sudden inability to focus eyes together

Written by Dr.Bayat
Associate Professor of Orthopedic expert,Brigham Hostpital

Can't you focus both of your eyes on an object at the same time when looking at close objects?

Have you noticed that you have recently suddenly lost the ability to focus your eyes at the same time?

Do you know what blurred vision is?

Are you looking for information about Double Vision?

In this article, we intend to provide you with the answers to the above questions in a scientific and principled way.

If you have convergence insufficiency, read on.

convergence insufficiency is a term used by physicians when one's eye cannot work in unison.

This problem becomes apparent when you try to focus on an object that is close to you. The visual impairment you will encounter is double vision or so-called diplopia.

Most people with double vision are identified at the school age. These students do not have the ability to read the text accurately, and it is the parents or teachers of these children who discover and notice the slow learning and reading difficulties of these students. 







Read on to find out what the signs and symptoms of Convergence Disorder are.

Signs and symptoms will usually appear when you want to read a book or stare at an object near you.


Signs and symptoms include:

  • Fatigue and discomfort in the eyes (Eyestrain)
  • Difficulty reading, when you are looking at a piece of writing paper near you, words seem to float, for example, affected children are reluctant to do their homework perfectly.
  • You may experience headaches
  • Visual focus and focus on writing will be reduced
  • Double vision or so-called diplopia by doctors
  • Rubbing or closing one eye to create proper vision





The exact cause of convergence insufficiency is still unknown.

Some of the causes are:

Eyes Misalignment:

This is due to the involvement of the muscles that move the eyes when you look closely at an object.

That is, when you need to focus your eyes on a word in front of you, your eye moves outward.

It is interesting to know that the above problem will not be possible in routine eye examinations.

It is not found even in school-based routine screening.



Affected children will have difficulty in reading and it will be difficult for them to learn.

Diagnostic measures will be as follows:

  • An accurate history is obtained
  • Routine eye examinations are performed.
  • Measure the near point of convergence or NPC for short:

This test measures the distance at which your eyes can have full vision without double vision.

The examiner gradually brings a marked test page or a panlight close to your eyes from a certain distance to determine this distance.

  • Assess positive fusion all vergence or PFD for short:

In this test, you are supposed to read the text on a board in front of you until you get double vision, but this is done through the prism lenses.



  • pencil pushups:
  • computer vision therapy
  • reading glasses


Sudden double vision

Any sudden change in the visual field and visual condition requires immediate medical attention.

diplopia can involve one eye or two eyes.

With a simple test, monocular diplopia will be differentiated from binocular diplopia.


If the diplopia is binocular, the causes are:

  • Nervous injuries
  • Diabetes
  • Cranial nerve palsy
  • High blood pressure that is associated with nerve damage.


Myasthenia gravis, in which the function of the nerves with the muscles is disturbed.

In pediatric double vision, physicians should also consider strabismus.


monocular diplopia:

  • Severe astigmatism
  • Corneal surface changes such as keratoconus
  • Dry eyes
  • Cataracts


  • pterygium


Concluding remarks

We emphasize that sudden double vision can occur due to a serious vascular complication in the brain or an acute accident in the skull, so any acute disturbance in convergence should be investigated immediately by a physician.

Any sudden change in vision or visual acuity will require immediate examination. To prevent permanent vision loss and other life-threatening events and complications, immediate examination of any visual impairment is required.


Written by Dr.Bayat
Associate Professor of Orthopedic expert,Brigham Hostpital



  • Hwang JM, Wright KW: Combined study on the causes of strabismus after the retinal surgery.

  • Capó H, Guyton DL: Ipsilateral hypertropia after cataract surgery.

  • Kang SJ, Jang JH: Motility restriction after resection of an extraocular muscle.

  • Rutstein RP: Use of Bangerter Alters with adults having intractable diplopia.

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