Which prism would be effective in helping EXOtropia?

To understand why a base in prism is effective in helping with exotropia, it's important to recognize the nature of this condition. Exotropia is characterized by a misalignment where one or both eyes turn outward. This outward deviation can cause issues with binocular vision and depth perception.

A base in prism works by shifting the visual line of sight towards the nose, effectively helping to align the eyes more closely. When a person with exotropia uses a base in prism, it provides a visual cue that encourages the outward-turned eye to turn inward, promoting better alignment and helping the brain to integrate visual information from both eyes more effectively. This assists in correcting the eye's position and enhancing the person’s ability to use their eyes together for clearer and more comfortable vision.

Other types of prisms, such as base out, base up, or base down, do not directly address the misalignment caused by exotropia, as they would either exacerbate the outward deviation or provide support that is not suitable for correcting the specific type of eye turn presented in exotropia. Therefore, the use of a base in prism is specifically targeted to provide the necessary correction for alignment in cases of exotropia.