Questioning Diplopia: A Clinical Guide for Orthoptic Students

Assessing double vision will be a large part of your role as an Orthoptist. In this post we will outline how taking a detailed and focused case history can help you lay the foundations for your diagnosis as well as outlining what each question can reveal. 

When asking questions in your case history, your aim is to narrow down the likely causes, possible diagnoses and any potential red flags. This post will guide you through the clinical reasoning process, so you can approach each case with clarity and confidence.

Step 1: Determine the Type of Diplopia

Before diving deep into history, always clarify whether the diplopia is binocular or monocular.

Binocular diplopia disappears when either eye is closed. 

Monocular diplopia persists when one eye is closed and is not typically orthoptic in origin. Causes include:

• Corneal irregularities

• Lens issues (e.g., cataract)

• Retinal or cortical disturbances

Refer monocular diplopia to general ophthalmology or eye casualty for further medical work-up. Your role as an Orthoptist is to identify it, not diagnose it.

Step 2: Take a Focused History

Once you’ve established the diplopia is binocular, the next step is to gather a structured and purposeful history. Here’s how:

1.Onset: Sudden vs Gradual

• Sudden 

• Patient reports double vision came on suddenly, they may have woken up with it for example. Usually they present within a short time frame of onset - a few days to a few weeks after onset. 

• Raises suspicion of acute neurological or vascular causes (e.g. cranial nerve palsy, stroke).

• Gradual 

• Patient may report worsening double vision that has been there for a while, a few months to a few years

• May suggest decompensating phoria, thyroid eye disease, or myasthenia gravis.

2. History of Illness or Injury

Ask about recent viral illnesses, head trauma, or surgeries. These can indicate underlying neuromuscular or inflammatory conditions.

3. Direction and Duration

Horizontal vs vertical vs diagonal diplopia can help you localise the affected muscle or nerve.

4. Is it constant or intermittent?

Constant diplopia may point to a mechanical or neurological restriction.

Intermittent cases could indicate:

• Myasthenia Gravis (MG)

• Decompensated phoria

• Giant Cell Arteritis (GCA)

5. Associated Symptoms

Always ask about any associated:

• Ptosis

• Headaches

• Limb weakness or numbness

• Facial pain

• Jaw claudication

These symptoms may suggest neuromuscular or systemic conditions.

6. Systemic Red Flags

Look out for:

• Anisocoria (unequal pupils)

• Proptosis

• Nystagmus

• Reduced acuity

These are urgent signs and may indicate orbital disease, brainstem pathology, or compressive lesions. Escalate appropriately.

Step 3: Assess Concomitancy

Once you’ve taken a detailed history and confirmed binocular diplopia, identify whether the deviation is:

1.Concomitant - Same angle of deviation in all positions of gaze.

Often seen in:

• Longstanding childhood strabismus

• Decompensated phoria

New-onset concomitant diplopia must be evaluated carefully to rule out subtle pathology. If associated with red flags or concerning history, consider further imaging and referral to Eye Casualty.

2. Incomitant - Varying angle of deviation in different gaze positions.

Often points to:

Mechanical restriction (e.g., thyroid eye disease, orbital trauma) 

Neurological restriction (e.g., CN III/IV/VI palsy) - Requires full neuro workup, including neuroimaging.

3. Chronic vs Acute Diplopia

Always ask if the diplopia is longstanding:

Longstanding, stable diplopia with a known history may not require urgent action.

However, re-emerging diplopia in older adults or with new symptoms should not be dismissed.

Diplopia is more than just a symptom, it’s a potential window into complex underlying disease. Your job as an Orthoptist is not just to measure the deviation, but to ask the right questions, listen, and recognise when to escalate.

Remember these key questions when faced with a diplopia case:

1. Is it monocular or binocular?

2. Is it constant or intermittent?

3. Is the deviation concomitant or incomitant?

4. Are there red flag symptoms or systemic signs?

Mastering the art of questioning diplopia is a skill that develops over time, but with each case, you’ll grow sharper, more confident, and more capable of delivering high-quality care.