Surgical Anatomy of Eye — MCQs

10 questions

All are parts of anterior segment of eye except?

A boy presents with diplopia and restriction of eye movements following blunt trauma to his eye. X-ray reveals blow out fracture of orbit. Which part of orbit is most likely damaged?

All of the following take part in the blood supply of the optic chiasm except:

All the following extraocular muscles are supplied by the 3rd nerve, except:

Isolated painful third nerve palsy is a feature of aneurysms of:

Expulsive hemorrhage in cataract surgery is from?

A 58-year-old male with a history of hypertension and smoking presents with sudden severe back pain and hypotension. A CT scan reveals a 7 cm ruptured abdominal aortic aneurysm (AAA). What are the key factors in deciding whether to proceed with endovascular aneurysm repair (EVAR) or open surgical repair?

Gold standard procedure to reduce recurrence of pterygium after surgical excision is

All of the following statements are true regarding cavernous sinus thrombosis EXCEPT:

Q10

All of the following are true for sympathetic ophthalmitis except which of the following?

Surgical Anatomy of Eye Indian Medical PG Practice Questions and MCQs

Question 1: All are parts of anterior segment of eye except?

A. Lens
B. Cornea
C. Aqueous humor
D. Vitreous (Correct Answer)

Explanation: ***Vitreous*** - The **vitreous humor**, or simply vitreous, is a transparent, gel-like substance that fills the space posterior to the lens and anterior to the retina, making it part of the **posterior segment** of the eye [3]. - Its main function is to maintain the shape of the eye and keep the retina in place. *Lens* - The **lens** is a transparent, biconvex structure located behind the iris and in front of the vitreous, making it a key component of the **anterior segment** [2]. - It works to focus light onto the retina, changing shape to alter the focal length of the eye. *Cornea* - The **cornea** is the transparent, outermost layer of the eye that covers the iris, pupil, and anterior chamber, clearly positioning it within the **anterior segment** [2]. - It plays a crucial role in focusing light into the eye. *Aqueous humor* - The **aqueous humor** is a clear, watery fluid located in the space between the cornea and the lens (the anterior and posterior chambers), which is definitively part of the **anterior segment** [1]. - It nourishes the cornea and lens and maintains intraocular pressure.

Question 2: A boy presents with diplopia and restriction of eye movements following blunt trauma to his eye. X-ray reveals blow out fracture of orbit. Which part of orbit is most likely damaged?

A. Inferior wall (Correct Answer)
B. Medial wall
C. Lateral wall
D. Superior wall

Explanation: ***Inferior wall*** - The **inferior wall** (orbital floor) is the most common site for **blowout fractures** because it is the weakest and thinnest part of the orbital bone. - A fracture here often causes **entrapment** of the inferior rectus muscle and/or periorbital tissues, leading to **diplopia** and **restricted eye movements**, especially on upward gaze. *Medial wall* - While relatively thin, the medial wall is less commonly fractured in isolation than the inferior wall in typical blowout injuries. - Fractures here might involve the **ethmoid sinuses** and can lead to **subcutaneous emphysema** or **epistaxis**, which are not reported as primary symptoms in this case. *Lateral wall* - The lateral wall is the **thickest and strongest** part of the orbit, making fractures of this wall less common in isolated blowout injuries. - Fractures here typically require significant force and are often associated with other facial bone trauma. *Superior wall* - The superior wall (orbital roof) is made of the **frontal bone** and is relatively thick, making fractures here uncommon. - Fractures of the superior wall carry a risk of **intracranial injury** due to proximity to the brain, which is not suggested by the patient's presentation.

Question 3: All of the following take part in the blood supply of the optic chiasm except:

A. Anterior cerebral artery
B. Middle cerebral artery (Correct Answer)
C. Anterior communicating artery
D. Internal carotid artery

Explanation: ***Middle cerebral artery*** - The **middle cerebral artery (MCA)** primarily supplies the lateral surface of the cerebral hemispheres, including portions of the frontal, parietal, and temporal lobes, but does not typically contribute to the direct blood supply of the **optic chiasm** [2]. - Its branches are more directed towards the **sylvian fissure** and cortical structures, rather than the deep midline structures like the optic chiasm [2]. *Anterior cerebral artery* - The **anterior cerebral artery (ACA)**, through its branches, including the **anterior communicating artery**, helps supply the anterior part of the optic chiasm [3]. - It forms part of the **Circle of Willis**, from which small perforating arteries can arise to supply deep brain structures [1]. *Anterior communicating artery* - The **anterior communicating artery (AComA)** connects the two anterior cerebral arteries and gives rise to small branches that directly contribute to the vascular supply of the **optic chiasm** [3]. - These branches are crucial for maintaining blood flow to this critical visual pathway structure. *Internal carotid artery* - The **internal carotid artery (ICA)** gives rise to the **ophthalmic artery** and the **anterior cerebral artery**, both of which contribute to the blood supply of the optic chiasm [3]. - Perforating branches from the ICA itself, particularly its terminal portion before bifurcating, can also directly supply the optic chiasm [3].

Question 4: All the following extraocular muscles are supplied by the 3rd nerve, except:

A. Superior rectus
B. Inferior oblique
C. Medial rectus
D. Lateral rectus (Correct Answer)

Explanation: ***Lateral rectus*** - The **lateral rectus** muscle is innervated by the **abducens nerve (cranial nerve VI)**, not the oculomotor nerve. [1] - Its primary action is to cause **abduction** of the eye (moving it laterally). [1] *Medial rectus* - The **medial rectus** muscle is one of the four rectus muscles supplied by the oculomotor nerve (cranial nerve III). - It is responsible for **adduction** of the eye, moving it towards the nose. [1] *Superior rectus* - The **superior rectus** muscle is also innervated by the oculomotor nerve (cranial nerve III). - Its main actions are **elevation** and adduction, and intorsion of the eye. [1] *Inferior oblique* - The **inferior oblique** muscle is one of the two oblique muscles supplied by the oculomotor nerve (cranial nerve III). - It contributes to **elevation** and abduction, and extorsion of the eye. [1]

Question 5: Isolated painful third nerve palsy is a feature of aneurysms of:

A. Aneurysm of the posterior communicating artery (Correct Answer)
B. Aneurysm of the anterior communicating artery
C. Aneurysm of the vertebrobasillary artery
D. Aneurysm of the ophthalmic artery

Explanation: ***Aneurysm of the posterior communicating artery*** - An aneurysm of the **posterior communicating artery (PCOM)** can compress the ipsilateral **oculomotor nerve (CN III)** as it exits the brainstem. - This compression typically affects the **superficial parasympathetic fibers** first, leading to a **dilated pupil** (mydriasis) along with ophthalmoplegia and ptosis, making the third nerve palsy "painful" and "isolated" without other focal neurological deficits. *Aneurysm of the anterior communicating artery* - Aneurysms of the **anterior communicating artery (ACoM)** are more commonly associated with **subarachnoid hemorrhage** and can cause **visual field defects** or **frontal lobe dysfunction**, but generally not isolated CN III palsy. - While rupture can lead to various neurological deficits, isolated painful third nerve palsy due to ACoM aneurysm is atypical. *Aneurysm of the vertebrobasillary artery* - Aneurysms in the **vertebrobasillar system** typically present with symptoms related to **brainstem compression** or ischemia, such as cranial nerve palsies beyond the third nerve, ataxia, or motor/sensory deficits. - Isolated third nerve palsy is an uncommon presentation for vertebrobasilar aneurysms compared to PCOM aneurysms. *Aneurysm of the ophthalmic artery* - **Ophthalmic artery aneurysms** are usually **intraorbital** and can cause **visual loss** due to direct compression of the **optic nerve (CN II)** or orbital structures. - They are less likely to cause isolated painful third nerve palsy, as the third nerve's course is generally not directly compromised by ophthalmic artery aneurysms.

Question 6: Expulsive hemorrhage in cataract surgery is from?

A. Vortex vein
B. Choroidal vein
C. Ciliary artery (Correct Answer)
D. None of the options

Explanation: ***Ciliary artery*** - Expulsive hemorrhage is a rare but devastating complication, typically resulting from the rupture of a **posterior ciliary artery** within the choroid. - This arterial rupture leads to a sudden, massive increase in intraocular pressure and extrusion of intraocular contents. *Vortex vein* - **Vortex veins** drain the choroid, and while their rupture could lead to hemorrhage, it is less likely to cause the highly pressurized, expulsive nature of a choroidal hemorrhage. - Hemorrhage from a vortex vein is generally less severe and less rapid in onset compared to arterial bleeding. *Choroidal vein* - **Choroidal veins** are part of the venous drainage system; bleeding from these vessels would typically be lower pressure and less likely to cause an expulsive hemorrhage. - Venous bleeds are generally slower and do not generate the rapid, violent pressure increase characteristic of expulsive hemorrhage. *None of the options* - This option is incorrect because the rupture of a ciliary artery is the direct cause of expulsive hemorrhage. - The other options are incorrect for the reasons stated above.

Question 7: A 58-year-old male with a history of hypertension and smoking presents with sudden severe back pain and hypotension. A CT scan reveals a 7 cm ruptured abdominal aortic aneurysm (AAA). What are the key factors in deciding whether to proceed with endovascular aneurysm repair (EVAR) or open surgical repair?

A. Patient's hemodynamic stability, anatomy of the aneurysm, and access to EVAR equipment (Correct Answer)
B. Patient's hemodynamic stability and anatomy of the aneurysm
C. Access to EVAR equipment and patient's age
D. Surgeon's experience with EVAR procedures

Explanation: ***Patient's hemodynamic stability, anatomy of the aneurysm, and access to EVAR equipment*** - **Hemodynamic stability** is crucial; unstable patients may benefit from more rapid intervention, potentially open repair, or require stabilization before EVAR. - The **anatomy of the aneurysm** (e.g., neck length, angulation, iliac artery access) dictates suitability for EVAR, as specific morphological criteria must be met for stent-graft placement. - **Access to EVAR equipment and trained personnel** is also a practical consideration for emergency intervention. *Patient's hemodynamic stability and anatomy of the aneurysm* - While **hemodynamic stability** and **aneurysm anatomy** are critical factors, access to specialized EVAR equipment and facilities is also a practical determinant of whether EVAR can even be attempted, especially in an emergent setting. - This option overlooks the logistical requirements necessary for performing an **EVAR procedure**. *Access to EVAR equipment and patient's age* - **Access to EVAR equipment** is important, but **patient's age** is generally less critical than factors like physiological status, comorbidities, and aneurysm morphology when deciding between EVAR and open repair for ruptured AAAs. - Younger patients may tolerate open surgery better, but age alone does not preclude EVAR if anatomy is suitable. *Surgeon's experience with EVAR procedures* - While **surgeon experience** is important for procedural success and outcomes, it is considered secondary to the immediate patient-centered and anatomical factors. - In emergency settings, the decision primarily hinges on the **patient's hemodynamic status**, **aneurysm anatomical suitability**, and **immediate availability of EVAR resources**, rather than being driven by surgeon preference based on experience alone. - Institutional protocols typically guide whether EVAR or open repair should be attempted based on the factors in the correct answer.

Question 8: Gold standard procedure to reduce recurrence of pterygium after surgical excision is

A. Thiotepa
B. Amniotic membrane grafting
C. Conjunctival autograft (Correct Answer)
D. Beta-radiation

Explanation: ***Conjunctival autograft*** - **Conjunctival autografting** involves transplanting a piece of healthy conjunctiva from the superior bulbar conjunctiva to the bare scleral bed after pterygium excision, acting as a barrier to fibrovascular proliferation. - This technique has consistently shown the **lowest recurrence rates** in comparative studies, making it the **gold standard** for preventing pterygium recurrence due to its high success rate and safety profile. *Thiotepa* - **Thiotepa** is an **antimetabolite** that inhibits DNA synthesis and cell proliferation, used topically post-excision to reduce recurrence by suppressing fibroblast activity. - While it can lower recurrence rates compared to simple excision, its efficacy is generally **less than conjunctival autografting**, and it carries risks of corneal toxicity and limbal stem cell deficiency. *Amniotic membrane grafting* - **Amniotic membrane grafting** involves placing processed amniotic membrane over the scleral bed, which has anti-inflammatory, anti-scarring, and pro-epithelialization properties. - It is an effective option, especially for **large pterygia** or for patients at high risk of recurrence, but its recurrence rates are generally **not as low as those achieved with conjunctival autografting**, and the graft can sometimes detach. *B- radiation* - **Beta-radiation** (strontium-90) is a form of adjuvant therapy applied to the scleral bed immediately after pterygium excision to inhibit fibroblast proliferation and reduce recurrence. - It is effective but associated with potential complications such as **scleral melt**, corneal scarring, and cataract formation, making it a less preferred option than conjunctival autografting, especially in primary cases.

Question 9: All of the following statements are true regarding cavernous sinus thrombosis EXCEPT:

A. Loss of jaw jerk (Correct Answer)
B. Loss of sensation around the eye
C. Sphenoid sinusitis is the most common cause
D. Inferior ophthalmic vein can spread infection from dangerous area of face

Explanation: ***Loss of jaw jerk*** - The **jaw jerk reflex** is mediated by the **trigeminal nerve (V3)** and its mesencephalic nucleus, which lies within the brainstem, superior to the cavernous sinus. - Cavernous sinus thrombosis primarily affects structures passing *through* or *adjacent* to the sinus, predominantly **cranial nerves III, IV, V1, V2, and VI**, but typically does not directly impact the brainstem structures responsible for the jaw jerk reflex in its localized progression. *Inferior ophthalmic vein can spread infection from dangerous area of face* - The **inferior ophthalmic vein** drains into the **cavernous sinus**, providing a direct route for infection from the **"dangerous area" of the face** (e.g., upper lip, nose, medial canthus). - This venous connection allows pathogens to enter the cavernous sinus and cause **thrombosis**. *Sphenoid sinusitis is the most common cause* - **Sphenoid sinusitis** is a common cause of **cavernous sinus thrombosis** due to the close anatomical proximity of the sphenoid sinuses to the cavernous sinuses. - Inflammation and infection in the sphenoid sinus can easily spread directly into the adjacent cavernous sinus. *Loss of sensation around the eye* - The **ophthalmic division (V1)** of the trigeminal nerve passes through the **cavernous sinus** and provides sensation to the forehead, upper eyelid, and **area around the eye**. - Compression or involvement of V1 due to thrombosis can result in **sensory deficits** in this distribution.

Question 10: All of the following are true for sympathetic ophthalmitis except which of the following?

A. Mostly results from a penetrating wound
B. Autoimmune etiology
C. Dalen-Fuchs nodules may be seen
D. Affects the injured eye (Correct Answer)

Explanation: ***Affects the injured eye*** - Sympathetic ophthalmia is a **bilateral, granulomatous panuveitis** that characteristically affects the **fellow, uninjured eye** (sympathizing eye) following trauma or surgery to the other eye (exciting eye). - The disease involves an immune response directed against ocular antigens, typically from the uveal tissue, in the uninjured eye. *Mostly results from a penetrating wound* - This statement is true; **penetrating ocular trauma** (e.g., from surgery or injury) is the most common trigger for sympathetic ophthalmia. - The exposure of uveal antigens from the injured eye initiates an autoimmune response. *Autoimmune etiology* - This statement is true; sympathetic ophthalmia is an **autoimmune disease** mediated by T-lymphocytes against uveal antigens. - The condition is characterized by a delayed hypersensitivity reaction against exposed uveal proteins. *Dalen Fuch's nodules may be seen* - This statement is true; **Dalen-Fuchs nodules** are characteristic histopathological findings in sympathetic ophthalmia. - These are accumulations of epithelioid cells and lymphocytes located between the retinal pigment epithelium and Bruch's membrane.

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