What do rx contact/eyeglass numbers mean in terms of myopia severity? how severe would an rx number of -3.75 (left eye) and -3.50 (right eye) be considered?

Moderate myopia: An Rx of -3.50 for the right eye and -3.75 for the left would not be considered severe myopia. It would be more moderate. In general, high myopia (severe) is considered to be -6.00 or more myopia. An Rx of -3.50 means that the farthest the right eye could see clearly without any correction (glasses or contacts) would be 1 meter divided by 3.50 or about 11.25 inches.