What type of charts use letters or symbols in calibrated heights to check visual acuity?

The correct choice is Snellen charts, which are specifically designed to measure visual acuity. These charts typically feature letters arranged in rows that decrease in size, allowing healthcare professionals to determine how well a patient can see at various distances. The Snellen chart is calibrated in such a way that each line corresponds to a specific level of visual acuity. For example, the top rows might have larger letters that a person with normal vision can see from a greater distance, while the smaller letters at the bottom are intended for patients with corrected vision.

While terms like "optometry charts," "vision charts," and "eye exam charts" might imply general tools for assessing vision or eye health, they do not specifically refer to the standardized system used for visual acuity testing as defined by the Snellen method. Therefore, the specificity of the Snellen chart makes it the most accurate answer.