The image shows a
PD Ruler (Pupillary Distance Ruler), which is used to measure the distance between the centers of your pupils. This measurement is important for fitting eyeglasses correctly.
Looking at the ruler:
- The left side has markings from 0 to 60 mm (for the right eye, labeled “R”).
- The right side also has markings from 0 to 60 mm (for the left eye, labeled “L”).
- In the center, there’s a nose bridge cutout — you place this over the patient’s nose.
- You look through the holes and align the zero mark with the center of one pupil, then read where the other pupil lines up on the opposite scale.
But here’s the key:
this tool doesn’t give a single number by itself. It’s designed so that when you use it properly (placing it on someone’s face and looking through the windows), you can read the PD directly off the scales.
Since no actual person or alignment is shown in the image, and no specific reading is indicated (like an arrow pointing to a number), we cannot extract a numerical PD value from this static image alone.
However — if this is part of a homework problem asking *what this tool measures*, then the answer is:
> Pupillary Distance (PD) — the distance in millimeters between the centers of the two pupils.
If the question was meant to ask “What does this device measure?” → Answer: Pupillary Distance.
If the question was “Read the PD from this image” → There’s no measurable value because no alignment or subject is shown.
Given typical educational contexts, and since the user uploaded only the image without additional text, I assume the intent is to identify what the tool is for.
Final Answer:
This tool measures pupillary distance (PD), which is the distance between the centers of the two pupils, usually in millimeters.
Parent Tip: Review the logic above to help your child master the concept of printable pupillary distance ruler online.
