Strabismus Surgery — MCQs
Which of the following is the most devastating complication of cataract surgery?
The most common type of strabismus seen in myopes is?
Which muscles are responsible for the elevation of the eye?
Which muscle is most commonly operated on during squint surgery?
Postoperative complications of cataract surgery are all except?
Action of the right superior oblique muscle is:
What is the treatment of choice for amblyopia?
Obstacles in concomitant squint are:
A patient presents with convergent squint in one eye. Vision in the squinting eye is 6/60, and vision in the non-squinting eye is also 6/60. What is the most appropriate next step in management?
The muscle first affected in thyroid ophthalmopathy is:
Strabismus Surgery Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following is the most devastating complication of cataract surgery?
- A. Endophthalmitis (Correct Answer)
- B. Optic neuropathy
- C. Retinal detachment
- D. Vitreous loss
Explanation: ***Endophthalmitis*** - **Endophthalmitis** is a severe intraocular infection following cataract surgery that can rapidly lead to irreversible vision loss or even loss of the eye if not promptly treated. - It is considered the most devastating complication due to its acute onset and high potential for **permanent vision impairment**. *Optic neuropathy* - While optic neuropathy can cause visual loss, it is a less common direct complication of cataract surgery compared to endophthalmitis. - It typically results from processes like **ischemia** or severe orbital inflammation, which are rare occurrences immediately post-cataract surgery. *Retinal detachment* - **Retinal detachment** is a serious complication, but generally occurs at a lower rate than endophthalmitis and often has a better visual prognosis with timely surgical repair. - It is a known risk, particularly in patients with pre-existing **myopia** or prior posterior capsular rupture, but not necessarily the *most* devastating. *Vitreous loss* - **Vitreous loss** is an intraoperative complication that increases the risk of other issues like retinal detachment, cystoid macular edema, and endophthalmitis but is not, in itself, the most devastating. - Proper surgical technique and management during the procedure can mitigate many of its long-term sequelae.
Question 2: The most common type of strabismus seen in myopes is?
- A. Intermittent Exotropia (Correct Answer)
- B. Intermittent Esotropia
- C. Esotropia Hypotropia complex
- D. Exotropia Hypotropia complex
Explanation: ***Intermittent Exotropia*** - Myopes often employ less **accommodative effort** for near tasks, leading to reduced **accommodative convergence** and an increased tendency for the eyes to drift outwards. - This outward deviation, or **exotropia**, is frequently intermittent, especially during fatigue or inattention. *Intermittent Esotropia* - **Esotropia** is an inward turn of the eye and is typically associated with **hyperopia** due to excessive accommodative effort leading to increased accommodative convergence. - While it can be intermittent, it is not the most common form of strabismus in myopic individuals. *Esotropia hypotropia complex* - This complex involves both an inward deviation (**esotropia**) and a downward deviation (**hypotropia**). - It is not typically seen in healthy myopes and would suggest other underlying **neurological** or **structural abnormalities**. *Exotropia Hypotropia complex* - While **exotropia** can be common in myopes, the additional presence of **hypotropia** (downward deviation) suggests a more complex strabismic picture. - This combination is not the most frequent strabismus seen in uncomplicated myopia and may indicate **cranial nerve palsies** or **orbital anomalies**.
Question 3: Which muscles are responsible for the elevation of the eye?
- A. SR and IO (Correct Answer)
- B. IO and SO
- C. IR and SR
- D. SO and IR
Explanation: ***SR and IO*** - The **superior rectus (SR)** muscle primarily elevates the eye, especially when the eye is **abducted** [1]. - The **inferior oblique (IO)** muscle also contributes to elevation, particularly when the eye is **adducted** [1]. *IO and SO* - While the **inferior oblique (IO)** elevates the eye, the **superior oblique (SO)** muscle is responsible for **depression** and **intorsion**, not elevation [1]. - Therefore, this combination does not exclusively perform elevation. *IR and SR* - The **superior rectus (SR)** muscle elevates the eye, but the **inferior rectus (IR)** muscle is responsible for **depression** of the eye, not elevation [1]. - This pair has opposing primary actions in vertical movement. *SO and IR* - Both the **superior oblique (SO)** and **inferior rectus (IR)** muscles are primarily involved in **depression** of the eye [1]. - The superior oblique also causes **intorsion**, and the inferior rectus causes **extorsion** [1].
Question 4: Which muscle is most commonly operated on during squint surgery?
- A. Medial rectus (MR) (Correct Answer)
- B. Lateral rectus (LR)
- C. Superior rectus (SR)
- D. Superior oblique (SO)
Explanation: ***MR*** - The **medial rectus (MR)** muscle is the most frequently operated on during squint (strabismus) surgery, especially in cases of **esotropia** (inward turning of the eye). - This is because esotropia is a common form of strabismus, and weakening the medial rectus muscle (recession) helps to correct the inward deviation. *LR* - The **lateral rectus (LR)** muscle is operated on less frequently than the medial rectus, primarily in cases of **exotropia** (outward turning of the eye). - While it can be strengthened (resection) or weakened (recession), esotropia is generally more prevalent, making the MR more commonly targeted. *SR* - The **superior rectus (SR)** muscle primarily elevates the eye and is typically involved in vertical strabismus or cyclovertical deviations. - Surgery on the superior rectus is less common than on the horizontal recti (MR and LR) because horizontal deviations are more prevalent. *SO* - The **superior oblique (SO)** muscle is responsible for intorsion, depression, and abduction of the eye; it is often involved in cyclovertical strabismus. - Surgery on the superior oblique is complex and less frequently performed than on the horizontal recti due to the lower incidence of isolated superior oblique dysfunction requiring surgical correction.
Question 5: Postoperative complications of cataract surgery are all except?
- A. Endophthalmitis
- B. Glaucoma
- C. Scleritis (Correct Answer)
- D. After cataract
Explanation: ***Scleritis*** - **Scleritis** is an inflammatory condition of the sclera, which is the white outer layer of the eye, and is generally not a direct postoperative complication of cataract surgery. - While it can occur in patients with systemic inflammatory diseases, it is not causally linked to cataract surgery itself. *Endophthalmitis* - **Endophthalmitis** is a severe infection of the intraocular fluids (vitreous and aqueous humor) and tissues, representing a rare but devastating complication of cataract surgery. - It typically presents with rapidly progressive vision loss, pain, and hypopyon (pus in the anterior chamber) within days to weeks post-surgery. *Glaucoma* - **Glaucoma** can develop or worsen after cataract surgery due to various mechanisms, such as inflammation leading to trabecular meshwork dysfunction, pupillary block, or retained lens material. - Postoperative intraocular pressure (IOP) elevation can result in optic nerve damage if not promptly managed. *After cataract* - **After cataract**, also known as **posterior capsule opacification (PCO)**, is the most common long-term complication of cataract surgery. - It occurs when residual lens epithelial cells proliferate and migrate onto the posterior lens capsule, causing blurring of vision months to years after surgery, and is typically treated with Nd:YAG laser capsulotomy.
Question 6: Action of the right superior oblique muscle is:
- A. Laevoelevation
- B. Laevodepression
- C. Dextroelevation
- D. Dextrodepression (Correct Answer)
Explanation: ***Dextrodepression*** - The **right superior oblique muscle** has three primary actions: **depression** (downward movement), **abduction** (outward/lateral movement), and **intorsion** (internal rotation) [1]. - In the context of conjugate gaze movements, the right superior oblique contributes to **dextrodepression** (downward and rightward gaze) by depressing and abducting the right eye. - When the eye is **adducted** (looking nasally toward the nose), the superior oblique acts as the **primary depressor**, making its depressive action most evident [1]. - The combination of **depression + abduction** of the right eye aligns with the dextrodepression movement pattern [1]. *Laevoelevation* - This refers to upward and leftward gaze movement, which involves **elevation** (not depression). - The right superior oblique is a **depressor**, not an elevator, so it does not contribute to laevoelevation. - This movement is primarily mediated by elevators like the **left inferior oblique** and other elevating muscles [1]. *Laevodepression* - This refers to downward and leftward gaze movement. - While the right superior oblique is a depressor, it causes **abduction** (lateral movement) of the right eye, moving it **rightward/temporally**, not leftward [1]. - Laevodepression is primarily controlled by the **left superior oblique** and other muscles that depress while moving the eyes leftward. *Dextroelevation* - This refers to upward and rightward gaze movement, involving **elevation**. - The right superior oblique is a **depressor**, not an elevator, so it cannot contribute to elevation movements. - This movement is mainly caused by elevating muscles like the **right inferior oblique** [1].
Question 7: What is the treatment of choice for amblyopia?
- A. Corrective spectacles
- B. Surgical intervention
- C. Occlusion therapy (Correct Answer)
- D. Convergent exercises for vision therapy
Explanation: ***Occlusion therapy*** - **Occlusion therapy** involves patching the stronger eye to force the weaker, amblyopic eye to work harder, thereby strengthening its neural connections. - This treatment is most effective when initiated during the **critical period of visual development** in childhood. *Corrective spectacles* - While essential for addressing **refractive errors** that may contribute to amblyopia, spectacles alone are often insufficient to resolve the amblyopia. - Spectacles primarily optimize the image quality on the retina, but don't directly address the **cortical suppression** of the amblyopic eye. *Surgical intervention* - **Surgical intervention** is typically reserved for correcting structural issues like **strabismus** (misalignment of the eyes) that contribute to amblyopia. - Surgery for strabismus aims to align the eyes, which can then be followed by occlusion therapy or other treatments to address the functional amblyopia. *Convergent exercises for vision therapy* - **Vision therapy exercises**, including convergent exercises, may be used as an adjunct to occlusion therapy or in cases of **convergence insufficiency**. - However, they are not the primary or solitary treatment of choice for amblyopia, which requires direct stimulation of the amblyopic eye.
Question 8: Obstacles in concomitant squint are:
- A. Sensory obstacles
- B. Motor obstacles
- C. Central obstacles
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - **Concomitant squint** involves **sensory obstacles** (e.g., amblyopia, eccentric fixation), **motor obstacles** (e.g., muscle imbalance, inadequate fusional vergence), and **central obstacles** (e.g., defective brain processing of visual information). - All these factors interact to cause and maintain the misalignment of the eyes. *Sensory obstacles* - These include conditions like **amblyopia** (lazy eye) due to suppression of the deviated eye's image, and **eccentric fixation**, where the fovea is not used for central vision. - While significant, sensory obstacles alone do not fully explain concomitant squint, as motor and central components are also crucial. *Motor obstacles* - These involve issues with the **extraocular muscles**, such as imbalance in muscle tone, or problems with the **neural control** of eye movements, leading to a deviation that is relatively constant in all gaze positions. - Motor obstacles are a key component but are often influenced by central and sensory factors. *Central obstacles* - These refer to problems within the brain's visual pathways and centers responsible for **fusion**, **vergence**, and maintaining **ocular alignment**. - Defective processing of visual input or an inability to maintain binocular vision can directly contribute to squint, highlighting the brain's role in coordinating eye movements.
Question 9: A patient presents with convergent squint in one eye. Vision in the squinting eye is 6/60, and vision in the non-squinting eye is also 6/60. What is the most appropriate next step in management?
- A. Glasses
- B. Refraction and treat underlying cause of poor vision (Correct Answer)
- C. Squint surgery
- D. Botulinum toxin
Explanation: ***Refraction and treat underlying cause of poor vision*** - When **both eyes have equally poor vision (6/60)** with a convergent squint, this suggests a **bilateral pathology** affecting visual acuity, not simply a refractive accommodative esotropia. - The **first step** is comprehensive **cycloplegic refraction** to determine if refractive error contributes to the poor vision. - **Equally important** is identifying the **underlying cause** of bilateral vision loss (6/60 in both eyes), which could be: - **Bilateral amblyopia** (though unusual to have equal severity) - **Uncorrected high refractive error** (hypermetropia causing accommodative esotropia) - **Cataracts** (congenital or developmental) - **Retinal pathology** or **optic nerve disorders** - Only after identifying and treating the underlying cause can definitive management of the squint be planned. *Glasses* - While **glasses** may be part of the treatment if refractive error is found, **prescribing glasses alone** without first performing refraction and investigating why both eyes have 6/60 vision is incomplete management. - This option is too narrow and doesn't address the need to identify the underlying pathology causing bilateral poor vision. *Squint surgery* - **Squint surgery** addresses ocular misalignment but does **not improve vision**. - Surgery should only be considered **after** refractive correction, treatment of amblyopia (if present), and management of any underlying pathology. - Operating without addressing the cause of poor vision would be premature. *Botulinum toxin* - **Botulinum toxin** is used for certain types of strabismus as a temporary or alternative to surgery. - Like surgery, it addresses alignment but **not visual acuity**. - The priority is to improve vision and identify the underlying cause before considering alignment procedures.
Question 10: The muscle first affected in thyroid ophthalmopathy is:
- A. Medial rectus
- B. Lateral rectus
- C. Inferior rectus (Correct Answer)
- D. Superior rectus
Explanation: ***Inferior rectus*** - The **inferior rectus** is the extrinsic eye muscle most commonly and earliest affected in **thyroid ophthalmopathy**, making it difficult to look upwards. - This involvement leads to **fibrosis** and **restriction**, causing **diplopia** and **proptosis**. *Medial rectus* - While the medial rectus can be affected in thyroid ophthalmopathy, it is typically involved later or less severely than the **inferior rectus**. - Involvement may lead to **difficulty with adduction** (moving the eye medially). *Lateral rectus* - The **lateral rectus** is generally one of the **least affected muscles** in thyroid ophthalmopathy. - Its involvement would primarily impact **abduction** (moving the eye laterally). *Superior rectus* - The **superior rectus** can be affected in thyroid ophthalmopathy, but it is less frequently the initial muscle involved compared to the **inferior rectus**. - Dysfunction would primarily cause **difficulty looking downwards**.
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