critically important for patients with an ocular disorder or a systemic disease, as well as for the geriatric cat. CLINICAL CHALLENGES: Cats may need short breaks between portions of the eye exam in order to minimize stress. For the clinician, use of ophthalmic equipment and interpretation of normal vs abnormal findings may take some practice in order to develop proficiency. AUDIENCE: This review is aimed at veterinary practitioners and outlines all the steps and equipment necessary to perform a complete ophthalmic examination in the cat. EQUIPMENT: Although some specialized equipment is required, a complete eye exam can be performed with a modest investment in equipment and supplies. EVIDENCE BASE: This article draws on published references for normal parameters measured in the feline eye exam, as well as the experience of the authors.