Final answer:
The pupillary distance of a patient with vision in only one eye can be measured by using a corneal reflex or ruler method to estimate the measurement from the nose bridge to the functioning pupil and doubling it or determining the fitting height for the lens placement.
Step-by-step explanation:
To measure a patient's PD (pupillary distance) when they can only see from one eye, you would use an alternative method such as using a corneal reflex method or ruler method. The patient would gaze at a point directly in front of them while the examiner uses a PD ruler to measure the distance between the center of the bridge of the nose and the center of the pupil of the functioning eye.
This measurement can be doubled to estimate the total PD, or the fitting height can be used to determine the vertical position of a corrective lens relative to the one-eyed vision.