Question:medium
A 65-year-old man with a history of hypertension and diabetes presents to the OPD with diplopia and squint. On examination, the secondary deviation is more than the primary deviation. Which of the following is the most likely diagnosis?
A 65-year-old man with a history of hypertension and diabetes presents to the OPD with diplopia and squint. On examination, the secondary deviation is more than the primary deviation. Which of the following is the most likely diagnosis?
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Secondary deviation greater than primary is the signature of a nerve palsy, common in a diabetic, hypertensive elder.
Updated On: Jun 23, 2026
- Concomitant squint
- Paralytic squint
- Restrictive squint
- Pseudosquint
Show Solution
The Correct Option is B
Solution and Explanation
Sign-spotting approach. Lock onto the single discriminating finding: secondary deviation is greater than primary deviation. In a concomitant squint the two are equal, so an inequality immediately marks the squint as incomitant, that is, paralytic.
Why does the secondary deviation overshoot? By Hering's law, when the patient fixes with the weak (paralysed) eye the brain pumps out extra innervation to drive it, and the same surplus floods the healthy yoke muscle, throwing the good eye far off line. Hence secondary > primary.
The clinical backdrop seals it: a 65-year-old with diabetes and hypertension is the textbook candidate for an ischaemic cranial nerve palsy (III, IV or VI) presenting as sudden diplopia and squint. Restrictive squint would come from mechanical tethering, and a pseudosquint has no true misalignment. So the diagnosis is paralytic squint. Ref: GPonline, Basics of Strabismus.
Why does the secondary deviation overshoot? By Hering's law, when the patient fixes with the weak (paralysed) eye the brain pumps out extra innervation to drive it, and the same surplus floods the healthy yoke muscle, throwing the good eye far off line. Hence secondary > primary.
The clinical backdrop seals it: a 65-year-old with diabetes and hypertension is the textbook candidate for an ischaemic cranial nerve palsy (III, IV or VI) presenting as sudden diplopia and squint. Restrictive squint would come from mechanical tethering, and a pseudosquint has no true misalignment. So the diagnosis is paralytic squint. Ref: GPonline, Basics of Strabismus.
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