PURPOSE: The purpose of the study was to compare different methods of photographic evaluation of cataract formation in rats in response to different regimes of naphthalene treatment. Furthermore, we intended to study the relationship between cataract extension and biochemical parameters.METHODS: Brown Norway rats were treated with 0.10-1.5 g naphthalene/kg body weight, twice a week for ten weeks to induce cataract or placebo. Slit illumination and retroillumination (SI and RI) photographs were produced by an EAS-1000 instrument to document cataract formation as light-scattering intensity. The degree of the cataractous changes was quantified in SI photographs by the peak height and the integrated peak area, and in RI photographs by threshold setting. Finally, the lens concentration of Na(+) and K( +) and the protein composition were analyzed and correlated to the photographic analysis.RESULTS: The degree of the cataractous changes was most linearly related to dose and duration when the integrated peak area was estimated. However, protein fractions were non-linearly related to the cataractous changes estimated. Alterations in concentration of Na(+) and K(+) were small or insignificant, which indicate that naphthalene-induced cataract is not caused by osmotic changes. The lowest possible naphthalene dose to induce cataractous changes was between 0.10 and 0.50 g/kg twice a week for ten weeks.CONCLUSIONS: 0.50 and 1.0 g naphthalene/kg twice a week appeared to be optimal, because the rats in these groups were healthy and the cataractous changes were consistent between animals. Thus, the combination of the animal model with the cataract quantification system has the potential to be useful and reliable in studies of cataract-preventive compounds.
Animals Cataract