The near point of convergence is defined as the point of intersection of the lines of sight of the eyes when maximum convergence is used. It is measured as the distance from this point of intersection to the midpoint between the eyes. Measuring the near point of convergence involves having a patient fixate on a target that is slowly moved toward them while maintaining fusion until their eyes can no longer converge or they see double. This distance is used to assess a patient's ability to converge their eyes for near vision tasks. A near point further than 10cm may indicate convergence insufficiency while one closer than 5cm suggests convergence excess.

1. Near Point
of
Convergen
ce

2. Definition:
Convergence

Is the only disjunctive movement that
is under conscious control. It is a
fusional movement that may be
stimulated by volition, disparate
stimulation, and accommodation.

3. The near point of convergence
(NPC)
 Is
the point of intersection of the lines
of sight of the eyes when maximum
convergence is utilized.

4. The near point of convergence
distance
 Is
the distance from the near point of
convergence to the midpoint of the
line connecting the center of rotation
of the eyes.

5. Clinical use:

The near point of convergence
distance is a measurement of the
maximum convergence ability of a
patient. Patients who have reduced
near point of convergence distances
may have visual and ocular
discomfort when performing near
point vision tasks.

6. Instruments:
 Penlight
 Transilluminator
 Millimeter
ruler
 RAF near point rule

7. Clinical procedure

The measurement of the near point of
convergence distance should be
performed in free space, the clinical
procedure is as follows:
1. The patient is seated comfortably with
the habitual spectacles prescription in
place.

8. 2. A PD ruler is held below the line of sight
with the zero point coincident with a line
that would pass through the center of
rotation of the eye

9. 3. Full room illumination should be used. A
small accommodative target or penlight is
placed about 40 cm in front of the patient’s
midline.

10. 4. The patient is encouraged to maintain
fixation on the target and report when it
doubles.
5. Slowly move the target (about 5cm/sec)
along the midline toward the patient.

11. 6. Note the fixation distance when one eye
loses fixation on the target, or the patient
reports diplopia. This is the near point of
convergence. The eye that maintains
fixation is the dominant eye.

12. 7. Measure the distance from the near
point of convergence to the center of
rotation of the eye for both the subjective
and objective near points of convergence.
8.Slowly move the target away from the
patient along the midline and ask the
patient to report when fusion occurs. This
is the recovery distance.
9. This is recorded as break/recovery
(e.g., 10cm/15cm).

13. 10. This procedure may be repeated
several times to determine the effect of
fatigue. When the near point of
convergence is repeated five or more
times, symptomatic patients often show
significant decreased convergence ability
with repeated testing, whereas
asymptomatic patients demonstrate little
change.

14. The near point convergence can also be
determined using a red lens technique.
The clinical procedure for this follows:
1. The patient is seated with the habitual
Rx in place.
2. A PD ruler is held below the line of sight
with the zero point coincident with a line
that would pass through the center of
rotation of the eye


15. 3. A penlight or transilluminator is held at
40cm from the patient, aimed at the bridge
of the nose. A transilluminator is more
desirable than a penlight, since the
brightness of the light source may be
modified for patient comfort. Place a red
lens in front of one of the patient’s eyes.

16. 4. Move the light toward the patient at a
rate of about 5cm/sec.
5. The patient is instructed, and constantly
encouraged to fixate the light and to report
when a red light and white light are seen.
6. Note the fixation distance when the
patient reports seeing a red and white light
or the clinician sees one eye turn out. This
is the near point of convergence. Measure
the distance from the near point of
convergence to the center of rotation of
the eye.

17. 7. Slowly move the light away from the
patient along the midline, and ask the
patient to report when the red and white
lights go together. This is the recovery
distance.
8. Record the result as before.
 Clinical significance
Patients with a near point of convergence
may express symptoms such as diplopia,
frontal headaches, decreased reading
comprehension, asthenopia, and,
occasionally, fatigue when undertaking
near tasks.

18. Clinical interpretation
 The near point of convergence is
expected to be 6 to 10cm.
 Closer than 5cm is considered to be
convergence excess.
 A remote near point of convergence is
suspected to have convergence
insufficiency.
