Formation of an experimental cataract model in chick embryo

Cataract is a major occular disease that causes blindness in many developing countries of the world. Experimental model of cataract is a first necessity to study the preventive factors of cataract progression. Several studies have shown that some glucocorticoides such as Dexamethasone (DEX) can induce cataract. The aim of this study was to form cataract in chick embryo. During three consequent stages, 120 fertile eggs were used in this study. In each stage 40 eggs in 4 groups were selected and put them into an incubator. Incubation was carried out at 37.5 °C and 68% relative humidity. The day that the eggs were placed in the incubator was termed day 1. The first group received normal saline and the other three groups received 0.01, 0.02, and 0.04 micromole of dexamethasone (DEX) on the 14th, 15th, and 16th day of fertilization respectively. After 48 hours of DEX injection, lenses were removed and their opacity were classified into five stages by stereomicroscope (Olympus SZX) to determine the type of cataract. Microscopic study was done after hematoxylin-eosin staining. Data were collected and put in frequency tables and analyzed by Fisher and Chi Square tests in SPSS software and P<0.05 was taken as the significant level. This study showed that use of 0.02 micromole of DEX on the 15th and 16th days of embryonic period can induce cataract in 95% of lenses. Also, use of 0.04 micromole of this drug on the 15th and 16th days of embryonic period can induce cataract in the 100% and 95% of chick lenses, respectively. Differences between cataract frequency of lenses in the experimental groups and control group were significant (P<0.0000(, but there were no significant differences of cataract frequency between the experimental groups. Injection of 0.04 micromole of DEX on the 15th day of fertilization, as a choice dose and timecan induce cataract in chick embryo.