Ophthalmic Surgery Practice Questions

Q: Which technique involves blocking the facial nerve at the neck of the mandible?

O'Brien's block. **Explanation:** In ophthalmic surgery, **facial nerve blocks** are essential to achieve **akinesia of the orbicularis oculi muscle**, preventing the patient from squeezing their eyelids during intraocular procedures (like cataract surgery). **1. Why O’Brien’s Block is Correct:** The **O’Brien technique** is a "malar block" where the facial nerve is blocked at the level of the **neck of the mandible**. The needle is inserted just anterior to the tragus, over the condyle of the mandible. The anesthetic is injected as the needle is withdrawn, targeting the nerve as it passes over the condyloid process. **2. Analysis of Incorrect Options:** * **Van Lint’s Block:** This is a localized block where the anesthetic is injected at the **outer margin of the orbit** (lateral orbital rim). It targets the terminal branches of the facial nerve rather than the main trunk. * **Atkinson’s Block:** This involves injecting along the **inferior edge of the zygomatic bone**. It targets the superior (zygomatic) branches of the facial nerve. * **Nadbath Block:** This is a "basal block" where the nerve is blocked at the **stylomastoid foramen**, between the mastoid process and the ramus of the mandible. While effective, it carries a higher risk of respiratory distress or vocal cord paralysis due to proximity to other cranial nerves (IX, X, XI). **High-Yield Clinical Pearls for NEET-PG:** * **Facial Nerve (CN VII):** Provides motor supply to the muscles of facial expression, including the orbicularis oculi. * **Akinesia vs. Anesthesia:** Facial blocks provide *akinesia* (loss of movement), whereas retrobulbar or peribulbar blocks provide both *anesthesia* (loss of sensation) and akinesia of the extraocular muscles. * **Complication:** A common side effect of the O'Brien block is temporary pain at the site of injection due to the proximity of the temporomandibular joint.

Q: Peribulbar injection is given in which space?

Periorbital space. **Explanation:** **Peribulbar anesthesia** is a regional block used commonly in ophthalmic surgeries (like cataract extraction). The injection is placed into the **periorbital space**, which is the area within the orbit but **outside the muscle cone** (extraconal space). 1. **Why Option C is correct:** The goal of peribulbar anesthesia is to deposit local anesthetic into the extraconal orbital fat. From here, the drug diffuses into the muscle cone to reach the ciliary nerves and cranial nerves (III, IV, and VI), resulting in both anesthesia and akinesia. Unlike retrobulbar blocks, it carries a lower risk of optic nerve injury because the needle remains outside the muscle cone. 2. **Why other options are incorrect:** * **Anterior chamber (A):** This is the fluid-filled space between the iris and the innermost corneal surface. Injecting here is reserved for intracameral medications, not regional anesthesia. * **Subtenon space (B):** This lies between the Tenon’s capsule and the sclera. A "Sub-Tenon block" is a distinct technique using a blunt cannula, offering a faster onset than peribulbar but involving a different anatomical plane. * **Subperiorbital space (D):** This is the potential space between the orbital bone and the periosteum (periorbita). Injecting here would not allow the anesthetic to diffuse effectively to the globe or extraocular muscles. **High-Yield Clinical Pearls for NEET-PG:** * **Needle used:** Usually a 25-gauge, 25mm (1 inch) Atkinson needle. * **Site of injection:** Typically at the junction of the lateral one-third and medial two-thirds of the lower orbital rim. * **Advantage:** Lower risk of retrobulbar hemorrhage and globe perforation compared to retrobulbar blocks. * **Disadvantage:** Slower onset of action and may require a larger volume of anesthetic (6–10 ml).

Q: Retrobulbar injection is given in which space?

Inside muscle cone. **Explanation:** **Retrobulbar anesthesia** involves the injection of local anesthetic (typically a mixture of Lidocaine and Bupivacaine) directly into the **intraconal space** (inside the muscle cone). The muscle cone is formed by the four recti muscles originating from the Annulus of Zinn. 1. **Why Option A is Correct:** The primary goal of a retrobulbar block is to deposit anesthetic near the **ciliary ganglion** and the **cranial nerves (III, VI, and branches of V)** that reside within the muscle cone. This achieves rapid sensory anesthesia of the globe and complete akinesia (paralysis) of the extraocular muscles. 2. **Why Options B, C, and D are Incorrect:** * **Outside muscle cone (Peribulbar):** This describes a peribulbar injection. It is safer but requires a larger volume of anesthetic and more time to achieve effect as the drug must diffuse into the cone. * **Subtenon space:** This involves injecting anesthetic between the Tenon’s capsule and the sclera. It is a popular alternative that avoids the risks of "blind" needle penetration into the cone. * **Subperiosteum:** This space lies between the orbital bone and the periorbita; it is not a standard site for ophthalmic regional anesthesia. **High-Yield Clinical Pearls for NEET-PG:** * **Nerve spared:** The **Trochlear nerve (IV)** is the only motor nerve to the extraocular muscles that remains **outside** the muscle cone. Therefore, the Superior Oblique muscle may retain some function after a retrobulbar block. * **Complications:** The most serious complications include **retrobulbar hemorrhage**, globe perforation, and **"brainstem anesthesia"** (due to accidental injection into the optic nerve sheath, allowing the drug to travel to the midbrain). * **Classic Sign:** Successful block results in anesthesia, akinesia, and a "fixed" eye.

Q: In cataract surgery, when are spectacles typically advised post-operation?

6 weeks. **Explanation:** The correct answer is **6 weeks (Option A)**. **Why 6 weeks is correct:** Following cataract surgery (whether SICS or Phacoemulsification), the corneal incision undergoes a physiological healing process. It typically takes about **6 weeks** for the surgical wound to stabilize and for the resultant **post-operative astigmatism** to become permanent. Prescribing spectacles before this period is avoided because the refractive power of the eye fluctuates as the wound heals and sutures (if any) settle. By the end of 6 weeks, the "refractive stability" is achieved, ensuring the prescription remains accurate for the long term. **Why other options are incorrect:** * **10, 12, and 14 weeks (Options B, C, D):** While the eye continues to refine its strength over months, waiting this long is clinically unnecessary. Delaying spectacles beyond 6 weeks unnecessarily prolongs the patient's visual rehabilitation period. In modern Phacoemulsification (micro-incision), stability is often reached even earlier, but 6 weeks remains the standard teaching and gold-standard duration for conventional surgery. **High-Yield Clinical Pearls for NEET-PG:** * **Refractive Stability:** The primary goal of waiting 6 weeks is to allow for the stabilization of **Surgically Induced Astigmatism (SIA)**. * **Phacoemulsification vs. SICS:** In sutureless Phacoemulsification, some surgeons perform refraction at 2–3 weeks due to faster healing, but for exam purposes, **6 weeks** is the universal answer. * **Steroid Tapering:** The 6-week mark usually coincides with the completion of the post-operative topical steroid tapering schedule. * **Aphakia:** If a patient is left aphakic (no IOL), the standard prescription is **+10D sphere** with additional cylinders, also prescribed at 6 weeks.

Q: Deep anterior lamellar keratoplasty is indicated in:

Superficial corneal opacities. **Explanation:** **Deep Anterior Lamellar Keratoplasty (DALK)** is a partial-thickness cornea transplant procedure where the diseased corneal stroma is removed down to the level of Descemet’s membrane (DM) and the endothelium. The patient’s own healthy endothelium and DM are preserved. **Why Option D is Correct:** DALK is indicated for conditions involving the **anterior and mid-to-deep stroma** where the **endothelium is healthy and functional**. While "superficial corneal opacities" can be treated with simpler lamellar techniques, they are a valid indication for DALK if the scarring extends into the deeper stroma. Other classic indications include Keratoconus (with no history of hydrops), corneal dystrophies (e.g., Macular, Lattice), and scars from healed keratitis. **Why Other Options are Incorrect:** * **Option A & C:** Diseases involving **endothelial damage** (e.g., Fuchs' Dystrophy) or **Bullous Keratopathy** (caused by endothelial pump failure) are contraindications for DALK. These require either **Penetrating Keratoplasty (PKP)** or **Endothelial Keratoplasty (DSEK/DMEK)**. * **Option B:** **Full-thickness opacities** involve all layers, including the endothelium. Replacing only the anterior layers would leave the posterior scarring intact, resulting in poor visual outcomes. These require a PKP. **High-Yield Clinical Pearls for NEET-PG:** * **Advantage of DALK:** The primary benefit is the **elimination of endothelial graft rejection**, which is the most common cause of failure in full-thickness grafts. * **"Big Bubble" Technique:** This is the most popular surgical method (described by Anwar) to separate the stroma from the Descemet’s membrane using air. * **Key Contraindication:** Any condition with a damaged or diseased endothelium. * **Comparison:** If the question asks for the treatment of choice for **Keratoconus**, DALK is now preferred over PKP because it preserves the host endothelium.

Q: Which of the following instruments is NOT used in intracapsular lens extraction?

Phaco-emulsifier. **Explanation:** The core concept here is distinguishing between **Intracapsular Cataract Extraction (ICCE)** and **Extracapsular Cataract Extraction (ECCE)** techniques. **Why Phaco-emulsifier is the correct answer:** Phacoemulsification is a modern form of **ECCE**. It uses ultrasonic energy to fragment the lens nucleus *within* the lens capsule, followed by aspiration. In ICCE, the entire lens along with the intact capsule is removed; therefore, a machine designed to break up the lens inside the capsule is fundamentally incompatible with the ICCE technique. **Analysis of incorrect options (Instruments used in ICCE):** * **Cryo extractor:** This is the most common instrument for ICCE. It uses a probe cooled by CO2 or N2O to create a "cryo-adhesion" to the anterior capsule and the lens cortex, allowing the lens to be pulled out in toto. * **Elschning’s forceps:** These are specialized intracapsular forceps used to grasp the lens capsule (usually at the 6 o'clock position) to facilitate its delivery. * **Von Graefe’s cataract knife:** Historically used in ICCE to create a large (180-degree) limbal incision to allow the delivery of the entire lens. **High-Yield Clinical Pearls for NEET-PG:** * **ICCE Indication:** Currently, the primary indication for ICCE is **subluxated or dislocated lenses** (e.g., Marfan syndrome). * **Complications of ICCE:** Higher risk of vitreous loss, aphakic glaucoma, and **Cystoid Macular Edema (CME)** compared to ECCE. * **Enzymatic Zonulolysis:** Alpha-chymotrypsin was historically used in ICCE to dissolve zonules, facilitating easier lens removal. * **Phacoemulsification:** Uses a **Piezoelectric crystal** to convert electrical energy into mechanical vibrations (frequency ~40,000 Hz).

Q: In post trabeculectomy, shallow anterior chamber with increased IOP is due to all EXCEPT?

Choroidal detachment. To approach this question, remember the **"Shallow Anterior Chamber (AC) Rule"** post-trabeculectomy. A shallow AC can occur with either **Low IOP** or **High IOP**. This distinction is the most high-yield concept for this topic. ### 1. Why Choroidal Detachment is the Correct Answer **Choroidal Detachment** is associated with **Low IOP (Hypotony)**. It occurs due to over-filtration or a wound leak, leading to fluid accumulation in the suprachoroidal space. This pushes the iris-lens diaphragm forward, shallowing the AC, but because the primary cause is fluid loss/leakage, the pressure remains low. ### 2. Explanation of Incorrect Options (Causes of Shallow AC with High IOP) The other three options are classic causes of a shallow AC accompanied by **Increased IOP**: * **Pupillary Block:** Resistance to aqueous flow from the posterior to the anterior chamber causes "iris bombe," pushing the iris forward and raising IOP. * **Malignant Glaucoma (Ciliary Block):** Aqueous is misdirected into the vitreous cavity, pushing the entire lens-iris diaphragm forward. This is a surgical emergency with very high IOP. * **Suprachoroidal Hemorrhage:** Sudden bursting of long/short posterior ciliary arteries fills the suprachoroidal space with blood, acutely pushing the intraocular contents forward and spiking IOP. ### 3. NEET-PG High-Yield Pearls * **Malignant Glaucoma Management:** Initial treatment is medical (Atropine to relax ciliary muscles + Carbonic Anhydrase Inhibitors). If it fails, Pars Plana Vitrectomy is required. * **Differential Diagnosis Tip:** If the question mentions a shallow AC with **Low IOP**, think of **Choroidal Detachment** or **Wound Leak (Seidel’s Test positive)**. If it mentions **High IOP**, think of **Malignant Glaucoma** or **Pupillary Block**. * **Atropine Use:** Atropine is *indicated* in Malignant Glaucoma but *contraindicated* in Primary Angle Closure Glaucoma.

Q: Peribulbar injection is given in which space?

Periorbital space. **Explanation:** The **periorbital space** (also known as the extraconal space) is the anatomical area located outside the cone formed by the rectus muscles but within the bony orbit. In a **peribulbar block**, the local anesthetic is injected into this space, typically via the inferior-temporal quadrant. Unlike retrobulbar blocks, the needle does not penetrate the muscle cone, making it safer as it reduces the risk of optic nerve injury or brainstem anesthesia. **Analysis of Options:** * **A. Subtenon space:** This is the potential space between the Tenon’s capsule and the sclera. A "Sub-Tenon block" involves a blunt cannula and is a distinct technique from peribulbar anesthesia. * **B. Muscle space:** Also known as the **intraconal space**, this is the target for a **retrobulbar block**. Injecting here carries a higher risk of retrobulbar hemorrhage and globe perforation. * **D. Subperiorbital space:** This refers to the potential space between the orbital bones and the periosteum (periorbita). This is not a standard site for anesthetic deposition. **High-Yield Facts for NEET-PG:** * **Peribulbar vs. Retrobulbar:** Peribulbar is preferred today because it is less invasive. It relies on the diffusion of the anesthetic into the muscle cone to achieve akinesia. * **Nerves Blocked:** Both blocks aim to anesthetize CN III, IV, and VI (motor) and the ciliary nerves (sensory). * **Complications:** The most feared complication of orbital blocks is the "Post-block apnea syndrome," caused by accidental injection into the dural sheath of the optic nerve, leading to CNS spread.

Question 1

Which technique involves blocking the facial nerve at the neck of the mandible?

Accepted Answer

O'Brien's block

Answer

Van Lint's block

Answer

Nadbath block

Answer

Atkinson's block

Question 2

A patient is on follow-up after enucleation of a painful blind eye. After enucleation of the eyeball, a proper-sized artificial prosthetic eye is advised after a postoperative period of:

Accepted Answer

About 20 days

Answer

About 10 days

Answer

6-8 weeks

Answer

12-24 weeks

Question 3

Peribulbar injection is given in which space?

Accepted Answer

Periorbital space

Answer

Anterior chamber

Answer

Subtenon space

Answer

Subperiorbital space

Question 4

Retrobulbar injection is given in which space?

Accepted Answer

Inside muscle cone

Answer

Outside muscle cone

Answer

Subtenon space

Answer

Subperiosteum

Question 5

In cataract surgery, when are spectacles typically advised post-operation?

Accepted Answer

6 weeks

Answer

10 weeks

Answer

12 weeks

Answer

14 weeks

Question 6

Deep anterior lamellar keratoplasty is indicated in:

Accepted Answer

Superficial corneal opacities

Answer

Disease of deeper cornea e.g. endothelial damage

Answer

Full thickness corneal opacities

Answer

Bullous keratopathy

Question 7

Which of the following statements regarding phacoemulsification surgery is not true?

Accepted Answer

Hydrodissection is performed to separate the layers of the nucleus.

Answer

A clear corneal incision is preferred.

Answer

Capsulorhexis is performed to remove the anterior capsule.

Answer

The divide and conquer technique is used for nucleus removal.

Question 8

Which of the following instruments is NOT used in intracapsular lens extraction?

Accepted Answer

Phaco-emulsifier

Answer

Cryo extractor

Answer

Elschning's forceps

Answer

Von Graefe's cataract knife

Question 9

In post trabeculectomy, shallow anterior chamber with increased IOP is due to all EXCEPT?

Accepted Answer

Choroidal detachment

Answer

Suprachoroidal hemorrhage

Answer

Pupillary block

Answer

Malignant glaucoma

Question 10

Peribulbar injection is given in which space?

Accepted Answer

Periorbital space

Answer

Subtenon space

Answer

Muscle space

Answer

Subperiorbital space

Ophthalmic Surgery — MCQs

Ophthalmic Surgery — MCQs

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