A NEW STEROID-INDUCED CATARACT MODEL IN THE RAT - LONG-TERM PREDNISOLONE APPLICATIONS WITH A MINIMUM OF X-IRRADIATION

In order to induce experimental steroid cataracts in rat eyes similar morphologically to those seen in human eyes, prednisolone acetate was administered either topically or systemically for 12 months with a low dose of X-irradiation as a cocataractogenic factor, Twenty-seven Brow n-Norway rats were randomly divided into a control group (group I) wit h no steroid administration; an eyedrop group (group II) with a daily 1% prednisolone acetate instillation of a total volume of 1.0 mg/kg in both eyes, and a systemic group (group III) with a daily intramuscula r injection of 0.8-1.0 mg/kg prednisolone acetate. The right eyes of a nimals in each group were X-irradiated with a single dose of 2 Gy. Top ical and systemic steroid administrations started 2 weeks after X-irra diation. Anterior segment changes were documented with a slitlamp micr oscope and an anterior eye segment analysis system once a month. Body weight and blood glucose levels were examined every week and every 2 w eeks, respectively. The mortality rates in groups I, II and III were 0 , Il (1/9) and 25% (3/12), respectively. The both lenses in group I sh owed a gradual increase in lightscattering intensity in the nuclear an d supranuclear regions over time. Initial lens changes in both steroid -treated groups were Y-suture dissociation and a slight increase in li ght-scattering intensity in the posterior supranuclear region 3 months after prednisolone administration. Opacification of the anterior shal low cortex and the posterior subcapsular layer was observed after 10 m onths. X-irradiated eyes showed more prominent lens opacification as c ompared with nonirradiated eyes after 10 months in both group II and g roup III. Either topical or systemic administrations of prednisolone a cetate over a long term successfully induced morphological lenticular changes in the rat similar to those found in human steroid-induced cat aracts. A low dose of X-irradiation effectively accelerated opacificat ion as a cocataractogenic risk. This new model will allow future inves tigation of steroid cataracts.