Author: DanHung Nguyen
Diplopia is commonly referred to as “double vision”, or when patients report seeing two images instead of one. The ability to fuse the two distinct images from each eye is a complex one requiring both a central or sensory component as well as a neuromuscular or motor component. What is most concerning about sudden onset diplopia is that it can be the first manifestation of a systemic, muscular, or neurological disorder.
The first step in evaluating a patient with diplopia is a thorough history, including:
- Timing of onset: Sudden onset diplopia typically warrants urgent attention, whereas insidious onset diplopia tends to be less urgent.
- Binocular or monocular: When a patient complains of diplopia, an important distinction is whether it is monocular or binocular. If the patient doesn’t know (which they tend not to), instruct them to cover up either eye and see if the diplopia resolves. If the diplopia persists while covering one eye, than it is monocular diplopia and should be specified as being left or right-sided (see attached image).
- As a general rule, there are no emergent causes of “monocular” diplopia. Monocular diplopia is often a result of an irregularity with the cornea or lens, such as dry eye, astigmatism or cataract.
- Gaze dependent: Ask the patient if the diplopia is worse or more noticeable while looking in certain directions. The direction of gaze in which the double vision is the worst helps identify the culprit extraocular muscle(s) involved.
- Vertical vs Horizontal: Next ask the patient if the images are side by side (horizontal diplopia) or one above the other (vertical diplopia).
- Trauma: Diplopia from trauma could include either cranial nerve palsies or extraocular muscle entrapment from an orbital fracture. The latter is an emergency because an entrapped muscle is pinched in a way that cuts off its blood supply and quickly becomes ischemic and fibrotic.
- Vascular Risk Factors: Ischemic cranial nerve palsies are common in older patients, especially those with multiple vascular risk factors such as diabetes, hypertension, coronary artery disease, hypercholesterolemia and a history of smoking. An isolated cranial nerve palsy in an older patient with multiple risk factors typically doesn’t require neuroimaging but simply close monitoring.
- Variability: Diplopia that varies throughout the day or from day-to-day could indicate a decompensating intermittent strabismus (esotropia/exotropia) or myasthenia gravis.
- Headache: A non-specific sign but important clue in patients older than 65 years that would require you to include Giant Cell Arteritis in your differential. It could also be a sign of an intracranial compressive mass and thus would likely warrant some form of neuroimaging.
- Ophthalmic Exam: Do a complete eye exam including the 5 ophthalmic vital signs: visual acuity, careful pupillary exam, confrontational visual fields, motility (with special attention to limited motility in the gaze that is most symptomatic to the patient) and intraocular pressure check.
- Hirschberg testing – covered elsewhere in the curriculum.
- Ptosis and anisocoria suggests a possible 3rd Nerve Palsy
- Head tilt suggests a possible 4th Nerve Palsy.
Summary of Common Causes of Sudden-Onset Diplopia
- Decompensation of pre-existing phoria
- 3rd, 4th or 6th Cranial Nerve palsy: which can be compressive (neoplastic) or ischemic (vascular or vasculitis such as Giant Cell Arteritis)
- Myasthenia gravis
- Internuclear ophthalmoplegia (suggestive of a demyelinating condition such as multiple sclerosis)
- Thyroid eye disorders
- Multiple sclerosis
- “Diplopia (Double Vision).” April 13, 2017. http://emedicine.medscape.com/article/1214490-overview.
- “Red Flags in Neuro-ophthalmology.” Accessed September 17, 2017. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5365040/.
- Root, Timothy. OphthoBook. Amazon.com, 2012.