What is interpupillary distance, what is interpupillary distance, and how is it measured?

Interpupillary distance. In short, it is the distance between the pupils of each eye. A normal person's eyes look at the same object, and the object is in the retina of both eyes.

and overlap in the visual center of the brain to become a complete, three-dimensional single object, this function is called binocular monovision. However, in the process of binocular monovision, infants and young children are easily affected by external factors, resulting in one eye fixing on the target, and the other eye is deviated and cannot look at the same target, so strabismus occurs. In medicine, the inward squint of the eyeball when looking at an object is called esotropia, which is commonly known as "cross-eyed".

Interpupillary distance is simply the distance between the pupils of each eye.

Due to biological heritability, the interpupillary distance varies from person to person. We usually go to the optical store to buy glasses according to the conventional IPD setting, the IPD is too large or too small is not appropriate, so it is necessary to go to a professional optical store or eye hospital to measure the IPD.

When wearing glasses, you need to measure the interpupillary distance, and the interpupillary distance is divided into: distal interpupillary distance, near interpupillary distance, and commonly used interpupillary distance. When measured, these three interpupillary distances are measured at a certain distance.

For patients with nearsightedness or farsightedness, this parameter needs to be considered when wearing glasses. That is, the distance between the centers of the two lenses (optical center distance) should match the interpupillary distance of the patient, otherwise, even if the prescription is correct, the patient will feel uncomfortable after wearing glasses and affect vision.

Interpupillary distance refers to the distance between the center of the pupil of your two eyes, and it is generally necessary to measure your interpupillary distance when you wear glasses, so that you can transmit light from the optical center of the lens to the eye when you see with glasses. Suggestion: Glasses need to be dispensed to a regular eye store to avoid eye discomfort.

First of all, the interpupillary distance is divided into binocular interpupillary distance and monocular interpupillary distance, binocular interpupillary distance is the pupil distance between the two eyes, and monocular interpupillary distance is the distance from the pupil of one eye to the "midline".

Interpupillary distance measurement is divided into near interpupillary distance and distant interpupillary distance, near interpupillary distance is the state of simulating the human eye when reading a book, reading a newspaper and watching a computer, the visual distance is 30cm, and the distant interpupillary distance is the state of simulating the human eye when looking far away, driving, sports, etc., and the visual distance is infinite.

Optometrists who are not particular about the use of interpupillary distance rulers use interpupillary distance rulers, which are generally only used to measure the distance between the two eyes, and cannot measure the distance between monocular and near interpupillary distances, or the measurement error is large.

Regular optical stores use a pupil distance meter for measurement, and there is a lens in the pupil distance meter to change the distance, simulating the state of near and far vision of the human eye, and there are also light shields that can block the light path for monocular measurement.

Optometrists who are not particular about the use of interpupillary distance rulers use interpupillary distance rulers, which are generally only used to measure the distance between the two eyes, and cannot measure the distance between monocular and near interpupillary distances, or the measurement error is large.

Ordinary single vision lenses only need to measure the distance interpupillary distance of both eyes, progressive multifocal lenses need to measure the interpupillary distance of one eye, and higher grade progressive lenses also need to measure the near and far interpupillary distance of one eye.

The function of measuring interpupillary distance is to locate the position of the optical center of the lens when mounting the lens, simply put, the optical center of the mounted lens should coincide with the pupil of the human eye, and the greater the error, the more uncomfortable it will be. There are two possibilities for this error, one is the error when measuring the interpupillary distance, and the second is the error when grinding the lens assembly. Personal experience, ordinary single vision lenses, the error is within 1mm, the human eye can adapt, the error is more than 1mm, the adaptation will be accompanied by dizziness, headache and other uncomfortable symptoms.

Of course, this also varies from person to person.

(1) The examiner and the patient should be seated facing each other at a distance of 40 cm, so that the eyes of the two people are kept at the same height.

2) The examiner holds the IPF or ruler with the thumb and index finger of the right hand, rests the rest of the fingers on the patient's cheek, and then places the IPR at the lowest point of the bridge of the nose and slightly inclines along the angle of the bridge of the nose.

3) The examiner closes the right eye, makes the patient look at the left eye, and uses the left eye to fix the "zero" position of the interpupillary distance ruler at the center of the pupil of the patient's right eye.

4) The examiner opens the right eye, still asks the patient to continue to look at the left eye, and uses the right eye to read the value in the center of the pupil of the patient's left eye.

5) Repeat steps (3) and (4) three times, taking the average of them as the near interpupillary distance.

The distance from the last vertex of the optical system to the intersection of the exit pupil plane and the optical axis.

In visual optical instruments such as telescopes and microscopes, the pupil of the human eye must coincide with the exit pupil to see the entire field of view, and the exit pupil distance must not be less than a certain value in order to avoid the eyelashes from colliding with the last side of the system and hindering the view.

Laboratory instruments or general ordinary instruments, which require a minimum exit pupil distance of about 6mm; In military optical instruments, considering the addition of eye patches and gas masks, the exit pupil distance is longer, generally about 20mm.

The exit pupil distance, that is, the exit pupil distance, refers to the distance between the eye and the last lens of the eyepiece when the entire field of view can be seen clearly, and the optical middle refers to the distance from the last vertex of the optical system to the intersection of the exit pupil plane and the optical axis.

Its size is very important for myopic patients who wear glasses, and although they can still see a clear image after removing the glasses and refocusing, it is inconvenient when it is necessary to repeatedly alternate between the naked eye and binoculars to observe the starry sky. In addition, if a person who wears astigmatism glasses takes off his glasses, no matter how he focuses them, he will not be able to see a clear image.

The interpupillary distance of a normal person is generally between 55 and 70 mm. If the interpupillary distance is large, the three-dimensional effect may be slightly better. If the interpupillary distance is small, stereoscopic vision may be a little worse.

In general, there is a difference in the interpupillary distance of each person, and there is a difference between the interpupillary distance and the near vision. When looking at a distance, the eyes are spread outward, and the interpupillary distance is slightly larger.

Definition of interpupillary distance and precautions for measurement

Interpupillary distance refers to the distance from the center of the pupil of the right eye to the center of the pupil of the left eye, in daily life, people often ask about the interpupillary distance of myopia, how to measure this, in fact, this hospital has that kind of pupil distance, which can be measured very accurately, and the operation is also very simple, it may be measured in a minute or two.

When measuring the interpupillary distance, it is necessary to pay attention to the line of sight of the examiner and the patient, and when measuring, it should always be kept at the same height, and if the interpupillary distance ruler is used to measure, do not touch the patient's eyelashes to avoid the reaction of closing the eyes.

And when the pupillary distance ruler determines the zero position, it must be held steady, so as not to move, let the patient look at the specified direction, do not let him drift, and generally measure 2 to 3 times repeatedly to get a more accurate value.

1. Interpupillary distance refers to the distance between the center point of the pupil of two eyes, for example, the center point of the pupil of the right eye to the center point of the pupil of the left eye, this distance is called the interpupillary distance, the interpupillary distance is mainly used for glasses, we must measure the interpupillary distance when preparing glasses, the center of the lens passes through the center point of the pupil, and the two points should be in the same state.

2. If the pupillary distance is not measured accurately, our lenses may not be accurately configured, so the interpupillary distance must be measured at the time of glasses.