Does Your PD Change With Age? What Science Actually Says

Does PD Change with Age

Last updated: January 2025 | Reading time: 8 minutes

Your eyeglass prescription changes over the years. Your reading vision declines. Even your eye color can shift slightly with age. So it seems reasonable to wonder: does your pupillary distance change too?

The short answer is: mostly no, with some important nuances. Let's examine what actually happens to PD across the human lifespan.

The Growth Phase: Childhood Through Adolescence

During the first two decades of life, PD absolutely changes—and changes significantly.

Infancy

Newborns have an average PD around 40-42mm. The skull is relatively small, the facial bones are underdeveloped, and the eye sockets haven't reached their adult proportions.

Rapid Early Growth

The first year of life sees dramatic PD increase—typically 4-5mm. The skull expands rapidly as the brain grows, and the orbits move apart accordingly.

Steady Childhood Growth

From ages 1-10, PD increases approximately 1-2mm per year on average:

Age 2: ~46-48mm
Age 5: ~49-51mm
Age 8: ~53-55mm
Age 10: ~55-57mm

This growth correlates with overall skeletal development. PD increases as facial bones elongate and the skull approaches adult dimensions.

Adolescent Completion

Growth slows during adolescence and typically completes by ages 16-19 for most individuals. Some late bloomers continue growing into their early 20s.

By the end of this phase, adult PD is established:

Adult females: typically 55-68mm
Adult males: typically 58-72mm

The Adult Plateau: Stability for Decades

Once skeletal maturity is reached, PD becomes remarkably stable. Studies following adults over many years find minimal change:

Research Evidence

A longitudinal study published in Ophthalmic and Physiological Optics tracked adult PD measurements over a 10-year period. The findings:

Mean change: 0.3mm (statistically insignificant)
95% of subjects: less than 1mm change
Changes detected were within measurement error margins

Another study examining 1,200 adult subjects found that PD measurements taken 5 years apart differed by an average of 0.4mm—again, essentially measurement noise rather than true biological change.

Why Stability Makes Sense

After the skull finishes growing, the bony orbits (eye sockets) don't change size. The distance between them is fixed by skeletal anatomy.

Unlike soft tissues that can shift and change, bone structure remains constant throughout healthy adult life. Your PD is fundamentally a measurement of bone structure, so it stays put.

The Elderly Question: Does PD Decrease?

Some research suggests a slight PD reduction in elderly populations (70+ years), though the findings are controversial.

What Some Studies Show

A 2012 study by Pointer found that adults over 70 had PD measurements averaging 1-2mm less than adults aged 20-40. This finding has been replicated in some other studies, though not all.

Possible Explanations

If the reduction is real, potential causes include:

Soft Tissue Changes: While bone structure doesn't change, the soft tissues around the eyes do. Aging causes loss of periorbital fat and changes in eyelid and brow position. This might subtly affect how pupils appear to be positioned, even if the underlying anatomy hasn't changed.

Measurement Artifacts: Elderly eyes may present measurement challenges—smaller pupils, cataracts, changes in corneal surface—that could introduce systematic errors.

Cohort Effects: Today's 80-year-olds grew up in different nutritional conditions than today's 40-year-olds. It's possible older generations genuinely have smaller average PD due to developmental differences, not aging per se.

Practical Implications

Even if elderly PD reduction is real, 1-2mm is at the edge of clinical significance. It wouldn't typically require remeasurement for someone who already has accurate adult PD on record.

When Apparent PD Changes Occur

Sometimes PD seems to change when it actually hasn't:

Measurement Variability

No measurement is perfectly precise. Two measurements of the same face on the same day might differ by 0.5-1mm due to:

Examiner technique
Patient positioning
Pupil size variations
Instrument calibration

Over years, accumulated measurement variability can make it seem like PD changed when the actual anatomy is stable.

Pupil Response Changes

Your pupils dilate and constrict based on light levels and other factors. As eyes age, pupil response changes:

Elderly pupils tend to be smaller (senile miosis)
Response to light may be slower
Maximum dilation decreases

These changes don't affect true PD (the anatomical distance between pupil centers) but might affect how easily that center is identified during measurement.

Strabismus and Eye Position

Some people develop or have worsening strabismus (eye misalignment) with age. This affects where the pupil appears to be positioned, potentially creating apparent PD changes that really reflect eye turning rather than anatomical change.

Do You Need to Remeasure?

For adults with previously accurate PD measurements:

Generally No: Your adult PD measurement remains valid indefinitely for practical purposes. A measurement from age 25 is usable at age 65.

Consider Remeasurement If:

You've never had professional measurement (verifying accuracy is worthwhile)
Your previous measurement seems inconsistent with new glasses' performance
You have conditions affecting eye position (strabismus, orbital issues)
You want monocular PD and only have binocular on record

For Children: Remeasure annually at minimum. Their PD is a moving target that affects how glasses fit.

The Prescription Paradox

Your glasses prescription often changes while your PD stays the same. This seems contradictory but makes sense:

Prescription changes reflect the eye's internal optics—lens flexibility, corneal shape, axial length. These soft tissue properties do change with age.

PD reflects facial bone structure—the distance between orbits in the skull. This skeletal measurement doesn't change after growth completes.

They're measuring different things with different biological bases.

Practical Takeaways

For Adults:

A single accurate PD measurement lasts your lifetime
Don't assume PD has changed just because your prescription did
Apparent changes are more likely measurement variability than real anatomical shifts
One quality measurement is better than repeated approximate ones

For Parents:

Children's PD changes annually until late adolescence
Regular remeasurement is part of proper pediatric eye care
Old PD measurements become outdated quickly

For Everyone:

If glasses don't seem right, consider whether PD was ever measured accurately—not whether it "changed"
Quality of measurement matters more than frequency

Bottom Line

Your pupillary distance is determined by your skull structure, and skulls don't change in adulthood. Once you know your adult PD, you know it forever.

This is actually good news—one measurement, properly done, serves you for decades. Unlike prescriptions that need regular updates, PD is a one-time investment in self-knowledge.

Get it right once, and you're set.

Don't know your adult PD? Measure it once with our free online tool and have the number for life.