A patient has a horizontal visible iris diameter (HVID) of 12.5mm. What is the best choice of contact lens diameter?

When selecting a contact lens diameter, it's essential to consider the horizontal visible iris diameter (HVID) to ensure proper coverage and fit. The general guideline for choosing the lens diameter is to use a size that is slightly larger than the HVID, allowing for adequate movement and comfort.

In this scenario, the patient has an HVID of 12.5mm. The ideal contact lens diameter typically ranges from 1.0mm to 2.0mm larger than the HVID. Thus, the best choice from the options provided is 14.5mm. This diameter provides sufficient coverage over the iris while allowing for optimal movement and stability during blinking and eye movements.

Choosing a diameter that is too small could result in the lens not adequately covering the iris, leading to discomfort and potential complications. Conversely, a lens diameter that is too large could create excessive movement or edge instability, which may also be problematic for the patient. Therefore, selecting 14.5mm ensures a comfortable, well-fitting lens for the patient based on their specific measurements.