What does the term Hyperphoria indicate?

Hyperphoria refers specifically to a tendency of one eye to drift upward relative to the other eye. This condition is a form of eye misalignment that occurs when the muscles responsible for controlling eye movements are not working in perfect harmony. The term "phoria" generally indicates a latent deviation, meaning that the misalignment is not always present—only noticeable during specific conditions, such as when the patient is not focusing on something or when occlusion is applied to one eye.

The other options describe different concepts. A definite turning upward of the eye would imply a more pronounced condition, often referred to as hypertropia, which is a manifest deviation rather than a tendency. The mention of requiring a plus lens in one eye typically relates to issues with refraction or the need to address an imbalance in vision strength, which does not apply directly to hyperphoria. Similarly, the phrase "a functional eye that becomes a non-seeing eye" suggests a pathological condition or severe visual impairment, which is not what hyperphoria signifies. Therefore, defining hyperphoria as a tendency of the eye to turn upward captures the essence of this condition accurately.