Please answer the question below

Retinol (vitamin A1) has a diterpene structure obtained mainly from -carotene taken in the diet. For the vision process to occur, retinol must first be converted by oxidation into the all-trans-retinal aldehyde and then by isomerization to cis-retinal. The latter joins to the opsin protein in the retina which is sensitive to light producing a new isomerization to the trans form (as shown in the schematic), thus translating the light energy into a change molecule, which triggers a nerve impulse in the brain. The following drug inhibits vision in normal mice Why?

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