Why do I see double (Diplopia)?

Is double vision serious?

Double vision, also known as Diplopia, is a symptom where a person sees two images of a single object.

Yes, double vision can be serious, especially sudden onset as it may be a sign of a serious condition such as stroke or brain tumor.

Causes of double vision

Double vision can occur since young or suddenly during adulthood due to either cornea problems, muscles problems, nerve problems or brain problems. There are 2 types of double vision: Monocular and Binocular.

Monocular double vision

Double vision is still seen in one eye when the other eye is covered. Monocular double vision is more likely to be due to eye condition. The causes can be either (Most common to least common) :

  • High astigmatism
  • Cataract
  • Dry eyes
  • Keratoconus
  • IOL (artificial lens put in during cataract surgery) decentration
  • Bleeding at the back part of the eyes

Binocular double vision

The double vision is seen when both eyes are opened and resolves when one eye is closed. Binocular double vision is deemed to be more serious than monocular double vision as they can be due to neurological conditions, systemic disorder or even brain diseases which is life threatening. This can be caused by either (Most common to least common) :

  • Strabismus (Misalignment of eyes)
  • Surgical Trauma
    • Cataract surgery is the most common surgical case that result in double vision
  • Myasthenia gravis
  • Graves’ disease
  • Multiple sclerosis
  • Brain tumor
  • Migraine
  • High pressure in the brain due to bleeding, infection or trauma
  • Stroke in certain part of the brain

Sudden onset of double vision

Sudden development of double vision is dangerous and can be life threatening. It can be due to brain problem such as brain tumor. There can be other symptoms accompanied with double vision, such as headache, nausea. These can be signs of high pressure in the brain due to head trauma or brain tumor which is a matter of life and death. If you experience sudden onset of double vision, proceed to the A&E department immediately.


The treatment for double vision varies depending on what is causing the double vision. Treatment can be:

  • Using medications to treat medical conditions that is causing double vision
  • Patching
  • Eye exercise (only for certain condition)
  • Fresnel Stick-on prism
    • For prisms that are too high to be grind into the lenses, a stick-on prism will be paste on the lenses.
  • Grind prisms into glasses (available at Evershine Optical)
  • Surgery

Surgery is usually the last option for many people. If the double vision is not seious, as optometrist, we try to treat it optically. Prism is most commonly used. The amount of prism to resolve your double vision is determined after a series of binocular vision tests. You will get a feel of how the prism feels like before we put them into your glasses.

In some cases, prisms might not be able to relieve double vision and will make it difficult for patient to walk. To relieve the double vision temporarily before visiting the eye specialist, we can patch one of his eyes or prescribe him an opaque or a high plus contact lenses for one eye.

Some high myopes might see double after doing cataract surgery on just one eye due to the different refractive power in each eye. This results in different image size perceived by each eye, therefore causing double vision. To relieve the double vision temporarily before the next cataract surgery on the other eye, contact lens can be prescribed to reduce the difference in image size.

Binocular Vision Eye Examination @ Evershine Optical

If you present double vision at Evershine Optical, optometrists at Evershine Optical will ask a series of questions such as when did you first notice double vision, whether is it one eye or both eyes and more before conducting a thorough eye examination to find out the cause of the double vision:

  1. Refraction test
    • To check eye power for both distance and near
  2. Eye health check
    • To assess the health of the front and back part of the eyes
  3. Binocular vision test
    • To check the alignment, strength, flexibility and focusing ability of the eyes

Afterwards, we will share the findings with you. We will refer you to see an eye specialist if the cause of the double vision is serious, cannot be treated by an optometrist or the amount of prisms needed to relieve the double vision is too high to be grind into the spectacle lenses. If it is an urgent case such as high intracranial pressure, we will refer you urgently to the A&E.

For non-urgent cases or patient refuse strabismus surgery and the amount of the prisms can be grind into the lenses, we are able to test how much prisms is needed to relieve the double vision and prescribe accordingly. After dispensing the prism in glasses, we will do follow-up to ensure that the patients are able to cope well with the glasses, especially for first time wearer.

Double vision encountered @ Evershine Optical

Evershine Optical do encounter customers coming in complaining that they see double vision. Just this month, a lady came in wanting to do a new pair of spectacle. During our conversation, she told us she have been experiencing double vision when she look towards her left gaze. It only started after she had her cataract surgery.

We did a comprehensive eye examination to find out what might be the cause of her seeing double image. We realized that when she look towards the left, both of her eyes will jerk slightly and she will see double image. The cause of her double vision is most likely due surgical trauma to her extraocular muscles. To relief her double vision, we gave her prisms in her new glasses. With her new glasses prescribed with prisms, she feels more comfortable and do not experience any more double vision when looking at her left gaze.

We also have existing customers who experience double vision for years and have been wearing glasses prescribed with prisms to relief their double vision. One of our customers experience double vision due to misalignment of his eyes and have been using prism in glasses with us since 2005. He was referred to an eye specialist and was given an option to do eye surgery by the eye specialist.

However, due to personal reasons, he did not opt for eye surgery. Instead, he continue wearing glasses with prisms to correct his double vision. Just this month, he came back to do a pair of new lenses with prisms and we did a comprehensive eye examination to assess whether more prisms is needed. Thankfully, there was no change and he still feels comfortable with his current prescription.

Few years ago, we also had a lady who came in with a doctor’s prescription to make prism to correct her double vision. However, upon further checking, we referred her to Dr Leo Seo Wei for a second opinion. A MRI scan was done and the lady was found to have brain tumor which caused her double vision. You can read the post here .

If you encounter double vision, do make an appointment with us. https://evershineoptical.com.sg/contact-us/


  1. Dubow B. (2019). Double Vision and Diplopia. All About Vision.
  2. Bainter P.S. (2020). Double Vision (Diplopia). MedicineNet.