A 35-year-old male with bilateral asymmetrical ptosis and diplopia on watching TV or working on a laptop.Which test will be useful for diagnosis?
**Core Concept**
The patient's symptoms suggest an issue with the cranial nerves controlling eye movement, specifically the third cranial nerve (oculomotor nerve) which is responsible for controlling the movement of the eyeballs and eyelids. The patient's bilateral asymmetrical ptosis (drooping eyelids) and diplopia (double vision) on specific activities like watching TV or working on a laptop indicate a problem with the oculomotor nerve.
**Why the Correct Answer is Right**
Bilateral asymmetrical ptosis and diplopia can be indicative of a third cranial nerve palsy. The third cranial nerve controls the levator palpebrae superioris muscle, which elevates the eyelid, and the extraocular muscles responsible for eye movement. In third cranial nerve palsy, the patient may experience difficulty moving the eye laterally (outward) and may also experience ptosis due to weakness of the levator palpebrae superioris muscle. The **Hirschberg test** and **cover-uncover test** can be useful in diagnosing third cranial nerve palsy, but the most specific test is the **forced duction test**, which can confirm the diagnosis by demonstrating the mechanical restriction of eye movement. However, the question is asking for a useful test, and among the options provided, **B. Cover-Uncover Test** is a useful screening test for detecting third cranial nerve palsy.
**Why Each Wrong Option is Incorrect**
**Option A:** The Hirschberg test is used to estimate the amount of deviation of the visual axis and is not specific for third cranial nerve palsy.
**Option C:** The forced duction test is a more specific test for diagnosing third cranial nerve palsy, but it is not the first line of investigation.
**Option D:** The pupillary near reflex test assesses the response of the pupil to near vision and is not directly relevant to the diagnosis of third cranial nerve palsy.
**Clinical Pearl / High-Yield Fact**
Bilateral asymmetrical ptosis and diplopia on specific activities like watching TV or working on a laptop should raise suspicion for third cranial nerve palsy, and a thorough ophthalmological examination, including the cover-uncover test, should be performed to confirm the diagnosis.
**Correct Answer:** B. Cover-Uncover Test.