IPD Measurement for a patient

1. Measuring
Interpupillary Distance
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2. Anatomic pupillary distance
Distance from centre of one pupil to the centre of the
other pupil
Measured in millimeters(mm)
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3. Why to measureIPD?
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4. Instruments for measuringPD
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 P D ruler
Rodenstock Interpupillary gauge
Pupillometer (Elissor pupillometer)
Topcon Digital PD meter, Model PD 5
 C a l coast PD ruler

5. Instruments for measuringPD
Cal coast PD Meter Digital Essilor Pupillometer
PD ruler
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6. We can usethis
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7. Binocular Distance IPD
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8.  A : Between center of two pupil
 B : Right temporal pupillary margin to left nasal
pupillary margin
C:Right temporal limbus to left nasal limbus
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9. Technique
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Steps in Measuring binocular distance PD using a ruler
1.Dispenser position at 40 cm(16inches)
2.Dispenser closes right eye , patient fixes at dispensers open left eye
3.Dispenser lines up the ruler zero point on the subject’s right pupil, left pupillary
border or left limbus.
4. Dispenser closes left eye , patient fixes at dispensers open right eye
5.Dispenser reads scale directly in line with subject’s left pupil center ,left pupillary
border or left limbus
6.Dispenser closes right eye, opens left; subject fixates on dispenser’s left eye
7.Dispenser checks to make sure that zero point is still correct

10. Common difficulties andtheir
solution
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Problem Solution
1.Dispenser cannot close one eye Occlude the eye with free hand
2.Subject is strabismic Cover the subjects eye not been
observed
3.Subject is uncooperative child Take a canthus- canthus
measurement

11. Monocular DistanceIPD
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12. Technique
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Steps in Measuring monocular distance PD using a ruler
1.Measure the binocular PD using center of pupil as reference point
2.Before moving the ruler, note the reading at the center of the nose. This is
the monocular PD of oneeye
3.Stbtract this reading from the binocular reading to obtain the reading of
the other eye.

13. Near PD
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14. Near PD
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 Required for single vision reading glasses or for
multifocal lenses
 C a n be either measured or calculated

15. Technique
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Steps in Measuring near PD using a ruler
1.Dispenser places his/her dominant eye in front of the subject’s nose at the
subjects near working distance
2.Dispenser close the non-dominant eye
3.Subject fixates on dispenser’s open eye.
4.Dispenser places zero point of the PD ruler at the center of subject’s right
pupil.
5.Scale reading at the center of the subject’s left eye is read.

16. Calculating near PD
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 M o s t commonly usedis called three -quarter rule
 I t states that “for every diopter of dioptric demand, the
optical center of each reading lens, or the geometrical
center of each bifocal addition, should be insert
0.75(three-quarters) mm.”
Dioptric demand=inverse of reading distance in
meters
and is independent of actual bifocal addition power

17. Example
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 A spectacle lens wearer has the following
prescription:
OD: -1.00 DS
OS: -1.00 DS
Add: +2.00DS
Distance PD is 64mm.
What is the near PD at 40 cm?

18. Solution:
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Dioptric demand=1/0.40 =2.50 D
Insert per lens =2.50 x (3/4) =1.9mm
= 2.00mm (approx)
We need to deduct 2 mm from each lens i.e 4 mm from the distance IPD
Near IPD= 64mm- 64 mm
=60mm
Easiest Solution: Deduct 4 mm from distance PD for normal
working distance

19. Orthoptics as a career (ZG)