I see double: the most common causes after 60 years

Double vision is called diplopia. That means seeing two images instead of one. “Binocular vision is not a passive phenomenon. It involves neural circuits. Each eye gives an image, which the brain will fuse,’ explains ophthalmologist Dr. Stephanie Zwillinger. Diplopia may be monocular, double with only one eye, or binocular. In the latter case, you see double when you have both eyes open, but you no longer see double when you close one eye.

Causes of diplopia differ if it is monocular or binocular. “To determine the origin of double vision, a complete eye examination is performed and a Lancaster test is performed, the reference test for the exploration of diplopia,” says the specialist.

What causes monocular diplopia?

Monocular diplopia is always ophthalmologic. This double vision can be caused by an irregularity on the cornea, it can be keratoconus (the eye sees double due to irregularities on the corneal diopters), an anomaly on the crystalline diopters (the cataract), an erroneous optical correction, complications of refractive surgery, strong astigmatism, dry eye etc.

Binocular diplopia, the brain involved!

When diplopia is binocular, it means that it is not ophthalmologic. “The brain fuses the two images, so it’s a neurological diplopia. The brain can no longer integrate the two images at the same time and superimpose them. Diplopia may be vertical or horizontal, and it may not appear in the primary position (ie, when both eyes are looking ahead). In some cases, it can exist only in the lateral gaze, the vertical gaze, or only from near or far,’ Dr. Zwillinger explains.

This diplopia may be constant, intermittent. It may also occur only in the evening, during exertion, or when tired, when changing position. It may also be masked by a drooping eyelid (called ptosis).

Causes of Binocular Diplopia After Age 60

There are many causes of diplopia. These may include muscle disorders (e.g. myasthenia gravis), tumor-induced nerve disorders, inflammatory disorders, increased intracranial pressure, infectious diseases, cranial nerve palsies, head trauma, and cavernous sinus thrombosis. When bilateral involvement is present, diplopia may be caused by Guillain-Barré syndrome or a rare pituitary disorder.

‘In people over 60 years of age, thyroid dysophthalmopathy (the thyroid is a common cause in diplopia) with proptosis, when the eye exits, may also be the cause. It can also be a sign of damage to the oculomotor nerves due to an aneurysm, a carotid dissection or an ischaemic stroke,’ adds the specialist. The latter reminds us that if double vision is associated with pain, it is always an emergency.