If a surface is excessively flat, how will the mires in the keratometer appear?

When a surface is excessively flat, the mires observed in the keratometer will appear large. This occurs because a flatter corneal surface will produce a wider, more dispersed reflection of the mires compared to a more pronounced curvature. The keratometer measures the curvature of the front surface of the cornea, and flatter surfaces generally result in a broader area of measurement. Therefore, the mires will be more spread out, leading to an impression of being larger.

Additionally, it's important to understand that the relationship between corneal curvature and mire appearance is integral to determining the appropriate contact lens fit. A flatter cornea may require a different lens design than a more curved one, and recognizing how the mires change with corneal shape is a key aspect of interpreting keratometry readings effectively.