Reducing the diameter of a minus lens results in:

When the diameter of a minus lens is reduced, it leads to a decrease in the volume of the lens material used, which in turn typically results in a reduction in weight. The weight of a lens is influenced by both its thickness and the amount of material present. A smaller diameter lens means less surface area and less volume for the same prescription strength, which naturally contributes to a lighter lens overall.

In the context of lens design, while changes to the diameter can impact other parameters such as thickness or curvature, the primary effect of reducing diameter is the weight reduction. Therefore, selecting this answer accurately reflects an important aspect of lens manufacturing and design within optical practice.