Does the pupillary distance and axis have to be exact?
MAR 23, 2024
Question:
Do the pupillary distance (PD) and axis measurements have to be exact to not cause headache and nausea?
Answer:
The prescribed axis (the correction for astigmatism or an irregularly shaped lens) may vary due to the subjective answers given by a patient during a refractive exam.
However, you would want the prescribed axis to be close to the actual axis of your astigmatism. If the refraction is off or the glasses are off then it can cause the symptoms you describe. But the degree of symptoms are dependent on the severity of the astigmatism and the degrees that the axis is incorrect. For example, if you have 5 diopters of astigmatism having an incorrect axis by a few degrees may be problematic but if you have one diopter of astigmatism you may tolerate an axis off by ten degrees or more.
Regarding the pupillary distance (or PD, the distance between the pupils), that should be able to be measured close to the exact amount. If there is an error in the PD the degree of symptoms would again be dependent on the strength of the prescription and the degree of error. Progressive spectacles in a high plus or minus number may be problematic if the PD is off by a small amount. Single vision glasses in a low number may not cause symptoms even if the PD is off significantly.